Date ___________

Pag

e0

Physics

Lab Manual Year - 2012

GENERAL DEPARTMENT

L E COLLEGE MORBI

Date ___________

Pag

e0

My

Beloved Students

With all warm regards and wishes I am glad to present you this fruit of

toil taken by the Professors of General Department This manual is designed in

such a way that it becomes useful in grooming you in a better way It applies

the concept that you study in your theory classes

I hope this labour will inculcate in you the practical wisdom which you

require in your professional life This will widen your horizon and deepen your

knowledge for the subject

This is the toil taken for you by your professors keeping in mind your

need as a student They have tried their level best to form a uniform manual

which is perhaps the first in Degree side I am glad to have such a team of

intellectuals who worked hard and converted the idea into reality I

congratulate them all I feel proud that L E College Morbi is the pioneer in

generating manual for Degree students in General side

I wish you the very success in your life and pray to Almighty to help us

to groom you into a better Engineerhelliphellip

Prof PCVasani

Principal

L E College MORBI

ॐ સહના વવત સહનૌભનકત સહવીરયમ કરવા વહ

તજસવીના વદી તમસત માા વવદ વવસા વહ

ॐ શાાવત શાાવત શાાવત

Date ___________

Pag

e0

My

Beloved Students

With all warm regards and wishes I am glad to present you this fruit of

toil taken by the Professors of General Department This manual is designed in

such a way that it becomes useful in grooming you in a better way It applies

the concept that you study in your theory classes

I hope this labour will inculcate in you the practical wisdom which you

require in your professional life This will widen your horizon and deepen your

knowledge for the subject

This is the toil taken for you by your professors keeping in mind your

need as a student They have tried their level best to form a uniform manual

which is perhaps the first in Degree side I am glad to have such a team of

intellectuals who worked hard and converted the idea into reality I

congratulate them all I feel proud that L E College Morbi is the pioneer in

generating manual for Degree students in General side

I wish you the very success in your life and pray to Almighty to help us

to groom you into a better Engineerhelliphellip

Prof PCVasani

Principal

L E College MORBI

ॐ સહના વવત સહનૌભનકત સહવીરયમ કરવા વહ

તજસવીના વદી તમસત માા વવદ વવસા વહ

ॐ શાાવત શાાવત શાાવત

Date ___________

Pag

e0

Acknowledgements

We heartily extend our vote of thanks to the Principal

Prof PCVasani L E College Morbi to guide us and permit us to

bring our vision into a reality We are also grateful to our Head of

the Department Prof YNDangar for his constant support and

encouraging attitude

Our special thanks are due to our entire staff member who

supported us in compiling our work

Last but not the least to Almighty for his blessings

Compiled by

Asst Prof Jayant K Jogi

Asst Prof Prashant K Rathod

Date ___________

Pag

e1

Certificate

This is to Certify that Shri__________________________

Enroll No____________________ of BE _________________ Class

has Satisfactorily Completed the Course in Physics (110011)

Practicals within Four Walls of LUKHDHIRJI ENGINEERING

COLLEGE MORBI

Date of Submission_________ Staff in-charge_______________

Head of Department________________________________________

Date ___________

Pag

e2

INDEX

Sr

No Name of Experiment

Page

No

Date of

Exp

Performed

Signature

1 Study of resonance by resonance tube 03

2 Velocity of sound in air by resonance tube method

06

3 Refractive index of a liquid by liquid lens method

09

4 Pole strength of a magnet by the method of magnetometer

12

5 Co-efficient of kinetic friction between a block and an inclined plane

16

6 Electrical energy consumed in a circuit 20

7 Temperature of the filament of the bulb 24

8 Frequency of a vibrating string by the method of Meldersquos experiment

28

9 Forward and reverse bias characteristics of a P-N junction diode

33

10 Reverse bias characteristics of a Zener diode

41

11 Dispersive power of a prism using spectrometer

46

12

13

14

Date ___________

Pag

e3

Resonance Tube Experiment - 01

Aim To obtain the length of air column ( 119897 ) for 1st resonance for four different

frequencies using resonance tube Draw the graph of 119897 rarr (1f) and obtain

end correction Also obtain the corrected length of the air column (L) for 1st

resonance for different frequencies

Apparatus Resonance Tube Tuning Forks Vernier calipers

Procedure

Start your experiment with the tuning fork having max frequency

Now hit the tuning fork on the rubber pad put that vibrating tuning fork on

the mouth of the resonance tube Adjust the height of the air column in the

resonance tube in such a way that a louder sound (sound with max

intensity) come out from the resonance tube Stop adjusting the height of

the air column when the louder sound is heard Now note down that height

of the air column in observation table as 119897

Now repeat the same procedure for other tuning forks given to you

Theory

When the frequency of external periodic force becomes equal to the

natural frequency of the system resonance takes place and at that time

system vibrates with max amplitude

In our case when we are adjusting the length of the air column

means we are adjusting the natural frequency of it because natural

frequency of any system is inversely proportional to its length

So when we here a louder sound from the resonance rube it means

that natural frequency of the air column becomes equal to the frequency of

the tuning fork and resonance is taking place

Observations

(1) Least count of vernier calipers = 001 cm

(2) Inner diameter of resonance tubehellip d = _______ cm

Date ___________

Pag

e4

Observation Table

Sr

No

Freq (f)

in Hz

Length of air column at the time of resonance 1f

Hz-1 or sec 1198971 (cm) 1198972 (cm) Average 119897 (cm)

1

2

3

4

Graph 119897 rarr 1f

Here distance 0A on the graph is known as the End correction

Calculations

(1) Corrected length of the air column at the time of resonancehellip

L = 119897 + OA where OA = End correction obtained from graph

(2) Theoretical value of corrected lengthhellip

L = 119897 + (03) d where [(03) d] =Theoretical value of End Correction

Date ___________

Pag

e5

(1) L1 = 1198971 + OA (1) L1 = 1198971 + (03) d

(2) L2 = 1198972 + OA (2) L2 = 1198972 + (03) d

(3) L3 = 1198973 + OA (3) L3 = 1198973 + (03) d

(4) L4 = 1198974 + OA (4) L4 = 1198974 + (03) d

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e6

Velocity of sound in air by Resonance Tube method ndash 02

Aim To compare the frequencies of the tuning forks using resonance tube Also

obtain the velocity of sound from 1st - resonance

Apparatus Resonance Tube Tuning Forks Vernier calipers

Procedure

Start your experiment with the tuning fork having max frequency

Now hit the tuning fork on the rubber pad put that vibrating tuning fork on

the mouth of the resonance tube Adjust the height of the air column in the

resonance tube in such a way that a louder sound (sound with max

intensity) come out from the resonance tube Stop adjusting the height of

the air column when the louder sound is heard Now note down that height

of the air column in observation table as 119897

Now repeat the same procedure for other tuning forks given to you

Theory

When the frequency of external periodic force becomes equal to the

natural frequency of the system resonance takes place and at that time

system vibrates with max amplitude

In our case when we are adjusting the length of the air column we

are adjusting the natural frequency of it because natural frequency of any

system is inversely proportional to its length

So when we here a louder sound from the resonance tube it means

that natural frequency of air column has become equal to the frequency of

tuning fork and resonance is taking place

Observations

(1) Least count of vernier calipers = 001 cm

(2) Inner diameter of resonance tubehellip d = _______ cm

Date ___________

Pag

e7

Observation Table

Sr

No

Freq (f) in

Hz

Length of air column at the time of

resonance

Corrected length

L = 119897 + (03)d (cm)

1198971 (cm) 1198972 (cm) Average 119897 (cm)

1 f1 = L1 =

2 f2 = L2 =

3 f3 = L3 =

4 f4 = L4 =

Calculations

(1) Comparison of the frequencies of the two tuning forks

(i) f1f2 = L2L1 (ii) f3f4 = L4L3

(2) Velocity of SOUNDhellip

119907 = 119891 120582

where λ = Wavelength of the sound wave

119907 = 119891 (4119871)

(Because for 1st ndash resonance λ = 4L)

Date ___________

Pag

e8

(I) 1199071 = 1198911 (41198711) (ii) 1199072 = 1198912 (41198712)

(iii) 1199073 = 1198913 (41198713) (iv) 1199074 = 1198914 (41198714)

(3) Average Velocityhellip

119907 =1199071+1199072+1199073+1199074

4

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e9

Liquid Lens Experiment - 03

Aim To determine refractive index of a given liquid by forming a liquid lens

Apparatus Biconvex lens liquid plane mirror retort stand with clamp and pin

spherometer meter rule

Procedure

The plane mirror is placed on the base of the stand with the pin held

horizontally by the clamp above The convex lens is then placed on the

mirror and its focus is found by locating the position of the pin where it

coincides with its own image By measuring from this point to the lens its

focal length (fg ) is found The lens is now removed and a few drops of

liquid are placed on the mirror On placing the convex lens on the liquid a

combination of a convex (glass) and a plano-concave (liquid) lens results

The focal length (f) of the combination is found as above and the focal

length (fl) of the liquid lens calculated from f and fl The radius of curvature

(r) of the lens surface in contact with the liquid is now obtained by a

spherometer

Theory

The parallel rays meet at the principal focus of the focal length of (1)

Convex lens and (2) Combination lens ndash (Convex lens + Liquid lens) can be

measured experimentally By making use of combination forms the focal

length of liquid lens can be worked out By substituting the value of fl and R

η can be computed

Observations

(1) Least count of spherometer = _______ cm

(2) Distance between two legs of spherometerhellip

a1 = ________ cm a2 = ________ cm a3 = ________ cm

Mean a = ________ cm

(3) Sagita h = _______ div

= _______ cm

Date ___________

Pag

e10

Observation Table

Lens Type Measured Focal Length (cm)

1 2 3 4 5 Mean

Convex fg =_______

Combination f = _______

Calculations

(1) Least count of spherometerhellip

=Distance between two consecutive devisions on main scale

Total number of devisions on circular scale

(2) Radius of curvature hellip 119877 =1198862

6119893+

119893

2

(3) Focal length of a combination lens ( 119891 ) 1

119891=

1

119891119892+

1

119891119897

Date ___________

Pag

e11

(4) Refractive index of a given liquid ( η ) 1

119891119897= minus 120578 minus 1

1

119877

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e12

Deflection of Magnetometer Experiment - 04

Aim To find the magnetic moment (M) of given magnet by magnetometer (From

two different position Gauss-A and Gauss-B of magnetometer) Also obtain

the pole strength (m) of the magnet

Apparatus Magnetometer Magnet

Procedure

First set the magnetometer in Gauss-A position and then put the

magnet at a distance d on the arm of the magnetometer as shown in fig-1

Distance d should be selected in such a way that magnetometer show a

deflection between 30˚ and 60˚ Now note down the deflection shown by

the magnetometer as θ1 and θ2 then reverse the direction of the poles of

the magnet and note down the deflection as θ3 and θ4 Now put the magnet

on the opposite arm and repeat the experiment in a similar way and note

down the deflections as θ5 θ6 θ7 and θ8 Now calculate Magnetic

moment and Pole strength

Now set the magnetometer in Gauss-B position and repeat the

experiment in a similar way

Theory

The Magnetic moment is a measure of the strength of the magnet

Its unit is Gausscm3 For a magnet of Pole strength lsquomrsquo and length 2119897 the

magnetic moment M=2m119897 and points from the South Pole to the North

Pole of the magnet

Gauss-A Position of Magnetometer

Date ___________

Pag

e13

Gauss-B Position of Magnetometer

Observations

(1) Magnetic field intensity of the earthhellip H = 036 Gauss

(2) Magnetic length of the magnethellip 2119897 = 5L6 = __________ cm

119897 = ___________cm

Where L = Geometric length of the magnet = __________ cm

Observation Table for Gauss-A Position

Sr No

Distance d (cm)

Deflection of Magnetometer Avg

θ

tanθ

Magnetic Moment

M = (119837120784minus119897120784)120784

120784119837 H tanθ

θ1 θ2 θ3 θ4 θ5 θ6 θ7 θ8

1

2

Date ___________

Pag

e14

Observation Table for Gauss-B Position

Sr No

Distance d (cm)

Deflection of Magnetometer Avg

θ

tanθ

Magnetic Moment

M = (119837120784+119897120784)120785120784Htanθ

θ1 θ2 θ3 θ4 θ5 θ6 θ7 θ8

1

2

Calculations

(1) Magnetic Moments for Gauss-A position

(2) Magnetic Moments for Gauss-B Position

(1) MA = (119837120784minus119897120784)120784

120784119837 H tanθ

(2) MB = (119837120784+119897120784) 120785120784 H tanθ

(i)

(i)

(ii) (iii)

Date ___________

Pag

e15

(1) 119872119860119886119907119892 =119872119860 1+119872119860 2

2

(2) 119872119861119886119907119892 =119872119861 1+119872119861 2

2

(3) Pole Strength of the magnethellip m = M2119897

(For both Gauss-A amp Gauss-B Positions)

For Gauss-A For Gauss-B

119898119860 =119872119860119886119907119892

2119897

119898119861 =119872119861119886119907119892

2119897

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e16

Friction Experiment - 05

Aim To determine the coefficient of kinetic friction between plane and block

Apparatus Inclined plane Block Scale pan String Set of weights Scale

Procedure

Take the inclined plane and set an angle of inclination θ1 Now put the block

on the inclined plane and put some weight in the scale pan in such a way that

block moves up along the inclined plane with a constant speed Now measure the

height length and base of the inclined plane for that angle and calculate the

Coefficient of kinetic friction

Now repeat the experiment for the angles θ2 and θ3

Theory

When a force F tends to slide a body along a surface a frictional force from

the surface acts on the body The frictional force is parallel to the surface and

directed so as to oppose the sliding It is due to bonding between the body and

the surface

If the body does not slide the frictional force is a static frictional force fs If

there is sliding the frictional force is a kinetic (dynamic) frictional force fk If the

body is rolling then the frictional force is known as rolling frictional force fr

Three properties of friction

(1) If the body does not move then the static frictional force fs and the

component of F that is parallel to the surface are equal in magnitudes

and fs is directed opposite that component If that parallel component

increases magnitude fs also increases

(2) The magnitude of fs has a maximum value fsmax that is given by

fsmax = microsN Where micros is the coefficient of static friction and N is the

magnitude of the normal reaction If the component of F that is parallel

to the surface exceeds fsmax then the body slides on the surface

Date ___________

Pag

e17

(3) If the body begins to slide on the surface the magnitude of the frictional

force rapidly decreases to a constant value fk given by fk = microk N Where

microk is the coefficient of kinetic friction

The magnitude of the coefficients of frictions relative to each other is

given by micros gt microk gtgt micror Where micror is coefficient of rolling friction

Note Here quantities shown bold are vector quantities

Observations

(1) Weight of the blockhellip M = ________ gm

(2) Weight of the scale panhellip m1 = _______ gm

(3) Gravitational accelerationhellip g = 980 cms2

Observation Table

Sr

No

Inclination

of the

Plane (θ)

Effort required to start

the motion up (gm)

m=m1+m2

Avg Effort

m (gm)

Base of

the

Plane

b (cm)

Height

of the

Plane

h (cm)

Length

of the

Plane

l (cm)

cosθ=bl

sinθ=hl

Coefficient of

Kinetic Friction

μ = 119846119840 ndash 119820119840 119852119842119847 120521

119820119840 119836119848119852 120521

1

θ1 1

2

2

θ2 1

2

3

θ3 1

2

Here m2 = the weight put in the scale pan

Page18

Calculation

Coefficient of Kinetic Friction μ = mg ndash Mg sin θMg cos θ

(1) (2)

(3)

Average of Coefficient of Kinetic Friction

μ avg = μ 1 + μ 2 + μ 3

3

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Page19

Date____________

Pag

e20

Wattage of Bulb Experiment - 06

Aim To find the electrical energy consumed in a circuit (bulb)

Apparatus AC Ammeter(0-500 mA) AC Voltmeter(0-250 volt) Variac

Components Bulb

Circuit Diagram

Procedure

Connect the circuit as shown in the circuit diagram Now switch ON

the circuit and note down the reading shown by ammeter at 0 volt then

increase the voltage from 0 to 10 volt and note down the reading of

ammeter Now increase the voltage in order of 10 volts (up to 200 volts)

and note down the readings of the current shown by the ammeter Now

calculate the power consumed in a circuit at different stages

Theory

Experiments show that in stationary metallic conductors current does

work to increase their internal energy The heated conductor releases the

energy received to the surrounding bodies but this is done by means of

heat transfer This means that the quantity of heat released by a current

carrying conductor is equal to the total work done by the current

Date____________

Pag

e21

As we know that the work done by the current is given by 119830 = 119829119816119853helliphelliphelliphelliphelliphellip(1)

119830 = 119816120784119825119853 ( V = IR) helliphelliphelliphelliphelliphelliphellip (2)

The electrical power of a given device is simply the rate of doing

work or the amount of electric work done in one second

Therefore electric powerhellip

119823 =119830119848119851119844 119837119848119847119838 (119830)

119827119842119846119838 (119853)

119823 =119829119816119853

119853= 119829119816 helliphelliphelliphelliphelliphelliphellip (3)

Thus electric power is equal to the product of voltage by current

Watt is a unit of power Hence it can be expressed in terms of a volt

and an ampere by the formula for electric power Eqn (3)

Therefore

1 Watt = 1 volt ∙ 1 ampere

1 W = 1 V∙A

Thus if a potential difference of 1 volt causes a current of 1 ampere

to flow through a conductor (here a bulb) the electric power consumed is

1 watt and the electrical energy consumed is 1 joulesec this electrical

energy consumed in the bulb is converted into heat and light energy

Date____________

Pag

e22

Observation Table

Sr No Voltage V (volt) Current 119816 (mA) Power

119823 = 119829119816 (watt)

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

Date____________

Pag

e23

Calculation 119823 = 119829119816

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e24

Temperature of Tungsten Filament Experiment ndash 07

Aim To find the temperature of the tungsten filament of the bulb

Apparatus AC Ammeter(0-500 mA) AC Voltmeter(0-250 volt) Variac

Components Bulb

Circuit Diagram

Procedure

Connect the circuit as shown in the circuit diagram Now switch ON

the circuit and note down the reading shown by ammeter at 0 volt then

increase the voltage from 0 to 10 volt and note down the reading of

ammeter Now increase the voltage in order of 10 volts (up to 100 volts)

and note down the readings of the current shown by the ammeter Now

calculate the resistance and the temperature of the filament

Observations

(1) Room temperaturehellip t0 = _______ ˚C

(2) Resistance of the filament of the bulb at room temperaturehellip

R0 = _______ Ω

(3) Temperature coefficient of tungstenhellip α = 45times10-4 ˚C-1

Date____________

Pag

e25

Observation Table

Sr No Voltage V

(volt)

Current 119816

(mA)

Resistance of

The Filament

119825119853 =119829

119816 Ω

Temperature of The Filament

119853 =120783

120514[

119825119853

119825120782 120783 + 120514119853120782 minus 120783] ˚C

1

2

3

4

5

6

7

8

9

10

Graph Rt versus t

Date____________

Pag

e26

Calculations

(1) Resistance of The Filament Rt =V

I Ω

(2) Temperature of The Filament t =1

α[

Rt

R0 1 + αt0 minus 1] ˚C

Date____________

Pag

e27

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e28

Meldersquos Experiment - 08

Aim To find the frequency of the wave and the frequency of the tuning fork by

Meldersquos experiment

Apparatus Meldersquos experiment apparatus

Circuit Diagram

Transverse mode

Procedure

Set Meldersquos experiment apparatus as shown in circuit diagram in

longitudinal position and switch ON the power supply put some weight in

scale pan and adjust the length of the string in such a way that you find

some loops on the string (eg 2 loops) Now rotate the apparatus by 90˚ so

that it is set for lsquoBrsquo position for the same values of weight in pan and for

the same length of the string the number of loops created in lsquoBrsquo position

are double (eg 4 loops) than in lsquoArsquo position Note down these readings in

observation table Repeat the experiment for other values of weight in

scale pan

Date____________

Pag

e29

Theory

This is an easy and efficient method by which nodes and antinodes

formed on a string can be demonstrated

A tuning fork is fitted in a wooden block A long string or thread of

cotton is taken One end of this string is tied to one of the prongs of the

tuning fork and the second end of this string passes over a smooth pulley in

such a way that a small pan can be hang on it Small weights are put in the

pan to create tension in the string This arrangement is shown in the circuit

diagram

The fork is set into vibrations by lightly hitting the prong of the tuning

fork on which the string is not tied or by connecting an electric supply as

shown in the circuit diagram Thus the transverse vibrations are produced

in the string and by adjusting the length andor weights in the pan these

vibrations are reflected from the point of contact between the string and

the pulley and a number of loops appear on the string as shown in the

circuit diagram

When the prongs of the tuning fork vibrate in a plane parallel to the

direction of propagation of the waves it is called lsquoArsquo position or

longitudinal position

If the tuning fork along with the wooden block is rotated through

90˚ so that the plane of vibration of the tuning fork is normal (ie at right

angles) to the direction of propagation it is called lsquoBrsquo position or transverse

position

For the same length and same weight in the pan (ie for the same

tension) the number of loops in lsquoBrsquo position is double than in lsquoArsquo position

Thus either in lsquoArsquo position or in lsquoBrsquo position standing transverse

waves are generated in the string with a series of nodes and antinodes at

equal distances

The equation connecting number of loops (n or nrsquo) length of the

string (l) tension in the string (T) mass per unit length of the string (m) and

frequency of the string (f) is as follows

Date____________

Pag

e30

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position)

119943prime =119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

If the frequency of tuning fork is F then for lsquoArsquo position 119839 =119813

120784 and for lsquoBrsquo

position 119839prime = 119813

In the above equations if all the quantities on the RHS are known the

frequency of the tuning fork 119813 can be calculated

Observations

(1) Gravitational accelerationhellip g = 98 ms2

(2) Mass per unit length of the stringhellip m = _______ kgm

(3) Mass of the scale panhellip M1 = _______ kg

Observation Table

Sr

No

Total mass

suspended at

the end of the

stringhellip

M=M1+M2

(kg)

Tension

created

in the

stringhellip

T=Mg (N)

Length of the

vibrating string

Average

lengthhellip

119949 (m)

No of loops created on

the stringhellip

Frequency of the

vibrating stringhellip

Relation

between

f and frsquo 1199491 (m) 1199492 (m)

In

Longitudinal

Modehellip

n

In

Transverse

Modehellip

nrsquo

In

Longitudinal

Modehellip

119943 =119951

120784119949

119931

119950

In

Transverse

Modehellip

119943prime =119951prime

120784119949

119931

119950

1

2

3

4

Here M2 = the weight put in the scale pan

Page31

Date____________

Pag

e32

Calculations

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position) 119943prime =

119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e33

P-N Junction Diode Characteristics Experiment - 09

Aim To study the Forward and Reverse bias characteristics of a P-N junction

diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components P-N junction diode Resistors

Circuit Diagram

(Forward biased PN diode) (Reverse biased PN diode)

Procedure

For Forward Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 01 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 02 03 04hellip

volts and repeat the procedure Note down the knee voltage and

corresponding current in your observation table

For Reverse Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Date____________

Pag

e34

Theory

If donor (pentavalent) impurities are introduced on one side and

acceptors (trivalent) on the opposite side of a single crystal of an intrinsic

semiconductor like germanium or silicon a p-n junction is formed as shown

in Fig 11 In the figure a donor ion is indicated schematically by a plus sign

because after this impurity atom donates an electron it becomes a positive

ion

The acceptor ion is indicated by a minus sign because after this atom

accepts an electron it becomes a negative ion Initially there are only n-

type carriers to the right of the junction and only p-type carriers to the left

Because there is a density gradient across the junction holes will diffuse to

the right across the junction and electrons to the left As a result of the

displacement of these charges an electric field appears across the junction

Equilibrium is established when the field becomes large enough to restrain

the process of diffusion The positive holes which neutralize the acceptor

ions near the junction in p-type germanium disappear as a result of

combination with electrons which diffuse across the junction Similarly the

neutralizing electrons on the n side of the junction combine with holes

which cross the junction from the p side Since the region of the junction is

depleted of mobile charges it is called the depletion region or a potential

barrier

Forward Bias

An external voltage applied to the p-n junction with the polarity

shown in Fig 12 is known as forward bias The height of the potential

barrier at the junction is lowered by the applied forward voltage In other

words we can say that p-n junction diode is connected to an external

Date____________

Pag

e35

battery in such a way that depletion region is reduced in size or eliminated

altogether Which of these takes place is determined by the size of the

applied voltage The positive terminal of the battery repels the holes on the

p-side and pushes them towards the junction The negative terminal of the

battery repels the electrons and pushes them towards the junction This

collapses the depletion region With the depletion region gone the diode

can conduct

Reverse Bias

An external voltage applied with polarity in Fig 13 is called reverse

bias When reverse bias is applied to a junction diode the depletion region

does not collapse On the contrary it becomes wider The positive side of

battery is applied to the n-type material This attracts the free electrons

away from the junction The negative side of the battery attracts the holes

in p-type material away from the junction This makes the depletion region

wider than it was when no voltage is applied The depletion region is an

insulator and it will block the flow of current Actually a small current will

flow because of minority carriers The p-type material has a few minority

electrons These are pushed to the junction by the repulsion of the negative

side of the battery The n-type material has few minority holes These are

also pushed towards the junction Reverse bias forces the minority carriers

together and a small current - called leakage current - results

Diodes which are designed with adequate power dissipation

capability to operate in the breakdown region are none as Zener diodes

Two mechanisms of diode breakdown for increasing reverse voltage are

recognized In one mechanism the thermally generated electrons and

holes acquire sufficient energy from the applied potential to produce new

carriers by removing valence electrons from their bonds These new

carriers in turn produce additional carriers again through the process of

disrupting bonds This cumulative process is referred to as avalanche

breakdown Even if the initially available carriers do not acquire sufficient

energy to disrupt bonds it is possible to initiate breakdown through a

direct rupture of the bonds because of the existence of strong electric field

Under these conditions the breakdown is referred to as Zener breakdown

Date____________

Pag

e36

Zener breakdown occurs below 6 V Zener diodes are commonly used in

voltage-reference or constant-voltage devices

Characteristic curves of diode

Fig 14 shows V-I Characteristic curves for typical p-n junction diode

It is seen that the curve is not linear With 0 V across the diode the diode

will not conduct the diode will not begin to conduct until a few tenths of a

volt are applied across it This is the voltage needed to overcome the

potential barrier It requires about 02 V to turn on a germanium diode and

about 06 V to turn on a silicon diode Fig 18 also shows what happens

when reverse bias is applied to a diode At increasing levels of reverse

voltage the curve shows some reverse current This leakage current is

caused by minority carries It is usually very small

Graph

Fig-14

Date____________

Pag

e37

Observation Table for Forward bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Date____________

Pag

e38

Observation Table for Reverse bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e39

Calculation for Forward bias 119877 = 119881

119868

Calculation for Reverse bias 119877 = 119881

119868

Date____________

Pag

e40

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e41

Zener Diode Reverse Bias Characteristics Experiment - 10

Aim To study the reverse bias characteristics of a Zener diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components Zener diode Resistors

Circuit Diagram

Procedure

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Theory

A diode which is heavily doped (Si or Ge) and which operates in the

reverse breakdown region with a sharp breakdown voltage is called a zener

diode The schematic symbol of a zener diode is shown in Fig-1 This is

similar to a normal diode except that the line (bar) representing the

cathode is bent at both ends like the letter Z for zener diode

Date____________

Pag

e42

A C Fig-1

In a simple diode the doping is light as a result the breakdown

voltage is high and not sharp But if doping is made heavy the depletion

layer becomes very narrow and even the breakdown voltage gets reduced

to a sharp value The zener diode is designed to operate in the breakdown

region without damage

The reverse breakdown of a zener diode may occur either due to

zener effect or avalanche effect But zener diode primarily depends on

zener effect for its working When the electric field across the junction is

sufficiently high due to the applied voltage the zener breakdown occurs

because of breaking of covalent bonds This produces a large number of

electrons and holes which constitute a steep rise in the reverse saturation

current (also called zener current 119868Z) This effect is called as zener effect

Zener current is independent of the applied voltage and depends only on

the external resistance

The V - 119868 characteristic of a zener diode is shown in Fig-2 The

forward characteristic is simply that of an ordinary forward biased junction

diode

Fig-2

Date____________

Pag

e43

Under reverse bias condition breakdown of junction occurs This

breakdown depends upon the amount of doping It can be seen from Fig-2

that as the reverse voltage is increased the reverse current remains

negligibly small up to the lsquokneersquo of the curve

At this lsquoknee pointrsquo the effect of breakdown process begins The

voltage corresponding to the lsquoknee pointrsquo in the figure is called the zener

breakdown voltage or simply zener voltage (VZ) which is very sharp

compared to a simle p-n junction diode Beyond this voltage the reverse

current (119868Z) increases sharply to a high value

The zener diode is not immediately burnt just because it has entered

the breakdown region As long as the external resistance connected to the

diode in the circuit limits the diode current to less than the burn out value

the diode will not burn out The zener voltage VZ remains constant even

when zener current 119868Z increases greatly This ability of a diode is called

regulating ability and it enables us to use zener diode for voltage

regulation

Date____________

Pag

e44

Observation Table

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e45

Graph 119868 V

Calculations 119877 = 119881

119868

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e46

Dispersive Power of The Prism Experiment - 11

Aim To find the dispersive power (D) of the prism by using spectrometer

Apparatus Mercury vapor lamp Spectrometer Prism

Procedure

Levelling and alignment of collimator and telescope

1 Switch on the mercury lamp Adjust the leveling screws on the chassis

Keep the spirit level on the chassis and do finer adjustments of these

screws to bring the bubble in the sprit level to the centre Repeat this

placing the sprit level along a direction perpendicular to the earlier

direction

2 Repeat this procedure for the prism table

3 Close the slit at the other end of the collimator using the drum screw DS1

Open it to a reasonable width Place the spectrometer in front of the

mercury lamp window and rotate the collimator so that the slit faces of

window View the slit through the telescope If it is not in the centre of the

view level collimator and the telescope so as to bring it to the centre

Setting the prism in the minimum deviation position

1 Rotate the prism table such that lines ruled on the table become

perpendicular to the axis of collimator

2 Place prism over the prism table such that its rough surface BA is

perpendicular to the line on prism table (See Fig-1(a))

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e1

Certificate

This is to Certify that Shri__________________________

Enroll No____________________ of BE _________________ Class

has Satisfactorily Completed the Course in Physics (110011)

Practicals within Four Walls of LUKHDHIRJI ENGINEERING

COLLEGE MORBI

Date of Submission_________ Staff in-charge_______________

Head of Department________________________________________

Date ___________

Pag

e2

INDEX

Sr

No Name of Experiment

Page

No

Date of

Exp

Performed

Signature

1 Study of resonance by resonance tube 03

2 Velocity of sound in air by resonance tube method

06

3 Refractive index of a liquid by liquid lens method

09

4 Pole strength of a magnet by the method of magnetometer

12

5 Co-efficient of kinetic friction between a block and an inclined plane

16

6 Electrical energy consumed in a circuit 20

7 Temperature of the filament of the bulb 24

8 Frequency of a vibrating string by the method of Meldersquos experiment

28

9 Forward and reverse bias characteristics of a P-N junction diode

33

10 Reverse bias characteristics of a Zener diode

41

11 Dispersive power of a prism using spectrometer

46

12

13

14

Date ___________

Pag

e3

Resonance Tube Experiment - 01

Aim To obtain the length of air column ( 119897 ) for 1st resonance for four different

frequencies using resonance tube Draw the graph of 119897 rarr (1f) and obtain

end correction Also obtain the corrected length of the air column (L) for 1st

resonance for different frequencies

Apparatus Resonance Tube Tuning Forks Vernier calipers

Procedure

Start your experiment with the tuning fork having max frequency

Now hit the tuning fork on the rubber pad put that vibrating tuning fork on

the mouth of the resonance tube Adjust the height of the air column in the

resonance tube in such a way that a louder sound (sound with max

intensity) come out from the resonance tube Stop adjusting the height of

the air column when the louder sound is heard Now note down that height

of the air column in observation table as 119897

Now repeat the same procedure for other tuning forks given to you

Theory

When the frequency of external periodic force becomes equal to the

natural frequency of the system resonance takes place and at that time

system vibrates with max amplitude

In our case when we are adjusting the length of the air column

means we are adjusting the natural frequency of it because natural

frequency of any system is inversely proportional to its length

So when we here a louder sound from the resonance rube it means

that natural frequency of the air column becomes equal to the frequency of

the tuning fork and resonance is taking place

Observations

(1) Least count of vernier calipers = 001 cm

(2) Inner diameter of resonance tubehellip d = _______ cm

Date ___________

Pag

e4

Observation Table

Sr

No

Freq (f)

in Hz

Length of air column at the time of resonance 1f

Hz-1 or sec 1198971 (cm) 1198972 (cm) Average 119897 (cm)

1

2

3

4

Graph 119897 rarr 1f

Here distance 0A on the graph is known as the End correction

Calculations

(1) Corrected length of the air column at the time of resonancehellip

L = 119897 + OA where OA = End correction obtained from graph

(2) Theoretical value of corrected lengthhellip

L = 119897 + (03) d where [(03) d] =Theoretical value of End Correction

Date ___________

Pag

e5

(1) L1 = 1198971 + OA (1) L1 = 1198971 + (03) d

(2) L2 = 1198972 + OA (2) L2 = 1198972 + (03) d

(3) L3 = 1198973 + OA (3) L3 = 1198973 + (03) d

(4) L4 = 1198974 + OA (4) L4 = 1198974 + (03) d

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e6

Velocity of sound in air by Resonance Tube method ndash 02

Aim To compare the frequencies of the tuning forks using resonance tube Also

obtain the velocity of sound from 1st - resonance

Apparatus Resonance Tube Tuning Forks Vernier calipers

Procedure

Start your experiment with the tuning fork having max frequency

Now hit the tuning fork on the rubber pad put that vibrating tuning fork on

the mouth of the resonance tube Adjust the height of the air column in the

resonance tube in such a way that a louder sound (sound with max

intensity) come out from the resonance tube Stop adjusting the height of

the air column when the louder sound is heard Now note down that height

of the air column in observation table as 119897

Now repeat the same procedure for other tuning forks given to you

Theory

When the frequency of external periodic force becomes equal to the

natural frequency of the system resonance takes place and at that time

system vibrates with max amplitude

In our case when we are adjusting the length of the air column we

are adjusting the natural frequency of it because natural frequency of any

system is inversely proportional to its length

So when we here a louder sound from the resonance tube it means

that natural frequency of air column has become equal to the frequency of

tuning fork and resonance is taking place

Observations

(1) Least count of vernier calipers = 001 cm

(2) Inner diameter of resonance tubehellip d = _______ cm

Date ___________

Pag

e7

Observation Table

Sr

No

Freq (f) in

Hz

Length of air column at the time of

resonance

Corrected length

L = 119897 + (03)d (cm)

1198971 (cm) 1198972 (cm) Average 119897 (cm)

1 f1 = L1 =

2 f2 = L2 =

3 f3 = L3 =

4 f4 = L4 =

Calculations

(1) Comparison of the frequencies of the two tuning forks

(i) f1f2 = L2L1 (ii) f3f4 = L4L3

(2) Velocity of SOUNDhellip

119907 = 119891 120582

where λ = Wavelength of the sound wave

119907 = 119891 (4119871)

(Because for 1st ndash resonance λ = 4L)

Date ___________

Pag

e8

(I) 1199071 = 1198911 (41198711) (ii) 1199072 = 1198912 (41198712)

(iii) 1199073 = 1198913 (41198713) (iv) 1199074 = 1198914 (41198714)

(3) Average Velocityhellip

119907 =1199071+1199072+1199073+1199074

4

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e9

Liquid Lens Experiment - 03

Aim To determine refractive index of a given liquid by forming a liquid lens

Apparatus Biconvex lens liquid plane mirror retort stand with clamp and pin

spherometer meter rule

Procedure

The plane mirror is placed on the base of the stand with the pin held

horizontally by the clamp above The convex lens is then placed on the

mirror and its focus is found by locating the position of the pin where it

coincides with its own image By measuring from this point to the lens its

focal length (fg ) is found The lens is now removed and a few drops of

liquid are placed on the mirror On placing the convex lens on the liquid a

combination of a convex (glass) and a plano-concave (liquid) lens results

The focal length (f) of the combination is found as above and the focal

length (fl) of the liquid lens calculated from f and fl The radius of curvature

(r) of the lens surface in contact with the liquid is now obtained by a

spherometer

Theory

The parallel rays meet at the principal focus of the focal length of (1)

Convex lens and (2) Combination lens ndash (Convex lens + Liquid lens) can be

measured experimentally By making use of combination forms the focal

length of liquid lens can be worked out By substituting the value of fl and R

η can be computed

Observations

(1) Least count of spherometer = _______ cm

(2) Distance between two legs of spherometerhellip

a1 = ________ cm a2 = ________ cm a3 = ________ cm

Mean a = ________ cm

(3) Sagita h = _______ div

= _______ cm

Date ___________

Pag

e10

Observation Table

Lens Type Measured Focal Length (cm)

1 2 3 4 5 Mean

Convex fg =_______

Combination f = _______

Calculations

(1) Least count of spherometerhellip

=Distance between two consecutive devisions on main scale

Total number of devisions on circular scale

(2) Radius of curvature hellip 119877 =1198862

6119893+

119893

2

(3) Focal length of a combination lens ( 119891 ) 1

119891=

1

119891119892+

1

119891119897

Date ___________

Pag

e11

(4) Refractive index of a given liquid ( η ) 1

119891119897= minus 120578 minus 1

1

119877

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e12

Deflection of Magnetometer Experiment - 04

Aim To find the magnetic moment (M) of given magnet by magnetometer (From

two different position Gauss-A and Gauss-B of magnetometer) Also obtain

the pole strength (m) of the magnet

Apparatus Magnetometer Magnet

Procedure

First set the magnetometer in Gauss-A position and then put the

magnet at a distance d on the arm of the magnetometer as shown in fig-1

Distance d should be selected in such a way that magnetometer show a

deflection between 30˚ and 60˚ Now note down the deflection shown by

the magnetometer as θ1 and θ2 then reverse the direction of the poles of

the magnet and note down the deflection as θ3 and θ4 Now put the magnet

on the opposite arm and repeat the experiment in a similar way and note

down the deflections as θ5 θ6 θ7 and θ8 Now calculate Magnetic

moment and Pole strength

Now set the magnetometer in Gauss-B position and repeat the

experiment in a similar way

Theory

The Magnetic moment is a measure of the strength of the magnet

Its unit is Gausscm3 For a magnet of Pole strength lsquomrsquo and length 2119897 the

magnetic moment M=2m119897 and points from the South Pole to the North

Pole of the magnet

Gauss-A Position of Magnetometer

Date ___________

Pag

e13

Gauss-B Position of Magnetometer

Observations

(1) Magnetic field intensity of the earthhellip H = 036 Gauss

(2) Magnetic length of the magnethellip 2119897 = 5L6 = __________ cm

119897 = ___________cm

Where L = Geometric length of the magnet = __________ cm

Observation Table for Gauss-A Position

Sr No

Distance d (cm)

Deflection of Magnetometer Avg

θ

tanθ

Magnetic Moment

M = (119837120784minus119897120784)120784

120784119837 H tanθ

θ1 θ2 θ3 θ4 θ5 θ6 θ7 θ8

1

2

Date ___________

Pag

e14

Observation Table for Gauss-B Position

Sr No

Distance d (cm)

Deflection of Magnetometer Avg

θ

tanθ

Magnetic Moment

M = (119837120784+119897120784)120785120784Htanθ

θ1 θ2 θ3 θ4 θ5 θ6 θ7 θ8

1

2

Calculations

(1) Magnetic Moments for Gauss-A position

(2) Magnetic Moments for Gauss-B Position

(1) MA = (119837120784minus119897120784)120784

120784119837 H tanθ

(2) MB = (119837120784+119897120784) 120785120784 H tanθ

(i)

(i)

(ii) (iii)

Date ___________

Pag

e15

(1) 119872119860119886119907119892 =119872119860 1+119872119860 2

2

(2) 119872119861119886119907119892 =119872119861 1+119872119861 2

2

(3) Pole Strength of the magnethellip m = M2119897

(For both Gauss-A amp Gauss-B Positions)

For Gauss-A For Gauss-B

119898119860 =119872119860119886119907119892

2119897

119898119861 =119872119861119886119907119892

2119897

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e16

Friction Experiment - 05

Aim To determine the coefficient of kinetic friction between plane and block

Apparatus Inclined plane Block Scale pan String Set of weights Scale

Procedure

Take the inclined plane and set an angle of inclination θ1 Now put the block

on the inclined plane and put some weight in the scale pan in such a way that

block moves up along the inclined plane with a constant speed Now measure the

height length and base of the inclined plane for that angle and calculate the

Coefficient of kinetic friction

Now repeat the experiment for the angles θ2 and θ3

Theory

When a force F tends to slide a body along a surface a frictional force from

the surface acts on the body The frictional force is parallel to the surface and

directed so as to oppose the sliding It is due to bonding between the body and

the surface

If the body does not slide the frictional force is a static frictional force fs If

there is sliding the frictional force is a kinetic (dynamic) frictional force fk If the

body is rolling then the frictional force is known as rolling frictional force fr

Three properties of friction

(1) If the body does not move then the static frictional force fs and the

component of F that is parallel to the surface are equal in magnitudes

and fs is directed opposite that component If that parallel component

increases magnitude fs also increases

(2) The magnitude of fs has a maximum value fsmax that is given by

fsmax = microsN Where micros is the coefficient of static friction and N is the

magnitude of the normal reaction If the component of F that is parallel

to the surface exceeds fsmax then the body slides on the surface

Date ___________

Pag

e17

(3) If the body begins to slide on the surface the magnitude of the frictional

force rapidly decreases to a constant value fk given by fk = microk N Where

microk is the coefficient of kinetic friction

The magnitude of the coefficients of frictions relative to each other is

given by micros gt microk gtgt micror Where micror is coefficient of rolling friction

Note Here quantities shown bold are vector quantities

Observations

(1) Weight of the blockhellip M = ________ gm

(2) Weight of the scale panhellip m1 = _______ gm

(3) Gravitational accelerationhellip g = 980 cms2

Observation Table

Sr

No

Inclination

of the

Plane (θ)

Effort required to start

the motion up (gm)

m=m1+m2

Avg Effort

m (gm)

Base of

the

Plane

b (cm)

Height

of the

Plane

h (cm)

Length

of the

Plane

l (cm)

cosθ=bl

sinθ=hl

Coefficient of

Kinetic Friction

μ = 119846119840 ndash 119820119840 119852119842119847 120521

119820119840 119836119848119852 120521

1

θ1 1

2

2

θ2 1

2

3

θ3 1

2

Here m2 = the weight put in the scale pan

Page18

Calculation

Coefficient of Kinetic Friction μ = mg ndash Mg sin θMg cos θ

(1) (2)

(3)

Average of Coefficient of Kinetic Friction

μ avg = μ 1 + μ 2 + μ 3

3

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Page19

Date____________

Pag

e20

Wattage of Bulb Experiment - 06

Aim To find the electrical energy consumed in a circuit (bulb)

Apparatus AC Ammeter(0-500 mA) AC Voltmeter(0-250 volt) Variac

Components Bulb

Circuit Diagram

Procedure

Connect the circuit as shown in the circuit diagram Now switch ON

the circuit and note down the reading shown by ammeter at 0 volt then

increase the voltage from 0 to 10 volt and note down the reading of

ammeter Now increase the voltage in order of 10 volts (up to 200 volts)

and note down the readings of the current shown by the ammeter Now

calculate the power consumed in a circuit at different stages

Theory

Experiments show that in stationary metallic conductors current does

work to increase their internal energy The heated conductor releases the

energy received to the surrounding bodies but this is done by means of

heat transfer This means that the quantity of heat released by a current

carrying conductor is equal to the total work done by the current

Date____________

Pag

e21

As we know that the work done by the current is given by 119830 = 119829119816119853helliphelliphelliphelliphelliphellip(1)

119830 = 119816120784119825119853 ( V = IR) helliphelliphelliphelliphelliphelliphellip (2)

The electrical power of a given device is simply the rate of doing

work or the amount of electric work done in one second

Therefore electric powerhellip

119823 =119830119848119851119844 119837119848119847119838 (119830)

119827119842119846119838 (119853)

119823 =119829119816119853

119853= 119829119816 helliphelliphelliphelliphelliphelliphellip (3)

Thus electric power is equal to the product of voltage by current

Watt is a unit of power Hence it can be expressed in terms of a volt

and an ampere by the formula for electric power Eqn (3)

Therefore

1 Watt = 1 volt ∙ 1 ampere

1 W = 1 V∙A

Thus if a potential difference of 1 volt causes a current of 1 ampere

to flow through a conductor (here a bulb) the electric power consumed is

1 watt and the electrical energy consumed is 1 joulesec this electrical

energy consumed in the bulb is converted into heat and light energy

Date____________

Pag

e22

Observation Table

Sr No Voltage V (volt) Current 119816 (mA) Power

119823 = 119829119816 (watt)

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

Date____________

Pag

e23

Calculation 119823 = 119829119816

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e24

Temperature of Tungsten Filament Experiment ndash 07

Aim To find the temperature of the tungsten filament of the bulb

Apparatus AC Ammeter(0-500 mA) AC Voltmeter(0-250 volt) Variac

Components Bulb

Circuit Diagram

Procedure

Connect the circuit as shown in the circuit diagram Now switch ON

the circuit and note down the reading shown by ammeter at 0 volt then

increase the voltage from 0 to 10 volt and note down the reading of

ammeter Now increase the voltage in order of 10 volts (up to 100 volts)

and note down the readings of the current shown by the ammeter Now

calculate the resistance and the temperature of the filament

Observations

(1) Room temperaturehellip t0 = _______ ˚C

(2) Resistance of the filament of the bulb at room temperaturehellip

R0 = _______ Ω

(3) Temperature coefficient of tungstenhellip α = 45times10-4 ˚C-1

Date____________

Pag

e25

Observation Table

Sr No Voltage V

(volt)

Current 119816

(mA)

Resistance of

The Filament

119825119853 =119829

119816 Ω

Temperature of The Filament

119853 =120783

120514[

119825119853

119825120782 120783 + 120514119853120782 minus 120783] ˚C

1

2

3

4

5

6

7

8

9

10

Graph Rt versus t

Date____________

Pag

e26

Calculations

(1) Resistance of The Filament Rt =V

I Ω

(2) Temperature of The Filament t =1

α[

Rt

R0 1 + αt0 minus 1] ˚C

Date____________

Pag

e27

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e28

Meldersquos Experiment - 08

Aim To find the frequency of the wave and the frequency of the tuning fork by

Meldersquos experiment

Apparatus Meldersquos experiment apparatus

Circuit Diagram

Transverse mode

Procedure

Set Meldersquos experiment apparatus as shown in circuit diagram in

longitudinal position and switch ON the power supply put some weight in

scale pan and adjust the length of the string in such a way that you find

some loops on the string (eg 2 loops) Now rotate the apparatus by 90˚ so

that it is set for lsquoBrsquo position for the same values of weight in pan and for

the same length of the string the number of loops created in lsquoBrsquo position

are double (eg 4 loops) than in lsquoArsquo position Note down these readings in

observation table Repeat the experiment for other values of weight in

scale pan

Date____________

Pag

e29

Theory

This is an easy and efficient method by which nodes and antinodes

formed on a string can be demonstrated

A tuning fork is fitted in a wooden block A long string or thread of

cotton is taken One end of this string is tied to one of the prongs of the

tuning fork and the second end of this string passes over a smooth pulley in

such a way that a small pan can be hang on it Small weights are put in the

pan to create tension in the string This arrangement is shown in the circuit

diagram

The fork is set into vibrations by lightly hitting the prong of the tuning

fork on which the string is not tied or by connecting an electric supply as

shown in the circuit diagram Thus the transverse vibrations are produced

in the string and by adjusting the length andor weights in the pan these

vibrations are reflected from the point of contact between the string and

the pulley and a number of loops appear on the string as shown in the

circuit diagram

When the prongs of the tuning fork vibrate in a plane parallel to the

direction of propagation of the waves it is called lsquoArsquo position or

longitudinal position

If the tuning fork along with the wooden block is rotated through

90˚ so that the plane of vibration of the tuning fork is normal (ie at right

angles) to the direction of propagation it is called lsquoBrsquo position or transverse

position

For the same length and same weight in the pan (ie for the same

tension) the number of loops in lsquoBrsquo position is double than in lsquoArsquo position

Thus either in lsquoArsquo position or in lsquoBrsquo position standing transverse

waves are generated in the string with a series of nodes and antinodes at

equal distances

The equation connecting number of loops (n or nrsquo) length of the

string (l) tension in the string (T) mass per unit length of the string (m) and

frequency of the string (f) is as follows

Date____________

Pag

e30

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position)

119943prime =119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

If the frequency of tuning fork is F then for lsquoArsquo position 119839 =119813

120784 and for lsquoBrsquo

position 119839prime = 119813

In the above equations if all the quantities on the RHS are known the

frequency of the tuning fork 119813 can be calculated

Observations

(1) Gravitational accelerationhellip g = 98 ms2

(2) Mass per unit length of the stringhellip m = _______ kgm

(3) Mass of the scale panhellip M1 = _______ kg

Observation Table

Sr

No

Total mass

suspended at

the end of the

stringhellip

M=M1+M2

(kg)

Tension

created

in the

stringhellip

T=Mg (N)

Length of the

vibrating string

Average

lengthhellip

119949 (m)

No of loops created on

the stringhellip

Frequency of the

vibrating stringhellip

Relation

between

f and frsquo 1199491 (m) 1199492 (m)

In

Longitudinal

Modehellip

n

In

Transverse

Modehellip

nrsquo

In

Longitudinal

Modehellip

119943 =119951

120784119949

119931

119950

In

Transverse

Modehellip

119943prime =119951prime

120784119949

119931

119950

1

2

3

4

Here M2 = the weight put in the scale pan

Page31

Date____________

Pag

e32

Calculations

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position) 119943prime =

119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e33

P-N Junction Diode Characteristics Experiment - 09

Aim To study the Forward and Reverse bias characteristics of a P-N junction

diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components P-N junction diode Resistors

Circuit Diagram

(Forward biased PN diode) (Reverse biased PN diode)

Procedure

For Forward Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 01 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 02 03 04hellip

volts and repeat the procedure Note down the knee voltage and

corresponding current in your observation table

For Reverse Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Date____________

Pag

e34

Theory

If donor (pentavalent) impurities are introduced on one side and

acceptors (trivalent) on the opposite side of a single crystal of an intrinsic

semiconductor like germanium or silicon a p-n junction is formed as shown

in Fig 11 In the figure a donor ion is indicated schematically by a plus sign

because after this impurity atom donates an electron it becomes a positive

ion

The acceptor ion is indicated by a minus sign because after this atom

accepts an electron it becomes a negative ion Initially there are only n-

type carriers to the right of the junction and only p-type carriers to the left

Because there is a density gradient across the junction holes will diffuse to

the right across the junction and electrons to the left As a result of the

displacement of these charges an electric field appears across the junction

Equilibrium is established when the field becomes large enough to restrain

the process of diffusion The positive holes which neutralize the acceptor

ions near the junction in p-type germanium disappear as a result of

combination with electrons which diffuse across the junction Similarly the

neutralizing electrons on the n side of the junction combine with holes

which cross the junction from the p side Since the region of the junction is

depleted of mobile charges it is called the depletion region or a potential

barrier

Forward Bias

An external voltage applied to the p-n junction with the polarity

shown in Fig 12 is known as forward bias The height of the potential

barrier at the junction is lowered by the applied forward voltage In other

words we can say that p-n junction diode is connected to an external

Date____________

Pag

e35

battery in such a way that depletion region is reduced in size or eliminated

altogether Which of these takes place is determined by the size of the

applied voltage The positive terminal of the battery repels the holes on the

p-side and pushes them towards the junction The negative terminal of the

battery repels the electrons and pushes them towards the junction This

collapses the depletion region With the depletion region gone the diode

can conduct

Reverse Bias

An external voltage applied with polarity in Fig 13 is called reverse

bias When reverse bias is applied to a junction diode the depletion region

does not collapse On the contrary it becomes wider The positive side of

battery is applied to the n-type material This attracts the free electrons

away from the junction The negative side of the battery attracts the holes

in p-type material away from the junction This makes the depletion region

wider than it was when no voltage is applied The depletion region is an

insulator and it will block the flow of current Actually a small current will

flow because of minority carriers The p-type material has a few minority

electrons These are pushed to the junction by the repulsion of the negative

side of the battery The n-type material has few minority holes These are

also pushed towards the junction Reverse bias forces the minority carriers

together and a small current - called leakage current - results

Diodes which are designed with adequate power dissipation

capability to operate in the breakdown region are none as Zener diodes

Two mechanisms of diode breakdown for increasing reverse voltage are

recognized In one mechanism the thermally generated electrons and

holes acquire sufficient energy from the applied potential to produce new

carriers by removing valence electrons from their bonds These new

carriers in turn produce additional carriers again through the process of

disrupting bonds This cumulative process is referred to as avalanche

breakdown Even if the initially available carriers do not acquire sufficient

energy to disrupt bonds it is possible to initiate breakdown through a

direct rupture of the bonds because of the existence of strong electric field

Under these conditions the breakdown is referred to as Zener breakdown

Date____________

Pag

e36

Zener breakdown occurs below 6 V Zener diodes are commonly used in

voltage-reference or constant-voltage devices

Characteristic curves of diode

Fig 14 shows V-I Characteristic curves for typical p-n junction diode

It is seen that the curve is not linear With 0 V across the diode the diode

will not conduct the diode will not begin to conduct until a few tenths of a

volt are applied across it This is the voltage needed to overcome the

potential barrier It requires about 02 V to turn on a germanium diode and

about 06 V to turn on a silicon diode Fig 18 also shows what happens

when reverse bias is applied to a diode At increasing levels of reverse

voltage the curve shows some reverse current This leakage current is

caused by minority carries It is usually very small

Graph

Fig-14

Date____________

Pag

e37

Observation Table for Forward bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Date____________

Pag

e38

Observation Table for Reverse bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e39

Calculation for Forward bias 119877 = 119881

119868

Calculation for Reverse bias 119877 = 119881

119868

Date____________

Pag

e40

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e41

Zener Diode Reverse Bias Characteristics Experiment - 10

Aim To study the reverse bias characteristics of a Zener diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components Zener diode Resistors

Circuit Diagram

Procedure

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Theory

A diode which is heavily doped (Si or Ge) and which operates in the

reverse breakdown region with a sharp breakdown voltage is called a zener

diode The schematic symbol of a zener diode is shown in Fig-1 This is

similar to a normal diode except that the line (bar) representing the

cathode is bent at both ends like the letter Z for zener diode

Date____________

Pag

e42

A C Fig-1

In a simple diode the doping is light as a result the breakdown

voltage is high and not sharp But if doping is made heavy the depletion

layer becomes very narrow and even the breakdown voltage gets reduced

to a sharp value The zener diode is designed to operate in the breakdown

region without damage

The reverse breakdown of a zener diode may occur either due to

zener effect or avalanche effect But zener diode primarily depends on

zener effect for its working When the electric field across the junction is

sufficiently high due to the applied voltage the zener breakdown occurs

because of breaking of covalent bonds This produces a large number of

electrons and holes which constitute a steep rise in the reverse saturation

current (also called zener current 119868Z) This effect is called as zener effect

Zener current is independent of the applied voltage and depends only on

the external resistance

The V - 119868 characteristic of a zener diode is shown in Fig-2 The

forward characteristic is simply that of an ordinary forward biased junction

diode

Fig-2

Date____________

Pag

e43

Under reverse bias condition breakdown of junction occurs This

breakdown depends upon the amount of doping It can be seen from Fig-2

that as the reverse voltage is increased the reverse current remains

negligibly small up to the lsquokneersquo of the curve

At this lsquoknee pointrsquo the effect of breakdown process begins The

voltage corresponding to the lsquoknee pointrsquo in the figure is called the zener

breakdown voltage or simply zener voltage (VZ) which is very sharp

compared to a simle p-n junction diode Beyond this voltage the reverse

current (119868Z) increases sharply to a high value

The zener diode is not immediately burnt just because it has entered

the breakdown region As long as the external resistance connected to the

diode in the circuit limits the diode current to less than the burn out value

the diode will not burn out The zener voltage VZ remains constant even

when zener current 119868Z increases greatly This ability of a diode is called

regulating ability and it enables us to use zener diode for voltage

regulation

Date____________

Pag

e44

Observation Table

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e45

Graph 119868 V

Calculations 119877 = 119881

119868

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e46

Dispersive Power of The Prism Experiment - 11

Aim To find the dispersive power (D) of the prism by using spectrometer

Apparatus Mercury vapor lamp Spectrometer Prism

Procedure

Levelling and alignment of collimator and telescope

1 Switch on the mercury lamp Adjust the leveling screws on the chassis

Keep the spirit level on the chassis and do finer adjustments of these

screws to bring the bubble in the sprit level to the centre Repeat this

placing the sprit level along a direction perpendicular to the earlier

direction

2 Repeat this procedure for the prism table

3 Close the slit at the other end of the collimator using the drum screw DS1

Open it to a reasonable width Place the spectrometer in front of the

mercury lamp window and rotate the collimator so that the slit faces of

window View the slit through the telescope If it is not in the centre of the

view level collimator and the telescope so as to bring it to the centre

Setting the prism in the minimum deviation position

1 Rotate the prism table such that lines ruled on the table become

perpendicular to the axis of collimator

2 Place prism over the prism table such that its rough surface BA is

perpendicular to the line on prism table (See Fig-1(a))

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e2

INDEX

Sr

No Name of Experiment

Page

No

Date of

Exp

Performed

Signature

1 Study of resonance by resonance tube 03

2 Velocity of sound in air by resonance tube method

06

3 Refractive index of a liquid by liquid lens method

09

4 Pole strength of a magnet by the method of magnetometer

12

5 Co-efficient of kinetic friction between a block and an inclined plane

16

6 Electrical energy consumed in a circuit 20

7 Temperature of the filament of the bulb 24

8 Frequency of a vibrating string by the method of Meldersquos experiment

28

9 Forward and reverse bias characteristics of a P-N junction diode

33

10 Reverse bias characteristics of a Zener diode

41

11 Dispersive power of a prism using spectrometer

46

12

13

14

Date ___________

Pag

e3

Resonance Tube Experiment - 01

Aim To obtain the length of air column ( 119897 ) for 1st resonance for four different

frequencies using resonance tube Draw the graph of 119897 rarr (1f) and obtain

end correction Also obtain the corrected length of the air column (L) for 1st

resonance for different frequencies

Apparatus Resonance Tube Tuning Forks Vernier calipers

Procedure

Start your experiment with the tuning fork having max frequency

Now hit the tuning fork on the rubber pad put that vibrating tuning fork on

the mouth of the resonance tube Adjust the height of the air column in the

resonance tube in such a way that a louder sound (sound with max

intensity) come out from the resonance tube Stop adjusting the height of

the air column when the louder sound is heard Now note down that height

of the air column in observation table as 119897

Now repeat the same procedure for other tuning forks given to you

Theory

When the frequency of external periodic force becomes equal to the

natural frequency of the system resonance takes place and at that time

system vibrates with max amplitude

In our case when we are adjusting the length of the air column

means we are adjusting the natural frequency of it because natural

frequency of any system is inversely proportional to its length

So when we here a louder sound from the resonance rube it means

that natural frequency of the air column becomes equal to the frequency of

the tuning fork and resonance is taking place

Observations

(1) Least count of vernier calipers = 001 cm

(2) Inner diameter of resonance tubehellip d = _______ cm

Date ___________

Pag

e4

Observation Table

Sr

No

Freq (f)

in Hz

Length of air column at the time of resonance 1f

Hz-1 or sec 1198971 (cm) 1198972 (cm) Average 119897 (cm)

1

2

3

4

Graph 119897 rarr 1f

Here distance 0A on the graph is known as the End correction

Calculations

(1) Corrected length of the air column at the time of resonancehellip

L = 119897 + OA where OA = End correction obtained from graph

(2) Theoretical value of corrected lengthhellip

L = 119897 + (03) d where [(03) d] =Theoretical value of End Correction

Date ___________

Pag

e5

(1) L1 = 1198971 + OA (1) L1 = 1198971 + (03) d

(2) L2 = 1198972 + OA (2) L2 = 1198972 + (03) d

(3) L3 = 1198973 + OA (3) L3 = 1198973 + (03) d

(4) L4 = 1198974 + OA (4) L4 = 1198974 + (03) d

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e6

Velocity of sound in air by Resonance Tube method ndash 02

Aim To compare the frequencies of the tuning forks using resonance tube Also

obtain the velocity of sound from 1st - resonance

Apparatus Resonance Tube Tuning Forks Vernier calipers

Procedure

Start your experiment with the tuning fork having max frequency

Now hit the tuning fork on the rubber pad put that vibrating tuning fork on

the mouth of the resonance tube Adjust the height of the air column in the

resonance tube in such a way that a louder sound (sound with max

intensity) come out from the resonance tube Stop adjusting the height of

the air column when the louder sound is heard Now note down that height

of the air column in observation table as 119897

Now repeat the same procedure for other tuning forks given to you

Theory

When the frequency of external periodic force becomes equal to the

natural frequency of the system resonance takes place and at that time

system vibrates with max amplitude

In our case when we are adjusting the length of the air column we

are adjusting the natural frequency of it because natural frequency of any

system is inversely proportional to its length

So when we here a louder sound from the resonance tube it means

that natural frequency of air column has become equal to the frequency of

tuning fork and resonance is taking place

Observations

(1) Least count of vernier calipers = 001 cm

(2) Inner diameter of resonance tubehellip d = _______ cm

Date ___________

Pag

e7

Observation Table

Sr

No

Freq (f) in

Hz

Length of air column at the time of

resonance

Corrected length

L = 119897 + (03)d (cm)

1198971 (cm) 1198972 (cm) Average 119897 (cm)

1 f1 = L1 =

2 f2 = L2 =

3 f3 = L3 =

4 f4 = L4 =

Calculations

(1) Comparison of the frequencies of the two tuning forks

(i) f1f2 = L2L1 (ii) f3f4 = L4L3

(2) Velocity of SOUNDhellip

119907 = 119891 120582

where λ = Wavelength of the sound wave

119907 = 119891 (4119871)

(Because for 1st ndash resonance λ = 4L)

Date ___________

Pag

e8

(I) 1199071 = 1198911 (41198711) (ii) 1199072 = 1198912 (41198712)

(iii) 1199073 = 1198913 (41198713) (iv) 1199074 = 1198914 (41198714)

(3) Average Velocityhellip

119907 =1199071+1199072+1199073+1199074

4

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e9

Liquid Lens Experiment - 03

Aim To determine refractive index of a given liquid by forming a liquid lens

Apparatus Biconvex lens liquid plane mirror retort stand with clamp and pin

spherometer meter rule

Procedure

The plane mirror is placed on the base of the stand with the pin held

horizontally by the clamp above The convex lens is then placed on the

mirror and its focus is found by locating the position of the pin where it

coincides with its own image By measuring from this point to the lens its

focal length (fg ) is found The lens is now removed and a few drops of

liquid are placed on the mirror On placing the convex lens on the liquid a

combination of a convex (glass) and a plano-concave (liquid) lens results

The focal length (f) of the combination is found as above and the focal

length (fl) of the liquid lens calculated from f and fl The radius of curvature

(r) of the lens surface in contact with the liquid is now obtained by a

spherometer

Theory

The parallel rays meet at the principal focus of the focal length of (1)

Convex lens and (2) Combination lens ndash (Convex lens + Liquid lens) can be

measured experimentally By making use of combination forms the focal

length of liquid lens can be worked out By substituting the value of fl and R

η can be computed

Observations

(1) Least count of spherometer = _______ cm

(2) Distance between two legs of spherometerhellip

a1 = ________ cm a2 = ________ cm a3 = ________ cm

Mean a = ________ cm

(3) Sagita h = _______ div

= _______ cm

Date ___________

Pag

e10

Observation Table

Lens Type Measured Focal Length (cm)

1 2 3 4 5 Mean

Convex fg =_______

Combination f = _______

Calculations

(1) Least count of spherometerhellip

=Distance between two consecutive devisions on main scale

Total number of devisions on circular scale

(2) Radius of curvature hellip 119877 =1198862

6119893+

119893

2

(3) Focal length of a combination lens ( 119891 ) 1

119891=

1

119891119892+

1

119891119897

Date ___________

Pag

e11

(4) Refractive index of a given liquid ( η ) 1

119891119897= minus 120578 minus 1

1

119877

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e12

Deflection of Magnetometer Experiment - 04

Aim To find the magnetic moment (M) of given magnet by magnetometer (From

two different position Gauss-A and Gauss-B of magnetometer) Also obtain

the pole strength (m) of the magnet

Apparatus Magnetometer Magnet

Procedure

First set the magnetometer in Gauss-A position and then put the

magnet at a distance d on the arm of the magnetometer as shown in fig-1

Distance d should be selected in such a way that magnetometer show a

deflection between 30˚ and 60˚ Now note down the deflection shown by

the magnetometer as θ1 and θ2 then reverse the direction of the poles of

the magnet and note down the deflection as θ3 and θ4 Now put the magnet

on the opposite arm and repeat the experiment in a similar way and note

down the deflections as θ5 θ6 θ7 and θ8 Now calculate Magnetic

moment and Pole strength

Now set the magnetometer in Gauss-B position and repeat the

experiment in a similar way

Theory

The Magnetic moment is a measure of the strength of the magnet

Its unit is Gausscm3 For a magnet of Pole strength lsquomrsquo and length 2119897 the

magnetic moment M=2m119897 and points from the South Pole to the North

Pole of the magnet

Gauss-A Position of Magnetometer

Date ___________

Pag

e13

Gauss-B Position of Magnetometer

Observations

(1) Magnetic field intensity of the earthhellip H = 036 Gauss

(2) Magnetic length of the magnethellip 2119897 = 5L6 = __________ cm

119897 = ___________cm

Where L = Geometric length of the magnet = __________ cm

Observation Table for Gauss-A Position

Sr No

Distance d (cm)

Deflection of Magnetometer Avg

θ

tanθ

Magnetic Moment

M = (119837120784minus119897120784)120784

120784119837 H tanθ

θ1 θ2 θ3 θ4 θ5 θ6 θ7 θ8

1

2

Date ___________

Pag

e14

Observation Table for Gauss-B Position

Sr No

Distance d (cm)

Deflection of Magnetometer Avg

θ

tanθ

Magnetic Moment

M = (119837120784+119897120784)120785120784Htanθ

θ1 θ2 θ3 θ4 θ5 θ6 θ7 θ8

1

2

Calculations

(1) Magnetic Moments for Gauss-A position

(2) Magnetic Moments for Gauss-B Position

(1) MA = (119837120784minus119897120784)120784

120784119837 H tanθ

(2) MB = (119837120784+119897120784) 120785120784 H tanθ

(i)

(i)

(ii) (iii)

Date ___________

Pag

e15

(1) 119872119860119886119907119892 =119872119860 1+119872119860 2

2

(2) 119872119861119886119907119892 =119872119861 1+119872119861 2

2

(3) Pole Strength of the magnethellip m = M2119897

(For both Gauss-A amp Gauss-B Positions)

For Gauss-A For Gauss-B

119898119860 =119872119860119886119907119892

2119897

119898119861 =119872119861119886119907119892

2119897

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e16

Friction Experiment - 05

Aim To determine the coefficient of kinetic friction between plane and block

Apparatus Inclined plane Block Scale pan String Set of weights Scale

Procedure

Take the inclined plane and set an angle of inclination θ1 Now put the block

on the inclined plane and put some weight in the scale pan in such a way that

block moves up along the inclined plane with a constant speed Now measure the

height length and base of the inclined plane for that angle and calculate the

Coefficient of kinetic friction

Now repeat the experiment for the angles θ2 and θ3

Theory

When a force F tends to slide a body along a surface a frictional force from

the surface acts on the body The frictional force is parallel to the surface and

directed so as to oppose the sliding It is due to bonding between the body and

the surface

If the body does not slide the frictional force is a static frictional force fs If

there is sliding the frictional force is a kinetic (dynamic) frictional force fk If the

body is rolling then the frictional force is known as rolling frictional force fr

Three properties of friction

(1) If the body does not move then the static frictional force fs and the

component of F that is parallel to the surface are equal in magnitudes

and fs is directed opposite that component If that parallel component

increases magnitude fs also increases

(2) The magnitude of fs has a maximum value fsmax that is given by

fsmax = microsN Where micros is the coefficient of static friction and N is the

magnitude of the normal reaction If the component of F that is parallel

to the surface exceeds fsmax then the body slides on the surface

Date ___________

Pag

e17

(3) If the body begins to slide on the surface the magnitude of the frictional

force rapidly decreases to a constant value fk given by fk = microk N Where

microk is the coefficient of kinetic friction

The magnitude of the coefficients of frictions relative to each other is

given by micros gt microk gtgt micror Where micror is coefficient of rolling friction

Note Here quantities shown bold are vector quantities

Observations

(1) Weight of the blockhellip M = ________ gm

(2) Weight of the scale panhellip m1 = _______ gm

(3) Gravitational accelerationhellip g = 980 cms2

Observation Table

Sr

No

Inclination

of the

Plane (θ)

Effort required to start

the motion up (gm)

m=m1+m2

Avg Effort

m (gm)

Base of

the

Plane

b (cm)

Height

of the

Plane

h (cm)

Length

of the

Plane

l (cm)

cosθ=bl

sinθ=hl

Coefficient of

Kinetic Friction

μ = 119846119840 ndash 119820119840 119852119842119847 120521

119820119840 119836119848119852 120521

1

θ1 1

2

2

θ2 1

2

3

θ3 1

2

Here m2 = the weight put in the scale pan

Page18

Calculation

Coefficient of Kinetic Friction μ = mg ndash Mg sin θMg cos θ

(1) (2)

(3)

Average of Coefficient of Kinetic Friction

μ avg = μ 1 + μ 2 + μ 3

3

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Page19

Date____________

Pag

e20

Wattage of Bulb Experiment - 06

Aim To find the electrical energy consumed in a circuit (bulb)

Apparatus AC Ammeter(0-500 mA) AC Voltmeter(0-250 volt) Variac

Components Bulb

Circuit Diagram

Procedure

Connect the circuit as shown in the circuit diagram Now switch ON

the circuit and note down the reading shown by ammeter at 0 volt then

increase the voltage from 0 to 10 volt and note down the reading of

ammeter Now increase the voltage in order of 10 volts (up to 200 volts)

and note down the readings of the current shown by the ammeter Now

calculate the power consumed in a circuit at different stages

Theory

Experiments show that in stationary metallic conductors current does

work to increase their internal energy The heated conductor releases the

energy received to the surrounding bodies but this is done by means of

heat transfer This means that the quantity of heat released by a current

carrying conductor is equal to the total work done by the current

Date____________

Pag

e21

As we know that the work done by the current is given by 119830 = 119829119816119853helliphelliphelliphelliphelliphellip(1)

119830 = 119816120784119825119853 ( V = IR) helliphelliphelliphelliphelliphelliphellip (2)

The electrical power of a given device is simply the rate of doing

work or the amount of electric work done in one second

Therefore electric powerhellip

119823 =119830119848119851119844 119837119848119847119838 (119830)

119827119842119846119838 (119853)

119823 =119829119816119853

119853= 119829119816 helliphelliphelliphelliphelliphelliphellip (3)

Thus electric power is equal to the product of voltage by current

Watt is a unit of power Hence it can be expressed in terms of a volt

and an ampere by the formula for electric power Eqn (3)

Therefore

1 Watt = 1 volt ∙ 1 ampere

1 W = 1 V∙A

Thus if a potential difference of 1 volt causes a current of 1 ampere

to flow through a conductor (here a bulb) the electric power consumed is

1 watt and the electrical energy consumed is 1 joulesec this electrical

energy consumed in the bulb is converted into heat and light energy

Date____________

Pag

e22

Observation Table

Sr No Voltage V (volt) Current 119816 (mA) Power

119823 = 119829119816 (watt)

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

Date____________

Pag

e23

Calculation 119823 = 119829119816

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e24

Temperature of Tungsten Filament Experiment ndash 07

Aim To find the temperature of the tungsten filament of the bulb

Apparatus AC Ammeter(0-500 mA) AC Voltmeter(0-250 volt) Variac

Components Bulb

Circuit Diagram

Procedure

Connect the circuit as shown in the circuit diagram Now switch ON

the circuit and note down the reading shown by ammeter at 0 volt then

increase the voltage from 0 to 10 volt and note down the reading of

ammeter Now increase the voltage in order of 10 volts (up to 100 volts)

and note down the readings of the current shown by the ammeter Now

calculate the resistance and the temperature of the filament

Observations

(1) Room temperaturehellip t0 = _______ ˚C

(2) Resistance of the filament of the bulb at room temperaturehellip

R0 = _______ Ω

(3) Temperature coefficient of tungstenhellip α = 45times10-4 ˚C-1

Date____________

Pag

e25

Observation Table

Sr No Voltage V

(volt)

Current 119816

(mA)

Resistance of

The Filament

119825119853 =119829

119816 Ω

Temperature of The Filament

119853 =120783

120514[

119825119853

119825120782 120783 + 120514119853120782 minus 120783] ˚C

1

2

3

4

5

6

7

8

9

10

Graph Rt versus t

Date____________

Pag

e26

Calculations

(1) Resistance of The Filament Rt =V

I Ω

(2) Temperature of The Filament t =1

α[

Rt

R0 1 + αt0 minus 1] ˚C

Date____________

Pag

e27

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e28

Meldersquos Experiment - 08

Aim To find the frequency of the wave and the frequency of the tuning fork by

Meldersquos experiment

Apparatus Meldersquos experiment apparatus

Circuit Diagram

Transverse mode

Procedure

Set Meldersquos experiment apparatus as shown in circuit diagram in

longitudinal position and switch ON the power supply put some weight in

scale pan and adjust the length of the string in such a way that you find

some loops on the string (eg 2 loops) Now rotate the apparatus by 90˚ so

that it is set for lsquoBrsquo position for the same values of weight in pan and for

the same length of the string the number of loops created in lsquoBrsquo position

are double (eg 4 loops) than in lsquoArsquo position Note down these readings in

observation table Repeat the experiment for other values of weight in

scale pan

Date____________

Pag

e29

Theory

This is an easy and efficient method by which nodes and antinodes

formed on a string can be demonstrated

A tuning fork is fitted in a wooden block A long string or thread of

cotton is taken One end of this string is tied to one of the prongs of the

tuning fork and the second end of this string passes over a smooth pulley in

such a way that a small pan can be hang on it Small weights are put in the

pan to create tension in the string This arrangement is shown in the circuit

diagram

The fork is set into vibrations by lightly hitting the prong of the tuning

fork on which the string is not tied or by connecting an electric supply as

shown in the circuit diagram Thus the transverse vibrations are produced

in the string and by adjusting the length andor weights in the pan these

vibrations are reflected from the point of contact between the string and

the pulley and a number of loops appear on the string as shown in the

circuit diagram

When the prongs of the tuning fork vibrate in a plane parallel to the

direction of propagation of the waves it is called lsquoArsquo position or

longitudinal position

If the tuning fork along with the wooden block is rotated through

90˚ so that the plane of vibration of the tuning fork is normal (ie at right

angles) to the direction of propagation it is called lsquoBrsquo position or transverse

position

For the same length and same weight in the pan (ie for the same

tension) the number of loops in lsquoBrsquo position is double than in lsquoArsquo position

Thus either in lsquoArsquo position or in lsquoBrsquo position standing transverse

waves are generated in the string with a series of nodes and antinodes at

equal distances

The equation connecting number of loops (n or nrsquo) length of the

string (l) tension in the string (T) mass per unit length of the string (m) and

frequency of the string (f) is as follows

Date____________

Pag

e30

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position)

119943prime =119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

If the frequency of tuning fork is F then for lsquoArsquo position 119839 =119813

120784 and for lsquoBrsquo

position 119839prime = 119813

In the above equations if all the quantities on the RHS are known the

frequency of the tuning fork 119813 can be calculated

Observations

(1) Gravitational accelerationhellip g = 98 ms2

(2) Mass per unit length of the stringhellip m = _______ kgm

(3) Mass of the scale panhellip M1 = _______ kg

Observation Table

Sr

No

Total mass

suspended at

the end of the

stringhellip

M=M1+M2

(kg)

Tension

created

in the

stringhellip

T=Mg (N)

Length of the

vibrating string

Average

lengthhellip

119949 (m)

No of loops created on

the stringhellip

Frequency of the

vibrating stringhellip

Relation

between

f and frsquo 1199491 (m) 1199492 (m)

In

Longitudinal

Modehellip

n

In

Transverse

Modehellip

nrsquo

In

Longitudinal

Modehellip

119943 =119951

120784119949

119931

119950

In

Transverse

Modehellip

119943prime =119951prime

120784119949

119931

119950

1

2

3

4

Here M2 = the weight put in the scale pan

Page31

Date____________

Pag

e32

Calculations

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position) 119943prime =

119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e33

P-N Junction Diode Characteristics Experiment - 09

Aim To study the Forward and Reverse bias characteristics of a P-N junction

diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components P-N junction diode Resistors

Circuit Diagram

(Forward biased PN diode) (Reverse biased PN diode)

Procedure

For Forward Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 01 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 02 03 04hellip

volts and repeat the procedure Note down the knee voltage and

corresponding current in your observation table

For Reverse Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Date____________

Pag

e34

Theory

If donor (pentavalent) impurities are introduced on one side and

acceptors (trivalent) on the opposite side of a single crystal of an intrinsic

semiconductor like germanium or silicon a p-n junction is formed as shown

in Fig 11 In the figure a donor ion is indicated schematically by a plus sign

because after this impurity atom donates an electron it becomes a positive

ion

The acceptor ion is indicated by a minus sign because after this atom

accepts an electron it becomes a negative ion Initially there are only n-

type carriers to the right of the junction and only p-type carriers to the left

Because there is a density gradient across the junction holes will diffuse to

the right across the junction and electrons to the left As a result of the

displacement of these charges an electric field appears across the junction

Equilibrium is established when the field becomes large enough to restrain

the process of diffusion The positive holes which neutralize the acceptor

ions near the junction in p-type germanium disappear as a result of

combination with electrons which diffuse across the junction Similarly the

neutralizing electrons on the n side of the junction combine with holes

which cross the junction from the p side Since the region of the junction is

depleted of mobile charges it is called the depletion region or a potential

barrier

Forward Bias

An external voltage applied to the p-n junction with the polarity

shown in Fig 12 is known as forward bias The height of the potential

barrier at the junction is lowered by the applied forward voltage In other

words we can say that p-n junction diode is connected to an external

Date____________

Pag

e35

battery in such a way that depletion region is reduced in size or eliminated

altogether Which of these takes place is determined by the size of the

applied voltage The positive terminal of the battery repels the holes on the

p-side and pushes them towards the junction The negative terminal of the

battery repels the electrons and pushes them towards the junction This

collapses the depletion region With the depletion region gone the diode

can conduct

Reverse Bias

An external voltage applied with polarity in Fig 13 is called reverse

bias When reverse bias is applied to a junction diode the depletion region

does not collapse On the contrary it becomes wider The positive side of

battery is applied to the n-type material This attracts the free electrons

away from the junction The negative side of the battery attracts the holes

in p-type material away from the junction This makes the depletion region

wider than it was when no voltage is applied The depletion region is an

insulator and it will block the flow of current Actually a small current will

flow because of minority carriers The p-type material has a few minority

electrons These are pushed to the junction by the repulsion of the negative

side of the battery The n-type material has few minority holes These are

also pushed towards the junction Reverse bias forces the minority carriers

together and a small current - called leakage current - results

Diodes which are designed with adequate power dissipation

capability to operate in the breakdown region are none as Zener diodes

Two mechanisms of diode breakdown for increasing reverse voltage are

recognized In one mechanism the thermally generated electrons and

holes acquire sufficient energy from the applied potential to produce new

carriers by removing valence electrons from their bonds These new

carriers in turn produce additional carriers again through the process of

disrupting bonds This cumulative process is referred to as avalanche

breakdown Even if the initially available carriers do not acquire sufficient

energy to disrupt bonds it is possible to initiate breakdown through a

direct rupture of the bonds because of the existence of strong electric field

Under these conditions the breakdown is referred to as Zener breakdown

Date____________

Pag

e36

Zener breakdown occurs below 6 V Zener diodes are commonly used in

voltage-reference or constant-voltage devices

Characteristic curves of diode

Fig 14 shows V-I Characteristic curves for typical p-n junction diode

It is seen that the curve is not linear With 0 V across the diode the diode

will not conduct the diode will not begin to conduct until a few tenths of a

volt are applied across it This is the voltage needed to overcome the

potential barrier It requires about 02 V to turn on a germanium diode and

about 06 V to turn on a silicon diode Fig 18 also shows what happens

when reverse bias is applied to a diode At increasing levels of reverse

voltage the curve shows some reverse current This leakage current is

caused by minority carries It is usually very small

Graph

Fig-14

Date____________

Pag

e37

Observation Table for Forward bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Date____________

Pag

e38

Observation Table for Reverse bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e39

Calculation for Forward bias 119877 = 119881

119868

Calculation for Reverse bias 119877 = 119881

119868

Date____________

Pag

e40

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e41

Zener Diode Reverse Bias Characteristics Experiment - 10

Aim To study the reverse bias characteristics of a Zener diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components Zener diode Resistors

Circuit Diagram

Procedure

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Theory

A diode which is heavily doped (Si or Ge) and which operates in the

reverse breakdown region with a sharp breakdown voltage is called a zener

diode The schematic symbol of a zener diode is shown in Fig-1 This is

similar to a normal diode except that the line (bar) representing the

cathode is bent at both ends like the letter Z for zener diode

Date____________

Pag

e42

A C Fig-1

In a simple diode the doping is light as a result the breakdown

voltage is high and not sharp But if doping is made heavy the depletion

layer becomes very narrow and even the breakdown voltage gets reduced

to a sharp value The zener diode is designed to operate in the breakdown

region without damage

The reverse breakdown of a zener diode may occur either due to

zener effect or avalanche effect But zener diode primarily depends on

zener effect for its working When the electric field across the junction is

sufficiently high due to the applied voltage the zener breakdown occurs

because of breaking of covalent bonds This produces a large number of

electrons and holes which constitute a steep rise in the reverse saturation

current (also called zener current 119868Z) This effect is called as zener effect

Zener current is independent of the applied voltage and depends only on

the external resistance

The V - 119868 characteristic of a zener diode is shown in Fig-2 The

forward characteristic is simply that of an ordinary forward biased junction

diode

Fig-2

Date____________

Pag

e43

Under reverse bias condition breakdown of junction occurs This

breakdown depends upon the amount of doping It can be seen from Fig-2

that as the reverse voltage is increased the reverse current remains

negligibly small up to the lsquokneersquo of the curve

At this lsquoknee pointrsquo the effect of breakdown process begins The

voltage corresponding to the lsquoknee pointrsquo in the figure is called the zener

breakdown voltage or simply zener voltage (VZ) which is very sharp

compared to a simle p-n junction diode Beyond this voltage the reverse

current (119868Z) increases sharply to a high value

The zener diode is not immediately burnt just because it has entered

the breakdown region As long as the external resistance connected to the

diode in the circuit limits the diode current to less than the burn out value

the diode will not burn out The zener voltage VZ remains constant even

when zener current 119868Z increases greatly This ability of a diode is called

regulating ability and it enables us to use zener diode for voltage

regulation

Date____________

Pag

e44

Observation Table

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e45

Graph 119868 V

Calculations 119877 = 119881

119868

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e46

Dispersive Power of The Prism Experiment - 11

Aim To find the dispersive power (D) of the prism by using spectrometer

Apparatus Mercury vapor lamp Spectrometer Prism

Procedure

Levelling and alignment of collimator and telescope

1 Switch on the mercury lamp Adjust the leveling screws on the chassis

Keep the spirit level on the chassis and do finer adjustments of these

screws to bring the bubble in the sprit level to the centre Repeat this

placing the sprit level along a direction perpendicular to the earlier

direction

2 Repeat this procedure for the prism table

3 Close the slit at the other end of the collimator using the drum screw DS1

Open it to a reasonable width Place the spectrometer in front of the

mercury lamp window and rotate the collimator so that the slit faces of

window View the slit through the telescope If it is not in the centre of the

view level collimator and the telescope so as to bring it to the centre

Setting the prism in the minimum deviation position

1 Rotate the prism table such that lines ruled on the table become

perpendicular to the axis of collimator

2 Place prism over the prism table such that its rough surface BA is

perpendicular to the line on prism table (See Fig-1(a))

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e3

Resonance Tube Experiment - 01

Aim To obtain the length of air column ( 119897 ) for 1st resonance for four different

frequencies using resonance tube Draw the graph of 119897 rarr (1f) and obtain

end correction Also obtain the corrected length of the air column (L) for 1st

resonance for different frequencies

Apparatus Resonance Tube Tuning Forks Vernier calipers

Procedure

Start your experiment with the tuning fork having max frequency

Now hit the tuning fork on the rubber pad put that vibrating tuning fork on

the mouth of the resonance tube Adjust the height of the air column in the

resonance tube in such a way that a louder sound (sound with max

intensity) come out from the resonance tube Stop adjusting the height of

the air column when the louder sound is heard Now note down that height

of the air column in observation table as 119897

Now repeat the same procedure for other tuning forks given to you

Theory

When the frequency of external periodic force becomes equal to the

natural frequency of the system resonance takes place and at that time

system vibrates with max amplitude

In our case when we are adjusting the length of the air column

means we are adjusting the natural frequency of it because natural

frequency of any system is inversely proportional to its length

So when we here a louder sound from the resonance rube it means

that natural frequency of the air column becomes equal to the frequency of

the tuning fork and resonance is taking place

Observations

(1) Least count of vernier calipers = 001 cm

(2) Inner diameter of resonance tubehellip d = _______ cm

Date ___________

Pag

e4

Observation Table

Sr

No

Freq (f)

in Hz

Length of air column at the time of resonance 1f

Hz-1 or sec 1198971 (cm) 1198972 (cm) Average 119897 (cm)

1

2

3

4

Graph 119897 rarr 1f

Here distance 0A on the graph is known as the End correction

Calculations

(1) Corrected length of the air column at the time of resonancehellip

L = 119897 + OA where OA = End correction obtained from graph

(2) Theoretical value of corrected lengthhellip

L = 119897 + (03) d where [(03) d] =Theoretical value of End Correction

Date ___________

Pag

e5

(1) L1 = 1198971 + OA (1) L1 = 1198971 + (03) d

(2) L2 = 1198972 + OA (2) L2 = 1198972 + (03) d

(3) L3 = 1198973 + OA (3) L3 = 1198973 + (03) d

(4) L4 = 1198974 + OA (4) L4 = 1198974 + (03) d

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e6

Velocity of sound in air by Resonance Tube method ndash 02

Aim To compare the frequencies of the tuning forks using resonance tube Also

obtain the velocity of sound from 1st - resonance

Apparatus Resonance Tube Tuning Forks Vernier calipers

Procedure

Start your experiment with the tuning fork having max frequency

Now hit the tuning fork on the rubber pad put that vibrating tuning fork on

the mouth of the resonance tube Adjust the height of the air column in the

resonance tube in such a way that a louder sound (sound with max

intensity) come out from the resonance tube Stop adjusting the height of

the air column when the louder sound is heard Now note down that height

of the air column in observation table as 119897

Now repeat the same procedure for other tuning forks given to you

Theory

When the frequency of external periodic force becomes equal to the

natural frequency of the system resonance takes place and at that time

system vibrates with max amplitude

In our case when we are adjusting the length of the air column we

are adjusting the natural frequency of it because natural frequency of any

system is inversely proportional to its length

So when we here a louder sound from the resonance tube it means

that natural frequency of air column has become equal to the frequency of

tuning fork and resonance is taking place

Observations

(1) Least count of vernier calipers = 001 cm

(2) Inner diameter of resonance tubehellip d = _______ cm

Date ___________

Pag

e7

Observation Table

Sr

No

Freq (f) in

Hz

Length of air column at the time of

resonance

Corrected length

L = 119897 + (03)d (cm)

1198971 (cm) 1198972 (cm) Average 119897 (cm)

1 f1 = L1 =

2 f2 = L2 =

3 f3 = L3 =

4 f4 = L4 =

Calculations

(1) Comparison of the frequencies of the two tuning forks

(i) f1f2 = L2L1 (ii) f3f4 = L4L3

(2) Velocity of SOUNDhellip

119907 = 119891 120582

where λ = Wavelength of the sound wave

119907 = 119891 (4119871)

(Because for 1st ndash resonance λ = 4L)

Date ___________

Pag

e8

(I) 1199071 = 1198911 (41198711) (ii) 1199072 = 1198912 (41198712)

(iii) 1199073 = 1198913 (41198713) (iv) 1199074 = 1198914 (41198714)

(3) Average Velocityhellip

119907 =1199071+1199072+1199073+1199074

4

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e9

Liquid Lens Experiment - 03

Aim To determine refractive index of a given liquid by forming a liquid lens

Apparatus Biconvex lens liquid plane mirror retort stand with clamp and pin

spherometer meter rule

Procedure

The plane mirror is placed on the base of the stand with the pin held

horizontally by the clamp above The convex lens is then placed on the

mirror and its focus is found by locating the position of the pin where it

coincides with its own image By measuring from this point to the lens its

focal length (fg ) is found The lens is now removed and a few drops of

liquid are placed on the mirror On placing the convex lens on the liquid a

combination of a convex (glass) and a plano-concave (liquid) lens results

The focal length (f) of the combination is found as above and the focal

length (fl) of the liquid lens calculated from f and fl The radius of curvature

(r) of the lens surface in contact with the liquid is now obtained by a

spherometer

Theory

The parallel rays meet at the principal focus of the focal length of (1)

Convex lens and (2) Combination lens ndash (Convex lens + Liquid lens) can be

measured experimentally By making use of combination forms the focal

length of liquid lens can be worked out By substituting the value of fl and R

η can be computed

Observations

(1) Least count of spherometer = _______ cm

(2) Distance between two legs of spherometerhellip

a1 = ________ cm a2 = ________ cm a3 = ________ cm

Mean a = ________ cm

(3) Sagita h = _______ div

= _______ cm

Date ___________

Pag

e10

Observation Table

Lens Type Measured Focal Length (cm)

1 2 3 4 5 Mean

Convex fg =_______

Combination f = _______

Calculations

(1) Least count of spherometerhellip

=Distance between two consecutive devisions on main scale

Total number of devisions on circular scale

(2) Radius of curvature hellip 119877 =1198862

6119893+

119893

2

(3) Focal length of a combination lens ( 119891 ) 1

119891=

1

119891119892+

1

119891119897

Date ___________

Pag

e11

(4) Refractive index of a given liquid ( η ) 1

119891119897= minus 120578 minus 1

1

119877

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e12

Deflection of Magnetometer Experiment - 04

Aim To find the magnetic moment (M) of given magnet by magnetometer (From

two different position Gauss-A and Gauss-B of magnetometer) Also obtain

the pole strength (m) of the magnet

Apparatus Magnetometer Magnet

Procedure

First set the magnetometer in Gauss-A position and then put the

magnet at a distance d on the arm of the magnetometer as shown in fig-1

Distance d should be selected in such a way that magnetometer show a

deflection between 30˚ and 60˚ Now note down the deflection shown by

the magnetometer as θ1 and θ2 then reverse the direction of the poles of

the magnet and note down the deflection as θ3 and θ4 Now put the magnet

on the opposite arm and repeat the experiment in a similar way and note

down the deflections as θ5 θ6 θ7 and θ8 Now calculate Magnetic

moment and Pole strength

Now set the magnetometer in Gauss-B position and repeat the

experiment in a similar way

Theory

The Magnetic moment is a measure of the strength of the magnet

Its unit is Gausscm3 For a magnet of Pole strength lsquomrsquo and length 2119897 the

magnetic moment M=2m119897 and points from the South Pole to the North

Pole of the magnet

Gauss-A Position of Magnetometer

Date ___________

Pag

e13

Gauss-B Position of Magnetometer

Observations

(1) Magnetic field intensity of the earthhellip H = 036 Gauss

(2) Magnetic length of the magnethellip 2119897 = 5L6 = __________ cm

119897 = ___________cm

Where L = Geometric length of the magnet = __________ cm

Observation Table for Gauss-A Position

Sr No

Distance d (cm)

Deflection of Magnetometer Avg

θ

tanθ

Magnetic Moment

M = (119837120784minus119897120784)120784

120784119837 H tanθ

θ1 θ2 θ3 θ4 θ5 θ6 θ7 θ8

1

2

Date ___________

Pag

e14

Observation Table for Gauss-B Position

Sr No

Distance d (cm)

Deflection of Magnetometer Avg

θ

tanθ

Magnetic Moment

M = (119837120784+119897120784)120785120784Htanθ

θ1 θ2 θ3 θ4 θ5 θ6 θ7 θ8

1

2

Calculations

(1) Magnetic Moments for Gauss-A position

(2) Magnetic Moments for Gauss-B Position

(1) MA = (119837120784minus119897120784)120784

120784119837 H tanθ

(2) MB = (119837120784+119897120784) 120785120784 H tanθ

(i)

(i)

(ii) (iii)

Date ___________

Pag

e15

(1) 119872119860119886119907119892 =119872119860 1+119872119860 2

2

(2) 119872119861119886119907119892 =119872119861 1+119872119861 2

2

(3) Pole Strength of the magnethellip m = M2119897

(For both Gauss-A amp Gauss-B Positions)

For Gauss-A For Gauss-B

119898119860 =119872119860119886119907119892

2119897

119898119861 =119872119861119886119907119892

2119897

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e16

Friction Experiment - 05

Aim To determine the coefficient of kinetic friction between plane and block

Apparatus Inclined plane Block Scale pan String Set of weights Scale

Procedure

Take the inclined plane and set an angle of inclination θ1 Now put the block

on the inclined plane and put some weight in the scale pan in such a way that

block moves up along the inclined plane with a constant speed Now measure the

height length and base of the inclined plane for that angle and calculate the

Coefficient of kinetic friction

Now repeat the experiment for the angles θ2 and θ3

Theory

When a force F tends to slide a body along a surface a frictional force from

the surface acts on the body The frictional force is parallel to the surface and

directed so as to oppose the sliding It is due to bonding between the body and

the surface

If the body does not slide the frictional force is a static frictional force fs If

there is sliding the frictional force is a kinetic (dynamic) frictional force fk If the

body is rolling then the frictional force is known as rolling frictional force fr

Three properties of friction

(1) If the body does not move then the static frictional force fs and the

component of F that is parallel to the surface are equal in magnitudes

and fs is directed opposite that component If that parallel component

increases magnitude fs also increases

(2) The magnitude of fs has a maximum value fsmax that is given by

fsmax = microsN Where micros is the coefficient of static friction and N is the

magnitude of the normal reaction If the component of F that is parallel

to the surface exceeds fsmax then the body slides on the surface

Date ___________

Pag

e17

(3) If the body begins to slide on the surface the magnitude of the frictional

force rapidly decreases to a constant value fk given by fk = microk N Where

microk is the coefficient of kinetic friction

The magnitude of the coefficients of frictions relative to each other is

given by micros gt microk gtgt micror Where micror is coefficient of rolling friction

Note Here quantities shown bold are vector quantities

Observations

(1) Weight of the blockhellip M = ________ gm

(2) Weight of the scale panhellip m1 = _______ gm

(3) Gravitational accelerationhellip g = 980 cms2

Observation Table

Sr

No

Inclination

of the

Plane (θ)

Effort required to start

the motion up (gm)

m=m1+m2

Avg Effort

m (gm)

Base of

the

Plane

b (cm)

Height

of the

Plane

h (cm)

Length

of the

Plane

l (cm)

cosθ=bl

sinθ=hl

Coefficient of

Kinetic Friction

μ = 119846119840 ndash 119820119840 119852119842119847 120521

119820119840 119836119848119852 120521

1

θ1 1

2

2

θ2 1

2

3

θ3 1

2

Here m2 = the weight put in the scale pan

Page18

Calculation

Coefficient of Kinetic Friction μ = mg ndash Mg sin θMg cos θ

(1) (2)

(3)

Average of Coefficient of Kinetic Friction

μ avg = μ 1 + μ 2 + μ 3

3

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Page19

Date____________

Pag

e20

Wattage of Bulb Experiment - 06

Aim To find the electrical energy consumed in a circuit (bulb)

Apparatus AC Ammeter(0-500 mA) AC Voltmeter(0-250 volt) Variac

Components Bulb

Circuit Diagram

Procedure

Connect the circuit as shown in the circuit diagram Now switch ON

the circuit and note down the reading shown by ammeter at 0 volt then

increase the voltage from 0 to 10 volt and note down the reading of

ammeter Now increase the voltage in order of 10 volts (up to 200 volts)

and note down the readings of the current shown by the ammeter Now

calculate the power consumed in a circuit at different stages

Theory

Experiments show that in stationary metallic conductors current does

work to increase their internal energy The heated conductor releases the

energy received to the surrounding bodies but this is done by means of

heat transfer This means that the quantity of heat released by a current

carrying conductor is equal to the total work done by the current

Date____________

Pag

e21

As we know that the work done by the current is given by 119830 = 119829119816119853helliphelliphelliphelliphelliphellip(1)

119830 = 119816120784119825119853 ( V = IR) helliphelliphelliphelliphelliphelliphellip (2)

The electrical power of a given device is simply the rate of doing

work or the amount of electric work done in one second

Therefore electric powerhellip

119823 =119830119848119851119844 119837119848119847119838 (119830)

119827119842119846119838 (119853)

119823 =119829119816119853

119853= 119829119816 helliphelliphelliphelliphelliphelliphellip (3)

Thus electric power is equal to the product of voltage by current

Watt is a unit of power Hence it can be expressed in terms of a volt

and an ampere by the formula for electric power Eqn (3)

Therefore

1 Watt = 1 volt ∙ 1 ampere

1 W = 1 V∙A

Thus if a potential difference of 1 volt causes a current of 1 ampere

to flow through a conductor (here a bulb) the electric power consumed is

1 watt and the electrical energy consumed is 1 joulesec this electrical

energy consumed in the bulb is converted into heat and light energy

Date____________

Pag

e22

Observation Table

Sr No Voltage V (volt) Current 119816 (mA) Power

119823 = 119829119816 (watt)

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

Date____________

Pag

e23

Calculation 119823 = 119829119816

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e24

Temperature of Tungsten Filament Experiment ndash 07

Aim To find the temperature of the tungsten filament of the bulb

Apparatus AC Ammeter(0-500 mA) AC Voltmeter(0-250 volt) Variac

Components Bulb

Circuit Diagram

Procedure

Connect the circuit as shown in the circuit diagram Now switch ON

the circuit and note down the reading shown by ammeter at 0 volt then

increase the voltage from 0 to 10 volt and note down the reading of

ammeter Now increase the voltage in order of 10 volts (up to 100 volts)

and note down the readings of the current shown by the ammeter Now

calculate the resistance and the temperature of the filament

Observations

(1) Room temperaturehellip t0 = _______ ˚C

(2) Resistance of the filament of the bulb at room temperaturehellip

R0 = _______ Ω

(3) Temperature coefficient of tungstenhellip α = 45times10-4 ˚C-1

Date____________

Pag

e25

Observation Table

Sr No Voltage V

(volt)

Current 119816

(mA)

Resistance of

The Filament

119825119853 =119829

119816 Ω

Temperature of The Filament

119853 =120783

120514[

119825119853

119825120782 120783 + 120514119853120782 minus 120783] ˚C

1

2

3

4

5

6

7

8

9

10

Graph Rt versus t

Date____________

Pag

e26

Calculations

(1) Resistance of The Filament Rt =V

I Ω

(2) Temperature of The Filament t =1

α[

Rt

R0 1 + αt0 minus 1] ˚C

Date____________

Pag

e27

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e28

Meldersquos Experiment - 08

Aim To find the frequency of the wave and the frequency of the tuning fork by

Meldersquos experiment

Apparatus Meldersquos experiment apparatus

Circuit Diagram

Transverse mode

Procedure

Set Meldersquos experiment apparatus as shown in circuit diagram in

longitudinal position and switch ON the power supply put some weight in

scale pan and adjust the length of the string in such a way that you find

some loops on the string (eg 2 loops) Now rotate the apparatus by 90˚ so

that it is set for lsquoBrsquo position for the same values of weight in pan and for

the same length of the string the number of loops created in lsquoBrsquo position

are double (eg 4 loops) than in lsquoArsquo position Note down these readings in

observation table Repeat the experiment for other values of weight in

scale pan

Date____________

Pag

e29

Theory

This is an easy and efficient method by which nodes and antinodes

formed on a string can be demonstrated

A tuning fork is fitted in a wooden block A long string or thread of

cotton is taken One end of this string is tied to one of the prongs of the

tuning fork and the second end of this string passes over a smooth pulley in

such a way that a small pan can be hang on it Small weights are put in the

pan to create tension in the string This arrangement is shown in the circuit

diagram

The fork is set into vibrations by lightly hitting the prong of the tuning

fork on which the string is not tied or by connecting an electric supply as

shown in the circuit diagram Thus the transverse vibrations are produced

in the string and by adjusting the length andor weights in the pan these

vibrations are reflected from the point of contact between the string and

the pulley and a number of loops appear on the string as shown in the

circuit diagram

When the prongs of the tuning fork vibrate in a plane parallel to the

direction of propagation of the waves it is called lsquoArsquo position or

longitudinal position

If the tuning fork along with the wooden block is rotated through

90˚ so that the plane of vibration of the tuning fork is normal (ie at right

angles) to the direction of propagation it is called lsquoBrsquo position or transverse

position

For the same length and same weight in the pan (ie for the same

tension) the number of loops in lsquoBrsquo position is double than in lsquoArsquo position

Thus either in lsquoArsquo position or in lsquoBrsquo position standing transverse

waves are generated in the string with a series of nodes and antinodes at

equal distances

The equation connecting number of loops (n or nrsquo) length of the

string (l) tension in the string (T) mass per unit length of the string (m) and

frequency of the string (f) is as follows

Date____________

Pag

e30

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position)

119943prime =119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

If the frequency of tuning fork is F then for lsquoArsquo position 119839 =119813

120784 and for lsquoBrsquo

position 119839prime = 119813

In the above equations if all the quantities on the RHS are known the

frequency of the tuning fork 119813 can be calculated

Observations

(1) Gravitational accelerationhellip g = 98 ms2

(2) Mass per unit length of the stringhellip m = _______ kgm

(3) Mass of the scale panhellip M1 = _______ kg

Observation Table

Sr

No

Total mass

suspended at

the end of the

stringhellip

M=M1+M2

(kg)

Tension

created

in the

stringhellip

T=Mg (N)

Length of the

vibrating string

Average

lengthhellip

119949 (m)

No of loops created on

the stringhellip

Frequency of the

vibrating stringhellip

Relation

between

f and frsquo 1199491 (m) 1199492 (m)

In

Longitudinal

Modehellip

n

In

Transverse

Modehellip

nrsquo

In

Longitudinal

Modehellip

119943 =119951

120784119949

119931

119950

In

Transverse

Modehellip

119943prime =119951prime

120784119949

119931

119950

1

2

3

4

Here M2 = the weight put in the scale pan

Page31

Date____________

Pag

e32

Calculations

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position) 119943prime =

119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e33

P-N Junction Diode Characteristics Experiment - 09

Aim To study the Forward and Reverse bias characteristics of a P-N junction

diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components P-N junction diode Resistors

Circuit Diagram

(Forward biased PN diode) (Reverse biased PN diode)

Procedure

For Forward Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 01 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 02 03 04hellip

volts and repeat the procedure Note down the knee voltage and

corresponding current in your observation table

For Reverse Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Date____________

Pag

e34

Theory

If donor (pentavalent) impurities are introduced on one side and

acceptors (trivalent) on the opposite side of a single crystal of an intrinsic

semiconductor like germanium or silicon a p-n junction is formed as shown

in Fig 11 In the figure a donor ion is indicated schematically by a plus sign

because after this impurity atom donates an electron it becomes a positive

ion

The acceptor ion is indicated by a minus sign because after this atom

accepts an electron it becomes a negative ion Initially there are only n-

type carriers to the right of the junction and only p-type carriers to the left

Because there is a density gradient across the junction holes will diffuse to

the right across the junction and electrons to the left As a result of the

displacement of these charges an electric field appears across the junction

Equilibrium is established when the field becomes large enough to restrain

the process of diffusion The positive holes which neutralize the acceptor

ions near the junction in p-type germanium disappear as a result of

combination with electrons which diffuse across the junction Similarly the

neutralizing electrons on the n side of the junction combine with holes

which cross the junction from the p side Since the region of the junction is

depleted of mobile charges it is called the depletion region or a potential

barrier

Forward Bias

An external voltage applied to the p-n junction with the polarity

shown in Fig 12 is known as forward bias The height of the potential

barrier at the junction is lowered by the applied forward voltage In other

words we can say that p-n junction diode is connected to an external

Date____________

Pag

e35

battery in such a way that depletion region is reduced in size or eliminated

altogether Which of these takes place is determined by the size of the

applied voltage The positive terminal of the battery repels the holes on the

p-side and pushes them towards the junction The negative terminal of the

battery repels the electrons and pushes them towards the junction This

collapses the depletion region With the depletion region gone the diode

can conduct

Reverse Bias

An external voltage applied with polarity in Fig 13 is called reverse

bias When reverse bias is applied to a junction diode the depletion region

does not collapse On the contrary it becomes wider The positive side of

battery is applied to the n-type material This attracts the free electrons

away from the junction The negative side of the battery attracts the holes

in p-type material away from the junction This makes the depletion region

wider than it was when no voltage is applied The depletion region is an

insulator and it will block the flow of current Actually a small current will

flow because of minority carriers The p-type material has a few minority

electrons These are pushed to the junction by the repulsion of the negative

side of the battery The n-type material has few minority holes These are

also pushed towards the junction Reverse bias forces the minority carriers

together and a small current - called leakage current - results

Diodes which are designed with adequate power dissipation

capability to operate in the breakdown region are none as Zener diodes

Two mechanisms of diode breakdown for increasing reverse voltage are

recognized In one mechanism the thermally generated electrons and

holes acquire sufficient energy from the applied potential to produce new

carriers by removing valence electrons from their bonds These new

carriers in turn produce additional carriers again through the process of

disrupting bonds This cumulative process is referred to as avalanche

breakdown Even if the initially available carriers do not acquire sufficient

energy to disrupt bonds it is possible to initiate breakdown through a

direct rupture of the bonds because of the existence of strong electric field

Under these conditions the breakdown is referred to as Zener breakdown

Date____________

Pag

e36

Zener breakdown occurs below 6 V Zener diodes are commonly used in

voltage-reference or constant-voltage devices

Characteristic curves of diode

Fig 14 shows V-I Characteristic curves for typical p-n junction diode

It is seen that the curve is not linear With 0 V across the diode the diode

will not conduct the diode will not begin to conduct until a few tenths of a

volt are applied across it This is the voltage needed to overcome the

potential barrier It requires about 02 V to turn on a germanium diode and

about 06 V to turn on a silicon diode Fig 18 also shows what happens

when reverse bias is applied to a diode At increasing levels of reverse

voltage the curve shows some reverse current This leakage current is

caused by minority carries It is usually very small

Graph

Fig-14

Date____________

Pag

e37

Observation Table for Forward bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Date____________

Pag

e38

Observation Table for Reverse bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e39

Calculation for Forward bias 119877 = 119881

119868

Calculation for Reverse bias 119877 = 119881

119868

Date____________

Pag

e40

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e41

Zener Diode Reverse Bias Characteristics Experiment - 10

Aim To study the reverse bias characteristics of a Zener diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components Zener diode Resistors

Circuit Diagram

Procedure

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Theory

A diode which is heavily doped (Si or Ge) and which operates in the

reverse breakdown region with a sharp breakdown voltage is called a zener

diode The schematic symbol of a zener diode is shown in Fig-1 This is

similar to a normal diode except that the line (bar) representing the

cathode is bent at both ends like the letter Z for zener diode

Date____________

Pag

e42

A C Fig-1

In a simple diode the doping is light as a result the breakdown

voltage is high and not sharp But if doping is made heavy the depletion

layer becomes very narrow and even the breakdown voltage gets reduced

to a sharp value The zener diode is designed to operate in the breakdown

region without damage

The reverse breakdown of a zener diode may occur either due to

zener effect or avalanche effect But zener diode primarily depends on

zener effect for its working When the electric field across the junction is

sufficiently high due to the applied voltage the zener breakdown occurs

because of breaking of covalent bonds This produces a large number of

electrons and holes which constitute a steep rise in the reverse saturation

current (also called zener current 119868Z) This effect is called as zener effect

Zener current is independent of the applied voltage and depends only on

the external resistance

The V - 119868 characteristic of a zener diode is shown in Fig-2 The

forward characteristic is simply that of an ordinary forward biased junction

diode

Fig-2

Date____________

Pag

e43

Under reverse bias condition breakdown of junction occurs This

breakdown depends upon the amount of doping It can be seen from Fig-2

that as the reverse voltage is increased the reverse current remains

negligibly small up to the lsquokneersquo of the curve

At this lsquoknee pointrsquo the effect of breakdown process begins The

voltage corresponding to the lsquoknee pointrsquo in the figure is called the zener

breakdown voltage or simply zener voltage (VZ) which is very sharp

compared to a simle p-n junction diode Beyond this voltage the reverse

current (119868Z) increases sharply to a high value

The zener diode is not immediately burnt just because it has entered

the breakdown region As long as the external resistance connected to the

diode in the circuit limits the diode current to less than the burn out value

the diode will not burn out The zener voltage VZ remains constant even

when zener current 119868Z increases greatly This ability of a diode is called

regulating ability and it enables us to use zener diode for voltage

regulation

Date____________

Pag

e44

Observation Table

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e45

Graph 119868 V

Calculations 119877 = 119881

119868

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e46

Dispersive Power of The Prism Experiment - 11

Aim To find the dispersive power (D) of the prism by using spectrometer

Apparatus Mercury vapor lamp Spectrometer Prism

Procedure

Levelling and alignment of collimator and telescope

1 Switch on the mercury lamp Adjust the leveling screws on the chassis

Keep the spirit level on the chassis and do finer adjustments of these

screws to bring the bubble in the sprit level to the centre Repeat this

placing the sprit level along a direction perpendicular to the earlier

direction

2 Repeat this procedure for the prism table

3 Close the slit at the other end of the collimator using the drum screw DS1

Open it to a reasonable width Place the spectrometer in front of the

mercury lamp window and rotate the collimator so that the slit faces of

window View the slit through the telescope If it is not in the centre of the

view level collimator and the telescope so as to bring it to the centre

Setting the prism in the minimum deviation position

1 Rotate the prism table such that lines ruled on the table become

perpendicular to the axis of collimator

2 Place prism over the prism table such that its rough surface BA is

perpendicular to the line on prism table (See Fig-1(a))

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e4

Observation Table

Sr

No

Freq (f)

in Hz

Length of air column at the time of resonance 1f

Hz-1 or sec 1198971 (cm) 1198972 (cm) Average 119897 (cm)

1

2

3

4

Graph 119897 rarr 1f

Here distance 0A on the graph is known as the End correction

Calculations

(1) Corrected length of the air column at the time of resonancehellip

L = 119897 + OA where OA = End correction obtained from graph

(2) Theoretical value of corrected lengthhellip

L = 119897 + (03) d where [(03) d] =Theoretical value of End Correction

Date ___________

Pag

e5

(1) L1 = 1198971 + OA (1) L1 = 1198971 + (03) d

(2) L2 = 1198972 + OA (2) L2 = 1198972 + (03) d

(3) L3 = 1198973 + OA (3) L3 = 1198973 + (03) d

(4) L4 = 1198974 + OA (4) L4 = 1198974 + (03) d

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e6

Velocity of sound in air by Resonance Tube method ndash 02

Aim To compare the frequencies of the tuning forks using resonance tube Also

obtain the velocity of sound from 1st - resonance

Apparatus Resonance Tube Tuning Forks Vernier calipers

Procedure

Start your experiment with the tuning fork having max frequency

Now hit the tuning fork on the rubber pad put that vibrating tuning fork on

the mouth of the resonance tube Adjust the height of the air column in the

resonance tube in such a way that a louder sound (sound with max

intensity) come out from the resonance tube Stop adjusting the height of

the air column when the louder sound is heard Now note down that height

of the air column in observation table as 119897

Now repeat the same procedure for other tuning forks given to you

Theory

When the frequency of external periodic force becomes equal to the

natural frequency of the system resonance takes place and at that time

system vibrates with max amplitude

In our case when we are adjusting the length of the air column we

are adjusting the natural frequency of it because natural frequency of any

system is inversely proportional to its length

So when we here a louder sound from the resonance tube it means

that natural frequency of air column has become equal to the frequency of

tuning fork and resonance is taking place

Observations

(1) Least count of vernier calipers = 001 cm

(2) Inner diameter of resonance tubehellip d = _______ cm

Date ___________

Pag

e7

Observation Table

Sr

No

Freq (f) in

Hz

Length of air column at the time of

resonance

Corrected length

L = 119897 + (03)d (cm)

1198971 (cm) 1198972 (cm) Average 119897 (cm)

1 f1 = L1 =

2 f2 = L2 =

3 f3 = L3 =

4 f4 = L4 =

Calculations

(1) Comparison of the frequencies of the two tuning forks

(i) f1f2 = L2L1 (ii) f3f4 = L4L3

(2) Velocity of SOUNDhellip

119907 = 119891 120582

where λ = Wavelength of the sound wave

119907 = 119891 (4119871)

(Because for 1st ndash resonance λ = 4L)

Date ___________

Pag

e8

(I) 1199071 = 1198911 (41198711) (ii) 1199072 = 1198912 (41198712)

(iii) 1199073 = 1198913 (41198713) (iv) 1199074 = 1198914 (41198714)

(3) Average Velocityhellip

119907 =1199071+1199072+1199073+1199074

4

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e9

Liquid Lens Experiment - 03

Aim To determine refractive index of a given liquid by forming a liquid lens

Apparatus Biconvex lens liquid plane mirror retort stand with clamp and pin

spherometer meter rule

Procedure

The plane mirror is placed on the base of the stand with the pin held

horizontally by the clamp above The convex lens is then placed on the

mirror and its focus is found by locating the position of the pin where it

coincides with its own image By measuring from this point to the lens its

focal length (fg ) is found The lens is now removed and a few drops of

liquid are placed on the mirror On placing the convex lens on the liquid a

combination of a convex (glass) and a plano-concave (liquid) lens results

The focal length (f) of the combination is found as above and the focal

length (fl) of the liquid lens calculated from f and fl The radius of curvature

(r) of the lens surface in contact with the liquid is now obtained by a

spherometer

Theory

The parallel rays meet at the principal focus of the focal length of (1)

Convex lens and (2) Combination lens ndash (Convex lens + Liquid lens) can be

measured experimentally By making use of combination forms the focal

length of liquid lens can be worked out By substituting the value of fl and R

η can be computed

Observations

(1) Least count of spherometer = _______ cm

(2) Distance between two legs of spherometerhellip

a1 = ________ cm a2 = ________ cm a3 = ________ cm

Mean a = ________ cm

(3) Sagita h = _______ div

= _______ cm

Date ___________

Pag

e10

Observation Table

Lens Type Measured Focal Length (cm)

1 2 3 4 5 Mean

Convex fg =_______

Combination f = _______

Calculations

(1) Least count of spherometerhellip

=Distance between two consecutive devisions on main scale

Total number of devisions on circular scale

(2) Radius of curvature hellip 119877 =1198862

6119893+

119893

2

(3) Focal length of a combination lens ( 119891 ) 1

119891=

1

119891119892+

1

119891119897

Date ___________

Pag

e11

(4) Refractive index of a given liquid ( η ) 1

119891119897= minus 120578 minus 1

1

119877

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e12

Deflection of Magnetometer Experiment - 04

Aim To find the magnetic moment (M) of given magnet by magnetometer (From

two different position Gauss-A and Gauss-B of magnetometer) Also obtain

the pole strength (m) of the magnet

Apparatus Magnetometer Magnet

Procedure

First set the magnetometer in Gauss-A position and then put the

magnet at a distance d on the arm of the magnetometer as shown in fig-1

Distance d should be selected in such a way that magnetometer show a

deflection between 30˚ and 60˚ Now note down the deflection shown by

the magnetometer as θ1 and θ2 then reverse the direction of the poles of

the magnet and note down the deflection as θ3 and θ4 Now put the magnet

on the opposite arm and repeat the experiment in a similar way and note

down the deflections as θ5 θ6 θ7 and θ8 Now calculate Magnetic

moment and Pole strength

Now set the magnetometer in Gauss-B position and repeat the

experiment in a similar way

Theory

The Magnetic moment is a measure of the strength of the magnet

Its unit is Gausscm3 For a magnet of Pole strength lsquomrsquo and length 2119897 the

magnetic moment M=2m119897 and points from the South Pole to the North

Pole of the magnet

Gauss-A Position of Magnetometer

Date ___________

Pag

e13

Gauss-B Position of Magnetometer

Observations

(1) Magnetic field intensity of the earthhellip H = 036 Gauss

(2) Magnetic length of the magnethellip 2119897 = 5L6 = __________ cm

119897 = ___________cm

Where L = Geometric length of the magnet = __________ cm

Observation Table for Gauss-A Position

Sr No

Distance d (cm)

Deflection of Magnetometer Avg

θ

tanθ

Magnetic Moment

M = (119837120784minus119897120784)120784

120784119837 H tanθ

θ1 θ2 θ3 θ4 θ5 θ6 θ7 θ8

1

2

Date ___________

Pag

e14

Observation Table for Gauss-B Position

Sr No

Distance d (cm)

Deflection of Magnetometer Avg

θ

tanθ

Magnetic Moment

M = (119837120784+119897120784)120785120784Htanθ

θ1 θ2 θ3 θ4 θ5 θ6 θ7 θ8

1

2

Calculations

(1) Magnetic Moments for Gauss-A position

(2) Magnetic Moments for Gauss-B Position

(1) MA = (119837120784minus119897120784)120784

120784119837 H tanθ

(2) MB = (119837120784+119897120784) 120785120784 H tanθ

(i)

(i)

(ii) (iii)

Date ___________

Pag

e15

(1) 119872119860119886119907119892 =119872119860 1+119872119860 2

2

(2) 119872119861119886119907119892 =119872119861 1+119872119861 2

2

(3) Pole Strength of the magnethellip m = M2119897

(For both Gauss-A amp Gauss-B Positions)

For Gauss-A For Gauss-B

119898119860 =119872119860119886119907119892

2119897

119898119861 =119872119861119886119907119892

2119897

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e16

Friction Experiment - 05

Aim To determine the coefficient of kinetic friction between plane and block

Apparatus Inclined plane Block Scale pan String Set of weights Scale

Procedure

Take the inclined plane and set an angle of inclination θ1 Now put the block

on the inclined plane and put some weight in the scale pan in such a way that

block moves up along the inclined plane with a constant speed Now measure the

height length and base of the inclined plane for that angle and calculate the

Coefficient of kinetic friction

Now repeat the experiment for the angles θ2 and θ3

Theory

When a force F tends to slide a body along a surface a frictional force from

the surface acts on the body The frictional force is parallel to the surface and

directed so as to oppose the sliding It is due to bonding between the body and

the surface

If the body does not slide the frictional force is a static frictional force fs If

there is sliding the frictional force is a kinetic (dynamic) frictional force fk If the

body is rolling then the frictional force is known as rolling frictional force fr

Three properties of friction

(1) If the body does not move then the static frictional force fs and the

component of F that is parallel to the surface are equal in magnitudes

and fs is directed opposite that component If that parallel component

increases magnitude fs also increases

(2) The magnitude of fs has a maximum value fsmax that is given by

fsmax = microsN Where micros is the coefficient of static friction and N is the

magnitude of the normal reaction If the component of F that is parallel

to the surface exceeds fsmax then the body slides on the surface

Date ___________

Pag

e17

(3) If the body begins to slide on the surface the magnitude of the frictional

force rapidly decreases to a constant value fk given by fk = microk N Where

microk is the coefficient of kinetic friction

The magnitude of the coefficients of frictions relative to each other is

given by micros gt microk gtgt micror Where micror is coefficient of rolling friction

Note Here quantities shown bold are vector quantities

Observations

(1) Weight of the blockhellip M = ________ gm

(2) Weight of the scale panhellip m1 = _______ gm

(3) Gravitational accelerationhellip g = 980 cms2

Observation Table

Sr

No

Inclination

of the

Plane (θ)

Effort required to start

the motion up (gm)

m=m1+m2

Avg Effort

m (gm)

Base of

the

Plane

b (cm)

Height

of the

Plane

h (cm)

Length

of the

Plane

l (cm)

cosθ=bl

sinθ=hl

Coefficient of

Kinetic Friction

μ = 119846119840 ndash 119820119840 119852119842119847 120521

119820119840 119836119848119852 120521

1

θ1 1

2

2

θ2 1

2

3

θ3 1

2

Here m2 = the weight put in the scale pan

Page18

Calculation

Coefficient of Kinetic Friction μ = mg ndash Mg sin θMg cos θ

(1) (2)

(3)

Average of Coefficient of Kinetic Friction

μ avg = μ 1 + μ 2 + μ 3

3

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Page19

Date____________

Pag

e20

Wattage of Bulb Experiment - 06

Aim To find the electrical energy consumed in a circuit (bulb)

Apparatus AC Ammeter(0-500 mA) AC Voltmeter(0-250 volt) Variac

Components Bulb

Circuit Diagram

Procedure

Connect the circuit as shown in the circuit diagram Now switch ON

the circuit and note down the reading shown by ammeter at 0 volt then

increase the voltage from 0 to 10 volt and note down the reading of

ammeter Now increase the voltage in order of 10 volts (up to 200 volts)

and note down the readings of the current shown by the ammeter Now

calculate the power consumed in a circuit at different stages

Theory

Experiments show that in stationary metallic conductors current does

work to increase their internal energy The heated conductor releases the

energy received to the surrounding bodies but this is done by means of

heat transfer This means that the quantity of heat released by a current

carrying conductor is equal to the total work done by the current

Date____________

Pag

e21

As we know that the work done by the current is given by 119830 = 119829119816119853helliphelliphelliphelliphelliphellip(1)

119830 = 119816120784119825119853 ( V = IR) helliphelliphelliphelliphelliphelliphellip (2)

The electrical power of a given device is simply the rate of doing

work or the amount of electric work done in one second

Therefore electric powerhellip

119823 =119830119848119851119844 119837119848119847119838 (119830)

119827119842119846119838 (119853)

119823 =119829119816119853

119853= 119829119816 helliphelliphelliphelliphelliphelliphellip (3)

Thus electric power is equal to the product of voltage by current

Watt is a unit of power Hence it can be expressed in terms of a volt

and an ampere by the formula for electric power Eqn (3)

Therefore

1 Watt = 1 volt ∙ 1 ampere

1 W = 1 V∙A

Thus if a potential difference of 1 volt causes a current of 1 ampere

to flow through a conductor (here a bulb) the electric power consumed is

1 watt and the electrical energy consumed is 1 joulesec this electrical

energy consumed in the bulb is converted into heat and light energy

Date____________

Pag

e22

Observation Table

Sr No Voltage V (volt) Current 119816 (mA) Power

119823 = 119829119816 (watt)

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

Date____________

Pag

e23

Calculation 119823 = 119829119816

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e24

Temperature of Tungsten Filament Experiment ndash 07

Aim To find the temperature of the tungsten filament of the bulb

Apparatus AC Ammeter(0-500 mA) AC Voltmeter(0-250 volt) Variac

Components Bulb

Circuit Diagram

Procedure

Connect the circuit as shown in the circuit diagram Now switch ON

the circuit and note down the reading shown by ammeter at 0 volt then

increase the voltage from 0 to 10 volt and note down the reading of

ammeter Now increase the voltage in order of 10 volts (up to 100 volts)

and note down the readings of the current shown by the ammeter Now

calculate the resistance and the temperature of the filament

Observations

(1) Room temperaturehellip t0 = _______ ˚C

(2) Resistance of the filament of the bulb at room temperaturehellip

R0 = _______ Ω

(3) Temperature coefficient of tungstenhellip α = 45times10-4 ˚C-1

Date____________

Pag

e25

Observation Table

Sr No Voltage V

(volt)

Current 119816

(mA)

Resistance of

The Filament

119825119853 =119829

119816 Ω

Temperature of The Filament

119853 =120783

120514[

119825119853

119825120782 120783 + 120514119853120782 minus 120783] ˚C

1

2

3

4

5

6

7

8

9

10

Graph Rt versus t

Date____________

Pag

e26

Calculations

(1) Resistance of The Filament Rt =V

I Ω

(2) Temperature of The Filament t =1

α[

Rt

R0 1 + αt0 minus 1] ˚C

Date____________

Pag

e27

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e28

Meldersquos Experiment - 08

Aim To find the frequency of the wave and the frequency of the tuning fork by

Meldersquos experiment

Apparatus Meldersquos experiment apparatus

Circuit Diagram

Transverse mode

Procedure

Set Meldersquos experiment apparatus as shown in circuit diagram in

longitudinal position and switch ON the power supply put some weight in

scale pan and adjust the length of the string in such a way that you find

some loops on the string (eg 2 loops) Now rotate the apparatus by 90˚ so

that it is set for lsquoBrsquo position for the same values of weight in pan and for

the same length of the string the number of loops created in lsquoBrsquo position

are double (eg 4 loops) than in lsquoArsquo position Note down these readings in

observation table Repeat the experiment for other values of weight in

scale pan

Date____________

Pag

e29

Theory

This is an easy and efficient method by which nodes and antinodes

formed on a string can be demonstrated

A tuning fork is fitted in a wooden block A long string or thread of

cotton is taken One end of this string is tied to one of the prongs of the

tuning fork and the second end of this string passes over a smooth pulley in

such a way that a small pan can be hang on it Small weights are put in the

pan to create tension in the string This arrangement is shown in the circuit

diagram

The fork is set into vibrations by lightly hitting the prong of the tuning

fork on which the string is not tied or by connecting an electric supply as

shown in the circuit diagram Thus the transverse vibrations are produced

in the string and by adjusting the length andor weights in the pan these

vibrations are reflected from the point of contact between the string and

the pulley and a number of loops appear on the string as shown in the

circuit diagram

When the prongs of the tuning fork vibrate in a plane parallel to the

direction of propagation of the waves it is called lsquoArsquo position or

longitudinal position

If the tuning fork along with the wooden block is rotated through

90˚ so that the plane of vibration of the tuning fork is normal (ie at right

angles) to the direction of propagation it is called lsquoBrsquo position or transverse

position

For the same length and same weight in the pan (ie for the same

tension) the number of loops in lsquoBrsquo position is double than in lsquoArsquo position

Thus either in lsquoArsquo position or in lsquoBrsquo position standing transverse

waves are generated in the string with a series of nodes and antinodes at

equal distances

The equation connecting number of loops (n or nrsquo) length of the

string (l) tension in the string (T) mass per unit length of the string (m) and

frequency of the string (f) is as follows

Date____________

Pag

e30

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position)

119943prime =119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

If the frequency of tuning fork is F then for lsquoArsquo position 119839 =119813

120784 and for lsquoBrsquo

position 119839prime = 119813

In the above equations if all the quantities on the RHS are known the

frequency of the tuning fork 119813 can be calculated

Observations

(1) Gravitational accelerationhellip g = 98 ms2

(2) Mass per unit length of the stringhellip m = _______ kgm

(3) Mass of the scale panhellip M1 = _______ kg

Observation Table

Sr

No

Total mass

suspended at

the end of the

stringhellip

M=M1+M2

(kg)

Tension

created

in the

stringhellip

T=Mg (N)

Length of the

vibrating string

Average

lengthhellip

119949 (m)

No of loops created on

the stringhellip

Frequency of the

vibrating stringhellip

Relation

between

f and frsquo 1199491 (m) 1199492 (m)

In

Longitudinal

Modehellip

n

In

Transverse

Modehellip

nrsquo

In

Longitudinal

Modehellip

119943 =119951

120784119949

119931

119950

In

Transverse

Modehellip

119943prime =119951prime

120784119949

119931

119950

1

2

3

4

Here M2 = the weight put in the scale pan

Page31

Date____________

Pag

e32

Calculations

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position) 119943prime =

119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e33

P-N Junction Diode Characteristics Experiment - 09

Aim To study the Forward and Reverse bias characteristics of a P-N junction

diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components P-N junction diode Resistors

Circuit Diagram

(Forward biased PN diode) (Reverse biased PN diode)

Procedure

For Forward Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 01 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 02 03 04hellip

volts and repeat the procedure Note down the knee voltage and

corresponding current in your observation table

For Reverse Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Date____________

Pag

e34

Theory

If donor (pentavalent) impurities are introduced on one side and

acceptors (trivalent) on the opposite side of a single crystal of an intrinsic

semiconductor like germanium or silicon a p-n junction is formed as shown

in Fig 11 In the figure a donor ion is indicated schematically by a plus sign

because after this impurity atom donates an electron it becomes a positive

ion

The acceptor ion is indicated by a minus sign because after this atom

accepts an electron it becomes a negative ion Initially there are only n-

type carriers to the right of the junction and only p-type carriers to the left

Because there is a density gradient across the junction holes will diffuse to

the right across the junction and electrons to the left As a result of the

displacement of these charges an electric field appears across the junction

Equilibrium is established when the field becomes large enough to restrain

the process of diffusion The positive holes which neutralize the acceptor

ions near the junction in p-type germanium disappear as a result of

combination with electrons which diffuse across the junction Similarly the

neutralizing electrons on the n side of the junction combine with holes

which cross the junction from the p side Since the region of the junction is

depleted of mobile charges it is called the depletion region or a potential

barrier

Forward Bias

An external voltage applied to the p-n junction with the polarity

shown in Fig 12 is known as forward bias The height of the potential

barrier at the junction is lowered by the applied forward voltage In other

words we can say that p-n junction diode is connected to an external

Date____________

Pag

e35

battery in such a way that depletion region is reduced in size or eliminated

altogether Which of these takes place is determined by the size of the

applied voltage The positive terminal of the battery repels the holes on the

p-side and pushes them towards the junction The negative terminal of the

battery repels the electrons and pushes them towards the junction This

collapses the depletion region With the depletion region gone the diode

can conduct

Reverse Bias

An external voltage applied with polarity in Fig 13 is called reverse

bias When reverse bias is applied to a junction diode the depletion region

does not collapse On the contrary it becomes wider The positive side of

battery is applied to the n-type material This attracts the free electrons

away from the junction The negative side of the battery attracts the holes

in p-type material away from the junction This makes the depletion region

wider than it was when no voltage is applied The depletion region is an

insulator and it will block the flow of current Actually a small current will

flow because of minority carriers The p-type material has a few minority

electrons These are pushed to the junction by the repulsion of the negative

side of the battery The n-type material has few minority holes These are

also pushed towards the junction Reverse bias forces the minority carriers

together and a small current - called leakage current - results

Diodes which are designed with adequate power dissipation

capability to operate in the breakdown region are none as Zener diodes

Two mechanisms of diode breakdown for increasing reverse voltage are

recognized In one mechanism the thermally generated electrons and

holes acquire sufficient energy from the applied potential to produce new

carriers by removing valence electrons from their bonds These new

carriers in turn produce additional carriers again through the process of

disrupting bonds This cumulative process is referred to as avalanche

breakdown Even if the initially available carriers do not acquire sufficient

energy to disrupt bonds it is possible to initiate breakdown through a

direct rupture of the bonds because of the existence of strong electric field

Under these conditions the breakdown is referred to as Zener breakdown

Date____________

Pag

e36

Zener breakdown occurs below 6 V Zener diodes are commonly used in

voltage-reference or constant-voltage devices

Characteristic curves of diode

Fig 14 shows V-I Characteristic curves for typical p-n junction diode

It is seen that the curve is not linear With 0 V across the diode the diode

will not conduct the diode will not begin to conduct until a few tenths of a

volt are applied across it This is the voltage needed to overcome the

potential barrier It requires about 02 V to turn on a germanium diode and

about 06 V to turn on a silicon diode Fig 18 also shows what happens

when reverse bias is applied to a diode At increasing levels of reverse

voltage the curve shows some reverse current This leakage current is

caused by minority carries It is usually very small

Graph

Fig-14

Date____________

Pag

e37

Observation Table for Forward bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Date____________

Pag

e38

Observation Table for Reverse bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e39

Calculation for Forward bias 119877 = 119881

119868

Calculation for Reverse bias 119877 = 119881

119868

Date____________

Pag

e40

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e41

Zener Diode Reverse Bias Characteristics Experiment - 10

Aim To study the reverse bias characteristics of a Zener diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components Zener diode Resistors

Circuit Diagram

Procedure

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Theory

A diode which is heavily doped (Si or Ge) and which operates in the

reverse breakdown region with a sharp breakdown voltage is called a zener

diode The schematic symbol of a zener diode is shown in Fig-1 This is

similar to a normal diode except that the line (bar) representing the

cathode is bent at both ends like the letter Z for zener diode

Date____________

Pag

e42

A C Fig-1

In a simple diode the doping is light as a result the breakdown

voltage is high and not sharp But if doping is made heavy the depletion

layer becomes very narrow and even the breakdown voltage gets reduced

to a sharp value The zener diode is designed to operate in the breakdown

region without damage

The reverse breakdown of a zener diode may occur either due to

zener effect or avalanche effect But zener diode primarily depends on

zener effect for its working When the electric field across the junction is

sufficiently high due to the applied voltage the zener breakdown occurs

because of breaking of covalent bonds This produces a large number of

electrons and holes which constitute a steep rise in the reverse saturation

current (also called zener current 119868Z) This effect is called as zener effect

Zener current is independent of the applied voltage and depends only on

the external resistance

The V - 119868 characteristic of a zener diode is shown in Fig-2 The

forward characteristic is simply that of an ordinary forward biased junction

diode

Fig-2

Date____________

Pag

e43

Under reverse bias condition breakdown of junction occurs This

breakdown depends upon the amount of doping It can be seen from Fig-2

that as the reverse voltage is increased the reverse current remains

negligibly small up to the lsquokneersquo of the curve

At this lsquoknee pointrsquo the effect of breakdown process begins The

voltage corresponding to the lsquoknee pointrsquo in the figure is called the zener

breakdown voltage or simply zener voltage (VZ) which is very sharp

compared to a simle p-n junction diode Beyond this voltage the reverse

current (119868Z) increases sharply to a high value

The zener diode is not immediately burnt just because it has entered

the breakdown region As long as the external resistance connected to the

diode in the circuit limits the diode current to less than the burn out value

the diode will not burn out The zener voltage VZ remains constant even

when zener current 119868Z increases greatly This ability of a diode is called

regulating ability and it enables us to use zener diode for voltage

regulation

Date____________

Pag

e44

Observation Table

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e45

Graph 119868 V

Calculations 119877 = 119881

119868

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e46

Dispersive Power of The Prism Experiment - 11

Aim To find the dispersive power (D) of the prism by using spectrometer

Apparatus Mercury vapor lamp Spectrometer Prism

Procedure

Levelling and alignment of collimator and telescope

1 Switch on the mercury lamp Adjust the leveling screws on the chassis

Keep the spirit level on the chassis and do finer adjustments of these

screws to bring the bubble in the sprit level to the centre Repeat this

placing the sprit level along a direction perpendicular to the earlier

direction

2 Repeat this procedure for the prism table

3 Close the slit at the other end of the collimator using the drum screw DS1

Open it to a reasonable width Place the spectrometer in front of the

mercury lamp window and rotate the collimator so that the slit faces of

window View the slit through the telescope If it is not in the centre of the

view level collimator and the telescope so as to bring it to the centre

Setting the prism in the minimum deviation position

1 Rotate the prism table such that lines ruled on the table become

perpendicular to the axis of collimator

2 Place prism over the prism table such that its rough surface BA is

perpendicular to the line on prism table (See Fig-1(a))

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e5

(1) L1 = 1198971 + OA (1) L1 = 1198971 + (03) d

(2) L2 = 1198972 + OA (2) L2 = 1198972 + (03) d

(3) L3 = 1198973 + OA (3) L3 = 1198973 + (03) d

(4) L4 = 1198974 + OA (4) L4 = 1198974 + (03) d

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e6

Velocity of sound in air by Resonance Tube method ndash 02

Aim To compare the frequencies of the tuning forks using resonance tube Also

obtain the velocity of sound from 1st - resonance

Apparatus Resonance Tube Tuning Forks Vernier calipers

Procedure

Start your experiment with the tuning fork having max frequency

Now hit the tuning fork on the rubber pad put that vibrating tuning fork on

the mouth of the resonance tube Adjust the height of the air column in the

resonance tube in such a way that a louder sound (sound with max

intensity) come out from the resonance tube Stop adjusting the height of

the air column when the louder sound is heard Now note down that height

of the air column in observation table as 119897

Now repeat the same procedure for other tuning forks given to you

Theory

When the frequency of external periodic force becomes equal to the

natural frequency of the system resonance takes place and at that time

system vibrates with max amplitude

In our case when we are adjusting the length of the air column we

are adjusting the natural frequency of it because natural frequency of any

system is inversely proportional to its length

So when we here a louder sound from the resonance tube it means

that natural frequency of air column has become equal to the frequency of

tuning fork and resonance is taking place

Observations

(1) Least count of vernier calipers = 001 cm

(2) Inner diameter of resonance tubehellip d = _______ cm

Date ___________

Pag

e7

Observation Table

Sr

No

Freq (f) in

Hz

Length of air column at the time of

resonance

Corrected length

L = 119897 + (03)d (cm)

1198971 (cm) 1198972 (cm) Average 119897 (cm)

1 f1 = L1 =

2 f2 = L2 =

3 f3 = L3 =

4 f4 = L4 =

Calculations

(1) Comparison of the frequencies of the two tuning forks

(i) f1f2 = L2L1 (ii) f3f4 = L4L3

(2) Velocity of SOUNDhellip

119907 = 119891 120582

where λ = Wavelength of the sound wave

119907 = 119891 (4119871)

(Because for 1st ndash resonance λ = 4L)

Date ___________

Pag

e8

(I) 1199071 = 1198911 (41198711) (ii) 1199072 = 1198912 (41198712)

(iii) 1199073 = 1198913 (41198713) (iv) 1199074 = 1198914 (41198714)

(3) Average Velocityhellip

119907 =1199071+1199072+1199073+1199074

4

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e9

Liquid Lens Experiment - 03

Aim To determine refractive index of a given liquid by forming a liquid lens

Apparatus Biconvex lens liquid plane mirror retort stand with clamp and pin

spherometer meter rule

Procedure

The plane mirror is placed on the base of the stand with the pin held

horizontally by the clamp above The convex lens is then placed on the

mirror and its focus is found by locating the position of the pin where it

coincides with its own image By measuring from this point to the lens its

focal length (fg ) is found The lens is now removed and a few drops of

liquid are placed on the mirror On placing the convex lens on the liquid a

combination of a convex (glass) and a plano-concave (liquid) lens results

The focal length (f) of the combination is found as above and the focal

length (fl) of the liquid lens calculated from f and fl The radius of curvature

(r) of the lens surface in contact with the liquid is now obtained by a

spherometer

Theory

The parallel rays meet at the principal focus of the focal length of (1)

Convex lens and (2) Combination lens ndash (Convex lens + Liquid lens) can be

measured experimentally By making use of combination forms the focal

length of liquid lens can be worked out By substituting the value of fl and R

η can be computed

Observations

(1) Least count of spherometer = _______ cm

(2) Distance between two legs of spherometerhellip

a1 = ________ cm a2 = ________ cm a3 = ________ cm

Mean a = ________ cm

(3) Sagita h = _______ div

= _______ cm

Date ___________

Pag

e10

Observation Table

Lens Type Measured Focal Length (cm)

1 2 3 4 5 Mean

Convex fg =_______

Combination f = _______

Calculations

(1) Least count of spherometerhellip

=Distance between two consecutive devisions on main scale

Total number of devisions on circular scale

(2) Radius of curvature hellip 119877 =1198862

6119893+

119893

2

(3) Focal length of a combination lens ( 119891 ) 1

119891=

1

119891119892+

1

119891119897

Date ___________

Pag

e11

(4) Refractive index of a given liquid ( η ) 1

119891119897= minus 120578 minus 1

1

119877

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e12

Deflection of Magnetometer Experiment - 04

Aim To find the magnetic moment (M) of given magnet by magnetometer (From

two different position Gauss-A and Gauss-B of magnetometer) Also obtain

the pole strength (m) of the magnet

Apparatus Magnetometer Magnet

Procedure

First set the magnetometer in Gauss-A position and then put the

magnet at a distance d on the arm of the magnetometer as shown in fig-1

Distance d should be selected in such a way that magnetometer show a

deflection between 30˚ and 60˚ Now note down the deflection shown by

the magnetometer as θ1 and θ2 then reverse the direction of the poles of

the magnet and note down the deflection as θ3 and θ4 Now put the magnet

on the opposite arm and repeat the experiment in a similar way and note

down the deflections as θ5 θ6 θ7 and θ8 Now calculate Magnetic

moment and Pole strength

Now set the magnetometer in Gauss-B position and repeat the

experiment in a similar way

Theory

The Magnetic moment is a measure of the strength of the magnet

Its unit is Gausscm3 For a magnet of Pole strength lsquomrsquo and length 2119897 the

magnetic moment M=2m119897 and points from the South Pole to the North

Pole of the magnet

Gauss-A Position of Magnetometer

Date ___________

Pag

e13

Gauss-B Position of Magnetometer

Observations

(1) Magnetic field intensity of the earthhellip H = 036 Gauss

(2) Magnetic length of the magnethellip 2119897 = 5L6 = __________ cm

119897 = ___________cm

Where L = Geometric length of the magnet = __________ cm

Observation Table for Gauss-A Position

Sr No

Distance d (cm)

Deflection of Magnetometer Avg

θ

tanθ

Magnetic Moment

M = (119837120784minus119897120784)120784

120784119837 H tanθ

θ1 θ2 θ3 θ4 θ5 θ6 θ7 θ8

1

2

Date ___________

Pag

e14

Observation Table for Gauss-B Position

Sr No

Distance d (cm)

Deflection of Magnetometer Avg

θ

tanθ

Magnetic Moment

M = (119837120784+119897120784)120785120784Htanθ

θ1 θ2 θ3 θ4 θ5 θ6 θ7 θ8

1

2

Calculations

(1) Magnetic Moments for Gauss-A position

(2) Magnetic Moments for Gauss-B Position

(1) MA = (119837120784minus119897120784)120784

120784119837 H tanθ

(2) MB = (119837120784+119897120784) 120785120784 H tanθ

(i)

(i)

(ii) (iii)

Date ___________

Pag

e15

(1) 119872119860119886119907119892 =119872119860 1+119872119860 2

2

(2) 119872119861119886119907119892 =119872119861 1+119872119861 2

2

(3) Pole Strength of the magnethellip m = M2119897

(For both Gauss-A amp Gauss-B Positions)

For Gauss-A For Gauss-B

119898119860 =119872119860119886119907119892

2119897

119898119861 =119872119861119886119907119892

2119897

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e16

Friction Experiment - 05

Aim To determine the coefficient of kinetic friction between plane and block

Apparatus Inclined plane Block Scale pan String Set of weights Scale

Procedure

Take the inclined plane and set an angle of inclination θ1 Now put the block

on the inclined plane and put some weight in the scale pan in such a way that

block moves up along the inclined plane with a constant speed Now measure the

height length and base of the inclined plane for that angle and calculate the

Coefficient of kinetic friction

Now repeat the experiment for the angles θ2 and θ3

Theory

When a force F tends to slide a body along a surface a frictional force from

the surface acts on the body The frictional force is parallel to the surface and

directed so as to oppose the sliding It is due to bonding between the body and

the surface

If the body does not slide the frictional force is a static frictional force fs If

there is sliding the frictional force is a kinetic (dynamic) frictional force fk If the

body is rolling then the frictional force is known as rolling frictional force fr

Three properties of friction

(1) If the body does not move then the static frictional force fs and the

component of F that is parallel to the surface are equal in magnitudes

and fs is directed opposite that component If that parallel component

increases magnitude fs also increases

(2) The magnitude of fs has a maximum value fsmax that is given by

fsmax = microsN Where micros is the coefficient of static friction and N is the

magnitude of the normal reaction If the component of F that is parallel

to the surface exceeds fsmax then the body slides on the surface

Date ___________

Pag

e17

(3) If the body begins to slide on the surface the magnitude of the frictional

force rapidly decreases to a constant value fk given by fk = microk N Where

microk is the coefficient of kinetic friction

The magnitude of the coefficients of frictions relative to each other is

given by micros gt microk gtgt micror Where micror is coefficient of rolling friction

Note Here quantities shown bold are vector quantities

Observations

(1) Weight of the blockhellip M = ________ gm

(2) Weight of the scale panhellip m1 = _______ gm

(3) Gravitational accelerationhellip g = 980 cms2

Observation Table

Sr

No

Inclination

of the

Plane (θ)

Effort required to start

the motion up (gm)

m=m1+m2

Avg Effort

m (gm)

Base of

the

Plane

b (cm)

Height

of the

Plane

h (cm)

Length

of the

Plane

l (cm)

cosθ=bl

sinθ=hl

Coefficient of

Kinetic Friction

μ = 119846119840 ndash 119820119840 119852119842119847 120521

119820119840 119836119848119852 120521

1

θ1 1

2

2

θ2 1

2

3

θ3 1

2

Here m2 = the weight put in the scale pan

Page18

Calculation

Coefficient of Kinetic Friction μ = mg ndash Mg sin θMg cos θ

(1) (2)

(3)

Average of Coefficient of Kinetic Friction

μ avg = μ 1 + μ 2 + μ 3

3

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Page19

Date____________

Pag

e20

Wattage of Bulb Experiment - 06

Aim To find the electrical energy consumed in a circuit (bulb)

Apparatus AC Ammeter(0-500 mA) AC Voltmeter(0-250 volt) Variac

Components Bulb

Circuit Diagram

Procedure

Connect the circuit as shown in the circuit diagram Now switch ON

the circuit and note down the reading shown by ammeter at 0 volt then

increase the voltage from 0 to 10 volt and note down the reading of

ammeter Now increase the voltage in order of 10 volts (up to 200 volts)

and note down the readings of the current shown by the ammeter Now

calculate the power consumed in a circuit at different stages

Theory

Experiments show that in stationary metallic conductors current does

work to increase their internal energy The heated conductor releases the

energy received to the surrounding bodies but this is done by means of

heat transfer This means that the quantity of heat released by a current

carrying conductor is equal to the total work done by the current

Date____________

Pag

e21

As we know that the work done by the current is given by 119830 = 119829119816119853helliphelliphelliphelliphelliphellip(1)

119830 = 119816120784119825119853 ( V = IR) helliphelliphelliphelliphelliphelliphellip (2)

The electrical power of a given device is simply the rate of doing

work or the amount of electric work done in one second

Therefore electric powerhellip

119823 =119830119848119851119844 119837119848119847119838 (119830)

119827119842119846119838 (119853)

119823 =119829119816119853

119853= 119829119816 helliphelliphelliphelliphelliphelliphellip (3)

Thus electric power is equal to the product of voltage by current

Watt is a unit of power Hence it can be expressed in terms of a volt

and an ampere by the formula for electric power Eqn (3)

Therefore

1 Watt = 1 volt ∙ 1 ampere

1 W = 1 V∙A

Thus if a potential difference of 1 volt causes a current of 1 ampere

to flow through a conductor (here a bulb) the electric power consumed is

1 watt and the electrical energy consumed is 1 joulesec this electrical

energy consumed in the bulb is converted into heat and light energy

Date____________

Pag

e22

Observation Table

Sr No Voltage V (volt) Current 119816 (mA) Power

119823 = 119829119816 (watt)

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

Date____________

Pag

e23

Calculation 119823 = 119829119816

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e24

Temperature of Tungsten Filament Experiment ndash 07

Aim To find the temperature of the tungsten filament of the bulb

Apparatus AC Ammeter(0-500 mA) AC Voltmeter(0-250 volt) Variac

Components Bulb

Circuit Diagram

Procedure

Connect the circuit as shown in the circuit diagram Now switch ON

the circuit and note down the reading shown by ammeter at 0 volt then

increase the voltage from 0 to 10 volt and note down the reading of

ammeter Now increase the voltage in order of 10 volts (up to 100 volts)

and note down the readings of the current shown by the ammeter Now

calculate the resistance and the temperature of the filament

Observations

(1) Room temperaturehellip t0 = _______ ˚C

(2) Resistance of the filament of the bulb at room temperaturehellip

R0 = _______ Ω

(3) Temperature coefficient of tungstenhellip α = 45times10-4 ˚C-1

Date____________

Pag

e25

Observation Table

Sr No Voltage V

(volt)

Current 119816

(mA)

Resistance of

The Filament

119825119853 =119829

119816 Ω

Temperature of The Filament

119853 =120783

120514[

119825119853

119825120782 120783 + 120514119853120782 minus 120783] ˚C

1

2

3

4

5

6

7

8

9

10

Graph Rt versus t

Date____________

Pag

e26

Calculations

(1) Resistance of The Filament Rt =V

I Ω

(2) Temperature of The Filament t =1

α[

Rt

R0 1 + αt0 minus 1] ˚C

Date____________

Pag

e27

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e28

Meldersquos Experiment - 08

Aim To find the frequency of the wave and the frequency of the tuning fork by

Meldersquos experiment

Apparatus Meldersquos experiment apparatus

Circuit Diagram

Transverse mode

Procedure

Set Meldersquos experiment apparatus as shown in circuit diagram in

longitudinal position and switch ON the power supply put some weight in

scale pan and adjust the length of the string in such a way that you find

some loops on the string (eg 2 loops) Now rotate the apparatus by 90˚ so

that it is set for lsquoBrsquo position for the same values of weight in pan and for

the same length of the string the number of loops created in lsquoBrsquo position

are double (eg 4 loops) than in lsquoArsquo position Note down these readings in

observation table Repeat the experiment for other values of weight in

scale pan

Date____________

Pag

e29

Theory

This is an easy and efficient method by which nodes and antinodes

formed on a string can be demonstrated

A tuning fork is fitted in a wooden block A long string or thread of

cotton is taken One end of this string is tied to one of the prongs of the

tuning fork and the second end of this string passes over a smooth pulley in

such a way that a small pan can be hang on it Small weights are put in the

pan to create tension in the string This arrangement is shown in the circuit

diagram

The fork is set into vibrations by lightly hitting the prong of the tuning

fork on which the string is not tied or by connecting an electric supply as

shown in the circuit diagram Thus the transverse vibrations are produced

in the string and by adjusting the length andor weights in the pan these

vibrations are reflected from the point of contact between the string and

the pulley and a number of loops appear on the string as shown in the

circuit diagram

When the prongs of the tuning fork vibrate in a plane parallel to the

direction of propagation of the waves it is called lsquoArsquo position or

longitudinal position

If the tuning fork along with the wooden block is rotated through

90˚ so that the plane of vibration of the tuning fork is normal (ie at right

angles) to the direction of propagation it is called lsquoBrsquo position or transverse

position

For the same length and same weight in the pan (ie for the same

tension) the number of loops in lsquoBrsquo position is double than in lsquoArsquo position

Thus either in lsquoArsquo position or in lsquoBrsquo position standing transverse

waves are generated in the string with a series of nodes and antinodes at

equal distances

The equation connecting number of loops (n or nrsquo) length of the

string (l) tension in the string (T) mass per unit length of the string (m) and

frequency of the string (f) is as follows

Date____________

Pag

e30

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position)

119943prime =119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

If the frequency of tuning fork is F then for lsquoArsquo position 119839 =119813

120784 and for lsquoBrsquo

position 119839prime = 119813

In the above equations if all the quantities on the RHS are known the

frequency of the tuning fork 119813 can be calculated

Observations

(1) Gravitational accelerationhellip g = 98 ms2

(2) Mass per unit length of the stringhellip m = _______ kgm

(3) Mass of the scale panhellip M1 = _______ kg

Observation Table

Sr

No

Total mass

suspended at

the end of the

stringhellip

M=M1+M2

(kg)

Tension

created

in the

stringhellip

T=Mg (N)

Length of the

vibrating string

Average

lengthhellip

119949 (m)

No of loops created on

the stringhellip

Frequency of the

vibrating stringhellip

Relation

between

f and frsquo 1199491 (m) 1199492 (m)

In

Longitudinal

Modehellip

n

In

Transverse

Modehellip

nrsquo

In

Longitudinal

Modehellip

119943 =119951

120784119949

119931

119950

In

Transverse

Modehellip

119943prime =119951prime

120784119949

119931

119950

1

2

3

4

Here M2 = the weight put in the scale pan

Page31

Date____________

Pag

e32

Calculations

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position) 119943prime =

119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e33

P-N Junction Diode Characteristics Experiment - 09

Aim To study the Forward and Reverse bias characteristics of a P-N junction

diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components P-N junction diode Resistors

Circuit Diagram

(Forward biased PN diode) (Reverse biased PN diode)

Procedure

For Forward Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 01 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 02 03 04hellip

volts and repeat the procedure Note down the knee voltage and

corresponding current in your observation table

For Reverse Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Date____________

Pag

e34

Theory

If donor (pentavalent) impurities are introduced on one side and

acceptors (trivalent) on the opposite side of a single crystal of an intrinsic

semiconductor like germanium or silicon a p-n junction is formed as shown

in Fig 11 In the figure a donor ion is indicated schematically by a plus sign

because after this impurity atom donates an electron it becomes a positive

ion

The acceptor ion is indicated by a minus sign because after this atom

accepts an electron it becomes a negative ion Initially there are only n-

type carriers to the right of the junction and only p-type carriers to the left

Because there is a density gradient across the junction holes will diffuse to

the right across the junction and electrons to the left As a result of the

displacement of these charges an electric field appears across the junction

Equilibrium is established when the field becomes large enough to restrain

the process of diffusion The positive holes which neutralize the acceptor

ions near the junction in p-type germanium disappear as a result of

combination with electrons which diffuse across the junction Similarly the

neutralizing electrons on the n side of the junction combine with holes

which cross the junction from the p side Since the region of the junction is

depleted of mobile charges it is called the depletion region or a potential

barrier

Forward Bias

An external voltage applied to the p-n junction with the polarity

shown in Fig 12 is known as forward bias The height of the potential

barrier at the junction is lowered by the applied forward voltage In other

words we can say that p-n junction diode is connected to an external

Date____________

Pag

e35

battery in such a way that depletion region is reduced in size or eliminated

altogether Which of these takes place is determined by the size of the

applied voltage The positive terminal of the battery repels the holes on the

p-side and pushes them towards the junction The negative terminal of the

battery repels the electrons and pushes them towards the junction This

collapses the depletion region With the depletion region gone the diode

can conduct

Reverse Bias

An external voltage applied with polarity in Fig 13 is called reverse

bias When reverse bias is applied to a junction diode the depletion region

does not collapse On the contrary it becomes wider The positive side of

battery is applied to the n-type material This attracts the free electrons

away from the junction The negative side of the battery attracts the holes

in p-type material away from the junction This makes the depletion region

wider than it was when no voltage is applied The depletion region is an

insulator and it will block the flow of current Actually a small current will

flow because of minority carriers The p-type material has a few minority

electrons These are pushed to the junction by the repulsion of the negative

side of the battery The n-type material has few minority holes These are

also pushed towards the junction Reverse bias forces the minority carriers

together and a small current - called leakage current - results

Diodes which are designed with adequate power dissipation

capability to operate in the breakdown region are none as Zener diodes

Two mechanisms of diode breakdown for increasing reverse voltage are

recognized In one mechanism the thermally generated electrons and

holes acquire sufficient energy from the applied potential to produce new

carriers by removing valence electrons from their bonds These new

carriers in turn produce additional carriers again through the process of

disrupting bonds This cumulative process is referred to as avalanche

breakdown Even if the initially available carriers do not acquire sufficient

energy to disrupt bonds it is possible to initiate breakdown through a

direct rupture of the bonds because of the existence of strong electric field

Under these conditions the breakdown is referred to as Zener breakdown

Date____________

Pag

e36

Zener breakdown occurs below 6 V Zener diodes are commonly used in

voltage-reference or constant-voltage devices

Characteristic curves of diode

Fig 14 shows V-I Characteristic curves for typical p-n junction diode

It is seen that the curve is not linear With 0 V across the diode the diode

will not conduct the diode will not begin to conduct until a few tenths of a

volt are applied across it This is the voltage needed to overcome the

potential barrier It requires about 02 V to turn on a germanium diode and

about 06 V to turn on a silicon diode Fig 18 also shows what happens

when reverse bias is applied to a diode At increasing levels of reverse

voltage the curve shows some reverse current This leakage current is

caused by minority carries It is usually very small

Graph

Fig-14

Date____________

Pag

e37

Observation Table for Forward bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Date____________

Pag

e38

Observation Table for Reverse bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e39

Calculation for Forward bias 119877 = 119881

119868

Calculation for Reverse bias 119877 = 119881

119868

Date____________

Pag

e40

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e41

Zener Diode Reverse Bias Characteristics Experiment - 10

Aim To study the reverse bias characteristics of a Zener diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components Zener diode Resistors

Circuit Diagram

Procedure

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Theory

A diode which is heavily doped (Si or Ge) and which operates in the

reverse breakdown region with a sharp breakdown voltage is called a zener

diode The schematic symbol of a zener diode is shown in Fig-1 This is

similar to a normal diode except that the line (bar) representing the

cathode is bent at both ends like the letter Z for zener diode

Date____________

Pag

e42

A C Fig-1

In a simple diode the doping is light as a result the breakdown

voltage is high and not sharp But if doping is made heavy the depletion

layer becomes very narrow and even the breakdown voltage gets reduced

to a sharp value The zener diode is designed to operate in the breakdown

region without damage

The reverse breakdown of a zener diode may occur either due to

zener effect or avalanche effect But zener diode primarily depends on

zener effect for its working When the electric field across the junction is

sufficiently high due to the applied voltage the zener breakdown occurs

because of breaking of covalent bonds This produces a large number of

electrons and holes which constitute a steep rise in the reverse saturation

current (also called zener current 119868Z) This effect is called as zener effect

Zener current is independent of the applied voltage and depends only on

the external resistance

The V - 119868 characteristic of a zener diode is shown in Fig-2 The

forward characteristic is simply that of an ordinary forward biased junction

diode

Fig-2

Date____________

Pag

e43

Under reverse bias condition breakdown of junction occurs This

breakdown depends upon the amount of doping It can be seen from Fig-2

that as the reverse voltage is increased the reverse current remains

negligibly small up to the lsquokneersquo of the curve

At this lsquoknee pointrsquo the effect of breakdown process begins The

voltage corresponding to the lsquoknee pointrsquo in the figure is called the zener

breakdown voltage or simply zener voltage (VZ) which is very sharp

compared to a simle p-n junction diode Beyond this voltage the reverse

current (119868Z) increases sharply to a high value

The zener diode is not immediately burnt just because it has entered

the breakdown region As long as the external resistance connected to the

diode in the circuit limits the diode current to less than the burn out value

the diode will not burn out The zener voltage VZ remains constant even

when zener current 119868Z increases greatly This ability of a diode is called

regulating ability and it enables us to use zener diode for voltage

regulation

Date____________

Pag

e44

Observation Table

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e45

Graph 119868 V

Calculations 119877 = 119881

119868

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e46

Dispersive Power of The Prism Experiment - 11

Aim To find the dispersive power (D) of the prism by using spectrometer

Apparatus Mercury vapor lamp Spectrometer Prism

Procedure

Levelling and alignment of collimator and telescope

1 Switch on the mercury lamp Adjust the leveling screws on the chassis

Keep the spirit level on the chassis and do finer adjustments of these

screws to bring the bubble in the sprit level to the centre Repeat this

placing the sprit level along a direction perpendicular to the earlier

direction

2 Repeat this procedure for the prism table

3 Close the slit at the other end of the collimator using the drum screw DS1

Open it to a reasonable width Place the spectrometer in front of the

mercury lamp window and rotate the collimator so that the slit faces of

window View the slit through the telescope If it is not in the centre of the

view level collimator and the telescope so as to bring it to the centre

Setting the prism in the minimum deviation position

1 Rotate the prism table such that lines ruled on the table become

perpendicular to the axis of collimator

2 Place prism over the prism table such that its rough surface BA is

perpendicular to the line on prism table (See Fig-1(a))

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e6

Velocity of sound in air by Resonance Tube method ndash 02

Aim To compare the frequencies of the tuning forks using resonance tube Also

obtain the velocity of sound from 1st - resonance

Apparatus Resonance Tube Tuning Forks Vernier calipers

Procedure

Start your experiment with the tuning fork having max frequency

Now hit the tuning fork on the rubber pad put that vibrating tuning fork on

the mouth of the resonance tube Adjust the height of the air column in the

resonance tube in such a way that a louder sound (sound with max

intensity) come out from the resonance tube Stop adjusting the height of

the air column when the louder sound is heard Now note down that height

of the air column in observation table as 119897

Now repeat the same procedure for other tuning forks given to you

Theory

When the frequency of external periodic force becomes equal to the

natural frequency of the system resonance takes place and at that time

system vibrates with max amplitude

In our case when we are adjusting the length of the air column we

are adjusting the natural frequency of it because natural frequency of any

system is inversely proportional to its length

So when we here a louder sound from the resonance tube it means

that natural frequency of air column has become equal to the frequency of

tuning fork and resonance is taking place

Observations

(1) Least count of vernier calipers = 001 cm

(2) Inner diameter of resonance tubehellip d = _______ cm

Date ___________

Pag

e7

Observation Table

Sr

No

Freq (f) in

Hz

Length of air column at the time of

resonance

Corrected length

L = 119897 + (03)d (cm)

1198971 (cm) 1198972 (cm) Average 119897 (cm)

1 f1 = L1 =

2 f2 = L2 =

3 f3 = L3 =

4 f4 = L4 =

Calculations

(1) Comparison of the frequencies of the two tuning forks

(i) f1f2 = L2L1 (ii) f3f4 = L4L3

(2) Velocity of SOUNDhellip

119907 = 119891 120582

where λ = Wavelength of the sound wave

119907 = 119891 (4119871)

(Because for 1st ndash resonance λ = 4L)

Date ___________

Pag

e8

(I) 1199071 = 1198911 (41198711) (ii) 1199072 = 1198912 (41198712)

(iii) 1199073 = 1198913 (41198713) (iv) 1199074 = 1198914 (41198714)

(3) Average Velocityhellip

119907 =1199071+1199072+1199073+1199074

4

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e9

Liquid Lens Experiment - 03

Aim To determine refractive index of a given liquid by forming a liquid lens

Apparatus Biconvex lens liquid plane mirror retort stand with clamp and pin

spherometer meter rule

Procedure

The plane mirror is placed on the base of the stand with the pin held

horizontally by the clamp above The convex lens is then placed on the

mirror and its focus is found by locating the position of the pin where it

coincides with its own image By measuring from this point to the lens its

focal length (fg ) is found The lens is now removed and a few drops of

liquid are placed on the mirror On placing the convex lens on the liquid a

combination of a convex (glass) and a plano-concave (liquid) lens results

The focal length (f) of the combination is found as above and the focal

length (fl) of the liquid lens calculated from f and fl The radius of curvature

(r) of the lens surface in contact with the liquid is now obtained by a

spherometer

Theory

The parallel rays meet at the principal focus of the focal length of (1)

Convex lens and (2) Combination lens ndash (Convex lens + Liquid lens) can be

measured experimentally By making use of combination forms the focal

length of liquid lens can be worked out By substituting the value of fl and R

η can be computed

Observations

(1) Least count of spherometer = _______ cm

(2) Distance between two legs of spherometerhellip

a1 = ________ cm a2 = ________ cm a3 = ________ cm

Mean a = ________ cm

(3) Sagita h = _______ div

= _______ cm

Date ___________

Pag

e10

Observation Table

Lens Type Measured Focal Length (cm)

1 2 3 4 5 Mean

Convex fg =_______

Combination f = _______

Calculations

(1) Least count of spherometerhellip

=Distance between two consecutive devisions on main scale

Total number of devisions on circular scale

(2) Radius of curvature hellip 119877 =1198862

6119893+

119893

2

(3) Focal length of a combination lens ( 119891 ) 1

119891=

1

119891119892+

1

119891119897

Date ___________

Pag

e11

(4) Refractive index of a given liquid ( η ) 1

119891119897= minus 120578 minus 1

1

119877

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e12

Deflection of Magnetometer Experiment - 04

Aim To find the magnetic moment (M) of given magnet by magnetometer (From

two different position Gauss-A and Gauss-B of magnetometer) Also obtain

the pole strength (m) of the magnet

Apparatus Magnetometer Magnet

Procedure

First set the magnetometer in Gauss-A position and then put the

magnet at a distance d on the arm of the magnetometer as shown in fig-1

Distance d should be selected in such a way that magnetometer show a

deflection between 30˚ and 60˚ Now note down the deflection shown by

the magnetometer as θ1 and θ2 then reverse the direction of the poles of

the magnet and note down the deflection as θ3 and θ4 Now put the magnet

on the opposite arm and repeat the experiment in a similar way and note

down the deflections as θ5 θ6 θ7 and θ8 Now calculate Magnetic

moment and Pole strength

Now set the magnetometer in Gauss-B position and repeat the

experiment in a similar way

Theory

The Magnetic moment is a measure of the strength of the magnet

Its unit is Gausscm3 For a magnet of Pole strength lsquomrsquo and length 2119897 the

magnetic moment M=2m119897 and points from the South Pole to the North

Pole of the magnet

Gauss-A Position of Magnetometer

Date ___________

Pag

e13

Gauss-B Position of Magnetometer

Observations

(1) Magnetic field intensity of the earthhellip H = 036 Gauss

(2) Magnetic length of the magnethellip 2119897 = 5L6 = __________ cm

119897 = ___________cm

Where L = Geometric length of the magnet = __________ cm

Observation Table for Gauss-A Position

Sr No

Distance d (cm)

Deflection of Magnetometer Avg

θ

tanθ

Magnetic Moment

M = (119837120784minus119897120784)120784

120784119837 H tanθ

θ1 θ2 θ3 θ4 θ5 θ6 θ7 θ8

1

2

Date ___________

Pag

e14

Observation Table for Gauss-B Position

Sr No

Distance d (cm)

Deflection of Magnetometer Avg

θ

tanθ

Magnetic Moment

M = (119837120784+119897120784)120785120784Htanθ

θ1 θ2 θ3 θ4 θ5 θ6 θ7 θ8

1

2

Calculations

(1) Magnetic Moments for Gauss-A position

(2) Magnetic Moments for Gauss-B Position

(1) MA = (119837120784minus119897120784)120784

120784119837 H tanθ

(2) MB = (119837120784+119897120784) 120785120784 H tanθ

(i)

(i)

(ii) (iii)

Date ___________

Pag

e15

(1) 119872119860119886119907119892 =119872119860 1+119872119860 2

2

(2) 119872119861119886119907119892 =119872119861 1+119872119861 2

2

(3) Pole Strength of the magnethellip m = M2119897

(For both Gauss-A amp Gauss-B Positions)

For Gauss-A For Gauss-B

119898119860 =119872119860119886119907119892

2119897

119898119861 =119872119861119886119907119892

2119897

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e16

Friction Experiment - 05

Aim To determine the coefficient of kinetic friction between plane and block

Apparatus Inclined plane Block Scale pan String Set of weights Scale

Procedure

Take the inclined plane and set an angle of inclination θ1 Now put the block

on the inclined plane and put some weight in the scale pan in such a way that

block moves up along the inclined plane with a constant speed Now measure the

height length and base of the inclined plane for that angle and calculate the

Coefficient of kinetic friction

Now repeat the experiment for the angles θ2 and θ3

Theory

When a force F tends to slide a body along a surface a frictional force from

the surface acts on the body The frictional force is parallel to the surface and

directed so as to oppose the sliding It is due to bonding between the body and

the surface

If the body does not slide the frictional force is a static frictional force fs If

there is sliding the frictional force is a kinetic (dynamic) frictional force fk If the

body is rolling then the frictional force is known as rolling frictional force fr

Three properties of friction

(1) If the body does not move then the static frictional force fs and the

component of F that is parallel to the surface are equal in magnitudes

and fs is directed opposite that component If that parallel component

increases magnitude fs also increases

(2) The magnitude of fs has a maximum value fsmax that is given by

fsmax = microsN Where micros is the coefficient of static friction and N is the

magnitude of the normal reaction If the component of F that is parallel

to the surface exceeds fsmax then the body slides on the surface

Date ___________

Pag

e17

(3) If the body begins to slide on the surface the magnitude of the frictional

force rapidly decreases to a constant value fk given by fk = microk N Where

microk is the coefficient of kinetic friction

The magnitude of the coefficients of frictions relative to each other is

given by micros gt microk gtgt micror Where micror is coefficient of rolling friction

Note Here quantities shown bold are vector quantities

Observations

(1) Weight of the blockhellip M = ________ gm

(2) Weight of the scale panhellip m1 = _______ gm

(3) Gravitational accelerationhellip g = 980 cms2

Observation Table

Sr

No

Inclination

of the

Plane (θ)

Effort required to start

the motion up (gm)

m=m1+m2

Avg Effort

m (gm)

Base of

the

Plane

b (cm)

Height

of the

Plane

h (cm)

Length

of the

Plane

l (cm)

cosθ=bl

sinθ=hl

Coefficient of

Kinetic Friction

μ = 119846119840 ndash 119820119840 119852119842119847 120521

119820119840 119836119848119852 120521

1

θ1 1

2

2

θ2 1

2

3

θ3 1

2

Here m2 = the weight put in the scale pan

Page18

Calculation

Coefficient of Kinetic Friction μ = mg ndash Mg sin θMg cos θ

(1) (2)

(3)

Average of Coefficient of Kinetic Friction

μ avg = μ 1 + μ 2 + μ 3

3

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Page19

Date____________

Pag

e20

Wattage of Bulb Experiment - 06

Aim To find the electrical energy consumed in a circuit (bulb)

Apparatus AC Ammeter(0-500 mA) AC Voltmeter(0-250 volt) Variac

Components Bulb

Circuit Diagram

Procedure

Connect the circuit as shown in the circuit diagram Now switch ON

the circuit and note down the reading shown by ammeter at 0 volt then

increase the voltage from 0 to 10 volt and note down the reading of

ammeter Now increase the voltage in order of 10 volts (up to 200 volts)

and note down the readings of the current shown by the ammeter Now

calculate the power consumed in a circuit at different stages

Theory

Experiments show that in stationary metallic conductors current does

work to increase their internal energy The heated conductor releases the

energy received to the surrounding bodies but this is done by means of

heat transfer This means that the quantity of heat released by a current

carrying conductor is equal to the total work done by the current

Date____________

Pag

e21

As we know that the work done by the current is given by 119830 = 119829119816119853helliphelliphelliphelliphelliphellip(1)

119830 = 119816120784119825119853 ( V = IR) helliphelliphelliphelliphelliphelliphellip (2)

The electrical power of a given device is simply the rate of doing

work or the amount of electric work done in one second

Therefore electric powerhellip

119823 =119830119848119851119844 119837119848119847119838 (119830)

119827119842119846119838 (119853)

119823 =119829119816119853

119853= 119829119816 helliphelliphelliphelliphelliphelliphellip (3)

Thus electric power is equal to the product of voltage by current

Watt is a unit of power Hence it can be expressed in terms of a volt

and an ampere by the formula for electric power Eqn (3)

Therefore

1 Watt = 1 volt ∙ 1 ampere

1 W = 1 V∙A

Thus if a potential difference of 1 volt causes a current of 1 ampere

to flow through a conductor (here a bulb) the electric power consumed is

1 watt and the electrical energy consumed is 1 joulesec this electrical

energy consumed in the bulb is converted into heat and light energy

Date____________

Pag

e22

Observation Table

Sr No Voltage V (volt) Current 119816 (mA) Power

119823 = 119829119816 (watt)

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

Date____________

Pag

e23

Calculation 119823 = 119829119816

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e24

Temperature of Tungsten Filament Experiment ndash 07

Aim To find the temperature of the tungsten filament of the bulb

Apparatus AC Ammeter(0-500 mA) AC Voltmeter(0-250 volt) Variac

Components Bulb

Circuit Diagram

Procedure

Connect the circuit as shown in the circuit diagram Now switch ON

the circuit and note down the reading shown by ammeter at 0 volt then

increase the voltage from 0 to 10 volt and note down the reading of

ammeter Now increase the voltage in order of 10 volts (up to 100 volts)

and note down the readings of the current shown by the ammeter Now

calculate the resistance and the temperature of the filament

Observations

(1) Room temperaturehellip t0 = _______ ˚C

(2) Resistance of the filament of the bulb at room temperaturehellip

R0 = _______ Ω

(3) Temperature coefficient of tungstenhellip α = 45times10-4 ˚C-1

Date____________

Pag

e25

Observation Table

Sr No Voltage V

(volt)

Current 119816

(mA)

Resistance of

The Filament

119825119853 =119829

119816 Ω

Temperature of The Filament

119853 =120783

120514[

119825119853

119825120782 120783 + 120514119853120782 minus 120783] ˚C

1

2

3

4

5

6

7

8

9

10

Graph Rt versus t

Date____________

Pag

e26

Calculations

(1) Resistance of The Filament Rt =V

I Ω

(2) Temperature of The Filament t =1

α[

Rt

R0 1 + αt0 minus 1] ˚C

Date____________

Pag

e27

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e28

Meldersquos Experiment - 08

Aim To find the frequency of the wave and the frequency of the tuning fork by

Meldersquos experiment

Apparatus Meldersquos experiment apparatus

Circuit Diagram

Transverse mode

Procedure

Set Meldersquos experiment apparatus as shown in circuit diagram in

longitudinal position and switch ON the power supply put some weight in

scale pan and adjust the length of the string in such a way that you find

some loops on the string (eg 2 loops) Now rotate the apparatus by 90˚ so

that it is set for lsquoBrsquo position for the same values of weight in pan and for

the same length of the string the number of loops created in lsquoBrsquo position

are double (eg 4 loops) than in lsquoArsquo position Note down these readings in

observation table Repeat the experiment for other values of weight in

scale pan

Date____________

Pag

e29

Theory

This is an easy and efficient method by which nodes and antinodes

formed on a string can be demonstrated

A tuning fork is fitted in a wooden block A long string or thread of

cotton is taken One end of this string is tied to one of the prongs of the

tuning fork and the second end of this string passes over a smooth pulley in

such a way that a small pan can be hang on it Small weights are put in the

pan to create tension in the string This arrangement is shown in the circuit

diagram

The fork is set into vibrations by lightly hitting the prong of the tuning

fork on which the string is not tied or by connecting an electric supply as

shown in the circuit diagram Thus the transverse vibrations are produced

in the string and by adjusting the length andor weights in the pan these

vibrations are reflected from the point of contact between the string and

the pulley and a number of loops appear on the string as shown in the

circuit diagram

When the prongs of the tuning fork vibrate in a plane parallel to the

direction of propagation of the waves it is called lsquoArsquo position or

longitudinal position

If the tuning fork along with the wooden block is rotated through

90˚ so that the plane of vibration of the tuning fork is normal (ie at right

angles) to the direction of propagation it is called lsquoBrsquo position or transverse

position

For the same length and same weight in the pan (ie for the same

tension) the number of loops in lsquoBrsquo position is double than in lsquoArsquo position

Thus either in lsquoArsquo position or in lsquoBrsquo position standing transverse

waves are generated in the string with a series of nodes and antinodes at

equal distances

The equation connecting number of loops (n or nrsquo) length of the

string (l) tension in the string (T) mass per unit length of the string (m) and

frequency of the string (f) is as follows

Date____________

Pag

e30

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position)

119943prime =119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

If the frequency of tuning fork is F then for lsquoArsquo position 119839 =119813

120784 and for lsquoBrsquo

position 119839prime = 119813

In the above equations if all the quantities on the RHS are known the

frequency of the tuning fork 119813 can be calculated

Observations

(1) Gravitational accelerationhellip g = 98 ms2

(2) Mass per unit length of the stringhellip m = _______ kgm

(3) Mass of the scale panhellip M1 = _______ kg

Observation Table

Sr

No

Total mass

suspended at

the end of the

stringhellip

M=M1+M2

(kg)

Tension

created

in the

stringhellip

T=Mg (N)

Length of the

vibrating string

Average

lengthhellip

119949 (m)

No of loops created on

the stringhellip

Frequency of the

vibrating stringhellip

Relation

between

f and frsquo 1199491 (m) 1199492 (m)

In

Longitudinal

Modehellip

n

In

Transverse

Modehellip

nrsquo

In

Longitudinal

Modehellip

119943 =119951

120784119949

119931

119950

In

Transverse

Modehellip

119943prime =119951prime

120784119949

119931

119950

1

2

3

4

Here M2 = the weight put in the scale pan

Page31

Date____________

Pag

e32

Calculations

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position) 119943prime =

119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e33

P-N Junction Diode Characteristics Experiment - 09

Aim To study the Forward and Reverse bias characteristics of a P-N junction

diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components P-N junction diode Resistors

Circuit Diagram

(Forward biased PN diode) (Reverse biased PN diode)

Procedure

For Forward Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 01 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 02 03 04hellip

volts and repeat the procedure Note down the knee voltage and

corresponding current in your observation table

For Reverse Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Date____________

Pag

e34

Theory

If donor (pentavalent) impurities are introduced on one side and

acceptors (trivalent) on the opposite side of a single crystal of an intrinsic

semiconductor like germanium or silicon a p-n junction is formed as shown

in Fig 11 In the figure a donor ion is indicated schematically by a plus sign

because after this impurity atom donates an electron it becomes a positive

ion

The acceptor ion is indicated by a minus sign because after this atom

accepts an electron it becomes a negative ion Initially there are only n-

type carriers to the right of the junction and only p-type carriers to the left

Because there is a density gradient across the junction holes will diffuse to

the right across the junction and electrons to the left As a result of the

displacement of these charges an electric field appears across the junction

Equilibrium is established when the field becomes large enough to restrain

the process of diffusion The positive holes which neutralize the acceptor

ions near the junction in p-type germanium disappear as a result of

combination with electrons which diffuse across the junction Similarly the

neutralizing electrons on the n side of the junction combine with holes

which cross the junction from the p side Since the region of the junction is

depleted of mobile charges it is called the depletion region or a potential

barrier

Forward Bias

An external voltage applied to the p-n junction with the polarity

shown in Fig 12 is known as forward bias The height of the potential

barrier at the junction is lowered by the applied forward voltage In other

words we can say that p-n junction diode is connected to an external

Date____________

Pag

e35

battery in such a way that depletion region is reduced in size or eliminated

altogether Which of these takes place is determined by the size of the

applied voltage The positive terminal of the battery repels the holes on the

p-side and pushes them towards the junction The negative terminal of the

battery repels the electrons and pushes them towards the junction This

collapses the depletion region With the depletion region gone the diode

can conduct

Reverse Bias

An external voltage applied with polarity in Fig 13 is called reverse

bias When reverse bias is applied to a junction diode the depletion region

does not collapse On the contrary it becomes wider The positive side of

battery is applied to the n-type material This attracts the free electrons

away from the junction The negative side of the battery attracts the holes

in p-type material away from the junction This makes the depletion region

wider than it was when no voltage is applied The depletion region is an

insulator and it will block the flow of current Actually a small current will

flow because of minority carriers The p-type material has a few minority

electrons These are pushed to the junction by the repulsion of the negative

side of the battery The n-type material has few minority holes These are

also pushed towards the junction Reverse bias forces the minority carriers

together and a small current - called leakage current - results

Diodes which are designed with adequate power dissipation

capability to operate in the breakdown region are none as Zener diodes

Two mechanisms of diode breakdown for increasing reverse voltage are

recognized In one mechanism the thermally generated electrons and

holes acquire sufficient energy from the applied potential to produce new

carriers by removing valence electrons from their bonds These new

carriers in turn produce additional carriers again through the process of

disrupting bonds This cumulative process is referred to as avalanche

breakdown Even if the initially available carriers do not acquire sufficient

energy to disrupt bonds it is possible to initiate breakdown through a

direct rupture of the bonds because of the existence of strong electric field

Under these conditions the breakdown is referred to as Zener breakdown

Date____________

Pag

e36

Zener breakdown occurs below 6 V Zener diodes are commonly used in

voltage-reference or constant-voltage devices

Characteristic curves of diode

Fig 14 shows V-I Characteristic curves for typical p-n junction diode

It is seen that the curve is not linear With 0 V across the diode the diode

will not conduct the diode will not begin to conduct until a few tenths of a

volt are applied across it This is the voltage needed to overcome the

potential barrier It requires about 02 V to turn on a germanium diode and

about 06 V to turn on a silicon diode Fig 18 also shows what happens

when reverse bias is applied to a diode At increasing levels of reverse

voltage the curve shows some reverse current This leakage current is

caused by minority carries It is usually very small

Graph

Fig-14

Date____________

Pag

e37

Observation Table for Forward bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Date____________

Pag

e38

Observation Table for Reverse bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e39

Calculation for Forward bias 119877 = 119881

119868

Calculation for Reverse bias 119877 = 119881

119868

Date____________

Pag

e40

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e41

Zener Diode Reverse Bias Characteristics Experiment - 10

Aim To study the reverse bias characteristics of a Zener diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components Zener diode Resistors

Circuit Diagram

Procedure

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Theory

A diode which is heavily doped (Si or Ge) and which operates in the

reverse breakdown region with a sharp breakdown voltage is called a zener

diode The schematic symbol of a zener diode is shown in Fig-1 This is

similar to a normal diode except that the line (bar) representing the

cathode is bent at both ends like the letter Z for zener diode

Date____________

Pag

e42

A C Fig-1

In a simple diode the doping is light as a result the breakdown

voltage is high and not sharp But if doping is made heavy the depletion

layer becomes very narrow and even the breakdown voltage gets reduced

to a sharp value The zener diode is designed to operate in the breakdown

region without damage

The reverse breakdown of a zener diode may occur either due to

zener effect or avalanche effect But zener diode primarily depends on

zener effect for its working When the electric field across the junction is

sufficiently high due to the applied voltage the zener breakdown occurs

because of breaking of covalent bonds This produces a large number of

electrons and holes which constitute a steep rise in the reverse saturation

current (also called zener current 119868Z) This effect is called as zener effect

Zener current is independent of the applied voltage and depends only on

the external resistance

The V - 119868 characteristic of a zener diode is shown in Fig-2 The

forward characteristic is simply that of an ordinary forward biased junction

diode

Fig-2

Date____________

Pag

e43

Under reverse bias condition breakdown of junction occurs This

breakdown depends upon the amount of doping It can be seen from Fig-2

that as the reverse voltage is increased the reverse current remains

negligibly small up to the lsquokneersquo of the curve

At this lsquoknee pointrsquo the effect of breakdown process begins The

voltage corresponding to the lsquoknee pointrsquo in the figure is called the zener

breakdown voltage or simply zener voltage (VZ) which is very sharp

compared to a simle p-n junction diode Beyond this voltage the reverse

current (119868Z) increases sharply to a high value

The zener diode is not immediately burnt just because it has entered

the breakdown region As long as the external resistance connected to the

diode in the circuit limits the diode current to less than the burn out value

the diode will not burn out The zener voltage VZ remains constant even

when zener current 119868Z increases greatly This ability of a diode is called

regulating ability and it enables us to use zener diode for voltage

regulation

Date____________

Pag

e44

Observation Table

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e45

Graph 119868 V

Calculations 119877 = 119881

119868

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e46

Dispersive Power of The Prism Experiment - 11

Aim To find the dispersive power (D) of the prism by using spectrometer

Apparatus Mercury vapor lamp Spectrometer Prism

Procedure

Levelling and alignment of collimator and telescope

1 Switch on the mercury lamp Adjust the leveling screws on the chassis

Keep the spirit level on the chassis and do finer adjustments of these

screws to bring the bubble in the sprit level to the centre Repeat this

placing the sprit level along a direction perpendicular to the earlier

direction

2 Repeat this procedure for the prism table

3 Close the slit at the other end of the collimator using the drum screw DS1

Open it to a reasonable width Place the spectrometer in front of the

mercury lamp window and rotate the collimator so that the slit faces of

window View the slit through the telescope If it is not in the centre of the

view level collimator and the telescope so as to bring it to the centre

Setting the prism in the minimum deviation position

1 Rotate the prism table such that lines ruled on the table become

perpendicular to the axis of collimator

2 Place prism over the prism table such that its rough surface BA is

perpendicular to the line on prism table (See Fig-1(a))

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e7

Observation Table

Sr

No

Freq (f) in

Hz

Length of air column at the time of

resonance

Corrected length

L = 119897 + (03)d (cm)

1198971 (cm) 1198972 (cm) Average 119897 (cm)

1 f1 = L1 =

2 f2 = L2 =

3 f3 = L3 =

4 f4 = L4 =

Calculations

(1) Comparison of the frequencies of the two tuning forks

(i) f1f2 = L2L1 (ii) f3f4 = L4L3

(2) Velocity of SOUNDhellip

119907 = 119891 120582

where λ = Wavelength of the sound wave

119907 = 119891 (4119871)

(Because for 1st ndash resonance λ = 4L)

Date ___________

Pag

e8

(I) 1199071 = 1198911 (41198711) (ii) 1199072 = 1198912 (41198712)

(iii) 1199073 = 1198913 (41198713) (iv) 1199074 = 1198914 (41198714)

(3) Average Velocityhellip

119907 =1199071+1199072+1199073+1199074

4

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e9

Liquid Lens Experiment - 03

Aim To determine refractive index of a given liquid by forming a liquid lens

Apparatus Biconvex lens liquid plane mirror retort stand with clamp and pin

spherometer meter rule

Procedure

The plane mirror is placed on the base of the stand with the pin held

horizontally by the clamp above The convex lens is then placed on the

mirror and its focus is found by locating the position of the pin where it

coincides with its own image By measuring from this point to the lens its

focal length (fg ) is found The lens is now removed and a few drops of

liquid are placed on the mirror On placing the convex lens on the liquid a

combination of a convex (glass) and a plano-concave (liquid) lens results

The focal length (f) of the combination is found as above and the focal

length (fl) of the liquid lens calculated from f and fl The radius of curvature

(r) of the lens surface in contact with the liquid is now obtained by a

spherometer

Theory

The parallel rays meet at the principal focus of the focal length of (1)

Convex lens and (2) Combination lens ndash (Convex lens + Liquid lens) can be

measured experimentally By making use of combination forms the focal

length of liquid lens can be worked out By substituting the value of fl and R

η can be computed

Observations

(1) Least count of spherometer = _______ cm

(2) Distance between two legs of spherometerhellip

a1 = ________ cm a2 = ________ cm a3 = ________ cm

Mean a = ________ cm

(3) Sagita h = _______ div

= _______ cm

Date ___________

Pag

e10

Observation Table

Lens Type Measured Focal Length (cm)

1 2 3 4 5 Mean

Convex fg =_______

Combination f = _______

Calculations

(1) Least count of spherometerhellip

=Distance between two consecutive devisions on main scale

Total number of devisions on circular scale

(2) Radius of curvature hellip 119877 =1198862

6119893+

119893

2

(3) Focal length of a combination lens ( 119891 ) 1

119891=

1

119891119892+

1

119891119897

Date ___________

Pag

e11

(4) Refractive index of a given liquid ( η ) 1

119891119897= minus 120578 minus 1

1

119877

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e12

Deflection of Magnetometer Experiment - 04

Aim To find the magnetic moment (M) of given magnet by magnetometer (From

two different position Gauss-A and Gauss-B of magnetometer) Also obtain

the pole strength (m) of the magnet

Apparatus Magnetometer Magnet

Procedure

First set the magnetometer in Gauss-A position and then put the

magnet at a distance d on the arm of the magnetometer as shown in fig-1

Distance d should be selected in such a way that magnetometer show a

deflection between 30˚ and 60˚ Now note down the deflection shown by

the magnetometer as θ1 and θ2 then reverse the direction of the poles of

the magnet and note down the deflection as θ3 and θ4 Now put the magnet

on the opposite arm and repeat the experiment in a similar way and note

down the deflections as θ5 θ6 θ7 and θ8 Now calculate Magnetic

moment and Pole strength

Now set the magnetometer in Gauss-B position and repeat the

experiment in a similar way

Theory

The Magnetic moment is a measure of the strength of the magnet

Its unit is Gausscm3 For a magnet of Pole strength lsquomrsquo and length 2119897 the

magnetic moment M=2m119897 and points from the South Pole to the North

Pole of the magnet

Gauss-A Position of Magnetometer

Date ___________

Pag

e13

Gauss-B Position of Magnetometer

Observations

(1) Magnetic field intensity of the earthhellip H = 036 Gauss

(2) Magnetic length of the magnethellip 2119897 = 5L6 = __________ cm

119897 = ___________cm

Where L = Geometric length of the magnet = __________ cm

Observation Table for Gauss-A Position

Sr No

Distance d (cm)

Deflection of Magnetometer Avg

θ

tanθ

Magnetic Moment

M = (119837120784minus119897120784)120784

120784119837 H tanθ

θ1 θ2 θ3 θ4 θ5 θ6 θ7 θ8

1

2

Date ___________

Pag

e14

Observation Table for Gauss-B Position

Sr No

Distance d (cm)

Deflection of Magnetometer Avg

θ

tanθ

Magnetic Moment

M = (119837120784+119897120784)120785120784Htanθ

θ1 θ2 θ3 θ4 θ5 θ6 θ7 θ8

1

2

Calculations

(1) Magnetic Moments for Gauss-A position

(2) Magnetic Moments for Gauss-B Position

(1) MA = (119837120784minus119897120784)120784

120784119837 H tanθ

(2) MB = (119837120784+119897120784) 120785120784 H tanθ

(i)

(i)

(ii) (iii)

Date ___________

Pag

e15

(1) 119872119860119886119907119892 =119872119860 1+119872119860 2

2

(2) 119872119861119886119907119892 =119872119861 1+119872119861 2

2

(3) Pole Strength of the magnethellip m = M2119897

(For both Gauss-A amp Gauss-B Positions)

For Gauss-A For Gauss-B

119898119860 =119872119860119886119907119892

2119897

119898119861 =119872119861119886119907119892

2119897

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e16

Friction Experiment - 05

Aim To determine the coefficient of kinetic friction between plane and block

Apparatus Inclined plane Block Scale pan String Set of weights Scale

Procedure

Take the inclined plane and set an angle of inclination θ1 Now put the block

on the inclined plane and put some weight in the scale pan in such a way that

block moves up along the inclined plane with a constant speed Now measure the

height length and base of the inclined plane for that angle and calculate the

Coefficient of kinetic friction

Now repeat the experiment for the angles θ2 and θ3

Theory

When a force F tends to slide a body along a surface a frictional force from

the surface acts on the body The frictional force is parallel to the surface and

directed so as to oppose the sliding It is due to bonding between the body and

the surface

If the body does not slide the frictional force is a static frictional force fs If

there is sliding the frictional force is a kinetic (dynamic) frictional force fk If the

body is rolling then the frictional force is known as rolling frictional force fr

Three properties of friction

(1) If the body does not move then the static frictional force fs and the

component of F that is parallel to the surface are equal in magnitudes

and fs is directed opposite that component If that parallel component

increases magnitude fs also increases

(2) The magnitude of fs has a maximum value fsmax that is given by

fsmax = microsN Where micros is the coefficient of static friction and N is the

magnitude of the normal reaction If the component of F that is parallel

to the surface exceeds fsmax then the body slides on the surface

Date ___________

Pag

e17

(3) If the body begins to slide on the surface the magnitude of the frictional

force rapidly decreases to a constant value fk given by fk = microk N Where

microk is the coefficient of kinetic friction

The magnitude of the coefficients of frictions relative to each other is

given by micros gt microk gtgt micror Where micror is coefficient of rolling friction

Note Here quantities shown bold are vector quantities

Observations

(1) Weight of the blockhellip M = ________ gm

(2) Weight of the scale panhellip m1 = _______ gm

(3) Gravitational accelerationhellip g = 980 cms2

Observation Table

Sr

No

Inclination

of the

Plane (θ)

Effort required to start

the motion up (gm)

m=m1+m2

Avg Effort

m (gm)

Base of

the

Plane

b (cm)

Height

of the

Plane

h (cm)

Length

of the

Plane

l (cm)

cosθ=bl

sinθ=hl

Coefficient of

Kinetic Friction

μ = 119846119840 ndash 119820119840 119852119842119847 120521

119820119840 119836119848119852 120521

1

θ1 1

2

2

θ2 1

2

3

θ3 1

2

Here m2 = the weight put in the scale pan

Page18

Calculation

Coefficient of Kinetic Friction μ = mg ndash Mg sin θMg cos θ

(1) (2)

(3)

Average of Coefficient of Kinetic Friction

μ avg = μ 1 + μ 2 + μ 3

3

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Page19

Date____________

Pag

e20

Wattage of Bulb Experiment - 06

Aim To find the electrical energy consumed in a circuit (bulb)

Apparatus AC Ammeter(0-500 mA) AC Voltmeter(0-250 volt) Variac

Components Bulb

Circuit Diagram

Procedure

Connect the circuit as shown in the circuit diagram Now switch ON

the circuit and note down the reading shown by ammeter at 0 volt then

increase the voltage from 0 to 10 volt and note down the reading of

ammeter Now increase the voltage in order of 10 volts (up to 200 volts)

and note down the readings of the current shown by the ammeter Now

calculate the power consumed in a circuit at different stages

Theory

Experiments show that in stationary metallic conductors current does

work to increase their internal energy The heated conductor releases the

energy received to the surrounding bodies but this is done by means of

heat transfer This means that the quantity of heat released by a current

carrying conductor is equal to the total work done by the current

Date____________

Pag

e21

As we know that the work done by the current is given by 119830 = 119829119816119853helliphelliphelliphelliphelliphellip(1)

119830 = 119816120784119825119853 ( V = IR) helliphelliphelliphelliphelliphelliphellip (2)

The electrical power of a given device is simply the rate of doing

work or the amount of electric work done in one second

Therefore electric powerhellip

119823 =119830119848119851119844 119837119848119847119838 (119830)

119827119842119846119838 (119853)

119823 =119829119816119853

119853= 119829119816 helliphelliphelliphelliphelliphelliphellip (3)

Thus electric power is equal to the product of voltage by current

Watt is a unit of power Hence it can be expressed in terms of a volt

and an ampere by the formula for electric power Eqn (3)

Therefore

1 Watt = 1 volt ∙ 1 ampere

1 W = 1 V∙A

Thus if a potential difference of 1 volt causes a current of 1 ampere

to flow through a conductor (here a bulb) the electric power consumed is

1 watt and the electrical energy consumed is 1 joulesec this electrical

energy consumed in the bulb is converted into heat and light energy

Date____________

Pag

e22

Observation Table

Sr No Voltage V (volt) Current 119816 (mA) Power

119823 = 119829119816 (watt)

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

Date____________

Pag

e23

Calculation 119823 = 119829119816

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e24

Temperature of Tungsten Filament Experiment ndash 07

Aim To find the temperature of the tungsten filament of the bulb

Apparatus AC Ammeter(0-500 mA) AC Voltmeter(0-250 volt) Variac

Components Bulb

Circuit Diagram

Procedure

Connect the circuit as shown in the circuit diagram Now switch ON

the circuit and note down the reading shown by ammeter at 0 volt then

increase the voltage from 0 to 10 volt and note down the reading of

ammeter Now increase the voltage in order of 10 volts (up to 100 volts)

and note down the readings of the current shown by the ammeter Now

calculate the resistance and the temperature of the filament

Observations

(1) Room temperaturehellip t0 = _______ ˚C

(2) Resistance of the filament of the bulb at room temperaturehellip

R0 = _______ Ω

(3) Temperature coefficient of tungstenhellip α = 45times10-4 ˚C-1

Date____________

Pag

e25

Observation Table

Sr No Voltage V

(volt)

Current 119816

(mA)

Resistance of

The Filament

119825119853 =119829

119816 Ω

Temperature of The Filament

119853 =120783

120514[

119825119853

119825120782 120783 + 120514119853120782 minus 120783] ˚C

1

2

3

4

5

6

7

8

9

10

Graph Rt versus t

Date____________

Pag

e26

Calculations

(1) Resistance of The Filament Rt =V

I Ω

(2) Temperature of The Filament t =1

α[

Rt

R0 1 + αt0 minus 1] ˚C

Date____________

Pag

e27

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e28

Meldersquos Experiment - 08

Aim To find the frequency of the wave and the frequency of the tuning fork by

Meldersquos experiment

Apparatus Meldersquos experiment apparatus

Circuit Diagram

Transverse mode

Procedure

Set Meldersquos experiment apparatus as shown in circuit diagram in

longitudinal position and switch ON the power supply put some weight in

scale pan and adjust the length of the string in such a way that you find

some loops on the string (eg 2 loops) Now rotate the apparatus by 90˚ so

that it is set for lsquoBrsquo position for the same values of weight in pan and for

the same length of the string the number of loops created in lsquoBrsquo position

are double (eg 4 loops) than in lsquoArsquo position Note down these readings in

observation table Repeat the experiment for other values of weight in

scale pan

Date____________

Pag

e29

Theory

This is an easy and efficient method by which nodes and antinodes

formed on a string can be demonstrated

A tuning fork is fitted in a wooden block A long string or thread of

cotton is taken One end of this string is tied to one of the prongs of the

tuning fork and the second end of this string passes over a smooth pulley in

such a way that a small pan can be hang on it Small weights are put in the

pan to create tension in the string This arrangement is shown in the circuit

diagram

The fork is set into vibrations by lightly hitting the prong of the tuning

fork on which the string is not tied or by connecting an electric supply as

shown in the circuit diagram Thus the transverse vibrations are produced

in the string and by adjusting the length andor weights in the pan these

vibrations are reflected from the point of contact between the string and

the pulley and a number of loops appear on the string as shown in the

circuit diagram

When the prongs of the tuning fork vibrate in a plane parallel to the

direction of propagation of the waves it is called lsquoArsquo position or

longitudinal position

If the tuning fork along with the wooden block is rotated through

90˚ so that the plane of vibration of the tuning fork is normal (ie at right

angles) to the direction of propagation it is called lsquoBrsquo position or transverse

position

For the same length and same weight in the pan (ie for the same

tension) the number of loops in lsquoBrsquo position is double than in lsquoArsquo position

Thus either in lsquoArsquo position or in lsquoBrsquo position standing transverse

waves are generated in the string with a series of nodes and antinodes at

equal distances

The equation connecting number of loops (n or nrsquo) length of the

string (l) tension in the string (T) mass per unit length of the string (m) and

frequency of the string (f) is as follows

Date____________

Pag

e30

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position)

119943prime =119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

If the frequency of tuning fork is F then for lsquoArsquo position 119839 =119813

120784 and for lsquoBrsquo

position 119839prime = 119813

In the above equations if all the quantities on the RHS are known the

frequency of the tuning fork 119813 can be calculated

Observations

(1) Gravitational accelerationhellip g = 98 ms2

(2) Mass per unit length of the stringhellip m = _______ kgm

(3) Mass of the scale panhellip M1 = _______ kg

Observation Table

Sr

No

Total mass

suspended at

the end of the

stringhellip

M=M1+M2

(kg)

Tension

created

in the

stringhellip

T=Mg (N)

Length of the

vibrating string

Average

lengthhellip

119949 (m)

No of loops created on

the stringhellip

Frequency of the

vibrating stringhellip

Relation

between

f and frsquo 1199491 (m) 1199492 (m)

In

Longitudinal

Modehellip

n

In

Transverse

Modehellip

nrsquo

In

Longitudinal

Modehellip

119943 =119951

120784119949

119931

119950

In

Transverse

Modehellip

119943prime =119951prime

120784119949

119931

119950

1

2

3

4

Here M2 = the weight put in the scale pan

Page31

Date____________

Pag

e32

Calculations

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position) 119943prime =

119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e33

P-N Junction Diode Characteristics Experiment - 09

Aim To study the Forward and Reverse bias characteristics of a P-N junction

diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components P-N junction diode Resistors

Circuit Diagram

(Forward biased PN diode) (Reverse biased PN diode)

Procedure

For Forward Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 01 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 02 03 04hellip

volts and repeat the procedure Note down the knee voltage and

corresponding current in your observation table

For Reverse Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Date____________

Pag

e34

Theory

If donor (pentavalent) impurities are introduced on one side and

acceptors (trivalent) on the opposite side of a single crystal of an intrinsic

semiconductor like germanium or silicon a p-n junction is formed as shown

in Fig 11 In the figure a donor ion is indicated schematically by a plus sign

because after this impurity atom donates an electron it becomes a positive

ion

The acceptor ion is indicated by a minus sign because after this atom

accepts an electron it becomes a negative ion Initially there are only n-

type carriers to the right of the junction and only p-type carriers to the left

Because there is a density gradient across the junction holes will diffuse to

the right across the junction and electrons to the left As a result of the

displacement of these charges an electric field appears across the junction

Equilibrium is established when the field becomes large enough to restrain

the process of diffusion The positive holes which neutralize the acceptor

ions near the junction in p-type germanium disappear as a result of

combination with electrons which diffuse across the junction Similarly the

neutralizing electrons on the n side of the junction combine with holes

which cross the junction from the p side Since the region of the junction is

depleted of mobile charges it is called the depletion region or a potential

barrier

Forward Bias

An external voltage applied to the p-n junction with the polarity

shown in Fig 12 is known as forward bias The height of the potential

barrier at the junction is lowered by the applied forward voltage In other

words we can say that p-n junction diode is connected to an external

Date____________

Pag

e35

battery in such a way that depletion region is reduced in size or eliminated

altogether Which of these takes place is determined by the size of the

applied voltage The positive terminal of the battery repels the holes on the

p-side and pushes them towards the junction The negative terminal of the

battery repels the electrons and pushes them towards the junction This

collapses the depletion region With the depletion region gone the diode

can conduct

Reverse Bias

An external voltage applied with polarity in Fig 13 is called reverse

bias When reverse bias is applied to a junction diode the depletion region

does not collapse On the contrary it becomes wider The positive side of

battery is applied to the n-type material This attracts the free electrons

away from the junction The negative side of the battery attracts the holes

in p-type material away from the junction This makes the depletion region

wider than it was when no voltage is applied The depletion region is an

insulator and it will block the flow of current Actually a small current will

flow because of minority carriers The p-type material has a few minority

electrons These are pushed to the junction by the repulsion of the negative

side of the battery The n-type material has few minority holes These are

also pushed towards the junction Reverse bias forces the minority carriers

together and a small current - called leakage current - results

Diodes which are designed with adequate power dissipation

capability to operate in the breakdown region are none as Zener diodes

Two mechanisms of diode breakdown for increasing reverse voltage are

recognized In one mechanism the thermally generated electrons and

holes acquire sufficient energy from the applied potential to produce new

carriers by removing valence electrons from their bonds These new

carriers in turn produce additional carriers again through the process of

disrupting bonds This cumulative process is referred to as avalanche

breakdown Even if the initially available carriers do not acquire sufficient

energy to disrupt bonds it is possible to initiate breakdown through a

direct rupture of the bonds because of the existence of strong electric field

Under these conditions the breakdown is referred to as Zener breakdown

Date____________

Pag

e36

Zener breakdown occurs below 6 V Zener diodes are commonly used in

voltage-reference or constant-voltage devices

Characteristic curves of diode

Fig 14 shows V-I Characteristic curves for typical p-n junction diode

It is seen that the curve is not linear With 0 V across the diode the diode

will not conduct the diode will not begin to conduct until a few tenths of a

volt are applied across it This is the voltage needed to overcome the

potential barrier It requires about 02 V to turn on a germanium diode and

about 06 V to turn on a silicon diode Fig 18 also shows what happens

when reverse bias is applied to a diode At increasing levels of reverse

voltage the curve shows some reverse current This leakage current is

caused by minority carries It is usually very small

Graph

Fig-14

Date____________

Pag

e37

Observation Table for Forward bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Date____________

Pag

e38

Observation Table for Reverse bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e39

Calculation for Forward bias 119877 = 119881

119868

Calculation for Reverse bias 119877 = 119881

119868

Date____________

Pag

e40

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e41

Zener Diode Reverse Bias Characteristics Experiment - 10

Aim To study the reverse bias characteristics of a Zener diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components Zener diode Resistors

Circuit Diagram

Procedure

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Theory

A diode which is heavily doped (Si or Ge) and which operates in the

reverse breakdown region with a sharp breakdown voltage is called a zener

diode The schematic symbol of a zener diode is shown in Fig-1 This is

similar to a normal diode except that the line (bar) representing the

cathode is bent at both ends like the letter Z for zener diode

Date____________

Pag

e42

A C Fig-1

In a simple diode the doping is light as a result the breakdown

voltage is high and not sharp But if doping is made heavy the depletion

layer becomes very narrow and even the breakdown voltage gets reduced

to a sharp value The zener diode is designed to operate in the breakdown

region without damage

The reverse breakdown of a zener diode may occur either due to

zener effect or avalanche effect But zener diode primarily depends on

zener effect for its working When the electric field across the junction is

sufficiently high due to the applied voltage the zener breakdown occurs

because of breaking of covalent bonds This produces a large number of

electrons and holes which constitute a steep rise in the reverse saturation

current (also called zener current 119868Z) This effect is called as zener effect

Zener current is independent of the applied voltage and depends only on

the external resistance

The V - 119868 characteristic of a zener diode is shown in Fig-2 The

forward characteristic is simply that of an ordinary forward biased junction

diode

Fig-2

Date____________

Pag

e43

Under reverse bias condition breakdown of junction occurs This

breakdown depends upon the amount of doping It can be seen from Fig-2

that as the reverse voltage is increased the reverse current remains

negligibly small up to the lsquokneersquo of the curve

At this lsquoknee pointrsquo the effect of breakdown process begins The

voltage corresponding to the lsquoknee pointrsquo in the figure is called the zener

breakdown voltage or simply zener voltage (VZ) which is very sharp

compared to a simle p-n junction diode Beyond this voltage the reverse

current (119868Z) increases sharply to a high value

The zener diode is not immediately burnt just because it has entered

the breakdown region As long as the external resistance connected to the

diode in the circuit limits the diode current to less than the burn out value

the diode will not burn out The zener voltage VZ remains constant even

when zener current 119868Z increases greatly This ability of a diode is called

regulating ability and it enables us to use zener diode for voltage

regulation

Date____________

Pag

e44

Observation Table

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e45

Graph 119868 V

Calculations 119877 = 119881

119868

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e46

Dispersive Power of The Prism Experiment - 11

Aim To find the dispersive power (D) of the prism by using spectrometer

Apparatus Mercury vapor lamp Spectrometer Prism

Procedure

Levelling and alignment of collimator and telescope

1 Switch on the mercury lamp Adjust the leveling screws on the chassis

Keep the spirit level on the chassis and do finer adjustments of these

screws to bring the bubble in the sprit level to the centre Repeat this

placing the sprit level along a direction perpendicular to the earlier

direction

2 Repeat this procedure for the prism table

3 Close the slit at the other end of the collimator using the drum screw DS1

Open it to a reasonable width Place the spectrometer in front of the

mercury lamp window and rotate the collimator so that the slit faces of

window View the slit through the telescope If it is not in the centre of the

view level collimator and the telescope so as to bring it to the centre

Setting the prism in the minimum deviation position

1 Rotate the prism table such that lines ruled on the table become

perpendicular to the axis of collimator

2 Place prism over the prism table such that its rough surface BA is

perpendicular to the line on prism table (See Fig-1(a))

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e8

(I) 1199071 = 1198911 (41198711) (ii) 1199072 = 1198912 (41198712)

(iii) 1199073 = 1198913 (41198713) (iv) 1199074 = 1198914 (41198714)

(3) Average Velocityhellip

119907 =1199071+1199072+1199073+1199074

4

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e9

Liquid Lens Experiment - 03

Aim To determine refractive index of a given liquid by forming a liquid lens

Apparatus Biconvex lens liquid plane mirror retort stand with clamp and pin

spherometer meter rule

Procedure

The plane mirror is placed on the base of the stand with the pin held

horizontally by the clamp above The convex lens is then placed on the

mirror and its focus is found by locating the position of the pin where it

coincides with its own image By measuring from this point to the lens its

focal length (fg ) is found The lens is now removed and a few drops of

liquid are placed on the mirror On placing the convex lens on the liquid a

combination of a convex (glass) and a plano-concave (liquid) lens results

The focal length (f) of the combination is found as above and the focal

length (fl) of the liquid lens calculated from f and fl The radius of curvature

(r) of the lens surface in contact with the liquid is now obtained by a

spherometer

Theory

The parallel rays meet at the principal focus of the focal length of (1)

Convex lens and (2) Combination lens ndash (Convex lens + Liquid lens) can be

measured experimentally By making use of combination forms the focal

length of liquid lens can be worked out By substituting the value of fl and R

η can be computed

Observations

(1) Least count of spherometer = _______ cm

(2) Distance between two legs of spherometerhellip

a1 = ________ cm a2 = ________ cm a3 = ________ cm

Mean a = ________ cm

(3) Sagita h = _______ div

= _______ cm

Date ___________

Pag

e10

Observation Table

Lens Type Measured Focal Length (cm)

1 2 3 4 5 Mean

Convex fg =_______

Combination f = _______

Calculations

(1) Least count of spherometerhellip

=Distance between two consecutive devisions on main scale

Total number of devisions on circular scale

(2) Radius of curvature hellip 119877 =1198862

6119893+

119893

2

(3) Focal length of a combination lens ( 119891 ) 1

119891=

1

119891119892+

1

119891119897

Date ___________

Pag

e11

(4) Refractive index of a given liquid ( η ) 1

119891119897= minus 120578 minus 1

1

119877

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e12

Deflection of Magnetometer Experiment - 04

Aim To find the magnetic moment (M) of given magnet by magnetometer (From

two different position Gauss-A and Gauss-B of magnetometer) Also obtain

the pole strength (m) of the magnet

Apparatus Magnetometer Magnet

Procedure

First set the magnetometer in Gauss-A position and then put the

magnet at a distance d on the arm of the magnetometer as shown in fig-1

Distance d should be selected in such a way that magnetometer show a

deflection between 30˚ and 60˚ Now note down the deflection shown by

the magnetometer as θ1 and θ2 then reverse the direction of the poles of

the magnet and note down the deflection as θ3 and θ4 Now put the magnet

on the opposite arm and repeat the experiment in a similar way and note

down the deflections as θ5 θ6 θ7 and θ8 Now calculate Magnetic

moment and Pole strength

Now set the magnetometer in Gauss-B position and repeat the

experiment in a similar way

Theory

The Magnetic moment is a measure of the strength of the magnet

Its unit is Gausscm3 For a magnet of Pole strength lsquomrsquo and length 2119897 the

magnetic moment M=2m119897 and points from the South Pole to the North

Pole of the magnet

Gauss-A Position of Magnetometer

Date ___________

Pag

e13

Gauss-B Position of Magnetometer

Observations

(1) Magnetic field intensity of the earthhellip H = 036 Gauss

(2) Magnetic length of the magnethellip 2119897 = 5L6 = __________ cm

119897 = ___________cm

Where L = Geometric length of the magnet = __________ cm

Observation Table for Gauss-A Position

Sr No

Distance d (cm)

Deflection of Magnetometer Avg

θ

tanθ

Magnetic Moment

M = (119837120784minus119897120784)120784

120784119837 H tanθ

θ1 θ2 θ3 θ4 θ5 θ6 θ7 θ8

1

2

Date ___________

Pag

e14

Observation Table for Gauss-B Position

Sr No

Distance d (cm)

Deflection of Magnetometer Avg

θ

tanθ

Magnetic Moment

M = (119837120784+119897120784)120785120784Htanθ

θ1 θ2 θ3 θ4 θ5 θ6 θ7 θ8

1

2

Calculations

(1) Magnetic Moments for Gauss-A position

(2) Magnetic Moments for Gauss-B Position

(1) MA = (119837120784minus119897120784)120784

120784119837 H tanθ

(2) MB = (119837120784+119897120784) 120785120784 H tanθ

(i)

(i)

(ii) (iii)

Date ___________

Pag

e15

(1) 119872119860119886119907119892 =119872119860 1+119872119860 2

2

(2) 119872119861119886119907119892 =119872119861 1+119872119861 2

2

(3) Pole Strength of the magnethellip m = M2119897

(For both Gauss-A amp Gauss-B Positions)

For Gauss-A For Gauss-B

119898119860 =119872119860119886119907119892

2119897

119898119861 =119872119861119886119907119892

2119897

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e16

Friction Experiment - 05

Aim To determine the coefficient of kinetic friction between plane and block

Apparatus Inclined plane Block Scale pan String Set of weights Scale

Procedure

Take the inclined plane and set an angle of inclination θ1 Now put the block

on the inclined plane and put some weight in the scale pan in such a way that

block moves up along the inclined plane with a constant speed Now measure the

height length and base of the inclined plane for that angle and calculate the

Coefficient of kinetic friction

Now repeat the experiment for the angles θ2 and θ3

Theory

When a force F tends to slide a body along a surface a frictional force from

the surface acts on the body The frictional force is parallel to the surface and

directed so as to oppose the sliding It is due to bonding between the body and

the surface

If the body does not slide the frictional force is a static frictional force fs If

there is sliding the frictional force is a kinetic (dynamic) frictional force fk If the

body is rolling then the frictional force is known as rolling frictional force fr

Three properties of friction

(1) If the body does not move then the static frictional force fs and the

component of F that is parallel to the surface are equal in magnitudes

and fs is directed opposite that component If that parallel component

increases magnitude fs also increases

(2) The magnitude of fs has a maximum value fsmax that is given by

fsmax = microsN Where micros is the coefficient of static friction and N is the

magnitude of the normal reaction If the component of F that is parallel

to the surface exceeds fsmax then the body slides on the surface

Date ___________

Pag

e17

(3) If the body begins to slide on the surface the magnitude of the frictional

force rapidly decreases to a constant value fk given by fk = microk N Where

microk is the coefficient of kinetic friction

The magnitude of the coefficients of frictions relative to each other is

given by micros gt microk gtgt micror Where micror is coefficient of rolling friction

Note Here quantities shown bold are vector quantities

Observations

(1) Weight of the blockhellip M = ________ gm

(2) Weight of the scale panhellip m1 = _______ gm

(3) Gravitational accelerationhellip g = 980 cms2

Observation Table

Sr

No

Inclination

of the

Plane (θ)

Effort required to start

the motion up (gm)

m=m1+m2

Avg Effort

m (gm)

Base of

the

Plane

b (cm)

Height

of the

Plane

h (cm)

Length

of the

Plane

l (cm)

cosθ=bl

sinθ=hl

Coefficient of

Kinetic Friction

μ = 119846119840 ndash 119820119840 119852119842119847 120521

119820119840 119836119848119852 120521

1

θ1 1

2

2

θ2 1

2

3

θ3 1

2

Here m2 = the weight put in the scale pan

Page18

Calculation

Coefficient of Kinetic Friction μ = mg ndash Mg sin θMg cos θ

(1) (2)

(3)

Average of Coefficient of Kinetic Friction

μ avg = μ 1 + μ 2 + μ 3

3

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Page19

Date____________

Pag

e20

Wattage of Bulb Experiment - 06

Aim To find the electrical energy consumed in a circuit (bulb)

Apparatus AC Ammeter(0-500 mA) AC Voltmeter(0-250 volt) Variac

Components Bulb

Circuit Diagram

Procedure

Connect the circuit as shown in the circuit diagram Now switch ON

the circuit and note down the reading shown by ammeter at 0 volt then

increase the voltage from 0 to 10 volt and note down the reading of

ammeter Now increase the voltage in order of 10 volts (up to 200 volts)

and note down the readings of the current shown by the ammeter Now

calculate the power consumed in a circuit at different stages

Theory

Experiments show that in stationary metallic conductors current does

work to increase their internal energy The heated conductor releases the

energy received to the surrounding bodies but this is done by means of

heat transfer This means that the quantity of heat released by a current

carrying conductor is equal to the total work done by the current

Date____________

Pag

e21

As we know that the work done by the current is given by 119830 = 119829119816119853helliphelliphelliphelliphelliphellip(1)

119830 = 119816120784119825119853 ( V = IR) helliphelliphelliphelliphelliphelliphellip (2)

The electrical power of a given device is simply the rate of doing

work or the amount of electric work done in one second

Therefore electric powerhellip

119823 =119830119848119851119844 119837119848119847119838 (119830)

119827119842119846119838 (119853)

119823 =119829119816119853

119853= 119829119816 helliphelliphelliphelliphelliphelliphellip (3)

Thus electric power is equal to the product of voltage by current

Watt is a unit of power Hence it can be expressed in terms of a volt

and an ampere by the formula for electric power Eqn (3)

Therefore

1 Watt = 1 volt ∙ 1 ampere

1 W = 1 V∙A

Thus if a potential difference of 1 volt causes a current of 1 ampere

to flow through a conductor (here a bulb) the electric power consumed is

1 watt and the electrical energy consumed is 1 joulesec this electrical

energy consumed in the bulb is converted into heat and light energy

Date____________

Pag

e22

Observation Table

Sr No Voltage V (volt) Current 119816 (mA) Power

119823 = 119829119816 (watt)

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

Date____________

Pag

e23

Calculation 119823 = 119829119816

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e24

Temperature of Tungsten Filament Experiment ndash 07

Aim To find the temperature of the tungsten filament of the bulb

Apparatus AC Ammeter(0-500 mA) AC Voltmeter(0-250 volt) Variac

Components Bulb

Circuit Diagram

Procedure

Connect the circuit as shown in the circuit diagram Now switch ON

the circuit and note down the reading shown by ammeter at 0 volt then

increase the voltage from 0 to 10 volt and note down the reading of

ammeter Now increase the voltage in order of 10 volts (up to 100 volts)

and note down the readings of the current shown by the ammeter Now

calculate the resistance and the temperature of the filament

Observations

(1) Room temperaturehellip t0 = _______ ˚C

(2) Resistance of the filament of the bulb at room temperaturehellip

R0 = _______ Ω

(3) Temperature coefficient of tungstenhellip α = 45times10-4 ˚C-1

Date____________

Pag

e25

Observation Table

Sr No Voltage V

(volt)

Current 119816

(mA)

Resistance of

The Filament

119825119853 =119829

119816 Ω

Temperature of The Filament

119853 =120783

120514[

119825119853

119825120782 120783 + 120514119853120782 minus 120783] ˚C

1

2

3

4

5

6

7

8

9

10

Graph Rt versus t

Date____________

Pag

e26

Calculations

(1) Resistance of The Filament Rt =V

I Ω

(2) Temperature of The Filament t =1

α[

Rt

R0 1 + αt0 minus 1] ˚C

Date____________

Pag

e27

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e28

Meldersquos Experiment - 08

Aim To find the frequency of the wave and the frequency of the tuning fork by

Meldersquos experiment

Apparatus Meldersquos experiment apparatus

Circuit Diagram

Transverse mode

Procedure

Set Meldersquos experiment apparatus as shown in circuit diagram in

longitudinal position and switch ON the power supply put some weight in

scale pan and adjust the length of the string in such a way that you find

some loops on the string (eg 2 loops) Now rotate the apparatus by 90˚ so

that it is set for lsquoBrsquo position for the same values of weight in pan and for

the same length of the string the number of loops created in lsquoBrsquo position

are double (eg 4 loops) than in lsquoArsquo position Note down these readings in

observation table Repeat the experiment for other values of weight in

scale pan

Date____________

Pag

e29

Theory

This is an easy and efficient method by which nodes and antinodes

formed on a string can be demonstrated

A tuning fork is fitted in a wooden block A long string or thread of

cotton is taken One end of this string is tied to one of the prongs of the

tuning fork and the second end of this string passes over a smooth pulley in

such a way that a small pan can be hang on it Small weights are put in the

pan to create tension in the string This arrangement is shown in the circuit

diagram

The fork is set into vibrations by lightly hitting the prong of the tuning

fork on which the string is not tied or by connecting an electric supply as

shown in the circuit diagram Thus the transverse vibrations are produced

in the string and by adjusting the length andor weights in the pan these

vibrations are reflected from the point of contact between the string and

the pulley and a number of loops appear on the string as shown in the

circuit diagram

When the prongs of the tuning fork vibrate in a plane parallel to the

direction of propagation of the waves it is called lsquoArsquo position or

longitudinal position

If the tuning fork along with the wooden block is rotated through

90˚ so that the plane of vibration of the tuning fork is normal (ie at right

angles) to the direction of propagation it is called lsquoBrsquo position or transverse

position

For the same length and same weight in the pan (ie for the same

tension) the number of loops in lsquoBrsquo position is double than in lsquoArsquo position

Thus either in lsquoArsquo position or in lsquoBrsquo position standing transverse

waves are generated in the string with a series of nodes and antinodes at

equal distances

The equation connecting number of loops (n or nrsquo) length of the

string (l) tension in the string (T) mass per unit length of the string (m) and

frequency of the string (f) is as follows

Date____________

Pag

e30

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position)

119943prime =119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

If the frequency of tuning fork is F then for lsquoArsquo position 119839 =119813

120784 and for lsquoBrsquo

position 119839prime = 119813

In the above equations if all the quantities on the RHS are known the

frequency of the tuning fork 119813 can be calculated

Observations

(1) Gravitational accelerationhellip g = 98 ms2

(2) Mass per unit length of the stringhellip m = _______ kgm

(3) Mass of the scale panhellip M1 = _______ kg

Observation Table

Sr

No

Total mass

suspended at

the end of the

stringhellip

M=M1+M2

(kg)

Tension

created

in the

stringhellip

T=Mg (N)

Length of the

vibrating string

Average

lengthhellip

119949 (m)

No of loops created on

the stringhellip

Frequency of the

vibrating stringhellip

Relation

between

f and frsquo 1199491 (m) 1199492 (m)

In

Longitudinal

Modehellip

n

In

Transverse

Modehellip

nrsquo

In

Longitudinal

Modehellip

119943 =119951

120784119949

119931

119950

In

Transverse

Modehellip

119943prime =119951prime

120784119949

119931

119950

1

2

3

4

Here M2 = the weight put in the scale pan

Page31

Date____________

Pag

e32

Calculations

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position) 119943prime =

119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e33

P-N Junction Diode Characteristics Experiment - 09

Aim To study the Forward and Reverse bias characteristics of a P-N junction

diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components P-N junction diode Resistors

Circuit Diagram

(Forward biased PN diode) (Reverse biased PN diode)

Procedure

For Forward Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 01 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 02 03 04hellip

volts and repeat the procedure Note down the knee voltage and

corresponding current in your observation table

For Reverse Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Date____________

Pag

e34

Theory

If donor (pentavalent) impurities are introduced on one side and

acceptors (trivalent) on the opposite side of a single crystal of an intrinsic

semiconductor like germanium or silicon a p-n junction is formed as shown

in Fig 11 In the figure a donor ion is indicated schematically by a plus sign

because after this impurity atom donates an electron it becomes a positive

ion

The acceptor ion is indicated by a minus sign because after this atom

accepts an electron it becomes a negative ion Initially there are only n-

type carriers to the right of the junction and only p-type carriers to the left

Because there is a density gradient across the junction holes will diffuse to

the right across the junction and electrons to the left As a result of the

displacement of these charges an electric field appears across the junction

Equilibrium is established when the field becomes large enough to restrain

the process of diffusion The positive holes which neutralize the acceptor

ions near the junction in p-type germanium disappear as a result of

combination with electrons which diffuse across the junction Similarly the

neutralizing electrons on the n side of the junction combine with holes

which cross the junction from the p side Since the region of the junction is

depleted of mobile charges it is called the depletion region or a potential

barrier

Forward Bias

An external voltage applied to the p-n junction with the polarity

shown in Fig 12 is known as forward bias The height of the potential

barrier at the junction is lowered by the applied forward voltage In other

words we can say that p-n junction diode is connected to an external

Date____________

Pag

e35

battery in such a way that depletion region is reduced in size or eliminated

altogether Which of these takes place is determined by the size of the

applied voltage The positive terminal of the battery repels the holes on the

p-side and pushes them towards the junction The negative terminal of the

battery repels the electrons and pushes them towards the junction This

collapses the depletion region With the depletion region gone the diode

can conduct

Reverse Bias

An external voltage applied with polarity in Fig 13 is called reverse

bias When reverse bias is applied to a junction diode the depletion region

does not collapse On the contrary it becomes wider The positive side of

battery is applied to the n-type material This attracts the free electrons

away from the junction The negative side of the battery attracts the holes

in p-type material away from the junction This makes the depletion region

wider than it was when no voltage is applied The depletion region is an

insulator and it will block the flow of current Actually a small current will

flow because of minority carriers The p-type material has a few minority

electrons These are pushed to the junction by the repulsion of the negative

side of the battery The n-type material has few minority holes These are

also pushed towards the junction Reverse bias forces the minority carriers

together and a small current - called leakage current - results

Diodes which are designed with adequate power dissipation

capability to operate in the breakdown region are none as Zener diodes

Two mechanisms of diode breakdown for increasing reverse voltage are

recognized In one mechanism the thermally generated electrons and

holes acquire sufficient energy from the applied potential to produce new

carriers by removing valence electrons from their bonds These new

carriers in turn produce additional carriers again through the process of

disrupting bonds This cumulative process is referred to as avalanche

breakdown Even if the initially available carriers do not acquire sufficient

energy to disrupt bonds it is possible to initiate breakdown through a

direct rupture of the bonds because of the existence of strong electric field

Under these conditions the breakdown is referred to as Zener breakdown

Date____________

Pag

e36

Zener breakdown occurs below 6 V Zener diodes are commonly used in

voltage-reference or constant-voltage devices

Characteristic curves of diode

Fig 14 shows V-I Characteristic curves for typical p-n junction diode

It is seen that the curve is not linear With 0 V across the diode the diode

will not conduct the diode will not begin to conduct until a few tenths of a

volt are applied across it This is the voltage needed to overcome the

potential barrier It requires about 02 V to turn on a germanium diode and

about 06 V to turn on a silicon diode Fig 18 also shows what happens

when reverse bias is applied to a diode At increasing levels of reverse

voltage the curve shows some reverse current This leakage current is

caused by minority carries It is usually very small

Graph

Fig-14

Date____________

Pag

e37

Observation Table for Forward bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Date____________

Pag

e38

Observation Table for Reverse bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e39

Calculation for Forward bias 119877 = 119881

119868

Calculation for Reverse bias 119877 = 119881

119868

Date____________

Pag

e40

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e41

Zener Diode Reverse Bias Characteristics Experiment - 10

Aim To study the reverse bias characteristics of a Zener diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components Zener diode Resistors

Circuit Diagram

Procedure

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Theory

A diode which is heavily doped (Si or Ge) and which operates in the

reverse breakdown region with a sharp breakdown voltage is called a zener

diode The schematic symbol of a zener diode is shown in Fig-1 This is

similar to a normal diode except that the line (bar) representing the

cathode is bent at both ends like the letter Z for zener diode

Date____________

Pag

e42

A C Fig-1

In a simple diode the doping is light as a result the breakdown

voltage is high and not sharp But if doping is made heavy the depletion

layer becomes very narrow and even the breakdown voltage gets reduced

to a sharp value The zener diode is designed to operate in the breakdown

region without damage

The reverse breakdown of a zener diode may occur either due to

zener effect or avalanche effect But zener diode primarily depends on

zener effect for its working When the electric field across the junction is

sufficiently high due to the applied voltage the zener breakdown occurs

because of breaking of covalent bonds This produces a large number of

electrons and holes which constitute a steep rise in the reverse saturation

current (also called zener current 119868Z) This effect is called as zener effect

Zener current is independent of the applied voltage and depends only on

the external resistance

The V - 119868 characteristic of a zener diode is shown in Fig-2 The

forward characteristic is simply that of an ordinary forward biased junction

diode

Fig-2

Date____________

Pag

e43

Under reverse bias condition breakdown of junction occurs This

breakdown depends upon the amount of doping It can be seen from Fig-2

that as the reverse voltage is increased the reverse current remains

negligibly small up to the lsquokneersquo of the curve

At this lsquoknee pointrsquo the effect of breakdown process begins The

voltage corresponding to the lsquoknee pointrsquo in the figure is called the zener

breakdown voltage or simply zener voltage (VZ) which is very sharp

compared to a simle p-n junction diode Beyond this voltage the reverse

current (119868Z) increases sharply to a high value

The zener diode is not immediately burnt just because it has entered

the breakdown region As long as the external resistance connected to the

diode in the circuit limits the diode current to less than the burn out value

the diode will not burn out The zener voltage VZ remains constant even

when zener current 119868Z increases greatly This ability of a diode is called

regulating ability and it enables us to use zener diode for voltage

regulation

Date____________

Pag

e44

Observation Table

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e45

Graph 119868 V

Calculations 119877 = 119881

119868

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e46

Dispersive Power of The Prism Experiment - 11

Aim To find the dispersive power (D) of the prism by using spectrometer

Apparatus Mercury vapor lamp Spectrometer Prism

Procedure

Levelling and alignment of collimator and telescope

1 Switch on the mercury lamp Adjust the leveling screws on the chassis

Keep the spirit level on the chassis and do finer adjustments of these

screws to bring the bubble in the sprit level to the centre Repeat this

placing the sprit level along a direction perpendicular to the earlier

direction

2 Repeat this procedure for the prism table

3 Close the slit at the other end of the collimator using the drum screw DS1

Open it to a reasonable width Place the spectrometer in front of the

mercury lamp window and rotate the collimator so that the slit faces of

window View the slit through the telescope If it is not in the centre of the

view level collimator and the telescope so as to bring it to the centre

Setting the prism in the minimum deviation position

1 Rotate the prism table such that lines ruled on the table become

perpendicular to the axis of collimator

2 Place prism over the prism table such that its rough surface BA is

perpendicular to the line on prism table (See Fig-1(a))

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e9

Liquid Lens Experiment - 03

Aim To determine refractive index of a given liquid by forming a liquid lens

Apparatus Biconvex lens liquid plane mirror retort stand with clamp and pin

spherometer meter rule

Procedure

The plane mirror is placed on the base of the stand with the pin held

horizontally by the clamp above The convex lens is then placed on the

mirror and its focus is found by locating the position of the pin where it

coincides with its own image By measuring from this point to the lens its

focal length (fg ) is found The lens is now removed and a few drops of

liquid are placed on the mirror On placing the convex lens on the liquid a

combination of a convex (glass) and a plano-concave (liquid) lens results

The focal length (f) of the combination is found as above and the focal

length (fl) of the liquid lens calculated from f and fl The radius of curvature

(r) of the lens surface in contact with the liquid is now obtained by a

spherometer

Theory

The parallel rays meet at the principal focus of the focal length of (1)

Convex lens and (2) Combination lens ndash (Convex lens + Liquid lens) can be

measured experimentally By making use of combination forms the focal

length of liquid lens can be worked out By substituting the value of fl and R

η can be computed

Observations

(1) Least count of spherometer = _______ cm

(2) Distance between two legs of spherometerhellip

a1 = ________ cm a2 = ________ cm a3 = ________ cm

Mean a = ________ cm

(3) Sagita h = _______ div

= _______ cm

Date ___________

Pag

e10

Observation Table

Lens Type Measured Focal Length (cm)

1 2 3 4 5 Mean

Convex fg =_______

Combination f = _______

Calculations

(1) Least count of spherometerhellip

=Distance between two consecutive devisions on main scale

Total number of devisions on circular scale

(2) Radius of curvature hellip 119877 =1198862

6119893+

119893

2

(3) Focal length of a combination lens ( 119891 ) 1

119891=

1

119891119892+

1

119891119897

Date ___________

Pag

e11

(4) Refractive index of a given liquid ( η ) 1

119891119897= minus 120578 minus 1

1

119877

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e12

Deflection of Magnetometer Experiment - 04

Aim To find the magnetic moment (M) of given magnet by magnetometer (From

two different position Gauss-A and Gauss-B of magnetometer) Also obtain

the pole strength (m) of the magnet

Apparatus Magnetometer Magnet

Procedure

First set the magnetometer in Gauss-A position and then put the

magnet at a distance d on the arm of the magnetometer as shown in fig-1

Distance d should be selected in such a way that magnetometer show a

deflection between 30˚ and 60˚ Now note down the deflection shown by

the magnetometer as θ1 and θ2 then reverse the direction of the poles of

the magnet and note down the deflection as θ3 and θ4 Now put the magnet

on the opposite arm and repeat the experiment in a similar way and note

down the deflections as θ5 θ6 θ7 and θ8 Now calculate Magnetic

moment and Pole strength

Now set the magnetometer in Gauss-B position and repeat the

experiment in a similar way

Theory

The Magnetic moment is a measure of the strength of the magnet

Its unit is Gausscm3 For a magnet of Pole strength lsquomrsquo and length 2119897 the

magnetic moment M=2m119897 and points from the South Pole to the North

Pole of the magnet

Gauss-A Position of Magnetometer

Date ___________

Pag

e13

Gauss-B Position of Magnetometer

Observations

(1) Magnetic field intensity of the earthhellip H = 036 Gauss

(2) Magnetic length of the magnethellip 2119897 = 5L6 = __________ cm

119897 = ___________cm

Where L = Geometric length of the magnet = __________ cm

Observation Table for Gauss-A Position

Sr No

Distance d (cm)

Deflection of Magnetometer Avg

θ

tanθ

Magnetic Moment

M = (119837120784minus119897120784)120784

120784119837 H tanθ

θ1 θ2 θ3 θ4 θ5 θ6 θ7 θ8

1

2

Date ___________

Pag

e14

Observation Table for Gauss-B Position

Sr No

Distance d (cm)

Deflection of Magnetometer Avg

θ

tanθ

Magnetic Moment

M = (119837120784+119897120784)120785120784Htanθ

θ1 θ2 θ3 θ4 θ5 θ6 θ7 θ8

1

2

Calculations

(1) Magnetic Moments for Gauss-A position

(2) Magnetic Moments for Gauss-B Position

(1) MA = (119837120784minus119897120784)120784

120784119837 H tanθ

(2) MB = (119837120784+119897120784) 120785120784 H tanθ

(i)

(i)

(ii) (iii)

Date ___________

Pag

e15

(1) 119872119860119886119907119892 =119872119860 1+119872119860 2

2

(2) 119872119861119886119907119892 =119872119861 1+119872119861 2

2

(3) Pole Strength of the magnethellip m = M2119897

(For both Gauss-A amp Gauss-B Positions)

For Gauss-A For Gauss-B

119898119860 =119872119860119886119907119892

2119897

119898119861 =119872119861119886119907119892

2119897

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e16

Friction Experiment - 05

Aim To determine the coefficient of kinetic friction between plane and block

Apparatus Inclined plane Block Scale pan String Set of weights Scale

Procedure

Take the inclined plane and set an angle of inclination θ1 Now put the block

on the inclined plane and put some weight in the scale pan in such a way that

block moves up along the inclined plane with a constant speed Now measure the

height length and base of the inclined plane for that angle and calculate the

Coefficient of kinetic friction

Now repeat the experiment for the angles θ2 and θ3

Theory

When a force F tends to slide a body along a surface a frictional force from

the surface acts on the body The frictional force is parallel to the surface and

directed so as to oppose the sliding It is due to bonding between the body and

the surface

If the body does not slide the frictional force is a static frictional force fs If

there is sliding the frictional force is a kinetic (dynamic) frictional force fk If the

body is rolling then the frictional force is known as rolling frictional force fr

Three properties of friction

(1) If the body does not move then the static frictional force fs and the

component of F that is parallel to the surface are equal in magnitudes

and fs is directed opposite that component If that parallel component

increases magnitude fs also increases

(2) The magnitude of fs has a maximum value fsmax that is given by

fsmax = microsN Where micros is the coefficient of static friction and N is the

magnitude of the normal reaction If the component of F that is parallel

to the surface exceeds fsmax then the body slides on the surface

Date ___________

Pag

e17

(3) If the body begins to slide on the surface the magnitude of the frictional

force rapidly decreases to a constant value fk given by fk = microk N Where

microk is the coefficient of kinetic friction

The magnitude of the coefficients of frictions relative to each other is

given by micros gt microk gtgt micror Where micror is coefficient of rolling friction

Note Here quantities shown bold are vector quantities

Observations

(1) Weight of the blockhellip M = ________ gm

(2) Weight of the scale panhellip m1 = _______ gm

(3) Gravitational accelerationhellip g = 980 cms2

Observation Table

Sr

No

Inclination

of the

Plane (θ)

Effort required to start

the motion up (gm)

m=m1+m2

Avg Effort

m (gm)

Base of

the

Plane

b (cm)

Height

of the

Plane

h (cm)

Length

of the

Plane

l (cm)

cosθ=bl

sinθ=hl

Coefficient of

Kinetic Friction

μ = 119846119840 ndash 119820119840 119852119842119847 120521

119820119840 119836119848119852 120521

1

θ1 1

2

2

θ2 1

2

3

θ3 1

2

Here m2 = the weight put in the scale pan

Page18

Calculation

Coefficient of Kinetic Friction μ = mg ndash Mg sin θMg cos θ

(1) (2)

(3)

Average of Coefficient of Kinetic Friction

μ avg = μ 1 + μ 2 + μ 3

3

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Page19

Date____________

Pag

e20

Wattage of Bulb Experiment - 06

Aim To find the electrical energy consumed in a circuit (bulb)

Apparatus AC Ammeter(0-500 mA) AC Voltmeter(0-250 volt) Variac

Components Bulb

Circuit Diagram

Procedure

Connect the circuit as shown in the circuit diagram Now switch ON

the circuit and note down the reading shown by ammeter at 0 volt then

increase the voltage from 0 to 10 volt and note down the reading of

ammeter Now increase the voltage in order of 10 volts (up to 200 volts)

and note down the readings of the current shown by the ammeter Now

calculate the power consumed in a circuit at different stages

Theory

Experiments show that in stationary metallic conductors current does

work to increase their internal energy The heated conductor releases the

energy received to the surrounding bodies but this is done by means of

heat transfer This means that the quantity of heat released by a current

carrying conductor is equal to the total work done by the current

Date____________

Pag

e21

As we know that the work done by the current is given by 119830 = 119829119816119853helliphelliphelliphelliphelliphellip(1)

119830 = 119816120784119825119853 ( V = IR) helliphelliphelliphelliphelliphelliphellip (2)

The electrical power of a given device is simply the rate of doing

work or the amount of electric work done in one second

Therefore electric powerhellip

119823 =119830119848119851119844 119837119848119847119838 (119830)

119827119842119846119838 (119853)

119823 =119829119816119853

119853= 119829119816 helliphelliphelliphelliphelliphelliphellip (3)

Thus electric power is equal to the product of voltage by current

Watt is a unit of power Hence it can be expressed in terms of a volt

and an ampere by the formula for electric power Eqn (3)

Therefore

1 Watt = 1 volt ∙ 1 ampere

1 W = 1 V∙A

Thus if a potential difference of 1 volt causes a current of 1 ampere

to flow through a conductor (here a bulb) the electric power consumed is

1 watt and the electrical energy consumed is 1 joulesec this electrical

energy consumed in the bulb is converted into heat and light energy

Date____________

Pag

e22

Observation Table

Sr No Voltage V (volt) Current 119816 (mA) Power

119823 = 119829119816 (watt)

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

Date____________

Pag

e23

Calculation 119823 = 119829119816

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e24

Temperature of Tungsten Filament Experiment ndash 07

Aim To find the temperature of the tungsten filament of the bulb

Apparatus AC Ammeter(0-500 mA) AC Voltmeter(0-250 volt) Variac

Components Bulb

Circuit Diagram

Procedure

Connect the circuit as shown in the circuit diagram Now switch ON

the circuit and note down the reading shown by ammeter at 0 volt then

increase the voltage from 0 to 10 volt and note down the reading of

ammeter Now increase the voltage in order of 10 volts (up to 100 volts)

and note down the readings of the current shown by the ammeter Now

calculate the resistance and the temperature of the filament

Observations

(1) Room temperaturehellip t0 = _______ ˚C

(2) Resistance of the filament of the bulb at room temperaturehellip

R0 = _______ Ω

(3) Temperature coefficient of tungstenhellip α = 45times10-4 ˚C-1

Date____________

Pag

e25

Observation Table

Sr No Voltage V

(volt)

Current 119816

(mA)

Resistance of

The Filament

119825119853 =119829

119816 Ω

Temperature of The Filament

119853 =120783

120514[

119825119853

119825120782 120783 + 120514119853120782 minus 120783] ˚C

1

2

3

4

5

6

7

8

9

10

Graph Rt versus t

Date____________

Pag

e26

Calculations

(1) Resistance of The Filament Rt =V

I Ω

(2) Temperature of The Filament t =1

α[

Rt

R0 1 + αt0 minus 1] ˚C

Date____________

Pag

e27

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e28

Meldersquos Experiment - 08

Aim To find the frequency of the wave and the frequency of the tuning fork by

Meldersquos experiment

Apparatus Meldersquos experiment apparatus

Circuit Diagram

Transverse mode

Procedure

Set Meldersquos experiment apparatus as shown in circuit diagram in

longitudinal position and switch ON the power supply put some weight in

scale pan and adjust the length of the string in such a way that you find

some loops on the string (eg 2 loops) Now rotate the apparatus by 90˚ so

that it is set for lsquoBrsquo position for the same values of weight in pan and for

the same length of the string the number of loops created in lsquoBrsquo position

are double (eg 4 loops) than in lsquoArsquo position Note down these readings in

observation table Repeat the experiment for other values of weight in

scale pan

Date____________

Pag

e29

Theory

This is an easy and efficient method by which nodes and antinodes

formed on a string can be demonstrated

A tuning fork is fitted in a wooden block A long string or thread of

cotton is taken One end of this string is tied to one of the prongs of the

tuning fork and the second end of this string passes over a smooth pulley in

such a way that a small pan can be hang on it Small weights are put in the

pan to create tension in the string This arrangement is shown in the circuit

diagram

The fork is set into vibrations by lightly hitting the prong of the tuning

fork on which the string is not tied or by connecting an electric supply as

shown in the circuit diagram Thus the transverse vibrations are produced

in the string and by adjusting the length andor weights in the pan these

vibrations are reflected from the point of contact between the string and

the pulley and a number of loops appear on the string as shown in the

circuit diagram

When the prongs of the tuning fork vibrate in a plane parallel to the

direction of propagation of the waves it is called lsquoArsquo position or

longitudinal position

If the tuning fork along with the wooden block is rotated through

90˚ so that the plane of vibration of the tuning fork is normal (ie at right

angles) to the direction of propagation it is called lsquoBrsquo position or transverse

position

For the same length and same weight in the pan (ie for the same

tension) the number of loops in lsquoBrsquo position is double than in lsquoArsquo position

Thus either in lsquoArsquo position or in lsquoBrsquo position standing transverse

waves are generated in the string with a series of nodes and antinodes at

equal distances

The equation connecting number of loops (n or nrsquo) length of the

string (l) tension in the string (T) mass per unit length of the string (m) and

frequency of the string (f) is as follows

Date____________

Pag

e30

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position)

119943prime =119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

If the frequency of tuning fork is F then for lsquoArsquo position 119839 =119813

120784 and for lsquoBrsquo

position 119839prime = 119813

In the above equations if all the quantities on the RHS are known the

frequency of the tuning fork 119813 can be calculated

Observations

(1) Gravitational accelerationhellip g = 98 ms2

(2) Mass per unit length of the stringhellip m = _______ kgm

(3) Mass of the scale panhellip M1 = _______ kg

Observation Table

Sr

No

Total mass

suspended at

the end of the

stringhellip

M=M1+M2

(kg)

Tension

created

in the

stringhellip

T=Mg (N)

Length of the

vibrating string

Average

lengthhellip

119949 (m)

No of loops created on

the stringhellip

Frequency of the

vibrating stringhellip

Relation

between

f and frsquo 1199491 (m) 1199492 (m)

In

Longitudinal

Modehellip

n

In

Transverse

Modehellip

nrsquo

In

Longitudinal

Modehellip

119943 =119951

120784119949

119931

119950

In

Transverse

Modehellip

119943prime =119951prime

120784119949

119931

119950

1

2

3

4

Here M2 = the weight put in the scale pan

Page31

Date____________

Pag

e32

Calculations

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position) 119943prime =

119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e33

P-N Junction Diode Characteristics Experiment - 09

Aim To study the Forward and Reverse bias characteristics of a P-N junction

diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components P-N junction diode Resistors

Circuit Diagram

(Forward biased PN diode) (Reverse biased PN diode)

Procedure

For Forward Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 01 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 02 03 04hellip

volts and repeat the procedure Note down the knee voltage and

corresponding current in your observation table

For Reverse Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Date____________

Pag

e34

Theory

If donor (pentavalent) impurities are introduced on one side and

acceptors (trivalent) on the opposite side of a single crystal of an intrinsic

semiconductor like germanium or silicon a p-n junction is formed as shown

in Fig 11 In the figure a donor ion is indicated schematically by a plus sign

because after this impurity atom donates an electron it becomes a positive

ion

The acceptor ion is indicated by a minus sign because after this atom

accepts an electron it becomes a negative ion Initially there are only n-

type carriers to the right of the junction and only p-type carriers to the left

Because there is a density gradient across the junction holes will diffuse to

the right across the junction and electrons to the left As a result of the

displacement of these charges an electric field appears across the junction

Equilibrium is established when the field becomes large enough to restrain

the process of diffusion The positive holes which neutralize the acceptor

ions near the junction in p-type germanium disappear as a result of

combination with electrons which diffuse across the junction Similarly the

neutralizing electrons on the n side of the junction combine with holes

which cross the junction from the p side Since the region of the junction is

depleted of mobile charges it is called the depletion region or a potential

barrier

Forward Bias

An external voltage applied to the p-n junction with the polarity

shown in Fig 12 is known as forward bias The height of the potential

barrier at the junction is lowered by the applied forward voltage In other

words we can say that p-n junction diode is connected to an external

Date____________

Pag

e35

battery in such a way that depletion region is reduced in size or eliminated

altogether Which of these takes place is determined by the size of the

applied voltage The positive terminal of the battery repels the holes on the

p-side and pushes them towards the junction The negative terminal of the

battery repels the electrons and pushes them towards the junction This

collapses the depletion region With the depletion region gone the diode

can conduct

Reverse Bias

An external voltage applied with polarity in Fig 13 is called reverse

bias When reverse bias is applied to a junction diode the depletion region

does not collapse On the contrary it becomes wider The positive side of

battery is applied to the n-type material This attracts the free electrons

away from the junction The negative side of the battery attracts the holes

in p-type material away from the junction This makes the depletion region

wider than it was when no voltage is applied The depletion region is an

insulator and it will block the flow of current Actually a small current will

flow because of minority carriers The p-type material has a few minority

electrons These are pushed to the junction by the repulsion of the negative

side of the battery The n-type material has few minority holes These are

also pushed towards the junction Reverse bias forces the minority carriers

together and a small current - called leakage current - results

Diodes which are designed with adequate power dissipation

capability to operate in the breakdown region are none as Zener diodes

Two mechanisms of diode breakdown for increasing reverse voltage are

recognized In one mechanism the thermally generated electrons and

holes acquire sufficient energy from the applied potential to produce new

carriers by removing valence electrons from their bonds These new

carriers in turn produce additional carriers again through the process of

disrupting bonds This cumulative process is referred to as avalanche

breakdown Even if the initially available carriers do not acquire sufficient

energy to disrupt bonds it is possible to initiate breakdown through a

direct rupture of the bonds because of the existence of strong electric field

Under these conditions the breakdown is referred to as Zener breakdown

Date____________

Pag

e36

Zener breakdown occurs below 6 V Zener diodes are commonly used in

voltage-reference or constant-voltage devices

Characteristic curves of diode

Fig 14 shows V-I Characteristic curves for typical p-n junction diode

It is seen that the curve is not linear With 0 V across the diode the diode

will not conduct the diode will not begin to conduct until a few tenths of a

volt are applied across it This is the voltage needed to overcome the

potential barrier It requires about 02 V to turn on a germanium diode and

about 06 V to turn on a silicon diode Fig 18 also shows what happens

when reverse bias is applied to a diode At increasing levels of reverse

voltage the curve shows some reverse current This leakage current is

caused by minority carries It is usually very small

Graph

Fig-14

Date____________

Pag

e37

Observation Table for Forward bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Date____________

Pag

e38

Observation Table for Reverse bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e39

Calculation for Forward bias 119877 = 119881

119868

Calculation for Reverse bias 119877 = 119881

119868

Date____________

Pag

e40

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e41

Zener Diode Reverse Bias Characteristics Experiment - 10

Aim To study the reverse bias characteristics of a Zener diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components Zener diode Resistors

Circuit Diagram

Procedure

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Theory

A diode which is heavily doped (Si or Ge) and which operates in the

reverse breakdown region with a sharp breakdown voltage is called a zener

diode The schematic symbol of a zener diode is shown in Fig-1 This is

similar to a normal diode except that the line (bar) representing the

cathode is bent at both ends like the letter Z for zener diode

Date____________

Pag

e42

A C Fig-1

In a simple diode the doping is light as a result the breakdown

voltage is high and not sharp But if doping is made heavy the depletion

layer becomes very narrow and even the breakdown voltage gets reduced

to a sharp value The zener diode is designed to operate in the breakdown

region without damage

The reverse breakdown of a zener diode may occur either due to

zener effect or avalanche effect But zener diode primarily depends on

zener effect for its working When the electric field across the junction is

sufficiently high due to the applied voltage the zener breakdown occurs

because of breaking of covalent bonds This produces a large number of

electrons and holes which constitute a steep rise in the reverse saturation

current (also called zener current 119868Z) This effect is called as zener effect

Zener current is independent of the applied voltage and depends only on

the external resistance

The V - 119868 characteristic of a zener diode is shown in Fig-2 The

forward characteristic is simply that of an ordinary forward biased junction

diode

Fig-2

Date____________

Pag

e43

Under reverse bias condition breakdown of junction occurs This

breakdown depends upon the amount of doping It can be seen from Fig-2

that as the reverse voltage is increased the reverse current remains

negligibly small up to the lsquokneersquo of the curve

At this lsquoknee pointrsquo the effect of breakdown process begins The

voltage corresponding to the lsquoknee pointrsquo in the figure is called the zener

breakdown voltage or simply zener voltage (VZ) which is very sharp

compared to a simle p-n junction diode Beyond this voltage the reverse

current (119868Z) increases sharply to a high value

The zener diode is not immediately burnt just because it has entered

the breakdown region As long as the external resistance connected to the

diode in the circuit limits the diode current to less than the burn out value

the diode will not burn out The zener voltage VZ remains constant even

when zener current 119868Z increases greatly This ability of a diode is called

regulating ability and it enables us to use zener diode for voltage

regulation

Date____________

Pag

e44

Observation Table

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e45

Graph 119868 V

Calculations 119877 = 119881

119868

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e46

Dispersive Power of The Prism Experiment - 11

Aim To find the dispersive power (D) of the prism by using spectrometer

Apparatus Mercury vapor lamp Spectrometer Prism

Procedure

Levelling and alignment of collimator and telescope

1 Switch on the mercury lamp Adjust the leveling screws on the chassis

Keep the spirit level on the chassis and do finer adjustments of these

screws to bring the bubble in the sprit level to the centre Repeat this

placing the sprit level along a direction perpendicular to the earlier

direction

2 Repeat this procedure for the prism table

3 Close the slit at the other end of the collimator using the drum screw DS1

Open it to a reasonable width Place the spectrometer in front of the

mercury lamp window and rotate the collimator so that the slit faces of

window View the slit through the telescope If it is not in the centre of the

view level collimator and the telescope so as to bring it to the centre

Setting the prism in the minimum deviation position

1 Rotate the prism table such that lines ruled on the table become

perpendicular to the axis of collimator

2 Place prism over the prism table such that its rough surface BA is

perpendicular to the line on prism table (See Fig-1(a))

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e10

Observation Table

Lens Type Measured Focal Length (cm)

1 2 3 4 5 Mean

Convex fg =_______

Combination f = _______

Calculations

(1) Least count of spherometerhellip

=Distance between two consecutive devisions on main scale

Total number of devisions on circular scale

(2) Radius of curvature hellip 119877 =1198862

6119893+

119893

2

(3) Focal length of a combination lens ( 119891 ) 1

119891=

1

119891119892+

1

119891119897

Date ___________

Pag

e11

(4) Refractive index of a given liquid ( η ) 1

119891119897= minus 120578 minus 1

1

119877

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e12

Deflection of Magnetometer Experiment - 04

Aim To find the magnetic moment (M) of given magnet by magnetometer (From

two different position Gauss-A and Gauss-B of magnetometer) Also obtain

the pole strength (m) of the magnet

Apparatus Magnetometer Magnet

Procedure

First set the magnetometer in Gauss-A position and then put the

magnet at a distance d on the arm of the magnetometer as shown in fig-1

Distance d should be selected in such a way that magnetometer show a

deflection between 30˚ and 60˚ Now note down the deflection shown by

the magnetometer as θ1 and θ2 then reverse the direction of the poles of

the magnet and note down the deflection as θ3 and θ4 Now put the magnet

on the opposite arm and repeat the experiment in a similar way and note

down the deflections as θ5 θ6 θ7 and θ8 Now calculate Magnetic

moment and Pole strength

Now set the magnetometer in Gauss-B position and repeat the

experiment in a similar way

Theory

The Magnetic moment is a measure of the strength of the magnet

Its unit is Gausscm3 For a magnet of Pole strength lsquomrsquo and length 2119897 the

magnetic moment M=2m119897 and points from the South Pole to the North

Pole of the magnet

Gauss-A Position of Magnetometer

Date ___________

Pag

e13

Gauss-B Position of Magnetometer

Observations

(1) Magnetic field intensity of the earthhellip H = 036 Gauss

(2) Magnetic length of the magnethellip 2119897 = 5L6 = __________ cm

119897 = ___________cm

Where L = Geometric length of the magnet = __________ cm

Observation Table for Gauss-A Position

Sr No

Distance d (cm)

Deflection of Magnetometer Avg

θ

tanθ

Magnetic Moment

M = (119837120784minus119897120784)120784

120784119837 H tanθ

θ1 θ2 θ3 θ4 θ5 θ6 θ7 θ8

1

2

Date ___________

Pag

e14

Observation Table for Gauss-B Position

Sr No

Distance d (cm)

Deflection of Magnetometer Avg

θ

tanθ

Magnetic Moment

M = (119837120784+119897120784)120785120784Htanθ

θ1 θ2 θ3 θ4 θ5 θ6 θ7 θ8

1

2

Calculations

(1) Magnetic Moments for Gauss-A position

(2) Magnetic Moments for Gauss-B Position

(1) MA = (119837120784minus119897120784)120784

120784119837 H tanθ

(2) MB = (119837120784+119897120784) 120785120784 H tanθ

(i)

(i)

(ii) (iii)

Date ___________

Pag

e15

(1) 119872119860119886119907119892 =119872119860 1+119872119860 2

2

(2) 119872119861119886119907119892 =119872119861 1+119872119861 2

2

(3) Pole Strength of the magnethellip m = M2119897

(For both Gauss-A amp Gauss-B Positions)

For Gauss-A For Gauss-B

119898119860 =119872119860119886119907119892

2119897

119898119861 =119872119861119886119907119892

2119897

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e16

Friction Experiment - 05

Aim To determine the coefficient of kinetic friction between plane and block

Apparatus Inclined plane Block Scale pan String Set of weights Scale

Procedure

Take the inclined plane and set an angle of inclination θ1 Now put the block

on the inclined plane and put some weight in the scale pan in such a way that

block moves up along the inclined plane with a constant speed Now measure the

height length and base of the inclined plane for that angle and calculate the

Coefficient of kinetic friction

Now repeat the experiment for the angles θ2 and θ3

Theory

When a force F tends to slide a body along a surface a frictional force from

the surface acts on the body The frictional force is parallel to the surface and

directed so as to oppose the sliding It is due to bonding between the body and

the surface

If the body does not slide the frictional force is a static frictional force fs If

there is sliding the frictional force is a kinetic (dynamic) frictional force fk If the

body is rolling then the frictional force is known as rolling frictional force fr

Three properties of friction

(1) If the body does not move then the static frictional force fs and the

component of F that is parallel to the surface are equal in magnitudes

and fs is directed opposite that component If that parallel component

increases magnitude fs also increases

(2) The magnitude of fs has a maximum value fsmax that is given by

fsmax = microsN Where micros is the coefficient of static friction and N is the

magnitude of the normal reaction If the component of F that is parallel

to the surface exceeds fsmax then the body slides on the surface

Date ___________

Pag

e17

(3) If the body begins to slide on the surface the magnitude of the frictional

force rapidly decreases to a constant value fk given by fk = microk N Where

microk is the coefficient of kinetic friction

The magnitude of the coefficients of frictions relative to each other is

given by micros gt microk gtgt micror Where micror is coefficient of rolling friction

Note Here quantities shown bold are vector quantities

Observations

(1) Weight of the blockhellip M = ________ gm

(2) Weight of the scale panhellip m1 = _______ gm

(3) Gravitational accelerationhellip g = 980 cms2

Observation Table

Sr

No

Inclination

of the

Plane (θ)

Effort required to start

the motion up (gm)

m=m1+m2

Avg Effort

m (gm)

Base of

the

Plane

b (cm)

Height

of the

Plane

h (cm)

Length

of the

Plane

l (cm)

cosθ=bl

sinθ=hl

Coefficient of

Kinetic Friction

μ = 119846119840 ndash 119820119840 119852119842119847 120521

119820119840 119836119848119852 120521

1

θ1 1

2

2

θ2 1

2

3

θ3 1

2

Here m2 = the weight put in the scale pan

Page18

Calculation

Coefficient of Kinetic Friction μ = mg ndash Mg sin θMg cos θ

(1) (2)

(3)

Average of Coefficient of Kinetic Friction

μ avg = μ 1 + μ 2 + μ 3

3

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Page19

Date____________

Pag

e20

Wattage of Bulb Experiment - 06

Aim To find the electrical energy consumed in a circuit (bulb)

Apparatus AC Ammeter(0-500 mA) AC Voltmeter(0-250 volt) Variac

Components Bulb

Circuit Diagram

Procedure

Connect the circuit as shown in the circuit diagram Now switch ON

the circuit and note down the reading shown by ammeter at 0 volt then

increase the voltage from 0 to 10 volt and note down the reading of

ammeter Now increase the voltage in order of 10 volts (up to 200 volts)

and note down the readings of the current shown by the ammeter Now

calculate the power consumed in a circuit at different stages

Theory

Experiments show that in stationary metallic conductors current does

work to increase their internal energy The heated conductor releases the

energy received to the surrounding bodies but this is done by means of

heat transfer This means that the quantity of heat released by a current

carrying conductor is equal to the total work done by the current

Date____________

Pag

e21

As we know that the work done by the current is given by 119830 = 119829119816119853helliphelliphelliphelliphelliphellip(1)

119830 = 119816120784119825119853 ( V = IR) helliphelliphelliphelliphelliphelliphellip (2)

The electrical power of a given device is simply the rate of doing

work or the amount of electric work done in one second

Therefore electric powerhellip

119823 =119830119848119851119844 119837119848119847119838 (119830)

119827119842119846119838 (119853)

119823 =119829119816119853

119853= 119829119816 helliphelliphelliphelliphelliphelliphellip (3)

Thus electric power is equal to the product of voltage by current

Watt is a unit of power Hence it can be expressed in terms of a volt

and an ampere by the formula for electric power Eqn (3)

Therefore

1 Watt = 1 volt ∙ 1 ampere

1 W = 1 V∙A

Thus if a potential difference of 1 volt causes a current of 1 ampere

to flow through a conductor (here a bulb) the electric power consumed is

1 watt and the electrical energy consumed is 1 joulesec this electrical

energy consumed in the bulb is converted into heat and light energy

Date____________

Pag

e22

Observation Table

Sr No Voltage V (volt) Current 119816 (mA) Power

119823 = 119829119816 (watt)

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

Date____________

Pag

e23

Calculation 119823 = 119829119816

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e24

Temperature of Tungsten Filament Experiment ndash 07

Aim To find the temperature of the tungsten filament of the bulb

Apparatus AC Ammeter(0-500 mA) AC Voltmeter(0-250 volt) Variac

Components Bulb

Circuit Diagram

Procedure

Connect the circuit as shown in the circuit diagram Now switch ON

the circuit and note down the reading shown by ammeter at 0 volt then

increase the voltage from 0 to 10 volt and note down the reading of

ammeter Now increase the voltage in order of 10 volts (up to 100 volts)

and note down the readings of the current shown by the ammeter Now

calculate the resistance and the temperature of the filament

Observations

(1) Room temperaturehellip t0 = _______ ˚C

(2) Resistance of the filament of the bulb at room temperaturehellip

R0 = _______ Ω

(3) Temperature coefficient of tungstenhellip α = 45times10-4 ˚C-1

Date____________

Pag

e25

Observation Table

Sr No Voltage V

(volt)

Current 119816

(mA)

Resistance of

The Filament

119825119853 =119829

119816 Ω

Temperature of The Filament

119853 =120783

120514[

119825119853

119825120782 120783 + 120514119853120782 minus 120783] ˚C

1

2

3

4

5

6

7

8

9

10

Graph Rt versus t

Date____________

Pag

e26

Calculations

(1) Resistance of The Filament Rt =V

I Ω

(2) Temperature of The Filament t =1

α[

Rt

R0 1 + αt0 minus 1] ˚C

Date____________

Pag

e27

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e28

Meldersquos Experiment - 08

Aim To find the frequency of the wave and the frequency of the tuning fork by

Meldersquos experiment

Apparatus Meldersquos experiment apparatus

Circuit Diagram

Transverse mode

Procedure

Set Meldersquos experiment apparatus as shown in circuit diagram in

longitudinal position and switch ON the power supply put some weight in

scale pan and adjust the length of the string in such a way that you find

some loops on the string (eg 2 loops) Now rotate the apparatus by 90˚ so

that it is set for lsquoBrsquo position for the same values of weight in pan and for

the same length of the string the number of loops created in lsquoBrsquo position

are double (eg 4 loops) than in lsquoArsquo position Note down these readings in

observation table Repeat the experiment for other values of weight in

scale pan

Date____________

Pag

e29

Theory

This is an easy and efficient method by which nodes and antinodes

formed on a string can be demonstrated

A tuning fork is fitted in a wooden block A long string or thread of

cotton is taken One end of this string is tied to one of the prongs of the

tuning fork and the second end of this string passes over a smooth pulley in

such a way that a small pan can be hang on it Small weights are put in the

pan to create tension in the string This arrangement is shown in the circuit

diagram

The fork is set into vibrations by lightly hitting the prong of the tuning

fork on which the string is not tied or by connecting an electric supply as

shown in the circuit diagram Thus the transverse vibrations are produced

in the string and by adjusting the length andor weights in the pan these

vibrations are reflected from the point of contact between the string and

the pulley and a number of loops appear on the string as shown in the

circuit diagram

When the prongs of the tuning fork vibrate in a plane parallel to the

direction of propagation of the waves it is called lsquoArsquo position or

longitudinal position

If the tuning fork along with the wooden block is rotated through

90˚ so that the plane of vibration of the tuning fork is normal (ie at right

angles) to the direction of propagation it is called lsquoBrsquo position or transverse

position

For the same length and same weight in the pan (ie for the same

tension) the number of loops in lsquoBrsquo position is double than in lsquoArsquo position

Thus either in lsquoArsquo position or in lsquoBrsquo position standing transverse

waves are generated in the string with a series of nodes and antinodes at

equal distances

The equation connecting number of loops (n or nrsquo) length of the

string (l) tension in the string (T) mass per unit length of the string (m) and

frequency of the string (f) is as follows

Date____________

Pag

e30

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position)

119943prime =119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

If the frequency of tuning fork is F then for lsquoArsquo position 119839 =119813

120784 and for lsquoBrsquo

position 119839prime = 119813

In the above equations if all the quantities on the RHS are known the

frequency of the tuning fork 119813 can be calculated

Observations

(1) Gravitational accelerationhellip g = 98 ms2

(2) Mass per unit length of the stringhellip m = _______ kgm

(3) Mass of the scale panhellip M1 = _______ kg

Observation Table

Sr

No

Total mass

suspended at

the end of the

stringhellip

M=M1+M2

(kg)

Tension

created

in the

stringhellip

T=Mg (N)

Length of the

vibrating string

Average

lengthhellip

119949 (m)

No of loops created on

the stringhellip

Frequency of the

vibrating stringhellip

Relation

between

f and frsquo 1199491 (m) 1199492 (m)

In

Longitudinal

Modehellip

n

In

Transverse

Modehellip

nrsquo

In

Longitudinal

Modehellip

119943 =119951

120784119949

119931

119950

In

Transverse

Modehellip

119943prime =119951prime

120784119949

119931

119950

1

2

3

4

Here M2 = the weight put in the scale pan

Page31

Date____________

Pag

e32

Calculations

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position) 119943prime =

119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e33

P-N Junction Diode Characteristics Experiment - 09

Aim To study the Forward and Reverse bias characteristics of a P-N junction

diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components P-N junction diode Resistors

Circuit Diagram

(Forward biased PN diode) (Reverse biased PN diode)

Procedure

For Forward Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 01 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 02 03 04hellip

volts and repeat the procedure Note down the knee voltage and

corresponding current in your observation table

For Reverse Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Date____________

Pag

e34

Theory

If donor (pentavalent) impurities are introduced on one side and

acceptors (trivalent) on the opposite side of a single crystal of an intrinsic

semiconductor like germanium or silicon a p-n junction is formed as shown

in Fig 11 In the figure a donor ion is indicated schematically by a plus sign

because after this impurity atom donates an electron it becomes a positive

ion

The acceptor ion is indicated by a minus sign because after this atom

accepts an electron it becomes a negative ion Initially there are only n-

type carriers to the right of the junction and only p-type carriers to the left

Because there is a density gradient across the junction holes will diffuse to

the right across the junction and electrons to the left As a result of the

displacement of these charges an electric field appears across the junction

Equilibrium is established when the field becomes large enough to restrain

the process of diffusion The positive holes which neutralize the acceptor

ions near the junction in p-type germanium disappear as a result of

combination with electrons which diffuse across the junction Similarly the

neutralizing electrons on the n side of the junction combine with holes

which cross the junction from the p side Since the region of the junction is

depleted of mobile charges it is called the depletion region or a potential

barrier

Forward Bias

An external voltage applied to the p-n junction with the polarity

shown in Fig 12 is known as forward bias The height of the potential

barrier at the junction is lowered by the applied forward voltage In other

words we can say that p-n junction diode is connected to an external

Date____________

Pag

e35

battery in such a way that depletion region is reduced in size or eliminated

altogether Which of these takes place is determined by the size of the

applied voltage The positive terminal of the battery repels the holes on the

p-side and pushes them towards the junction The negative terminal of the

battery repels the electrons and pushes them towards the junction This

collapses the depletion region With the depletion region gone the diode

can conduct

Reverse Bias

An external voltage applied with polarity in Fig 13 is called reverse

bias When reverse bias is applied to a junction diode the depletion region

does not collapse On the contrary it becomes wider The positive side of

battery is applied to the n-type material This attracts the free electrons

away from the junction The negative side of the battery attracts the holes

in p-type material away from the junction This makes the depletion region

wider than it was when no voltage is applied The depletion region is an

insulator and it will block the flow of current Actually a small current will

flow because of minority carriers The p-type material has a few minority

electrons These are pushed to the junction by the repulsion of the negative

side of the battery The n-type material has few minority holes These are

also pushed towards the junction Reverse bias forces the minority carriers

together and a small current - called leakage current - results

Diodes which are designed with adequate power dissipation

capability to operate in the breakdown region are none as Zener diodes

Two mechanisms of diode breakdown for increasing reverse voltage are

recognized In one mechanism the thermally generated electrons and

holes acquire sufficient energy from the applied potential to produce new

carriers by removing valence electrons from their bonds These new

carriers in turn produce additional carriers again through the process of

disrupting bonds This cumulative process is referred to as avalanche

breakdown Even if the initially available carriers do not acquire sufficient

energy to disrupt bonds it is possible to initiate breakdown through a

direct rupture of the bonds because of the existence of strong electric field

Under these conditions the breakdown is referred to as Zener breakdown

Date____________

Pag

e36

Zener breakdown occurs below 6 V Zener diodes are commonly used in

voltage-reference or constant-voltage devices

Characteristic curves of diode

Fig 14 shows V-I Characteristic curves for typical p-n junction diode

It is seen that the curve is not linear With 0 V across the diode the diode

will not conduct the diode will not begin to conduct until a few tenths of a

volt are applied across it This is the voltage needed to overcome the

potential barrier It requires about 02 V to turn on a germanium diode and

about 06 V to turn on a silicon diode Fig 18 also shows what happens

when reverse bias is applied to a diode At increasing levels of reverse

voltage the curve shows some reverse current This leakage current is

caused by minority carries It is usually very small

Graph

Fig-14

Date____________

Pag

e37

Observation Table for Forward bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Date____________

Pag

e38

Observation Table for Reverse bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e39

Calculation for Forward bias 119877 = 119881

119868

Calculation for Reverse bias 119877 = 119881

119868

Date____________

Pag

e40

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e41

Zener Diode Reverse Bias Characteristics Experiment - 10

Aim To study the reverse bias characteristics of a Zener diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components Zener diode Resistors

Circuit Diagram

Procedure

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Theory

A diode which is heavily doped (Si or Ge) and which operates in the

reverse breakdown region with a sharp breakdown voltage is called a zener

diode The schematic symbol of a zener diode is shown in Fig-1 This is

similar to a normal diode except that the line (bar) representing the

cathode is bent at both ends like the letter Z for zener diode

Date____________

Pag

e42

A C Fig-1

In a simple diode the doping is light as a result the breakdown

voltage is high and not sharp But if doping is made heavy the depletion

layer becomes very narrow and even the breakdown voltage gets reduced

to a sharp value The zener diode is designed to operate in the breakdown

region without damage

The reverse breakdown of a zener diode may occur either due to

zener effect or avalanche effect But zener diode primarily depends on

zener effect for its working When the electric field across the junction is

sufficiently high due to the applied voltage the zener breakdown occurs

because of breaking of covalent bonds This produces a large number of

electrons and holes which constitute a steep rise in the reverse saturation

current (also called zener current 119868Z) This effect is called as zener effect

Zener current is independent of the applied voltage and depends only on

the external resistance

The V - 119868 characteristic of a zener diode is shown in Fig-2 The

forward characteristic is simply that of an ordinary forward biased junction

diode

Fig-2

Date____________

Pag

e43

Under reverse bias condition breakdown of junction occurs This

breakdown depends upon the amount of doping It can be seen from Fig-2

that as the reverse voltage is increased the reverse current remains

negligibly small up to the lsquokneersquo of the curve

At this lsquoknee pointrsquo the effect of breakdown process begins The

voltage corresponding to the lsquoknee pointrsquo in the figure is called the zener

breakdown voltage or simply zener voltage (VZ) which is very sharp

compared to a simle p-n junction diode Beyond this voltage the reverse

current (119868Z) increases sharply to a high value

The zener diode is not immediately burnt just because it has entered

the breakdown region As long as the external resistance connected to the

diode in the circuit limits the diode current to less than the burn out value

the diode will not burn out The zener voltage VZ remains constant even

when zener current 119868Z increases greatly This ability of a diode is called

regulating ability and it enables us to use zener diode for voltage

regulation

Date____________

Pag

e44

Observation Table

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e45

Graph 119868 V

Calculations 119877 = 119881

119868

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e46

Dispersive Power of The Prism Experiment - 11

Aim To find the dispersive power (D) of the prism by using spectrometer

Apparatus Mercury vapor lamp Spectrometer Prism

Procedure

Levelling and alignment of collimator and telescope

1 Switch on the mercury lamp Adjust the leveling screws on the chassis

Keep the spirit level on the chassis and do finer adjustments of these

screws to bring the bubble in the sprit level to the centre Repeat this

placing the sprit level along a direction perpendicular to the earlier

direction

2 Repeat this procedure for the prism table

3 Close the slit at the other end of the collimator using the drum screw DS1

Open it to a reasonable width Place the spectrometer in front of the

mercury lamp window and rotate the collimator so that the slit faces of

window View the slit through the telescope If it is not in the centre of the

view level collimator and the telescope so as to bring it to the centre

Setting the prism in the minimum deviation position

1 Rotate the prism table such that lines ruled on the table become

perpendicular to the axis of collimator

2 Place prism over the prism table such that its rough surface BA is

perpendicular to the line on prism table (See Fig-1(a))

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e11

(4) Refractive index of a given liquid ( η ) 1

119891119897= minus 120578 minus 1

1

119877

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e12

Deflection of Magnetometer Experiment - 04

Aim To find the magnetic moment (M) of given magnet by magnetometer (From

two different position Gauss-A and Gauss-B of magnetometer) Also obtain

the pole strength (m) of the magnet

Apparatus Magnetometer Magnet

Procedure

First set the magnetometer in Gauss-A position and then put the

magnet at a distance d on the arm of the magnetometer as shown in fig-1

Distance d should be selected in such a way that magnetometer show a

deflection between 30˚ and 60˚ Now note down the deflection shown by

the magnetometer as θ1 and θ2 then reverse the direction of the poles of

the magnet and note down the deflection as θ3 and θ4 Now put the magnet

on the opposite arm and repeat the experiment in a similar way and note

down the deflections as θ5 θ6 θ7 and θ8 Now calculate Magnetic

moment and Pole strength

Now set the magnetometer in Gauss-B position and repeat the

experiment in a similar way

Theory

The Magnetic moment is a measure of the strength of the magnet

Its unit is Gausscm3 For a magnet of Pole strength lsquomrsquo and length 2119897 the

magnetic moment M=2m119897 and points from the South Pole to the North

Pole of the magnet

Gauss-A Position of Magnetometer

Date ___________

Pag

e13

Gauss-B Position of Magnetometer

Observations

(1) Magnetic field intensity of the earthhellip H = 036 Gauss

(2) Magnetic length of the magnethellip 2119897 = 5L6 = __________ cm

119897 = ___________cm

Where L = Geometric length of the magnet = __________ cm

Observation Table for Gauss-A Position

Sr No

Distance d (cm)

Deflection of Magnetometer Avg

θ

tanθ

Magnetic Moment

M = (119837120784minus119897120784)120784

120784119837 H tanθ

θ1 θ2 θ3 θ4 θ5 θ6 θ7 θ8

1

2

Date ___________

Pag

e14

Observation Table for Gauss-B Position

Sr No

Distance d (cm)

Deflection of Magnetometer Avg

θ

tanθ

Magnetic Moment

M = (119837120784+119897120784)120785120784Htanθ

θ1 θ2 θ3 θ4 θ5 θ6 θ7 θ8

1

2

Calculations

(1) Magnetic Moments for Gauss-A position

(2) Magnetic Moments for Gauss-B Position

(1) MA = (119837120784minus119897120784)120784

120784119837 H tanθ

(2) MB = (119837120784+119897120784) 120785120784 H tanθ

(i)

(i)

(ii) (iii)

Date ___________

Pag

e15

(1) 119872119860119886119907119892 =119872119860 1+119872119860 2

2

(2) 119872119861119886119907119892 =119872119861 1+119872119861 2

2

(3) Pole Strength of the magnethellip m = M2119897

(For both Gauss-A amp Gauss-B Positions)

For Gauss-A For Gauss-B

119898119860 =119872119860119886119907119892

2119897

119898119861 =119872119861119886119907119892

2119897

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e16

Friction Experiment - 05

Aim To determine the coefficient of kinetic friction between plane and block

Apparatus Inclined plane Block Scale pan String Set of weights Scale

Procedure

Take the inclined plane and set an angle of inclination θ1 Now put the block

on the inclined plane and put some weight in the scale pan in such a way that

block moves up along the inclined plane with a constant speed Now measure the

height length and base of the inclined plane for that angle and calculate the

Coefficient of kinetic friction

Now repeat the experiment for the angles θ2 and θ3

Theory

When a force F tends to slide a body along a surface a frictional force from

the surface acts on the body The frictional force is parallel to the surface and

directed so as to oppose the sliding It is due to bonding between the body and

the surface

If the body does not slide the frictional force is a static frictional force fs If

there is sliding the frictional force is a kinetic (dynamic) frictional force fk If the

body is rolling then the frictional force is known as rolling frictional force fr

Three properties of friction

(1) If the body does not move then the static frictional force fs and the

component of F that is parallel to the surface are equal in magnitudes

and fs is directed opposite that component If that parallel component

increases magnitude fs also increases

(2) The magnitude of fs has a maximum value fsmax that is given by

fsmax = microsN Where micros is the coefficient of static friction and N is the

magnitude of the normal reaction If the component of F that is parallel

to the surface exceeds fsmax then the body slides on the surface

Date ___________

Pag

e17

(3) If the body begins to slide on the surface the magnitude of the frictional

force rapidly decreases to a constant value fk given by fk = microk N Where

microk is the coefficient of kinetic friction

The magnitude of the coefficients of frictions relative to each other is

given by micros gt microk gtgt micror Where micror is coefficient of rolling friction

Note Here quantities shown bold are vector quantities

Observations

(1) Weight of the blockhellip M = ________ gm

(2) Weight of the scale panhellip m1 = _______ gm

(3) Gravitational accelerationhellip g = 980 cms2

Observation Table

Sr

No

Inclination

of the

Plane (θ)

Effort required to start

the motion up (gm)

m=m1+m2

Avg Effort

m (gm)

Base of

the

Plane

b (cm)

Height

of the

Plane

h (cm)

Length

of the

Plane

l (cm)

cosθ=bl

sinθ=hl

Coefficient of

Kinetic Friction

μ = 119846119840 ndash 119820119840 119852119842119847 120521

119820119840 119836119848119852 120521

1

θ1 1

2

2

θ2 1

2

3

θ3 1

2

Here m2 = the weight put in the scale pan

Page18

Calculation

Coefficient of Kinetic Friction μ = mg ndash Mg sin θMg cos θ

(1) (2)

(3)

Average of Coefficient of Kinetic Friction

μ avg = μ 1 + μ 2 + μ 3

3

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Page19

Date____________

Pag

e20

Wattage of Bulb Experiment - 06

Aim To find the electrical energy consumed in a circuit (bulb)

Apparatus AC Ammeter(0-500 mA) AC Voltmeter(0-250 volt) Variac

Components Bulb

Circuit Diagram

Procedure

Connect the circuit as shown in the circuit diagram Now switch ON

the circuit and note down the reading shown by ammeter at 0 volt then

increase the voltage from 0 to 10 volt and note down the reading of

ammeter Now increase the voltage in order of 10 volts (up to 200 volts)

and note down the readings of the current shown by the ammeter Now

calculate the power consumed in a circuit at different stages

Theory

Experiments show that in stationary metallic conductors current does

work to increase their internal energy The heated conductor releases the

energy received to the surrounding bodies but this is done by means of

heat transfer This means that the quantity of heat released by a current

carrying conductor is equal to the total work done by the current

Date____________

Pag

e21

As we know that the work done by the current is given by 119830 = 119829119816119853helliphelliphelliphelliphelliphellip(1)

119830 = 119816120784119825119853 ( V = IR) helliphelliphelliphelliphelliphelliphellip (2)

The electrical power of a given device is simply the rate of doing

work or the amount of electric work done in one second

Therefore electric powerhellip

119823 =119830119848119851119844 119837119848119847119838 (119830)

119827119842119846119838 (119853)

119823 =119829119816119853

119853= 119829119816 helliphelliphelliphelliphelliphelliphellip (3)

Thus electric power is equal to the product of voltage by current

Watt is a unit of power Hence it can be expressed in terms of a volt

and an ampere by the formula for electric power Eqn (3)

Therefore

1 Watt = 1 volt ∙ 1 ampere

1 W = 1 V∙A

Thus if a potential difference of 1 volt causes a current of 1 ampere

to flow through a conductor (here a bulb) the electric power consumed is

1 watt and the electrical energy consumed is 1 joulesec this electrical

energy consumed in the bulb is converted into heat and light energy

Date____________

Pag

e22

Observation Table

Sr No Voltage V (volt) Current 119816 (mA) Power

119823 = 119829119816 (watt)

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

Date____________

Pag

e23

Calculation 119823 = 119829119816

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e24

Temperature of Tungsten Filament Experiment ndash 07

Aim To find the temperature of the tungsten filament of the bulb

Apparatus AC Ammeter(0-500 mA) AC Voltmeter(0-250 volt) Variac

Components Bulb

Circuit Diagram

Procedure

Connect the circuit as shown in the circuit diagram Now switch ON

the circuit and note down the reading shown by ammeter at 0 volt then

increase the voltage from 0 to 10 volt and note down the reading of

ammeter Now increase the voltage in order of 10 volts (up to 100 volts)

and note down the readings of the current shown by the ammeter Now

calculate the resistance and the temperature of the filament

Observations

(1) Room temperaturehellip t0 = _______ ˚C

(2) Resistance of the filament of the bulb at room temperaturehellip

R0 = _______ Ω

(3) Temperature coefficient of tungstenhellip α = 45times10-4 ˚C-1

Date____________

Pag

e25

Observation Table

Sr No Voltage V

(volt)

Current 119816

(mA)

Resistance of

The Filament

119825119853 =119829

119816 Ω

Temperature of The Filament

119853 =120783

120514[

119825119853

119825120782 120783 + 120514119853120782 minus 120783] ˚C

1

2

3

4

5

6

7

8

9

10

Graph Rt versus t

Date____________

Pag

e26

Calculations

(1) Resistance of The Filament Rt =V

I Ω

(2) Temperature of The Filament t =1

α[

Rt

R0 1 + αt0 minus 1] ˚C

Date____________

Pag

e27

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e28

Meldersquos Experiment - 08

Aim To find the frequency of the wave and the frequency of the tuning fork by

Meldersquos experiment

Apparatus Meldersquos experiment apparatus

Circuit Diagram

Transverse mode

Procedure

Set Meldersquos experiment apparatus as shown in circuit diagram in

longitudinal position and switch ON the power supply put some weight in

scale pan and adjust the length of the string in such a way that you find

some loops on the string (eg 2 loops) Now rotate the apparatus by 90˚ so

that it is set for lsquoBrsquo position for the same values of weight in pan and for

the same length of the string the number of loops created in lsquoBrsquo position

are double (eg 4 loops) than in lsquoArsquo position Note down these readings in

observation table Repeat the experiment for other values of weight in

scale pan

Date____________

Pag

e29

Theory

This is an easy and efficient method by which nodes and antinodes

formed on a string can be demonstrated

A tuning fork is fitted in a wooden block A long string or thread of

cotton is taken One end of this string is tied to one of the prongs of the

tuning fork and the second end of this string passes over a smooth pulley in

such a way that a small pan can be hang on it Small weights are put in the

pan to create tension in the string This arrangement is shown in the circuit

diagram

The fork is set into vibrations by lightly hitting the prong of the tuning

fork on which the string is not tied or by connecting an electric supply as

shown in the circuit diagram Thus the transverse vibrations are produced

in the string and by adjusting the length andor weights in the pan these

vibrations are reflected from the point of contact between the string and

the pulley and a number of loops appear on the string as shown in the

circuit diagram

When the prongs of the tuning fork vibrate in a plane parallel to the

direction of propagation of the waves it is called lsquoArsquo position or

longitudinal position

If the tuning fork along with the wooden block is rotated through

90˚ so that the plane of vibration of the tuning fork is normal (ie at right

angles) to the direction of propagation it is called lsquoBrsquo position or transverse

position

For the same length and same weight in the pan (ie for the same

tension) the number of loops in lsquoBrsquo position is double than in lsquoArsquo position

Thus either in lsquoArsquo position or in lsquoBrsquo position standing transverse

waves are generated in the string with a series of nodes and antinodes at

equal distances

The equation connecting number of loops (n or nrsquo) length of the

string (l) tension in the string (T) mass per unit length of the string (m) and

frequency of the string (f) is as follows

Date____________

Pag

e30

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position)

119943prime =119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

If the frequency of tuning fork is F then for lsquoArsquo position 119839 =119813

120784 and for lsquoBrsquo

position 119839prime = 119813

In the above equations if all the quantities on the RHS are known the

frequency of the tuning fork 119813 can be calculated

Observations

(1) Gravitational accelerationhellip g = 98 ms2

(2) Mass per unit length of the stringhellip m = _______ kgm

(3) Mass of the scale panhellip M1 = _______ kg

Observation Table

Sr

No

Total mass

suspended at

the end of the

stringhellip

M=M1+M2

(kg)

Tension

created

in the

stringhellip

T=Mg (N)

Length of the

vibrating string

Average

lengthhellip

119949 (m)

No of loops created on

the stringhellip

Frequency of the

vibrating stringhellip

Relation

between

f and frsquo 1199491 (m) 1199492 (m)

In

Longitudinal

Modehellip

n

In

Transverse

Modehellip

nrsquo

In

Longitudinal

Modehellip

119943 =119951

120784119949

119931

119950

In

Transverse

Modehellip

119943prime =119951prime

120784119949

119931

119950

1

2

3

4

Here M2 = the weight put in the scale pan

Page31

Date____________

Pag

e32

Calculations

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position) 119943prime =

119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e33

P-N Junction Diode Characteristics Experiment - 09

Aim To study the Forward and Reverse bias characteristics of a P-N junction

diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components P-N junction diode Resistors

Circuit Diagram

(Forward biased PN diode) (Reverse biased PN diode)

Procedure

For Forward Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 01 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 02 03 04hellip

volts and repeat the procedure Note down the knee voltage and

corresponding current in your observation table

For Reverse Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Date____________

Pag

e34

Theory

If donor (pentavalent) impurities are introduced on one side and

acceptors (trivalent) on the opposite side of a single crystal of an intrinsic

semiconductor like germanium or silicon a p-n junction is formed as shown

in Fig 11 In the figure a donor ion is indicated schematically by a plus sign

because after this impurity atom donates an electron it becomes a positive

ion

The acceptor ion is indicated by a minus sign because after this atom

accepts an electron it becomes a negative ion Initially there are only n-

type carriers to the right of the junction and only p-type carriers to the left

Because there is a density gradient across the junction holes will diffuse to

the right across the junction and electrons to the left As a result of the

displacement of these charges an electric field appears across the junction

Equilibrium is established when the field becomes large enough to restrain

the process of diffusion The positive holes which neutralize the acceptor

ions near the junction in p-type germanium disappear as a result of

combination with electrons which diffuse across the junction Similarly the

neutralizing electrons on the n side of the junction combine with holes

which cross the junction from the p side Since the region of the junction is

depleted of mobile charges it is called the depletion region or a potential

barrier

Forward Bias

An external voltage applied to the p-n junction with the polarity

shown in Fig 12 is known as forward bias The height of the potential

barrier at the junction is lowered by the applied forward voltage In other

words we can say that p-n junction diode is connected to an external

Date____________

Pag

e35

battery in such a way that depletion region is reduced in size or eliminated

altogether Which of these takes place is determined by the size of the

applied voltage The positive terminal of the battery repels the holes on the

p-side and pushes them towards the junction The negative terminal of the

battery repels the electrons and pushes them towards the junction This

collapses the depletion region With the depletion region gone the diode

can conduct

Reverse Bias

An external voltage applied with polarity in Fig 13 is called reverse

bias When reverse bias is applied to a junction diode the depletion region

does not collapse On the contrary it becomes wider The positive side of

battery is applied to the n-type material This attracts the free electrons

away from the junction The negative side of the battery attracts the holes

in p-type material away from the junction This makes the depletion region

wider than it was when no voltage is applied The depletion region is an

insulator and it will block the flow of current Actually a small current will

flow because of minority carriers The p-type material has a few minority

electrons These are pushed to the junction by the repulsion of the negative

side of the battery The n-type material has few minority holes These are

also pushed towards the junction Reverse bias forces the minority carriers

together and a small current - called leakage current - results

Diodes which are designed with adequate power dissipation

capability to operate in the breakdown region are none as Zener diodes

Two mechanisms of diode breakdown for increasing reverse voltage are

recognized In one mechanism the thermally generated electrons and

holes acquire sufficient energy from the applied potential to produce new

carriers by removing valence electrons from their bonds These new

carriers in turn produce additional carriers again through the process of

disrupting bonds This cumulative process is referred to as avalanche

breakdown Even if the initially available carriers do not acquire sufficient

energy to disrupt bonds it is possible to initiate breakdown through a

direct rupture of the bonds because of the existence of strong electric field

Under these conditions the breakdown is referred to as Zener breakdown

Date____________

Pag

e36

Zener breakdown occurs below 6 V Zener diodes are commonly used in

voltage-reference or constant-voltage devices

Characteristic curves of diode

Fig 14 shows V-I Characteristic curves for typical p-n junction diode

It is seen that the curve is not linear With 0 V across the diode the diode

will not conduct the diode will not begin to conduct until a few tenths of a

volt are applied across it This is the voltage needed to overcome the

potential barrier It requires about 02 V to turn on a germanium diode and

about 06 V to turn on a silicon diode Fig 18 also shows what happens

when reverse bias is applied to a diode At increasing levels of reverse

voltage the curve shows some reverse current This leakage current is

caused by minority carries It is usually very small

Graph

Fig-14

Date____________

Pag

e37

Observation Table for Forward bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Date____________

Pag

e38

Observation Table for Reverse bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e39

Calculation for Forward bias 119877 = 119881

119868

Calculation for Reverse bias 119877 = 119881

119868

Date____________

Pag

e40

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e41

Zener Diode Reverse Bias Characteristics Experiment - 10

Aim To study the reverse bias characteristics of a Zener diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components Zener diode Resistors

Circuit Diagram

Procedure

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Theory

A diode which is heavily doped (Si or Ge) and which operates in the

reverse breakdown region with a sharp breakdown voltage is called a zener

diode The schematic symbol of a zener diode is shown in Fig-1 This is

similar to a normal diode except that the line (bar) representing the

cathode is bent at both ends like the letter Z for zener diode

Date____________

Pag

e42

A C Fig-1

In a simple diode the doping is light as a result the breakdown

voltage is high and not sharp But if doping is made heavy the depletion

layer becomes very narrow and even the breakdown voltage gets reduced

to a sharp value The zener diode is designed to operate in the breakdown

region without damage

The reverse breakdown of a zener diode may occur either due to

zener effect or avalanche effect But zener diode primarily depends on

zener effect for its working When the electric field across the junction is

sufficiently high due to the applied voltage the zener breakdown occurs

because of breaking of covalent bonds This produces a large number of

electrons and holes which constitute a steep rise in the reverse saturation

current (also called zener current 119868Z) This effect is called as zener effect

Zener current is independent of the applied voltage and depends only on

the external resistance

The V - 119868 characteristic of a zener diode is shown in Fig-2 The

forward characteristic is simply that of an ordinary forward biased junction

diode

Fig-2

Date____________

Pag

e43

Under reverse bias condition breakdown of junction occurs This

breakdown depends upon the amount of doping It can be seen from Fig-2

that as the reverse voltage is increased the reverse current remains

negligibly small up to the lsquokneersquo of the curve

At this lsquoknee pointrsquo the effect of breakdown process begins The

voltage corresponding to the lsquoknee pointrsquo in the figure is called the zener

breakdown voltage or simply zener voltage (VZ) which is very sharp

compared to a simle p-n junction diode Beyond this voltage the reverse

current (119868Z) increases sharply to a high value

The zener diode is not immediately burnt just because it has entered

the breakdown region As long as the external resistance connected to the

diode in the circuit limits the diode current to less than the burn out value

the diode will not burn out The zener voltage VZ remains constant even

when zener current 119868Z increases greatly This ability of a diode is called

regulating ability and it enables us to use zener diode for voltage

regulation

Date____________

Pag

e44

Observation Table

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e45

Graph 119868 V

Calculations 119877 = 119881

119868

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e46

Dispersive Power of The Prism Experiment - 11

Aim To find the dispersive power (D) of the prism by using spectrometer

Apparatus Mercury vapor lamp Spectrometer Prism

Procedure

Levelling and alignment of collimator and telescope

1 Switch on the mercury lamp Adjust the leveling screws on the chassis

Keep the spirit level on the chassis and do finer adjustments of these

screws to bring the bubble in the sprit level to the centre Repeat this

placing the sprit level along a direction perpendicular to the earlier

direction

2 Repeat this procedure for the prism table

3 Close the slit at the other end of the collimator using the drum screw DS1

Open it to a reasonable width Place the spectrometer in front of the

mercury lamp window and rotate the collimator so that the slit faces of

window View the slit through the telescope If it is not in the centre of the

view level collimator and the telescope so as to bring it to the centre

Setting the prism in the minimum deviation position

1 Rotate the prism table such that lines ruled on the table become

perpendicular to the axis of collimator

2 Place prism over the prism table such that its rough surface BA is

perpendicular to the line on prism table (See Fig-1(a))

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e12

Deflection of Magnetometer Experiment - 04

Aim To find the magnetic moment (M) of given magnet by magnetometer (From

two different position Gauss-A and Gauss-B of magnetometer) Also obtain

the pole strength (m) of the magnet

Apparatus Magnetometer Magnet

Procedure

First set the magnetometer in Gauss-A position and then put the

magnet at a distance d on the arm of the magnetometer as shown in fig-1

Distance d should be selected in such a way that magnetometer show a

deflection between 30˚ and 60˚ Now note down the deflection shown by

the magnetometer as θ1 and θ2 then reverse the direction of the poles of

the magnet and note down the deflection as θ3 and θ4 Now put the magnet

on the opposite arm and repeat the experiment in a similar way and note

down the deflections as θ5 θ6 θ7 and θ8 Now calculate Magnetic

moment and Pole strength

Now set the magnetometer in Gauss-B position and repeat the

experiment in a similar way

Theory

The Magnetic moment is a measure of the strength of the magnet

Its unit is Gausscm3 For a magnet of Pole strength lsquomrsquo and length 2119897 the

magnetic moment M=2m119897 and points from the South Pole to the North

Pole of the magnet

Gauss-A Position of Magnetometer

Date ___________

Pag

e13

Gauss-B Position of Magnetometer

Observations

(1) Magnetic field intensity of the earthhellip H = 036 Gauss

(2) Magnetic length of the magnethellip 2119897 = 5L6 = __________ cm

119897 = ___________cm

Where L = Geometric length of the magnet = __________ cm

Observation Table for Gauss-A Position

Sr No

Distance d (cm)

Deflection of Magnetometer Avg

θ

tanθ

Magnetic Moment

M = (119837120784minus119897120784)120784

120784119837 H tanθ

θ1 θ2 θ3 θ4 θ5 θ6 θ7 θ8

1

2

Date ___________

Pag

e14

Observation Table for Gauss-B Position

Sr No

Distance d (cm)

Deflection of Magnetometer Avg

θ

tanθ

Magnetic Moment

M = (119837120784+119897120784)120785120784Htanθ

θ1 θ2 θ3 θ4 θ5 θ6 θ7 θ8

1

2

Calculations

(1) Magnetic Moments for Gauss-A position

(2) Magnetic Moments for Gauss-B Position

(1) MA = (119837120784minus119897120784)120784

120784119837 H tanθ

(2) MB = (119837120784+119897120784) 120785120784 H tanθ

(i)

(i)

(ii) (iii)

Date ___________

Pag

e15

(1) 119872119860119886119907119892 =119872119860 1+119872119860 2

2

(2) 119872119861119886119907119892 =119872119861 1+119872119861 2

2

(3) Pole Strength of the magnethellip m = M2119897

(For both Gauss-A amp Gauss-B Positions)

For Gauss-A For Gauss-B

119898119860 =119872119860119886119907119892

2119897

119898119861 =119872119861119886119907119892

2119897

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e16

Friction Experiment - 05

Aim To determine the coefficient of kinetic friction between plane and block

Apparatus Inclined plane Block Scale pan String Set of weights Scale

Procedure

Take the inclined plane and set an angle of inclination θ1 Now put the block

on the inclined plane and put some weight in the scale pan in such a way that

block moves up along the inclined plane with a constant speed Now measure the

height length and base of the inclined plane for that angle and calculate the

Coefficient of kinetic friction

Now repeat the experiment for the angles θ2 and θ3

Theory

When a force F tends to slide a body along a surface a frictional force from

the surface acts on the body The frictional force is parallel to the surface and

directed so as to oppose the sliding It is due to bonding between the body and

the surface

If the body does not slide the frictional force is a static frictional force fs If

there is sliding the frictional force is a kinetic (dynamic) frictional force fk If the

body is rolling then the frictional force is known as rolling frictional force fr

Three properties of friction

(1) If the body does not move then the static frictional force fs and the

component of F that is parallel to the surface are equal in magnitudes

and fs is directed opposite that component If that parallel component

increases magnitude fs also increases

(2) The magnitude of fs has a maximum value fsmax that is given by

fsmax = microsN Where micros is the coefficient of static friction and N is the

magnitude of the normal reaction If the component of F that is parallel

to the surface exceeds fsmax then the body slides on the surface

Date ___________

Pag

e17

(3) If the body begins to slide on the surface the magnitude of the frictional

force rapidly decreases to a constant value fk given by fk = microk N Where

microk is the coefficient of kinetic friction

The magnitude of the coefficients of frictions relative to each other is

given by micros gt microk gtgt micror Where micror is coefficient of rolling friction

Note Here quantities shown bold are vector quantities

Observations

(1) Weight of the blockhellip M = ________ gm

(2) Weight of the scale panhellip m1 = _______ gm

(3) Gravitational accelerationhellip g = 980 cms2

Observation Table

Sr

No

Inclination

of the

Plane (θ)

Effort required to start

the motion up (gm)

m=m1+m2

Avg Effort

m (gm)

Base of

the

Plane

b (cm)

Height

of the

Plane

h (cm)

Length

of the

Plane

l (cm)

cosθ=bl

sinθ=hl

Coefficient of

Kinetic Friction

μ = 119846119840 ndash 119820119840 119852119842119847 120521

119820119840 119836119848119852 120521

1

θ1 1

2

2

θ2 1

2

3

θ3 1

2

Here m2 = the weight put in the scale pan

Page18

Calculation

Coefficient of Kinetic Friction μ = mg ndash Mg sin θMg cos θ

(1) (2)

(3)

Average of Coefficient of Kinetic Friction

μ avg = μ 1 + μ 2 + μ 3

3

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Page19

Date____________

Pag

e20

Wattage of Bulb Experiment - 06

Aim To find the electrical energy consumed in a circuit (bulb)

Apparatus AC Ammeter(0-500 mA) AC Voltmeter(0-250 volt) Variac

Components Bulb

Circuit Diagram

Procedure

Connect the circuit as shown in the circuit diagram Now switch ON

the circuit and note down the reading shown by ammeter at 0 volt then

increase the voltage from 0 to 10 volt and note down the reading of

ammeter Now increase the voltage in order of 10 volts (up to 200 volts)

and note down the readings of the current shown by the ammeter Now

calculate the power consumed in a circuit at different stages

Theory

Experiments show that in stationary metallic conductors current does

work to increase their internal energy The heated conductor releases the

energy received to the surrounding bodies but this is done by means of

heat transfer This means that the quantity of heat released by a current

carrying conductor is equal to the total work done by the current

Date____________

Pag

e21

As we know that the work done by the current is given by 119830 = 119829119816119853helliphelliphelliphelliphelliphellip(1)

119830 = 119816120784119825119853 ( V = IR) helliphelliphelliphelliphelliphelliphellip (2)

The electrical power of a given device is simply the rate of doing

work or the amount of electric work done in one second

Therefore electric powerhellip

119823 =119830119848119851119844 119837119848119847119838 (119830)

119827119842119846119838 (119853)

119823 =119829119816119853

119853= 119829119816 helliphelliphelliphelliphelliphelliphellip (3)

Thus electric power is equal to the product of voltage by current

Watt is a unit of power Hence it can be expressed in terms of a volt

and an ampere by the formula for electric power Eqn (3)

Therefore

1 Watt = 1 volt ∙ 1 ampere

1 W = 1 V∙A

Thus if a potential difference of 1 volt causes a current of 1 ampere

to flow through a conductor (here a bulb) the electric power consumed is

1 watt and the electrical energy consumed is 1 joulesec this electrical

energy consumed in the bulb is converted into heat and light energy

Date____________

Pag

e22

Observation Table

Sr No Voltage V (volt) Current 119816 (mA) Power

119823 = 119829119816 (watt)

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

Date____________

Pag

e23

Calculation 119823 = 119829119816

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e24

Temperature of Tungsten Filament Experiment ndash 07

Aim To find the temperature of the tungsten filament of the bulb

Apparatus AC Ammeter(0-500 mA) AC Voltmeter(0-250 volt) Variac

Components Bulb

Circuit Diagram

Procedure

Connect the circuit as shown in the circuit diagram Now switch ON

the circuit and note down the reading shown by ammeter at 0 volt then

increase the voltage from 0 to 10 volt and note down the reading of

ammeter Now increase the voltage in order of 10 volts (up to 100 volts)

and note down the readings of the current shown by the ammeter Now

calculate the resistance and the temperature of the filament

Observations

(1) Room temperaturehellip t0 = _______ ˚C

(2) Resistance of the filament of the bulb at room temperaturehellip

R0 = _______ Ω

(3) Temperature coefficient of tungstenhellip α = 45times10-4 ˚C-1

Date____________

Pag

e25

Observation Table

Sr No Voltage V

(volt)

Current 119816

(mA)

Resistance of

The Filament

119825119853 =119829

119816 Ω

Temperature of The Filament

119853 =120783

120514[

119825119853

119825120782 120783 + 120514119853120782 minus 120783] ˚C

1

2

3

4

5

6

7

8

9

10

Graph Rt versus t

Date____________

Pag

e26

Calculations

(1) Resistance of The Filament Rt =V

I Ω

(2) Temperature of The Filament t =1

α[

Rt

R0 1 + αt0 minus 1] ˚C

Date____________

Pag

e27

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e28

Meldersquos Experiment - 08

Aim To find the frequency of the wave and the frequency of the tuning fork by

Meldersquos experiment

Apparatus Meldersquos experiment apparatus

Circuit Diagram

Transverse mode

Procedure

Set Meldersquos experiment apparatus as shown in circuit diagram in

longitudinal position and switch ON the power supply put some weight in

scale pan and adjust the length of the string in such a way that you find

some loops on the string (eg 2 loops) Now rotate the apparatus by 90˚ so

that it is set for lsquoBrsquo position for the same values of weight in pan and for

the same length of the string the number of loops created in lsquoBrsquo position

are double (eg 4 loops) than in lsquoArsquo position Note down these readings in

observation table Repeat the experiment for other values of weight in

scale pan

Date____________

Pag

e29

Theory

This is an easy and efficient method by which nodes and antinodes

formed on a string can be demonstrated

A tuning fork is fitted in a wooden block A long string or thread of

cotton is taken One end of this string is tied to one of the prongs of the

tuning fork and the second end of this string passes over a smooth pulley in

such a way that a small pan can be hang on it Small weights are put in the

pan to create tension in the string This arrangement is shown in the circuit

diagram

The fork is set into vibrations by lightly hitting the prong of the tuning

fork on which the string is not tied or by connecting an electric supply as

shown in the circuit diagram Thus the transverse vibrations are produced

in the string and by adjusting the length andor weights in the pan these

vibrations are reflected from the point of contact between the string and

the pulley and a number of loops appear on the string as shown in the

circuit diagram

When the prongs of the tuning fork vibrate in a plane parallel to the

direction of propagation of the waves it is called lsquoArsquo position or

longitudinal position

If the tuning fork along with the wooden block is rotated through

90˚ so that the plane of vibration of the tuning fork is normal (ie at right

angles) to the direction of propagation it is called lsquoBrsquo position or transverse

position

For the same length and same weight in the pan (ie for the same

tension) the number of loops in lsquoBrsquo position is double than in lsquoArsquo position

Thus either in lsquoArsquo position or in lsquoBrsquo position standing transverse

waves are generated in the string with a series of nodes and antinodes at

equal distances

The equation connecting number of loops (n or nrsquo) length of the

string (l) tension in the string (T) mass per unit length of the string (m) and

frequency of the string (f) is as follows

Date____________

Pag

e30

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position)

119943prime =119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

If the frequency of tuning fork is F then for lsquoArsquo position 119839 =119813

120784 and for lsquoBrsquo

position 119839prime = 119813

In the above equations if all the quantities on the RHS are known the

frequency of the tuning fork 119813 can be calculated

Observations

(1) Gravitational accelerationhellip g = 98 ms2

(2) Mass per unit length of the stringhellip m = _______ kgm

(3) Mass of the scale panhellip M1 = _______ kg

Observation Table

Sr

No

Total mass

suspended at

the end of the

stringhellip

M=M1+M2

(kg)

Tension

created

in the

stringhellip

T=Mg (N)

Length of the

vibrating string

Average

lengthhellip

119949 (m)

No of loops created on

the stringhellip

Frequency of the

vibrating stringhellip

Relation

between

f and frsquo 1199491 (m) 1199492 (m)

In

Longitudinal

Modehellip

n

In

Transverse

Modehellip

nrsquo

In

Longitudinal

Modehellip

119943 =119951

120784119949

119931

119950

In

Transverse

Modehellip

119943prime =119951prime

120784119949

119931

119950

1

2

3

4

Here M2 = the weight put in the scale pan

Page31

Date____________

Pag

e32

Calculations

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position) 119943prime =

119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e33

P-N Junction Diode Characteristics Experiment - 09

Aim To study the Forward and Reverse bias characteristics of a P-N junction

diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components P-N junction diode Resistors

Circuit Diagram

(Forward biased PN diode) (Reverse biased PN diode)

Procedure

For Forward Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 01 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 02 03 04hellip

volts and repeat the procedure Note down the knee voltage and

corresponding current in your observation table

For Reverse Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Date____________

Pag

e34

Theory

If donor (pentavalent) impurities are introduced on one side and

acceptors (trivalent) on the opposite side of a single crystal of an intrinsic

semiconductor like germanium or silicon a p-n junction is formed as shown

in Fig 11 In the figure a donor ion is indicated schematically by a plus sign

because after this impurity atom donates an electron it becomes a positive

ion

The acceptor ion is indicated by a minus sign because after this atom

accepts an electron it becomes a negative ion Initially there are only n-

type carriers to the right of the junction and only p-type carriers to the left

Because there is a density gradient across the junction holes will diffuse to

the right across the junction and electrons to the left As a result of the

displacement of these charges an electric field appears across the junction

Equilibrium is established when the field becomes large enough to restrain

the process of diffusion The positive holes which neutralize the acceptor

ions near the junction in p-type germanium disappear as a result of

combination with electrons which diffuse across the junction Similarly the

neutralizing electrons on the n side of the junction combine with holes

which cross the junction from the p side Since the region of the junction is

depleted of mobile charges it is called the depletion region or a potential

barrier

Forward Bias

An external voltage applied to the p-n junction with the polarity

shown in Fig 12 is known as forward bias The height of the potential

barrier at the junction is lowered by the applied forward voltage In other

words we can say that p-n junction diode is connected to an external

Date____________

Pag

e35

battery in such a way that depletion region is reduced in size or eliminated

altogether Which of these takes place is determined by the size of the

applied voltage The positive terminal of the battery repels the holes on the

p-side and pushes them towards the junction The negative terminal of the

battery repels the electrons and pushes them towards the junction This

collapses the depletion region With the depletion region gone the diode

can conduct

Reverse Bias

An external voltage applied with polarity in Fig 13 is called reverse

bias When reverse bias is applied to a junction diode the depletion region

does not collapse On the contrary it becomes wider The positive side of

battery is applied to the n-type material This attracts the free electrons

away from the junction The negative side of the battery attracts the holes

in p-type material away from the junction This makes the depletion region

wider than it was when no voltage is applied The depletion region is an

insulator and it will block the flow of current Actually a small current will

flow because of minority carriers The p-type material has a few minority

electrons These are pushed to the junction by the repulsion of the negative

side of the battery The n-type material has few minority holes These are

also pushed towards the junction Reverse bias forces the minority carriers

together and a small current - called leakage current - results

Diodes which are designed with adequate power dissipation

capability to operate in the breakdown region are none as Zener diodes

Two mechanisms of diode breakdown for increasing reverse voltage are

recognized In one mechanism the thermally generated electrons and

holes acquire sufficient energy from the applied potential to produce new

carriers by removing valence electrons from their bonds These new

carriers in turn produce additional carriers again through the process of

disrupting bonds This cumulative process is referred to as avalanche

breakdown Even if the initially available carriers do not acquire sufficient

energy to disrupt bonds it is possible to initiate breakdown through a

direct rupture of the bonds because of the existence of strong electric field

Under these conditions the breakdown is referred to as Zener breakdown

Date____________

Pag

e36

Zener breakdown occurs below 6 V Zener diodes are commonly used in

voltage-reference or constant-voltage devices

Characteristic curves of diode

Fig 14 shows V-I Characteristic curves for typical p-n junction diode

It is seen that the curve is not linear With 0 V across the diode the diode

will not conduct the diode will not begin to conduct until a few tenths of a

volt are applied across it This is the voltage needed to overcome the

potential barrier It requires about 02 V to turn on a germanium diode and

about 06 V to turn on a silicon diode Fig 18 also shows what happens

when reverse bias is applied to a diode At increasing levels of reverse

voltage the curve shows some reverse current This leakage current is

caused by minority carries It is usually very small

Graph

Fig-14

Date____________

Pag

e37

Observation Table for Forward bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Date____________

Pag

e38

Observation Table for Reverse bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e39

Calculation for Forward bias 119877 = 119881

119868

Calculation for Reverse bias 119877 = 119881

119868

Date____________

Pag

e40

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e41

Zener Diode Reverse Bias Characteristics Experiment - 10

Aim To study the reverse bias characteristics of a Zener diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components Zener diode Resistors

Circuit Diagram

Procedure

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Theory

A diode which is heavily doped (Si or Ge) and which operates in the

reverse breakdown region with a sharp breakdown voltage is called a zener

diode The schematic symbol of a zener diode is shown in Fig-1 This is

similar to a normal diode except that the line (bar) representing the

cathode is bent at both ends like the letter Z for zener diode

Date____________

Pag

e42

A C Fig-1

In a simple diode the doping is light as a result the breakdown

voltage is high and not sharp But if doping is made heavy the depletion

layer becomes very narrow and even the breakdown voltage gets reduced

to a sharp value The zener diode is designed to operate in the breakdown

region without damage

The reverse breakdown of a zener diode may occur either due to

zener effect or avalanche effect But zener diode primarily depends on

zener effect for its working When the electric field across the junction is

sufficiently high due to the applied voltage the zener breakdown occurs

because of breaking of covalent bonds This produces a large number of

electrons and holes which constitute a steep rise in the reverse saturation

current (also called zener current 119868Z) This effect is called as zener effect

Zener current is independent of the applied voltage and depends only on

the external resistance

The V - 119868 characteristic of a zener diode is shown in Fig-2 The

forward characteristic is simply that of an ordinary forward biased junction

diode

Fig-2

Date____________

Pag

e43

Under reverse bias condition breakdown of junction occurs This

breakdown depends upon the amount of doping It can be seen from Fig-2

that as the reverse voltage is increased the reverse current remains

negligibly small up to the lsquokneersquo of the curve

At this lsquoknee pointrsquo the effect of breakdown process begins The

voltage corresponding to the lsquoknee pointrsquo in the figure is called the zener

breakdown voltage or simply zener voltage (VZ) which is very sharp

compared to a simle p-n junction diode Beyond this voltage the reverse

current (119868Z) increases sharply to a high value

The zener diode is not immediately burnt just because it has entered

the breakdown region As long as the external resistance connected to the

diode in the circuit limits the diode current to less than the burn out value

the diode will not burn out The zener voltage VZ remains constant even

when zener current 119868Z increases greatly This ability of a diode is called

regulating ability and it enables us to use zener diode for voltage

regulation

Date____________

Pag

e44

Observation Table

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e45

Graph 119868 V

Calculations 119877 = 119881

119868

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e46

Dispersive Power of The Prism Experiment - 11

Aim To find the dispersive power (D) of the prism by using spectrometer

Apparatus Mercury vapor lamp Spectrometer Prism

Procedure

Levelling and alignment of collimator and telescope

1 Switch on the mercury lamp Adjust the leveling screws on the chassis

Keep the spirit level on the chassis and do finer adjustments of these

screws to bring the bubble in the sprit level to the centre Repeat this

placing the sprit level along a direction perpendicular to the earlier

direction

2 Repeat this procedure for the prism table

3 Close the slit at the other end of the collimator using the drum screw DS1

Open it to a reasonable width Place the spectrometer in front of the

mercury lamp window and rotate the collimator so that the slit faces of

window View the slit through the telescope If it is not in the centre of the

view level collimator and the telescope so as to bring it to the centre

Setting the prism in the minimum deviation position

1 Rotate the prism table such that lines ruled on the table become

perpendicular to the axis of collimator

2 Place prism over the prism table such that its rough surface BA is

perpendicular to the line on prism table (See Fig-1(a))

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e13

Gauss-B Position of Magnetometer

Observations

(1) Magnetic field intensity of the earthhellip H = 036 Gauss

(2) Magnetic length of the magnethellip 2119897 = 5L6 = __________ cm

119897 = ___________cm

Where L = Geometric length of the magnet = __________ cm

Observation Table for Gauss-A Position

Sr No

Distance d (cm)

Deflection of Magnetometer Avg

θ

tanθ

Magnetic Moment

M = (119837120784minus119897120784)120784

120784119837 H tanθ

θ1 θ2 θ3 θ4 θ5 θ6 θ7 θ8

1

2

Date ___________

Pag

e14

Observation Table for Gauss-B Position

Sr No

Distance d (cm)

Deflection of Magnetometer Avg

θ

tanθ

Magnetic Moment

M = (119837120784+119897120784)120785120784Htanθ

θ1 θ2 θ3 θ4 θ5 θ6 θ7 θ8

1

2

Calculations

(1) Magnetic Moments for Gauss-A position

(2) Magnetic Moments for Gauss-B Position

(1) MA = (119837120784minus119897120784)120784

120784119837 H tanθ

(2) MB = (119837120784+119897120784) 120785120784 H tanθ

(i)

(i)

(ii) (iii)

Date ___________

Pag

e15

(1) 119872119860119886119907119892 =119872119860 1+119872119860 2

2

(2) 119872119861119886119907119892 =119872119861 1+119872119861 2

2

(3) Pole Strength of the magnethellip m = M2119897

(For both Gauss-A amp Gauss-B Positions)

For Gauss-A For Gauss-B

119898119860 =119872119860119886119907119892

2119897

119898119861 =119872119861119886119907119892

2119897

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e16

Friction Experiment - 05

Aim To determine the coefficient of kinetic friction between plane and block

Apparatus Inclined plane Block Scale pan String Set of weights Scale

Procedure

Take the inclined plane and set an angle of inclination θ1 Now put the block

on the inclined plane and put some weight in the scale pan in such a way that

block moves up along the inclined plane with a constant speed Now measure the

height length and base of the inclined plane for that angle and calculate the

Coefficient of kinetic friction

Now repeat the experiment for the angles θ2 and θ3

Theory

When a force F tends to slide a body along a surface a frictional force from

the surface acts on the body The frictional force is parallel to the surface and

directed so as to oppose the sliding It is due to bonding between the body and

the surface

If the body does not slide the frictional force is a static frictional force fs If

there is sliding the frictional force is a kinetic (dynamic) frictional force fk If the

body is rolling then the frictional force is known as rolling frictional force fr

Three properties of friction

(1) If the body does not move then the static frictional force fs and the

component of F that is parallel to the surface are equal in magnitudes

and fs is directed opposite that component If that parallel component

increases magnitude fs also increases

(2) The magnitude of fs has a maximum value fsmax that is given by

fsmax = microsN Where micros is the coefficient of static friction and N is the

magnitude of the normal reaction If the component of F that is parallel

to the surface exceeds fsmax then the body slides on the surface

Date ___________

Pag

e17

(3) If the body begins to slide on the surface the magnitude of the frictional

force rapidly decreases to a constant value fk given by fk = microk N Where

microk is the coefficient of kinetic friction

The magnitude of the coefficients of frictions relative to each other is

given by micros gt microk gtgt micror Where micror is coefficient of rolling friction

Note Here quantities shown bold are vector quantities

Observations

(1) Weight of the blockhellip M = ________ gm

(2) Weight of the scale panhellip m1 = _______ gm

(3) Gravitational accelerationhellip g = 980 cms2

Observation Table

Sr

No

Inclination

of the

Plane (θ)

Effort required to start

the motion up (gm)

m=m1+m2

Avg Effort

m (gm)

Base of

the

Plane

b (cm)

Height

of the

Plane

h (cm)

Length

of the

Plane

l (cm)

cosθ=bl

sinθ=hl

Coefficient of

Kinetic Friction

μ = 119846119840 ndash 119820119840 119852119842119847 120521

119820119840 119836119848119852 120521

1

θ1 1

2

2

θ2 1

2

3

θ3 1

2

Here m2 = the weight put in the scale pan

Page18

Calculation

Coefficient of Kinetic Friction μ = mg ndash Mg sin θMg cos θ

(1) (2)

(3)

Average of Coefficient of Kinetic Friction

μ avg = μ 1 + μ 2 + μ 3

3

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Page19

Date____________

Pag

e20

Wattage of Bulb Experiment - 06

Aim To find the electrical energy consumed in a circuit (bulb)

Apparatus AC Ammeter(0-500 mA) AC Voltmeter(0-250 volt) Variac

Components Bulb

Circuit Diagram

Procedure

Connect the circuit as shown in the circuit diagram Now switch ON

the circuit and note down the reading shown by ammeter at 0 volt then

increase the voltage from 0 to 10 volt and note down the reading of

ammeter Now increase the voltage in order of 10 volts (up to 200 volts)

and note down the readings of the current shown by the ammeter Now

calculate the power consumed in a circuit at different stages

Theory

Experiments show that in stationary metallic conductors current does

work to increase their internal energy The heated conductor releases the

energy received to the surrounding bodies but this is done by means of

heat transfer This means that the quantity of heat released by a current

carrying conductor is equal to the total work done by the current

Date____________

Pag

e21

As we know that the work done by the current is given by 119830 = 119829119816119853helliphelliphelliphelliphelliphellip(1)

119830 = 119816120784119825119853 ( V = IR) helliphelliphelliphelliphelliphelliphellip (2)

The electrical power of a given device is simply the rate of doing

work or the amount of electric work done in one second

Therefore electric powerhellip

119823 =119830119848119851119844 119837119848119847119838 (119830)

119827119842119846119838 (119853)

119823 =119829119816119853

119853= 119829119816 helliphelliphelliphelliphelliphelliphellip (3)

Thus electric power is equal to the product of voltage by current

Watt is a unit of power Hence it can be expressed in terms of a volt

and an ampere by the formula for electric power Eqn (3)

Therefore

1 Watt = 1 volt ∙ 1 ampere

1 W = 1 V∙A

Thus if a potential difference of 1 volt causes a current of 1 ampere

to flow through a conductor (here a bulb) the electric power consumed is

1 watt and the electrical energy consumed is 1 joulesec this electrical

energy consumed in the bulb is converted into heat and light energy

Date____________

Pag

e22

Observation Table

Sr No Voltage V (volt) Current 119816 (mA) Power

119823 = 119829119816 (watt)

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

Date____________

Pag

e23

Calculation 119823 = 119829119816

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e24

Temperature of Tungsten Filament Experiment ndash 07

Aim To find the temperature of the tungsten filament of the bulb

Apparatus AC Ammeter(0-500 mA) AC Voltmeter(0-250 volt) Variac

Components Bulb

Circuit Diagram

Procedure

Connect the circuit as shown in the circuit diagram Now switch ON

the circuit and note down the reading shown by ammeter at 0 volt then

increase the voltage from 0 to 10 volt and note down the reading of

ammeter Now increase the voltage in order of 10 volts (up to 100 volts)

and note down the readings of the current shown by the ammeter Now

calculate the resistance and the temperature of the filament

Observations

(1) Room temperaturehellip t0 = _______ ˚C

(2) Resistance of the filament of the bulb at room temperaturehellip

R0 = _______ Ω

(3) Temperature coefficient of tungstenhellip α = 45times10-4 ˚C-1

Date____________

Pag

e25

Observation Table

Sr No Voltage V

(volt)

Current 119816

(mA)

Resistance of

The Filament

119825119853 =119829

119816 Ω

Temperature of The Filament

119853 =120783

120514[

119825119853

119825120782 120783 + 120514119853120782 minus 120783] ˚C

1

2

3

4

5

6

7

8

9

10

Graph Rt versus t

Date____________

Pag

e26

Calculations

(1) Resistance of The Filament Rt =V

I Ω

(2) Temperature of The Filament t =1

α[

Rt

R0 1 + αt0 minus 1] ˚C

Date____________

Pag

e27

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e28

Meldersquos Experiment - 08

Aim To find the frequency of the wave and the frequency of the tuning fork by

Meldersquos experiment

Apparatus Meldersquos experiment apparatus

Circuit Diagram

Transverse mode

Procedure

Set Meldersquos experiment apparatus as shown in circuit diagram in

longitudinal position and switch ON the power supply put some weight in

scale pan and adjust the length of the string in such a way that you find

some loops on the string (eg 2 loops) Now rotate the apparatus by 90˚ so

that it is set for lsquoBrsquo position for the same values of weight in pan and for

the same length of the string the number of loops created in lsquoBrsquo position

are double (eg 4 loops) than in lsquoArsquo position Note down these readings in

observation table Repeat the experiment for other values of weight in

scale pan

Date____________

Pag

e29

Theory

This is an easy and efficient method by which nodes and antinodes

formed on a string can be demonstrated

A tuning fork is fitted in a wooden block A long string or thread of

cotton is taken One end of this string is tied to one of the prongs of the

tuning fork and the second end of this string passes over a smooth pulley in

such a way that a small pan can be hang on it Small weights are put in the

pan to create tension in the string This arrangement is shown in the circuit

diagram

The fork is set into vibrations by lightly hitting the prong of the tuning

fork on which the string is not tied or by connecting an electric supply as

shown in the circuit diagram Thus the transverse vibrations are produced

in the string and by adjusting the length andor weights in the pan these

vibrations are reflected from the point of contact between the string and

the pulley and a number of loops appear on the string as shown in the

circuit diagram

When the prongs of the tuning fork vibrate in a plane parallel to the

direction of propagation of the waves it is called lsquoArsquo position or

longitudinal position

If the tuning fork along with the wooden block is rotated through

90˚ so that the plane of vibration of the tuning fork is normal (ie at right

angles) to the direction of propagation it is called lsquoBrsquo position or transverse

position

For the same length and same weight in the pan (ie for the same

tension) the number of loops in lsquoBrsquo position is double than in lsquoArsquo position

Thus either in lsquoArsquo position or in lsquoBrsquo position standing transverse

waves are generated in the string with a series of nodes and antinodes at

equal distances

The equation connecting number of loops (n or nrsquo) length of the

string (l) tension in the string (T) mass per unit length of the string (m) and

frequency of the string (f) is as follows

Date____________

Pag

e30

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position)

119943prime =119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

If the frequency of tuning fork is F then for lsquoArsquo position 119839 =119813

120784 and for lsquoBrsquo

position 119839prime = 119813

In the above equations if all the quantities on the RHS are known the

frequency of the tuning fork 119813 can be calculated

Observations

(1) Gravitational accelerationhellip g = 98 ms2

(2) Mass per unit length of the stringhellip m = _______ kgm

(3) Mass of the scale panhellip M1 = _______ kg

Observation Table

Sr

No

Total mass

suspended at

the end of the

stringhellip

M=M1+M2

(kg)

Tension

created

in the

stringhellip

T=Mg (N)

Length of the

vibrating string

Average

lengthhellip

119949 (m)

No of loops created on

the stringhellip

Frequency of the

vibrating stringhellip

Relation

between

f and frsquo 1199491 (m) 1199492 (m)

In

Longitudinal

Modehellip

n

In

Transverse

Modehellip

nrsquo

In

Longitudinal

Modehellip

119943 =119951

120784119949

119931

119950

In

Transverse

Modehellip

119943prime =119951prime

120784119949

119931

119950

1

2

3

4

Here M2 = the weight put in the scale pan

Page31

Date____________

Pag

e32

Calculations

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position) 119943prime =

119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e33

P-N Junction Diode Characteristics Experiment - 09

Aim To study the Forward and Reverse bias characteristics of a P-N junction

diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components P-N junction diode Resistors

Circuit Diagram

(Forward biased PN diode) (Reverse biased PN diode)

Procedure

For Forward Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 01 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 02 03 04hellip

volts and repeat the procedure Note down the knee voltage and

corresponding current in your observation table

For Reverse Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Date____________

Pag

e34

Theory

If donor (pentavalent) impurities are introduced on one side and

acceptors (trivalent) on the opposite side of a single crystal of an intrinsic

semiconductor like germanium or silicon a p-n junction is formed as shown

in Fig 11 In the figure a donor ion is indicated schematically by a plus sign

because after this impurity atom donates an electron it becomes a positive

ion

The acceptor ion is indicated by a minus sign because after this atom

accepts an electron it becomes a negative ion Initially there are only n-

type carriers to the right of the junction and only p-type carriers to the left

Because there is a density gradient across the junction holes will diffuse to

the right across the junction and electrons to the left As a result of the

displacement of these charges an electric field appears across the junction

Equilibrium is established when the field becomes large enough to restrain

the process of diffusion The positive holes which neutralize the acceptor

ions near the junction in p-type germanium disappear as a result of

combination with electrons which diffuse across the junction Similarly the

neutralizing electrons on the n side of the junction combine with holes

which cross the junction from the p side Since the region of the junction is

depleted of mobile charges it is called the depletion region or a potential

barrier

Forward Bias

An external voltage applied to the p-n junction with the polarity

shown in Fig 12 is known as forward bias The height of the potential

barrier at the junction is lowered by the applied forward voltage In other

words we can say that p-n junction diode is connected to an external

Date____________

Pag

e35

battery in such a way that depletion region is reduced in size or eliminated

altogether Which of these takes place is determined by the size of the

applied voltage The positive terminal of the battery repels the holes on the

p-side and pushes them towards the junction The negative terminal of the

battery repels the electrons and pushes them towards the junction This

collapses the depletion region With the depletion region gone the diode

can conduct

Reverse Bias

An external voltage applied with polarity in Fig 13 is called reverse

bias When reverse bias is applied to a junction diode the depletion region

does not collapse On the contrary it becomes wider The positive side of

battery is applied to the n-type material This attracts the free electrons

away from the junction The negative side of the battery attracts the holes

in p-type material away from the junction This makes the depletion region

wider than it was when no voltage is applied The depletion region is an

insulator and it will block the flow of current Actually a small current will

flow because of minority carriers The p-type material has a few minority

electrons These are pushed to the junction by the repulsion of the negative

side of the battery The n-type material has few minority holes These are

also pushed towards the junction Reverse bias forces the minority carriers

together and a small current - called leakage current - results

Diodes which are designed with adequate power dissipation

capability to operate in the breakdown region are none as Zener diodes

Two mechanisms of diode breakdown for increasing reverse voltage are

recognized In one mechanism the thermally generated electrons and

holes acquire sufficient energy from the applied potential to produce new

carriers by removing valence electrons from their bonds These new

carriers in turn produce additional carriers again through the process of

disrupting bonds This cumulative process is referred to as avalanche

breakdown Even if the initially available carriers do not acquire sufficient

energy to disrupt bonds it is possible to initiate breakdown through a

direct rupture of the bonds because of the existence of strong electric field

Under these conditions the breakdown is referred to as Zener breakdown

Date____________

Pag

e36

Zener breakdown occurs below 6 V Zener diodes are commonly used in

voltage-reference or constant-voltage devices

Characteristic curves of diode

Fig 14 shows V-I Characteristic curves for typical p-n junction diode

It is seen that the curve is not linear With 0 V across the diode the diode

will not conduct the diode will not begin to conduct until a few tenths of a

volt are applied across it This is the voltage needed to overcome the

potential barrier It requires about 02 V to turn on a germanium diode and

about 06 V to turn on a silicon diode Fig 18 also shows what happens

when reverse bias is applied to a diode At increasing levels of reverse

voltage the curve shows some reverse current This leakage current is

caused by minority carries It is usually very small

Graph

Fig-14

Date____________

Pag

e37

Observation Table for Forward bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Date____________

Pag

e38

Observation Table for Reverse bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e39

Calculation for Forward bias 119877 = 119881

119868

Calculation for Reverse bias 119877 = 119881

119868

Date____________

Pag

e40

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e41

Zener Diode Reverse Bias Characteristics Experiment - 10

Aim To study the reverse bias characteristics of a Zener diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components Zener diode Resistors

Circuit Diagram

Procedure

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Theory

A diode which is heavily doped (Si or Ge) and which operates in the

reverse breakdown region with a sharp breakdown voltage is called a zener

diode The schematic symbol of a zener diode is shown in Fig-1 This is

similar to a normal diode except that the line (bar) representing the

cathode is bent at both ends like the letter Z for zener diode

Date____________

Pag

e42

A C Fig-1

In a simple diode the doping is light as a result the breakdown

voltage is high and not sharp But if doping is made heavy the depletion

layer becomes very narrow and even the breakdown voltage gets reduced

to a sharp value The zener diode is designed to operate in the breakdown

region without damage

The reverse breakdown of a zener diode may occur either due to

zener effect or avalanche effect But zener diode primarily depends on

zener effect for its working When the electric field across the junction is

sufficiently high due to the applied voltage the zener breakdown occurs

because of breaking of covalent bonds This produces a large number of

electrons and holes which constitute a steep rise in the reverse saturation

current (also called zener current 119868Z) This effect is called as zener effect

Zener current is independent of the applied voltage and depends only on

the external resistance

The V - 119868 characteristic of a zener diode is shown in Fig-2 The

forward characteristic is simply that of an ordinary forward biased junction

diode

Fig-2

Date____________

Pag

e43

Under reverse bias condition breakdown of junction occurs This

breakdown depends upon the amount of doping It can be seen from Fig-2

that as the reverse voltage is increased the reverse current remains

negligibly small up to the lsquokneersquo of the curve

At this lsquoknee pointrsquo the effect of breakdown process begins The

voltage corresponding to the lsquoknee pointrsquo in the figure is called the zener

breakdown voltage or simply zener voltage (VZ) which is very sharp

compared to a simle p-n junction diode Beyond this voltage the reverse

current (119868Z) increases sharply to a high value

The zener diode is not immediately burnt just because it has entered

the breakdown region As long as the external resistance connected to the

diode in the circuit limits the diode current to less than the burn out value

the diode will not burn out The zener voltage VZ remains constant even

when zener current 119868Z increases greatly This ability of a diode is called

regulating ability and it enables us to use zener diode for voltage

regulation

Date____________

Pag

e44

Observation Table

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e45

Graph 119868 V

Calculations 119877 = 119881

119868

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e46

Dispersive Power of The Prism Experiment - 11

Aim To find the dispersive power (D) of the prism by using spectrometer

Apparatus Mercury vapor lamp Spectrometer Prism

Procedure

Levelling and alignment of collimator and telescope

1 Switch on the mercury lamp Adjust the leveling screws on the chassis

Keep the spirit level on the chassis and do finer adjustments of these

screws to bring the bubble in the sprit level to the centre Repeat this

placing the sprit level along a direction perpendicular to the earlier

direction

2 Repeat this procedure for the prism table

3 Close the slit at the other end of the collimator using the drum screw DS1

Open it to a reasonable width Place the spectrometer in front of the

mercury lamp window and rotate the collimator so that the slit faces of

window View the slit through the telescope If it is not in the centre of the

view level collimator and the telescope so as to bring it to the centre

Setting the prism in the minimum deviation position

1 Rotate the prism table such that lines ruled on the table become

perpendicular to the axis of collimator

2 Place prism over the prism table such that its rough surface BA is

perpendicular to the line on prism table (See Fig-1(a))

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e14

Observation Table for Gauss-B Position

Sr No

Distance d (cm)

Deflection of Magnetometer Avg

θ

tanθ

Magnetic Moment

M = (119837120784+119897120784)120785120784Htanθ

θ1 θ2 θ3 θ4 θ5 θ6 θ7 θ8

1

2

Calculations

(1) Magnetic Moments for Gauss-A position

(2) Magnetic Moments for Gauss-B Position

(1) MA = (119837120784minus119897120784)120784

120784119837 H tanθ

(2) MB = (119837120784+119897120784) 120785120784 H tanθ

(i)

(i)

(ii) (iii)

Date ___________

Pag

e15

(1) 119872119860119886119907119892 =119872119860 1+119872119860 2

2

(2) 119872119861119886119907119892 =119872119861 1+119872119861 2

2

(3) Pole Strength of the magnethellip m = M2119897

(For both Gauss-A amp Gauss-B Positions)

For Gauss-A For Gauss-B

119898119860 =119872119860119886119907119892

2119897

119898119861 =119872119861119886119907119892

2119897

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e16

Friction Experiment - 05

Aim To determine the coefficient of kinetic friction between plane and block

Apparatus Inclined plane Block Scale pan String Set of weights Scale

Procedure

Take the inclined plane and set an angle of inclination θ1 Now put the block

on the inclined plane and put some weight in the scale pan in such a way that

block moves up along the inclined plane with a constant speed Now measure the

height length and base of the inclined plane for that angle and calculate the

Coefficient of kinetic friction

Now repeat the experiment for the angles θ2 and θ3

Theory

When a force F tends to slide a body along a surface a frictional force from

the surface acts on the body The frictional force is parallel to the surface and

directed so as to oppose the sliding It is due to bonding between the body and

the surface

If the body does not slide the frictional force is a static frictional force fs If

there is sliding the frictional force is a kinetic (dynamic) frictional force fk If the

body is rolling then the frictional force is known as rolling frictional force fr

Three properties of friction

(1) If the body does not move then the static frictional force fs and the

component of F that is parallel to the surface are equal in magnitudes

and fs is directed opposite that component If that parallel component

increases magnitude fs also increases

(2) The magnitude of fs has a maximum value fsmax that is given by

fsmax = microsN Where micros is the coefficient of static friction and N is the

magnitude of the normal reaction If the component of F that is parallel

to the surface exceeds fsmax then the body slides on the surface

Date ___________

Pag

e17

(3) If the body begins to slide on the surface the magnitude of the frictional

force rapidly decreases to a constant value fk given by fk = microk N Where

microk is the coefficient of kinetic friction

The magnitude of the coefficients of frictions relative to each other is

given by micros gt microk gtgt micror Where micror is coefficient of rolling friction

Note Here quantities shown bold are vector quantities

Observations

(1) Weight of the blockhellip M = ________ gm

(2) Weight of the scale panhellip m1 = _______ gm

(3) Gravitational accelerationhellip g = 980 cms2

Observation Table

Sr

No

Inclination

of the

Plane (θ)

Effort required to start

the motion up (gm)

m=m1+m2

Avg Effort

m (gm)

Base of

the

Plane

b (cm)

Height

of the

Plane

h (cm)

Length

of the

Plane

l (cm)

cosθ=bl

sinθ=hl

Coefficient of

Kinetic Friction

μ = 119846119840 ndash 119820119840 119852119842119847 120521

119820119840 119836119848119852 120521

1

θ1 1

2

2

θ2 1

2

3

θ3 1

2

Here m2 = the weight put in the scale pan

Page18

Calculation

Coefficient of Kinetic Friction μ = mg ndash Mg sin θMg cos θ

(1) (2)

(3)

Average of Coefficient of Kinetic Friction

μ avg = μ 1 + μ 2 + μ 3

3

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Page19

Date____________

Pag

e20

Wattage of Bulb Experiment - 06

Aim To find the electrical energy consumed in a circuit (bulb)

Apparatus AC Ammeter(0-500 mA) AC Voltmeter(0-250 volt) Variac

Components Bulb

Circuit Diagram

Procedure

Connect the circuit as shown in the circuit diagram Now switch ON

the circuit and note down the reading shown by ammeter at 0 volt then

increase the voltage from 0 to 10 volt and note down the reading of

ammeter Now increase the voltage in order of 10 volts (up to 200 volts)

and note down the readings of the current shown by the ammeter Now

calculate the power consumed in a circuit at different stages

Theory

Experiments show that in stationary metallic conductors current does

work to increase their internal energy The heated conductor releases the

energy received to the surrounding bodies but this is done by means of

heat transfer This means that the quantity of heat released by a current

carrying conductor is equal to the total work done by the current

Date____________

Pag

e21

As we know that the work done by the current is given by 119830 = 119829119816119853helliphelliphelliphelliphelliphellip(1)

119830 = 119816120784119825119853 ( V = IR) helliphelliphelliphelliphelliphelliphellip (2)

The electrical power of a given device is simply the rate of doing

work or the amount of electric work done in one second

Therefore electric powerhellip

119823 =119830119848119851119844 119837119848119847119838 (119830)

119827119842119846119838 (119853)

119823 =119829119816119853

119853= 119829119816 helliphelliphelliphelliphelliphelliphellip (3)

Thus electric power is equal to the product of voltage by current

Watt is a unit of power Hence it can be expressed in terms of a volt

and an ampere by the formula for electric power Eqn (3)

Therefore

1 Watt = 1 volt ∙ 1 ampere

1 W = 1 V∙A

Thus if a potential difference of 1 volt causes a current of 1 ampere

to flow through a conductor (here a bulb) the electric power consumed is

1 watt and the electrical energy consumed is 1 joulesec this electrical

energy consumed in the bulb is converted into heat and light energy

Date____________

Pag

e22

Observation Table

Sr No Voltage V (volt) Current 119816 (mA) Power

119823 = 119829119816 (watt)

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

Date____________

Pag

e23

Calculation 119823 = 119829119816

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e24

Temperature of Tungsten Filament Experiment ndash 07

Aim To find the temperature of the tungsten filament of the bulb

Apparatus AC Ammeter(0-500 mA) AC Voltmeter(0-250 volt) Variac

Components Bulb

Circuit Diagram

Procedure

Connect the circuit as shown in the circuit diagram Now switch ON

the circuit and note down the reading shown by ammeter at 0 volt then

increase the voltage from 0 to 10 volt and note down the reading of

ammeter Now increase the voltage in order of 10 volts (up to 100 volts)

and note down the readings of the current shown by the ammeter Now

calculate the resistance and the temperature of the filament

Observations

(1) Room temperaturehellip t0 = _______ ˚C

(2) Resistance of the filament of the bulb at room temperaturehellip

R0 = _______ Ω

(3) Temperature coefficient of tungstenhellip α = 45times10-4 ˚C-1

Date____________

Pag

e25

Observation Table

Sr No Voltage V

(volt)

Current 119816

(mA)

Resistance of

The Filament

119825119853 =119829

119816 Ω

Temperature of The Filament

119853 =120783

120514[

119825119853

119825120782 120783 + 120514119853120782 minus 120783] ˚C

1

2

3

4

5

6

7

8

9

10

Graph Rt versus t

Date____________

Pag

e26

Calculations

(1) Resistance of The Filament Rt =V

I Ω

(2) Temperature of The Filament t =1

α[

Rt

R0 1 + αt0 minus 1] ˚C

Date____________

Pag

e27

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e28

Meldersquos Experiment - 08

Aim To find the frequency of the wave and the frequency of the tuning fork by

Meldersquos experiment

Apparatus Meldersquos experiment apparatus

Circuit Diagram

Transverse mode

Procedure

Set Meldersquos experiment apparatus as shown in circuit diagram in

longitudinal position and switch ON the power supply put some weight in

scale pan and adjust the length of the string in such a way that you find

some loops on the string (eg 2 loops) Now rotate the apparatus by 90˚ so

that it is set for lsquoBrsquo position for the same values of weight in pan and for

the same length of the string the number of loops created in lsquoBrsquo position

are double (eg 4 loops) than in lsquoArsquo position Note down these readings in

observation table Repeat the experiment for other values of weight in

scale pan

Date____________

Pag

e29

Theory

This is an easy and efficient method by which nodes and antinodes

formed on a string can be demonstrated

A tuning fork is fitted in a wooden block A long string or thread of

cotton is taken One end of this string is tied to one of the prongs of the

tuning fork and the second end of this string passes over a smooth pulley in

such a way that a small pan can be hang on it Small weights are put in the

pan to create tension in the string This arrangement is shown in the circuit

diagram

The fork is set into vibrations by lightly hitting the prong of the tuning

fork on which the string is not tied or by connecting an electric supply as

shown in the circuit diagram Thus the transverse vibrations are produced

in the string and by adjusting the length andor weights in the pan these

vibrations are reflected from the point of contact between the string and

the pulley and a number of loops appear on the string as shown in the

circuit diagram

When the prongs of the tuning fork vibrate in a plane parallel to the

direction of propagation of the waves it is called lsquoArsquo position or

longitudinal position

If the tuning fork along with the wooden block is rotated through

90˚ so that the plane of vibration of the tuning fork is normal (ie at right

angles) to the direction of propagation it is called lsquoBrsquo position or transverse

position

For the same length and same weight in the pan (ie for the same

tension) the number of loops in lsquoBrsquo position is double than in lsquoArsquo position

Thus either in lsquoArsquo position or in lsquoBrsquo position standing transverse

waves are generated in the string with a series of nodes and antinodes at

equal distances

The equation connecting number of loops (n or nrsquo) length of the

string (l) tension in the string (T) mass per unit length of the string (m) and

frequency of the string (f) is as follows

Date____________

Pag

e30

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position)

119943prime =119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

If the frequency of tuning fork is F then for lsquoArsquo position 119839 =119813

120784 and for lsquoBrsquo

position 119839prime = 119813

In the above equations if all the quantities on the RHS are known the

frequency of the tuning fork 119813 can be calculated

Observations

(1) Gravitational accelerationhellip g = 98 ms2

(2) Mass per unit length of the stringhellip m = _______ kgm

(3) Mass of the scale panhellip M1 = _______ kg

Observation Table

Sr

No

Total mass

suspended at

the end of the

stringhellip

M=M1+M2

(kg)

Tension

created

in the

stringhellip

T=Mg (N)

Length of the

vibrating string

Average

lengthhellip

119949 (m)

No of loops created on

the stringhellip

Frequency of the

vibrating stringhellip

Relation

between

f and frsquo 1199491 (m) 1199492 (m)

In

Longitudinal

Modehellip

n

In

Transverse

Modehellip

nrsquo

In

Longitudinal

Modehellip

119943 =119951

120784119949

119931

119950

In

Transverse

Modehellip

119943prime =119951prime

120784119949

119931

119950

1

2

3

4

Here M2 = the weight put in the scale pan

Page31

Date____________

Pag

e32

Calculations

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position) 119943prime =

119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e33

P-N Junction Diode Characteristics Experiment - 09

Aim To study the Forward and Reverse bias characteristics of a P-N junction

diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components P-N junction diode Resistors

Circuit Diagram

(Forward biased PN diode) (Reverse biased PN diode)

Procedure

For Forward Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 01 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 02 03 04hellip

volts and repeat the procedure Note down the knee voltage and

corresponding current in your observation table

For Reverse Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Date____________

Pag

e34

Theory

If donor (pentavalent) impurities are introduced on one side and

acceptors (trivalent) on the opposite side of a single crystal of an intrinsic

semiconductor like germanium or silicon a p-n junction is formed as shown

in Fig 11 In the figure a donor ion is indicated schematically by a plus sign

because after this impurity atom donates an electron it becomes a positive

ion

The acceptor ion is indicated by a minus sign because after this atom

accepts an electron it becomes a negative ion Initially there are only n-

type carriers to the right of the junction and only p-type carriers to the left

Because there is a density gradient across the junction holes will diffuse to

the right across the junction and electrons to the left As a result of the

displacement of these charges an electric field appears across the junction

Equilibrium is established when the field becomes large enough to restrain

the process of diffusion The positive holes which neutralize the acceptor

ions near the junction in p-type germanium disappear as a result of

combination with electrons which diffuse across the junction Similarly the

neutralizing electrons on the n side of the junction combine with holes

which cross the junction from the p side Since the region of the junction is

depleted of mobile charges it is called the depletion region or a potential

barrier

Forward Bias

An external voltage applied to the p-n junction with the polarity

shown in Fig 12 is known as forward bias The height of the potential

barrier at the junction is lowered by the applied forward voltage In other

words we can say that p-n junction diode is connected to an external

Date____________

Pag

e35

battery in such a way that depletion region is reduced in size or eliminated

altogether Which of these takes place is determined by the size of the

applied voltage The positive terminal of the battery repels the holes on the

p-side and pushes them towards the junction The negative terminal of the

battery repels the electrons and pushes them towards the junction This

collapses the depletion region With the depletion region gone the diode

can conduct

Reverse Bias

An external voltage applied with polarity in Fig 13 is called reverse

bias When reverse bias is applied to a junction diode the depletion region

does not collapse On the contrary it becomes wider The positive side of

battery is applied to the n-type material This attracts the free electrons

away from the junction The negative side of the battery attracts the holes

in p-type material away from the junction This makes the depletion region

wider than it was when no voltage is applied The depletion region is an

insulator and it will block the flow of current Actually a small current will

flow because of minority carriers The p-type material has a few minority

electrons These are pushed to the junction by the repulsion of the negative

side of the battery The n-type material has few minority holes These are

also pushed towards the junction Reverse bias forces the minority carriers

together and a small current - called leakage current - results

Diodes which are designed with adequate power dissipation

capability to operate in the breakdown region are none as Zener diodes

Two mechanisms of diode breakdown for increasing reverse voltage are

recognized In one mechanism the thermally generated electrons and

holes acquire sufficient energy from the applied potential to produce new

carriers by removing valence electrons from their bonds These new

carriers in turn produce additional carriers again through the process of

disrupting bonds This cumulative process is referred to as avalanche

breakdown Even if the initially available carriers do not acquire sufficient

energy to disrupt bonds it is possible to initiate breakdown through a

direct rupture of the bonds because of the existence of strong electric field

Under these conditions the breakdown is referred to as Zener breakdown

Date____________

Pag

e36

Zener breakdown occurs below 6 V Zener diodes are commonly used in

voltage-reference or constant-voltage devices

Characteristic curves of diode

Fig 14 shows V-I Characteristic curves for typical p-n junction diode

It is seen that the curve is not linear With 0 V across the diode the diode

will not conduct the diode will not begin to conduct until a few tenths of a

volt are applied across it This is the voltage needed to overcome the

potential barrier It requires about 02 V to turn on a germanium diode and

about 06 V to turn on a silicon diode Fig 18 also shows what happens

when reverse bias is applied to a diode At increasing levels of reverse

voltage the curve shows some reverse current This leakage current is

caused by minority carries It is usually very small

Graph

Fig-14

Date____________

Pag

e37

Observation Table for Forward bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Date____________

Pag

e38

Observation Table for Reverse bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e39

Calculation for Forward bias 119877 = 119881

119868

Calculation for Reverse bias 119877 = 119881

119868

Date____________

Pag

e40

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e41

Zener Diode Reverse Bias Characteristics Experiment - 10

Aim To study the reverse bias characteristics of a Zener diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components Zener diode Resistors

Circuit Diagram

Procedure

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Theory

A diode which is heavily doped (Si or Ge) and which operates in the

reverse breakdown region with a sharp breakdown voltage is called a zener

diode The schematic symbol of a zener diode is shown in Fig-1 This is

similar to a normal diode except that the line (bar) representing the

cathode is bent at both ends like the letter Z for zener diode

Date____________

Pag

e42

A C Fig-1

In a simple diode the doping is light as a result the breakdown

voltage is high and not sharp But if doping is made heavy the depletion

layer becomes very narrow and even the breakdown voltage gets reduced

to a sharp value The zener diode is designed to operate in the breakdown

region without damage

The reverse breakdown of a zener diode may occur either due to

zener effect or avalanche effect But zener diode primarily depends on

zener effect for its working When the electric field across the junction is

sufficiently high due to the applied voltage the zener breakdown occurs

because of breaking of covalent bonds This produces a large number of

electrons and holes which constitute a steep rise in the reverse saturation

current (also called zener current 119868Z) This effect is called as zener effect

Zener current is independent of the applied voltage and depends only on

the external resistance

The V - 119868 characteristic of a zener diode is shown in Fig-2 The

forward characteristic is simply that of an ordinary forward biased junction

diode

Fig-2

Date____________

Pag

e43

Under reverse bias condition breakdown of junction occurs This

breakdown depends upon the amount of doping It can be seen from Fig-2

that as the reverse voltage is increased the reverse current remains

negligibly small up to the lsquokneersquo of the curve

At this lsquoknee pointrsquo the effect of breakdown process begins The

voltage corresponding to the lsquoknee pointrsquo in the figure is called the zener

breakdown voltage or simply zener voltage (VZ) which is very sharp

compared to a simle p-n junction diode Beyond this voltage the reverse

current (119868Z) increases sharply to a high value

The zener diode is not immediately burnt just because it has entered

the breakdown region As long as the external resistance connected to the

diode in the circuit limits the diode current to less than the burn out value

the diode will not burn out The zener voltage VZ remains constant even

when zener current 119868Z increases greatly This ability of a diode is called

regulating ability and it enables us to use zener diode for voltage

regulation

Date____________

Pag

e44

Observation Table

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e45

Graph 119868 V

Calculations 119877 = 119881

119868

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e46

Dispersive Power of The Prism Experiment - 11

Aim To find the dispersive power (D) of the prism by using spectrometer

Apparatus Mercury vapor lamp Spectrometer Prism

Procedure

Levelling and alignment of collimator and telescope

1 Switch on the mercury lamp Adjust the leveling screws on the chassis

Keep the spirit level on the chassis and do finer adjustments of these

screws to bring the bubble in the sprit level to the centre Repeat this

placing the sprit level along a direction perpendicular to the earlier

direction

2 Repeat this procedure for the prism table

3 Close the slit at the other end of the collimator using the drum screw DS1

Open it to a reasonable width Place the spectrometer in front of the

mercury lamp window and rotate the collimator so that the slit faces of

window View the slit through the telescope If it is not in the centre of the

view level collimator and the telescope so as to bring it to the centre

Setting the prism in the minimum deviation position

1 Rotate the prism table such that lines ruled on the table become

perpendicular to the axis of collimator

2 Place prism over the prism table such that its rough surface BA is

perpendicular to the line on prism table (See Fig-1(a))

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e15

(1) 119872119860119886119907119892 =119872119860 1+119872119860 2

2

(2) 119872119861119886119907119892 =119872119861 1+119872119861 2

2

(3) Pole Strength of the magnethellip m = M2119897

(For both Gauss-A amp Gauss-B Positions)

For Gauss-A For Gauss-B

119898119860 =119872119860119886119907119892

2119897

119898119861 =119872119861119886119907119892

2119897

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e16

Friction Experiment - 05

Aim To determine the coefficient of kinetic friction between plane and block

Apparatus Inclined plane Block Scale pan String Set of weights Scale

Procedure

Take the inclined plane and set an angle of inclination θ1 Now put the block

on the inclined plane and put some weight in the scale pan in such a way that

block moves up along the inclined plane with a constant speed Now measure the

height length and base of the inclined plane for that angle and calculate the

Coefficient of kinetic friction

Now repeat the experiment for the angles θ2 and θ3

Theory

When a force F tends to slide a body along a surface a frictional force from

the surface acts on the body The frictional force is parallel to the surface and

directed so as to oppose the sliding It is due to bonding between the body and

the surface

If the body does not slide the frictional force is a static frictional force fs If

there is sliding the frictional force is a kinetic (dynamic) frictional force fk If the

body is rolling then the frictional force is known as rolling frictional force fr

Three properties of friction

(1) If the body does not move then the static frictional force fs and the

component of F that is parallel to the surface are equal in magnitudes

and fs is directed opposite that component If that parallel component

increases magnitude fs also increases

(2) The magnitude of fs has a maximum value fsmax that is given by

fsmax = microsN Where micros is the coefficient of static friction and N is the

magnitude of the normal reaction If the component of F that is parallel

to the surface exceeds fsmax then the body slides on the surface

Date ___________

Pag

e17

(3) If the body begins to slide on the surface the magnitude of the frictional

force rapidly decreases to a constant value fk given by fk = microk N Where

microk is the coefficient of kinetic friction

The magnitude of the coefficients of frictions relative to each other is

given by micros gt microk gtgt micror Where micror is coefficient of rolling friction

Note Here quantities shown bold are vector quantities

Observations

(1) Weight of the blockhellip M = ________ gm

(2) Weight of the scale panhellip m1 = _______ gm

(3) Gravitational accelerationhellip g = 980 cms2

Observation Table

Sr

No

Inclination

of the

Plane (θ)

Effort required to start

the motion up (gm)

m=m1+m2

Avg Effort

m (gm)

Base of

the

Plane

b (cm)

Height

of the

Plane

h (cm)

Length

of the

Plane

l (cm)

cosθ=bl

sinθ=hl

Coefficient of

Kinetic Friction

μ = 119846119840 ndash 119820119840 119852119842119847 120521

119820119840 119836119848119852 120521

1

θ1 1

2

2

θ2 1

2

3

θ3 1

2

Here m2 = the weight put in the scale pan

Page18

Calculation

Coefficient of Kinetic Friction μ = mg ndash Mg sin θMg cos θ

(1) (2)

(3)

Average of Coefficient of Kinetic Friction

μ avg = μ 1 + μ 2 + μ 3

3

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Page19

Date____________

Pag

e20

Wattage of Bulb Experiment - 06

Aim To find the electrical energy consumed in a circuit (bulb)

Apparatus AC Ammeter(0-500 mA) AC Voltmeter(0-250 volt) Variac

Components Bulb

Circuit Diagram

Procedure

Connect the circuit as shown in the circuit diagram Now switch ON

the circuit and note down the reading shown by ammeter at 0 volt then

increase the voltage from 0 to 10 volt and note down the reading of

ammeter Now increase the voltage in order of 10 volts (up to 200 volts)

and note down the readings of the current shown by the ammeter Now

calculate the power consumed in a circuit at different stages

Theory

Experiments show that in stationary metallic conductors current does

work to increase their internal energy The heated conductor releases the

energy received to the surrounding bodies but this is done by means of

heat transfer This means that the quantity of heat released by a current

carrying conductor is equal to the total work done by the current

Date____________

Pag

e21

As we know that the work done by the current is given by 119830 = 119829119816119853helliphelliphelliphelliphelliphellip(1)

119830 = 119816120784119825119853 ( V = IR) helliphelliphelliphelliphelliphelliphellip (2)

The electrical power of a given device is simply the rate of doing

work or the amount of electric work done in one second

Therefore electric powerhellip

119823 =119830119848119851119844 119837119848119847119838 (119830)

119827119842119846119838 (119853)

119823 =119829119816119853

119853= 119829119816 helliphelliphelliphelliphelliphelliphellip (3)

Thus electric power is equal to the product of voltage by current

Watt is a unit of power Hence it can be expressed in terms of a volt

and an ampere by the formula for electric power Eqn (3)

Therefore

1 Watt = 1 volt ∙ 1 ampere

1 W = 1 V∙A

Thus if a potential difference of 1 volt causes a current of 1 ampere

to flow through a conductor (here a bulb) the electric power consumed is

1 watt and the electrical energy consumed is 1 joulesec this electrical

energy consumed in the bulb is converted into heat and light energy

Date____________

Pag

e22

Observation Table

Sr No Voltage V (volt) Current 119816 (mA) Power

119823 = 119829119816 (watt)

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

Date____________

Pag

e23

Calculation 119823 = 119829119816

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e24

Temperature of Tungsten Filament Experiment ndash 07

Aim To find the temperature of the tungsten filament of the bulb

Apparatus AC Ammeter(0-500 mA) AC Voltmeter(0-250 volt) Variac

Components Bulb

Circuit Diagram

Procedure

Connect the circuit as shown in the circuit diagram Now switch ON

the circuit and note down the reading shown by ammeter at 0 volt then

increase the voltage from 0 to 10 volt and note down the reading of

ammeter Now increase the voltage in order of 10 volts (up to 100 volts)

and note down the readings of the current shown by the ammeter Now

calculate the resistance and the temperature of the filament

Observations

(1) Room temperaturehellip t0 = _______ ˚C

(2) Resistance of the filament of the bulb at room temperaturehellip

R0 = _______ Ω

(3) Temperature coefficient of tungstenhellip α = 45times10-4 ˚C-1

Date____________

Pag

e25

Observation Table

Sr No Voltage V

(volt)

Current 119816

(mA)

Resistance of

The Filament

119825119853 =119829

119816 Ω

Temperature of The Filament

119853 =120783

120514[

119825119853

119825120782 120783 + 120514119853120782 minus 120783] ˚C

1

2

3

4

5

6

7

8

9

10

Graph Rt versus t

Date____________

Pag

e26

Calculations

(1) Resistance of The Filament Rt =V

I Ω

(2) Temperature of The Filament t =1

α[

Rt

R0 1 + αt0 minus 1] ˚C

Date____________

Pag

e27

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e28

Meldersquos Experiment - 08

Aim To find the frequency of the wave and the frequency of the tuning fork by

Meldersquos experiment

Apparatus Meldersquos experiment apparatus

Circuit Diagram

Transverse mode

Procedure

Set Meldersquos experiment apparatus as shown in circuit diagram in

longitudinal position and switch ON the power supply put some weight in

scale pan and adjust the length of the string in such a way that you find

some loops on the string (eg 2 loops) Now rotate the apparatus by 90˚ so

that it is set for lsquoBrsquo position for the same values of weight in pan and for

the same length of the string the number of loops created in lsquoBrsquo position

are double (eg 4 loops) than in lsquoArsquo position Note down these readings in

observation table Repeat the experiment for other values of weight in

scale pan

Date____________

Pag

e29

Theory

This is an easy and efficient method by which nodes and antinodes

formed on a string can be demonstrated

A tuning fork is fitted in a wooden block A long string or thread of

cotton is taken One end of this string is tied to one of the prongs of the

tuning fork and the second end of this string passes over a smooth pulley in

such a way that a small pan can be hang on it Small weights are put in the

pan to create tension in the string This arrangement is shown in the circuit

diagram

The fork is set into vibrations by lightly hitting the prong of the tuning

fork on which the string is not tied or by connecting an electric supply as

shown in the circuit diagram Thus the transverse vibrations are produced

in the string and by adjusting the length andor weights in the pan these

vibrations are reflected from the point of contact between the string and

the pulley and a number of loops appear on the string as shown in the

circuit diagram

When the prongs of the tuning fork vibrate in a plane parallel to the

direction of propagation of the waves it is called lsquoArsquo position or

longitudinal position

If the tuning fork along with the wooden block is rotated through

90˚ so that the plane of vibration of the tuning fork is normal (ie at right

angles) to the direction of propagation it is called lsquoBrsquo position or transverse

position

For the same length and same weight in the pan (ie for the same

tension) the number of loops in lsquoBrsquo position is double than in lsquoArsquo position

Thus either in lsquoArsquo position or in lsquoBrsquo position standing transverse

waves are generated in the string with a series of nodes and antinodes at

equal distances

The equation connecting number of loops (n or nrsquo) length of the

string (l) tension in the string (T) mass per unit length of the string (m) and

frequency of the string (f) is as follows

Date____________

Pag

e30

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position)

119943prime =119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

If the frequency of tuning fork is F then for lsquoArsquo position 119839 =119813

120784 and for lsquoBrsquo

position 119839prime = 119813

In the above equations if all the quantities on the RHS are known the

frequency of the tuning fork 119813 can be calculated

Observations

(1) Gravitational accelerationhellip g = 98 ms2

(2) Mass per unit length of the stringhellip m = _______ kgm

(3) Mass of the scale panhellip M1 = _______ kg

Observation Table

Sr

No

Total mass

suspended at

the end of the

stringhellip

M=M1+M2

(kg)

Tension

created

in the

stringhellip

T=Mg (N)

Length of the

vibrating string

Average

lengthhellip

119949 (m)

No of loops created on

the stringhellip

Frequency of the

vibrating stringhellip

Relation

between

f and frsquo 1199491 (m) 1199492 (m)

In

Longitudinal

Modehellip

n

In

Transverse

Modehellip

nrsquo

In

Longitudinal

Modehellip

119943 =119951

120784119949

119931

119950

In

Transverse

Modehellip

119943prime =119951prime

120784119949

119931

119950

1

2

3

4

Here M2 = the weight put in the scale pan

Page31

Date____________

Pag

e32

Calculations

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position) 119943prime =

119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e33

P-N Junction Diode Characteristics Experiment - 09

Aim To study the Forward and Reverse bias characteristics of a P-N junction

diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components P-N junction diode Resistors

Circuit Diagram

(Forward biased PN diode) (Reverse biased PN diode)

Procedure

For Forward Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 01 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 02 03 04hellip

volts and repeat the procedure Note down the knee voltage and

corresponding current in your observation table

For Reverse Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Date____________

Pag

e34

Theory

If donor (pentavalent) impurities are introduced on one side and

acceptors (trivalent) on the opposite side of a single crystal of an intrinsic

semiconductor like germanium or silicon a p-n junction is formed as shown

in Fig 11 In the figure a donor ion is indicated schematically by a plus sign

because after this impurity atom donates an electron it becomes a positive

ion

The acceptor ion is indicated by a minus sign because after this atom

accepts an electron it becomes a negative ion Initially there are only n-

type carriers to the right of the junction and only p-type carriers to the left

Because there is a density gradient across the junction holes will diffuse to

the right across the junction and electrons to the left As a result of the

displacement of these charges an electric field appears across the junction

Equilibrium is established when the field becomes large enough to restrain

the process of diffusion The positive holes which neutralize the acceptor

ions near the junction in p-type germanium disappear as a result of

combination with electrons which diffuse across the junction Similarly the

neutralizing electrons on the n side of the junction combine with holes

which cross the junction from the p side Since the region of the junction is

depleted of mobile charges it is called the depletion region or a potential

barrier

Forward Bias

An external voltage applied to the p-n junction with the polarity

shown in Fig 12 is known as forward bias The height of the potential

barrier at the junction is lowered by the applied forward voltage In other

words we can say that p-n junction diode is connected to an external

Date____________

Pag

e35

battery in such a way that depletion region is reduced in size or eliminated

altogether Which of these takes place is determined by the size of the

applied voltage The positive terminal of the battery repels the holes on the

p-side and pushes them towards the junction The negative terminal of the

battery repels the electrons and pushes them towards the junction This

collapses the depletion region With the depletion region gone the diode

can conduct

Reverse Bias

An external voltage applied with polarity in Fig 13 is called reverse

bias When reverse bias is applied to a junction diode the depletion region

does not collapse On the contrary it becomes wider The positive side of

battery is applied to the n-type material This attracts the free electrons

away from the junction The negative side of the battery attracts the holes

in p-type material away from the junction This makes the depletion region

wider than it was when no voltage is applied The depletion region is an

insulator and it will block the flow of current Actually a small current will

flow because of minority carriers The p-type material has a few minority

electrons These are pushed to the junction by the repulsion of the negative

side of the battery The n-type material has few minority holes These are

also pushed towards the junction Reverse bias forces the minority carriers

together and a small current - called leakage current - results

Diodes which are designed with adequate power dissipation

capability to operate in the breakdown region are none as Zener diodes

Two mechanisms of diode breakdown for increasing reverse voltage are

recognized In one mechanism the thermally generated electrons and

holes acquire sufficient energy from the applied potential to produce new

carriers by removing valence electrons from their bonds These new

carriers in turn produce additional carriers again through the process of

disrupting bonds This cumulative process is referred to as avalanche

breakdown Even if the initially available carriers do not acquire sufficient

energy to disrupt bonds it is possible to initiate breakdown through a

direct rupture of the bonds because of the existence of strong electric field

Under these conditions the breakdown is referred to as Zener breakdown

Date____________

Pag

e36

Zener breakdown occurs below 6 V Zener diodes are commonly used in

voltage-reference or constant-voltage devices

Characteristic curves of diode

Fig 14 shows V-I Characteristic curves for typical p-n junction diode

It is seen that the curve is not linear With 0 V across the diode the diode

will not conduct the diode will not begin to conduct until a few tenths of a

volt are applied across it This is the voltage needed to overcome the

potential barrier It requires about 02 V to turn on a germanium diode and

about 06 V to turn on a silicon diode Fig 18 also shows what happens

when reverse bias is applied to a diode At increasing levels of reverse

voltage the curve shows some reverse current This leakage current is

caused by minority carries It is usually very small

Graph

Fig-14

Date____________

Pag

e37

Observation Table for Forward bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Date____________

Pag

e38

Observation Table for Reverse bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e39

Calculation for Forward bias 119877 = 119881

119868

Calculation for Reverse bias 119877 = 119881

119868

Date____________

Pag

e40

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e41

Zener Diode Reverse Bias Characteristics Experiment - 10

Aim To study the reverse bias characteristics of a Zener diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components Zener diode Resistors

Circuit Diagram

Procedure

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Theory

A diode which is heavily doped (Si or Ge) and which operates in the

reverse breakdown region with a sharp breakdown voltage is called a zener

diode The schematic symbol of a zener diode is shown in Fig-1 This is

similar to a normal diode except that the line (bar) representing the

cathode is bent at both ends like the letter Z for zener diode

Date____________

Pag

e42

A C Fig-1

In a simple diode the doping is light as a result the breakdown

voltage is high and not sharp But if doping is made heavy the depletion

layer becomes very narrow and even the breakdown voltage gets reduced

to a sharp value The zener diode is designed to operate in the breakdown

region without damage

The reverse breakdown of a zener diode may occur either due to

zener effect or avalanche effect But zener diode primarily depends on

zener effect for its working When the electric field across the junction is

sufficiently high due to the applied voltage the zener breakdown occurs

because of breaking of covalent bonds This produces a large number of

electrons and holes which constitute a steep rise in the reverse saturation

current (also called zener current 119868Z) This effect is called as zener effect

Zener current is independent of the applied voltage and depends only on

the external resistance

The V - 119868 characteristic of a zener diode is shown in Fig-2 The

forward characteristic is simply that of an ordinary forward biased junction

diode

Fig-2

Date____________

Pag

e43

Under reverse bias condition breakdown of junction occurs This

breakdown depends upon the amount of doping It can be seen from Fig-2

that as the reverse voltage is increased the reverse current remains

negligibly small up to the lsquokneersquo of the curve

At this lsquoknee pointrsquo the effect of breakdown process begins The

voltage corresponding to the lsquoknee pointrsquo in the figure is called the zener

breakdown voltage or simply zener voltage (VZ) which is very sharp

compared to a simle p-n junction diode Beyond this voltage the reverse

current (119868Z) increases sharply to a high value

The zener diode is not immediately burnt just because it has entered

the breakdown region As long as the external resistance connected to the

diode in the circuit limits the diode current to less than the burn out value

the diode will not burn out The zener voltage VZ remains constant even

when zener current 119868Z increases greatly This ability of a diode is called

regulating ability and it enables us to use zener diode for voltage

regulation

Date____________

Pag

e44

Observation Table

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e45

Graph 119868 V

Calculations 119877 = 119881

119868

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e46

Dispersive Power of The Prism Experiment - 11

Aim To find the dispersive power (D) of the prism by using spectrometer

Apparatus Mercury vapor lamp Spectrometer Prism

Procedure

Levelling and alignment of collimator and telescope

1 Switch on the mercury lamp Adjust the leveling screws on the chassis

Keep the spirit level on the chassis and do finer adjustments of these

screws to bring the bubble in the sprit level to the centre Repeat this

placing the sprit level along a direction perpendicular to the earlier

direction

2 Repeat this procedure for the prism table

3 Close the slit at the other end of the collimator using the drum screw DS1

Open it to a reasonable width Place the spectrometer in front of the

mercury lamp window and rotate the collimator so that the slit faces of

window View the slit through the telescope If it is not in the centre of the

view level collimator and the telescope so as to bring it to the centre

Setting the prism in the minimum deviation position

1 Rotate the prism table such that lines ruled on the table become

perpendicular to the axis of collimator

2 Place prism over the prism table such that its rough surface BA is

perpendicular to the line on prism table (See Fig-1(a))

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e16

Friction Experiment - 05

Aim To determine the coefficient of kinetic friction between plane and block

Apparatus Inclined plane Block Scale pan String Set of weights Scale

Procedure

Take the inclined plane and set an angle of inclination θ1 Now put the block

on the inclined plane and put some weight in the scale pan in such a way that

block moves up along the inclined plane with a constant speed Now measure the

height length and base of the inclined plane for that angle and calculate the

Coefficient of kinetic friction

Now repeat the experiment for the angles θ2 and θ3

Theory

When a force F tends to slide a body along a surface a frictional force from

the surface acts on the body The frictional force is parallel to the surface and

directed so as to oppose the sliding It is due to bonding between the body and

the surface

If the body does not slide the frictional force is a static frictional force fs If

there is sliding the frictional force is a kinetic (dynamic) frictional force fk If the

body is rolling then the frictional force is known as rolling frictional force fr

Three properties of friction

(1) If the body does not move then the static frictional force fs and the

component of F that is parallel to the surface are equal in magnitudes

and fs is directed opposite that component If that parallel component

increases magnitude fs also increases

(2) The magnitude of fs has a maximum value fsmax that is given by

fsmax = microsN Where micros is the coefficient of static friction and N is the

magnitude of the normal reaction If the component of F that is parallel

to the surface exceeds fsmax then the body slides on the surface

Date ___________

Pag

e17

(3) If the body begins to slide on the surface the magnitude of the frictional

force rapidly decreases to a constant value fk given by fk = microk N Where

microk is the coefficient of kinetic friction

The magnitude of the coefficients of frictions relative to each other is

given by micros gt microk gtgt micror Where micror is coefficient of rolling friction

Note Here quantities shown bold are vector quantities

Observations

(1) Weight of the blockhellip M = ________ gm

(2) Weight of the scale panhellip m1 = _______ gm

(3) Gravitational accelerationhellip g = 980 cms2

Observation Table

Sr

No

Inclination

of the

Plane (θ)

Effort required to start

the motion up (gm)

m=m1+m2

Avg Effort

m (gm)

Base of

the

Plane

b (cm)

Height

of the

Plane

h (cm)

Length

of the

Plane

l (cm)

cosθ=bl

sinθ=hl

Coefficient of

Kinetic Friction

μ = 119846119840 ndash 119820119840 119852119842119847 120521

119820119840 119836119848119852 120521

1

θ1 1

2

2

θ2 1

2

3

θ3 1

2

Here m2 = the weight put in the scale pan

Page18

Calculation

Coefficient of Kinetic Friction μ = mg ndash Mg sin θMg cos θ

(1) (2)

(3)

Average of Coefficient of Kinetic Friction

μ avg = μ 1 + μ 2 + μ 3

3

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Page19

Date____________

Pag

e20

Wattage of Bulb Experiment - 06

Aim To find the electrical energy consumed in a circuit (bulb)

Apparatus AC Ammeter(0-500 mA) AC Voltmeter(0-250 volt) Variac

Components Bulb

Circuit Diagram

Procedure

Connect the circuit as shown in the circuit diagram Now switch ON

the circuit and note down the reading shown by ammeter at 0 volt then

increase the voltage from 0 to 10 volt and note down the reading of

ammeter Now increase the voltage in order of 10 volts (up to 200 volts)

and note down the readings of the current shown by the ammeter Now

calculate the power consumed in a circuit at different stages

Theory

Experiments show that in stationary metallic conductors current does

work to increase their internal energy The heated conductor releases the

energy received to the surrounding bodies but this is done by means of

heat transfer This means that the quantity of heat released by a current

carrying conductor is equal to the total work done by the current

Date____________

Pag

e21

As we know that the work done by the current is given by 119830 = 119829119816119853helliphelliphelliphelliphelliphellip(1)

119830 = 119816120784119825119853 ( V = IR) helliphelliphelliphelliphelliphelliphellip (2)

The electrical power of a given device is simply the rate of doing

work or the amount of electric work done in one second

Therefore electric powerhellip

119823 =119830119848119851119844 119837119848119847119838 (119830)

119827119842119846119838 (119853)

119823 =119829119816119853

119853= 119829119816 helliphelliphelliphelliphelliphelliphellip (3)

Thus electric power is equal to the product of voltage by current

Watt is a unit of power Hence it can be expressed in terms of a volt

and an ampere by the formula for electric power Eqn (3)

Therefore

1 Watt = 1 volt ∙ 1 ampere

1 W = 1 V∙A

Thus if a potential difference of 1 volt causes a current of 1 ampere

to flow through a conductor (here a bulb) the electric power consumed is

1 watt and the electrical energy consumed is 1 joulesec this electrical

energy consumed in the bulb is converted into heat and light energy

Date____________

Pag

e22

Observation Table

Sr No Voltage V (volt) Current 119816 (mA) Power

119823 = 119829119816 (watt)

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

Date____________

Pag

e23

Calculation 119823 = 119829119816

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e24

Temperature of Tungsten Filament Experiment ndash 07

Aim To find the temperature of the tungsten filament of the bulb

Apparatus AC Ammeter(0-500 mA) AC Voltmeter(0-250 volt) Variac

Components Bulb

Circuit Diagram

Procedure

Connect the circuit as shown in the circuit diagram Now switch ON

the circuit and note down the reading shown by ammeter at 0 volt then

increase the voltage from 0 to 10 volt and note down the reading of

ammeter Now increase the voltage in order of 10 volts (up to 100 volts)

and note down the readings of the current shown by the ammeter Now

calculate the resistance and the temperature of the filament

Observations

(1) Room temperaturehellip t0 = _______ ˚C

(2) Resistance of the filament of the bulb at room temperaturehellip

R0 = _______ Ω

(3) Temperature coefficient of tungstenhellip α = 45times10-4 ˚C-1

Date____________

Pag

e25

Observation Table

Sr No Voltage V

(volt)

Current 119816

(mA)

Resistance of

The Filament

119825119853 =119829

119816 Ω

Temperature of The Filament

119853 =120783

120514[

119825119853

119825120782 120783 + 120514119853120782 minus 120783] ˚C

1

2

3

4

5

6

7

8

9

10

Graph Rt versus t

Date____________

Pag

e26

Calculations

(1) Resistance of The Filament Rt =V

I Ω

(2) Temperature of The Filament t =1

α[

Rt

R0 1 + αt0 minus 1] ˚C

Date____________

Pag

e27

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e28

Meldersquos Experiment - 08

Aim To find the frequency of the wave and the frequency of the tuning fork by

Meldersquos experiment

Apparatus Meldersquos experiment apparatus

Circuit Diagram

Transverse mode

Procedure

Set Meldersquos experiment apparatus as shown in circuit diagram in

longitudinal position and switch ON the power supply put some weight in

scale pan and adjust the length of the string in such a way that you find

some loops on the string (eg 2 loops) Now rotate the apparatus by 90˚ so

that it is set for lsquoBrsquo position for the same values of weight in pan and for

the same length of the string the number of loops created in lsquoBrsquo position

are double (eg 4 loops) than in lsquoArsquo position Note down these readings in

observation table Repeat the experiment for other values of weight in

scale pan

Date____________

Pag

e29

Theory

This is an easy and efficient method by which nodes and antinodes

formed on a string can be demonstrated

A tuning fork is fitted in a wooden block A long string or thread of

cotton is taken One end of this string is tied to one of the prongs of the

tuning fork and the second end of this string passes over a smooth pulley in

such a way that a small pan can be hang on it Small weights are put in the

pan to create tension in the string This arrangement is shown in the circuit

diagram

The fork is set into vibrations by lightly hitting the prong of the tuning

fork on which the string is not tied or by connecting an electric supply as

shown in the circuit diagram Thus the transverse vibrations are produced

in the string and by adjusting the length andor weights in the pan these

vibrations are reflected from the point of contact between the string and

the pulley and a number of loops appear on the string as shown in the

circuit diagram

When the prongs of the tuning fork vibrate in a plane parallel to the

direction of propagation of the waves it is called lsquoArsquo position or

longitudinal position

If the tuning fork along with the wooden block is rotated through

90˚ so that the plane of vibration of the tuning fork is normal (ie at right

angles) to the direction of propagation it is called lsquoBrsquo position or transverse

position

For the same length and same weight in the pan (ie for the same

tension) the number of loops in lsquoBrsquo position is double than in lsquoArsquo position

Thus either in lsquoArsquo position or in lsquoBrsquo position standing transverse

waves are generated in the string with a series of nodes and antinodes at

equal distances

The equation connecting number of loops (n or nrsquo) length of the

string (l) tension in the string (T) mass per unit length of the string (m) and

frequency of the string (f) is as follows

Date____________

Pag

e30

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position)

119943prime =119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

If the frequency of tuning fork is F then for lsquoArsquo position 119839 =119813

120784 and for lsquoBrsquo

position 119839prime = 119813

In the above equations if all the quantities on the RHS are known the

frequency of the tuning fork 119813 can be calculated

Observations

(1) Gravitational accelerationhellip g = 98 ms2

(2) Mass per unit length of the stringhellip m = _______ kgm

(3) Mass of the scale panhellip M1 = _______ kg

Observation Table

Sr

No

Total mass

suspended at

the end of the

stringhellip

M=M1+M2

(kg)

Tension

created

in the

stringhellip

T=Mg (N)

Length of the

vibrating string

Average

lengthhellip

119949 (m)

No of loops created on

the stringhellip

Frequency of the

vibrating stringhellip

Relation

between

f and frsquo 1199491 (m) 1199492 (m)

In

Longitudinal

Modehellip

n

In

Transverse

Modehellip

nrsquo

In

Longitudinal

Modehellip

119943 =119951

120784119949

119931

119950

In

Transverse

Modehellip

119943prime =119951prime

120784119949

119931

119950

1

2

3

4

Here M2 = the weight put in the scale pan

Page31

Date____________

Pag

e32

Calculations

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position) 119943prime =

119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e33

P-N Junction Diode Characteristics Experiment - 09

Aim To study the Forward and Reverse bias characteristics of a P-N junction

diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components P-N junction diode Resistors

Circuit Diagram

(Forward biased PN diode) (Reverse biased PN diode)

Procedure

For Forward Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 01 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 02 03 04hellip

volts and repeat the procedure Note down the knee voltage and

corresponding current in your observation table

For Reverse Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Date____________

Pag

e34

Theory

If donor (pentavalent) impurities are introduced on one side and

acceptors (trivalent) on the opposite side of a single crystal of an intrinsic

semiconductor like germanium or silicon a p-n junction is formed as shown

in Fig 11 In the figure a donor ion is indicated schematically by a plus sign

because after this impurity atom donates an electron it becomes a positive

ion

The acceptor ion is indicated by a minus sign because after this atom

accepts an electron it becomes a negative ion Initially there are only n-

type carriers to the right of the junction and only p-type carriers to the left

Because there is a density gradient across the junction holes will diffuse to

the right across the junction and electrons to the left As a result of the

displacement of these charges an electric field appears across the junction

Equilibrium is established when the field becomes large enough to restrain

the process of diffusion The positive holes which neutralize the acceptor

ions near the junction in p-type germanium disappear as a result of

combination with electrons which diffuse across the junction Similarly the

neutralizing electrons on the n side of the junction combine with holes

which cross the junction from the p side Since the region of the junction is

depleted of mobile charges it is called the depletion region or a potential

barrier

Forward Bias

An external voltage applied to the p-n junction with the polarity

shown in Fig 12 is known as forward bias The height of the potential

barrier at the junction is lowered by the applied forward voltage In other

words we can say that p-n junction diode is connected to an external

Date____________

Pag

e35

battery in such a way that depletion region is reduced in size or eliminated

altogether Which of these takes place is determined by the size of the

applied voltage The positive terminal of the battery repels the holes on the

p-side and pushes them towards the junction The negative terminal of the

battery repels the electrons and pushes them towards the junction This

collapses the depletion region With the depletion region gone the diode

can conduct

Reverse Bias

An external voltage applied with polarity in Fig 13 is called reverse

bias When reverse bias is applied to a junction diode the depletion region

does not collapse On the contrary it becomes wider The positive side of

battery is applied to the n-type material This attracts the free electrons

away from the junction The negative side of the battery attracts the holes

in p-type material away from the junction This makes the depletion region

wider than it was when no voltage is applied The depletion region is an

insulator and it will block the flow of current Actually a small current will

flow because of minority carriers The p-type material has a few minority

electrons These are pushed to the junction by the repulsion of the negative

side of the battery The n-type material has few minority holes These are

also pushed towards the junction Reverse bias forces the minority carriers

together and a small current - called leakage current - results

Diodes which are designed with adequate power dissipation

capability to operate in the breakdown region are none as Zener diodes

Two mechanisms of diode breakdown for increasing reverse voltage are

recognized In one mechanism the thermally generated electrons and

holes acquire sufficient energy from the applied potential to produce new

carriers by removing valence electrons from their bonds These new

carriers in turn produce additional carriers again through the process of

disrupting bonds This cumulative process is referred to as avalanche

breakdown Even if the initially available carriers do not acquire sufficient

energy to disrupt bonds it is possible to initiate breakdown through a

direct rupture of the bonds because of the existence of strong electric field

Under these conditions the breakdown is referred to as Zener breakdown

Date____________

Pag

e36

Zener breakdown occurs below 6 V Zener diodes are commonly used in

voltage-reference or constant-voltage devices

Characteristic curves of diode

Fig 14 shows V-I Characteristic curves for typical p-n junction diode

It is seen that the curve is not linear With 0 V across the diode the diode

will not conduct the diode will not begin to conduct until a few tenths of a

volt are applied across it This is the voltage needed to overcome the

potential barrier It requires about 02 V to turn on a germanium diode and

about 06 V to turn on a silicon diode Fig 18 also shows what happens

when reverse bias is applied to a diode At increasing levels of reverse

voltage the curve shows some reverse current This leakage current is

caused by minority carries It is usually very small

Graph

Fig-14

Date____________

Pag

e37

Observation Table for Forward bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Date____________

Pag

e38

Observation Table for Reverse bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e39

Calculation for Forward bias 119877 = 119881

119868

Calculation for Reverse bias 119877 = 119881

119868

Date____________

Pag

e40

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e41

Zener Diode Reverse Bias Characteristics Experiment - 10

Aim To study the reverse bias characteristics of a Zener diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components Zener diode Resistors

Circuit Diagram

Procedure

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Theory

A diode which is heavily doped (Si or Ge) and which operates in the

reverse breakdown region with a sharp breakdown voltage is called a zener

diode The schematic symbol of a zener diode is shown in Fig-1 This is

similar to a normal diode except that the line (bar) representing the

cathode is bent at both ends like the letter Z for zener diode

Date____________

Pag

e42

A C Fig-1

In a simple diode the doping is light as a result the breakdown

voltage is high and not sharp But if doping is made heavy the depletion

layer becomes very narrow and even the breakdown voltage gets reduced

to a sharp value The zener diode is designed to operate in the breakdown

region without damage

The reverse breakdown of a zener diode may occur either due to

zener effect or avalanche effect But zener diode primarily depends on

zener effect for its working When the electric field across the junction is

sufficiently high due to the applied voltage the zener breakdown occurs

because of breaking of covalent bonds This produces a large number of

electrons and holes which constitute a steep rise in the reverse saturation

current (also called zener current 119868Z) This effect is called as zener effect

Zener current is independent of the applied voltage and depends only on

the external resistance

The V - 119868 characteristic of a zener diode is shown in Fig-2 The

forward characteristic is simply that of an ordinary forward biased junction

diode

Fig-2

Date____________

Pag

e43

Under reverse bias condition breakdown of junction occurs This

breakdown depends upon the amount of doping It can be seen from Fig-2

that as the reverse voltage is increased the reverse current remains

negligibly small up to the lsquokneersquo of the curve

At this lsquoknee pointrsquo the effect of breakdown process begins The

voltage corresponding to the lsquoknee pointrsquo in the figure is called the zener

breakdown voltage or simply zener voltage (VZ) which is very sharp

compared to a simle p-n junction diode Beyond this voltage the reverse

current (119868Z) increases sharply to a high value

The zener diode is not immediately burnt just because it has entered

the breakdown region As long as the external resistance connected to the

diode in the circuit limits the diode current to less than the burn out value

the diode will not burn out The zener voltage VZ remains constant even

when zener current 119868Z increases greatly This ability of a diode is called

regulating ability and it enables us to use zener diode for voltage

regulation

Date____________

Pag

e44

Observation Table

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e45

Graph 119868 V

Calculations 119877 = 119881

119868

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e46

Dispersive Power of The Prism Experiment - 11

Aim To find the dispersive power (D) of the prism by using spectrometer

Apparatus Mercury vapor lamp Spectrometer Prism

Procedure

Levelling and alignment of collimator and telescope

1 Switch on the mercury lamp Adjust the leveling screws on the chassis

Keep the spirit level on the chassis and do finer adjustments of these

screws to bring the bubble in the sprit level to the centre Repeat this

placing the sprit level along a direction perpendicular to the earlier

direction

2 Repeat this procedure for the prism table

3 Close the slit at the other end of the collimator using the drum screw DS1

Open it to a reasonable width Place the spectrometer in front of the

mercury lamp window and rotate the collimator so that the slit faces of

window View the slit through the telescope If it is not in the centre of the

view level collimator and the telescope so as to bring it to the centre

Setting the prism in the minimum deviation position

1 Rotate the prism table such that lines ruled on the table become

perpendicular to the axis of collimator

2 Place prism over the prism table such that its rough surface BA is

perpendicular to the line on prism table (See Fig-1(a))

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date ___________

Pag

e17

(3) If the body begins to slide on the surface the magnitude of the frictional

force rapidly decreases to a constant value fk given by fk = microk N Where

microk is the coefficient of kinetic friction

The magnitude of the coefficients of frictions relative to each other is

given by micros gt microk gtgt micror Where micror is coefficient of rolling friction

Note Here quantities shown bold are vector quantities

Observations

(1) Weight of the blockhellip M = ________ gm

(2) Weight of the scale panhellip m1 = _______ gm

(3) Gravitational accelerationhellip g = 980 cms2

Observation Table

Sr

No

Inclination

of the

Plane (θ)

Effort required to start

the motion up (gm)

m=m1+m2

Avg Effort

m (gm)

Base of

the

Plane

b (cm)

Height

of the

Plane

h (cm)

Length

of the

Plane

l (cm)

cosθ=bl

sinθ=hl

Coefficient of

Kinetic Friction

μ = 119846119840 ndash 119820119840 119852119842119847 120521

119820119840 119836119848119852 120521

1

θ1 1

2

2

θ2 1

2

3

θ3 1

2

Here m2 = the weight put in the scale pan

Page18

Calculation

Coefficient of Kinetic Friction μ = mg ndash Mg sin θMg cos θ

(1) (2)

(3)

Average of Coefficient of Kinetic Friction

μ avg = μ 1 + μ 2 + μ 3

3

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Page19

Date____________

Pag

e20

Wattage of Bulb Experiment - 06

Aim To find the electrical energy consumed in a circuit (bulb)

Apparatus AC Ammeter(0-500 mA) AC Voltmeter(0-250 volt) Variac

Components Bulb

Circuit Diagram

Procedure

Connect the circuit as shown in the circuit diagram Now switch ON

the circuit and note down the reading shown by ammeter at 0 volt then

increase the voltage from 0 to 10 volt and note down the reading of

ammeter Now increase the voltage in order of 10 volts (up to 200 volts)

and note down the readings of the current shown by the ammeter Now

calculate the power consumed in a circuit at different stages

Theory

Experiments show that in stationary metallic conductors current does

work to increase their internal energy The heated conductor releases the

energy received to the surrounding bodies but this is done by means of

heat transfer This means that the quantity of heat released by a current

carrying conductor is equal to the total work done by the current

Date____________

Pag

e21

As we know that the work done by the current is given by 119830 = 119829119816119853helliphelliphelliphelliphelliphellip(1)

119830 = 119816120784119825119853 ( V = IR) helliphelliphelliphelliphelliphelliphellip (2)

The electrical power of a given device is simply the rate of doing

work or the amount of electric work done in one second

Therefore electric powerhellip

119823 =119830119848119851119844 119837119848119847119838 (119830)

119827119842119846119838 (119853)

119823 =119829119816119853

119853= 119829119816 helliphelliphelliphelliphelliphelliphellip (3)

Thus electric power is equal to the product of voltage by current

Watt is a unit of power Hence it can be expressed in terms of a volt

and an ampere by the formula for electric power Eqn (3)

Therefore

1 Watt = 1 volt ∙ 1 ampere

1 W = 1 V∙A

Thus if a potential difference of 1 volt causes a current of 1 ampere

to flow through a conductor (here a bulb) the electric power consumed is

1 watt and the electrical energy consumed is 1 joulesec this electrical

energy consumed in the bulb is converted into heat and light energy

Date____________

Pag

e22

Observation Table

Sr No Voltage V (volt) Current 119816 (mA) Power

119823 = 119829119816 (watt)

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

Date____________

Pag

e23

Calculation 119823 = 119829119816

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e24

Temperature of Tungsten Filament Experiment ndash 07

Aim To find the temperature of the tungsten filament of the bulb

Apparatus AC Ammeter(0-500 mA) AC Voltmeter(0-250 volt) Variac

Components Bulb

Circuit Diagram

Procedure

Connect the circuit as shown in the circuit diagram Now switch ON

the circuit and note down the reading shown by ammeter at 0 volt then

increase the voltage from 0 to 10 volt and note down the reading of

ammeter Now increase the voltage in order of 10 volts (up to 100 volts)

and note down the readings of the current shown by the ammeter Now

calculate the resistance and the temperature of the filament

Observations

(1) Room temperaturehellip t0 = _______ ˚C

(2) Resistance of the filament of the bulb at room temperaturehellip

R0 = _______ Ω

(3) Temperature coefficient of tungstenhellip α = 45times10-4 ˚C-1

Date____________

Pag

e25

Observation Table

Sr No Voltage V

(volt)

Current 119816

(mA)

Resistance of

The Filament

119825119853 =119829

119816 Ω

Temperature of The Filament

119853 =120783

120514[

119825119853

119825120782 120783 + 120514119853120782 minus 120783] ˚C

1

2

3

4

5

6

7

8

9

10

Graph Rt versus t

Date____________

Pag

e26

Calculations

(1) Resistance of The Filament Rt =V

I Ω

(2) Temperature of The Filament t =1

α[

Rt

R0 1 + αt0 minus 1] ˚C

Date____________

Pag

e27

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e28

Meldersquos Experiment - 08

Aim To find the frequency of the wave and the frequency of the tuning fork by

Meldersquos experiment

Apparatus Meldersquos experiment apparatus

Circuit Diagram

Transverse mode

Procedure

Set Meldersquos experiment apparatus as shown in circuit diagram in

longitudinal position and switch ON the power supply put some weight in

scale pan and adjust the length of the string in such a way that you find

some loops on the string (eg 2 loops) Now rotate the apparatus by 90˚ so

that it is set for lsquoBrsquo position for the same values of weight in pan and for

the same length of the string the number of loops created in lsquoBrsquo position

are double (eg 4 loops) than in lsquoArsquo position Note down these readings in

observation table Repeat the experiment for other values of weight in

scale pan

Date____________

Pag

e29

Theory

This is an easy and efficient method by which nodes and antinodes

formed on a string can be demonstrated

A tuning fork is fitted in a wooden block A long string or thread of

cotton is taken One end of this string is tied to one of the prongs of the

tuning fork and the second end of this string passes over a smooth pulley in

such a way that a small pan can be hang on it Small weights are put in the

pan to create tension in the string This arrangement is shown in the circuit

diagram

The fork is set into vibrations by lightly hitting the prong of the tuning

fork on which the string is not tied or by connecting an electric supply as

shown in the circuit diagram Thus the transverse vibrations are produced

in the string and by adjusting the length andor weights in the pan these

vibrations are reflected from the point of contact between the string and

the pulley and a number of loops appear on the string as shown in the

circuit diagram

When the prongs of the tuning fork vibrate in a plane parallel to the

direction of propagation of the waves it is called lsquoArsquo position or

longitudinal position

If the tuning fork along with the wooden block is rotated through

90˚ so that the plane of vibration of the tuning fork is normal (ie at right

angles) to the direction of propagation it is called lsquoBrsquo position or transverse

position

For the same length and same weight in the pan (ie for the same

tension) the number of loops in lsquoBrsquo position is double than in lsquoArsquo position

Thus either in lsquoArsquo position or in lsquoBrsquo position standing transverse

waves are generated in the string with a series of nodes and antinodes at

equal distances

The equation connecting number of loops (n or nrsquo) length of the

string (l) tension in the string (T) mass per unit length of the string (m) and

frequency of the string (f) is as follows

Date____________

Pag

e30

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position)

119943prime =119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

If the frequency of tuning fork is F then for lsquoArsquo position 119839 =119813

120784 and for lsquoBrsquo

position 119839prime = 119813

In the above equations if all the quantities on the RHS are known the

frequency of the tuning fork 119813 can be calculated

Observations

(1) Gravitational accelerationhellip g = 98 ms2

(2) Mass per unit length of the stringhellip m = _______ kgm

(3) Mass of the scale panhellip M1 = _______ kg

Observation Table

Sr

No

Total mass

suspended at

the end of the

stringhellip

M=M1+M2

(kg)

Tension

created

in the

stringhellip

T=Mg (N)

Length of the

vibrating string

Average

lengthhellip

119949 (m)

No of loops created on

the stringhellip

Frequency of the

vibrating stringhellip

Relation

between

f and frsquo 1199491 (m) 1199492 (m)

In

Longitudinal

Modehellip

n

In

Transverse

Modehellip

nrsquo

In

Longitudinal

Modehellip

119943 =119951

120784119949

119931

119950

In

Transverse

Modehellip

119943prime =119951prime

120784119949

119931

119950

1

2

3

4

Here M2 = the weight put in the scale pan

Page31

Date____________

Pag

e32

Calculations

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position) 119943prime =

119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e33

P-N Junction Diode Characteristics Experiment - 09

Aim To study the Forward and Reverse bias characteristics of a P-N junction

diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components P-N junction diode Resistors

Circuit Diagram

(Forward biased PN diode) (Reverse biased PN diode)

Procedure

For Forward Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 01 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 02 03 04hellip

volts and repeat the procedure Note down the knee voltage and

corresponding current in your observation table

For Reverse Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Date____________

Pag

e34

Theory

If donor (pentavalent) impurities are introduced on one side and

acceptors (trivalent) on the opposite side of a single crystal of an intrinsic

semiconductor like germanium or silicon a p-n junction is formed as shown

in Fig 11 In the figure a donor ion is indicated schematically by a plus sign

because after this impurity atom donates an electron it becomes a positive

ion

The acceptor ion is indicated by a minus sign because after this atom

accepts an electron it becomes a negative ion Initially there are only n-

type carriers to the right of the junction and only p-type carriers to the left

Because there is a density gradient across the junction holes will diffuse to

the right across the junction and electrons to the left As a result of the

displacement of these charges an electric field appears across the junction

Equilibrium is established when the field becomes large enough to restrain

the process of diffusion The positive holes which neutralize the acceptor

ions near the junction in p-type germanium disappear as a result of

combination with electrons which diffuse across the junction Similarly the

neutralizing electrons on the n side of the junction combine with holes

which cross the junction from the p side Since the region of the junction is

depleted of mobile charges it is called the depletion region or a potential

barrier

Forward Bias

An external voltage applied to the p-n junction with the polarity

shown in Fig 12 is known as forward bias The height of the potential

barrier at the junction is lowered by the applied forward voltage In other

words we can say that p-n junction diode is connected to an external

Date____________

Pag

e35

battery in such a way that depletion region is reduced in size or eliminated

altogether Which of these takes place is determined by the size of the

applied voltage The positive terminal of the battery repels the holes on the

p-side and pushes them towards the junction The negative terminal of the

battery repels the electrons and pushes them towards the junction This

collapses the depletion region With the depletion region gone the diode

can conduct

Reverse Bias

An external voltage applied with polarity in Fig 13 is called reverse

bias When reverse bias is applied to a junction diode the depletion region

does not collapse On the contrary it becomes wider The positive side of

battery is applied to the n-type material This attracts the free electrons

away from the junction The negative side of the battery attracts the holes

in p-type material away from the junction This makes the depletion region

wider than it was when no voltage is applied The depletion region is an

insulator and it will block the flow of current Actually a small current will

flow because of minority carriers The p-type material has a few minority

electrons These are pushed to the junction by the repulsion of the negative

side of the battery The n-type material has few minority holes These are

also pushed towards the junction Reverse bias forces the minority carriers

together and a small current - called leakage current - results

Diodes which are designed with adequate power dissipation

capability to operate in the breakdown region are none as Zener diodes

Two mechanisms of diode breakdown for increasing reverse voltage are

recognized In one mechanism the thermally generated electrons and

holes acquire sufficient energy from the applied potential to produce new

carriers by removing valence electrons from their bonds These new

carriers in turn produce additional carriers again through the process of

disrupting bonds This cumulative process is referred to as avalanche

breakdown Even if the initially available carriers do not acquire sufficient

energy to disrupt bonds it is possible to initiate breakdown through a

direct rupture of the bonds because of the existence of strong electric field

Under these conditions the breakdown is referred to as Zener breakdown

Date____________

Pag

e36

Zener breakdown occurs below 6 V Zener diodes are commonly used in

voltage-reference or constant-voltage devices

Characteristic curves of diode

Fig 14 shows V-I Characteristic curves for typical p-n junction diode

It is seen that the curve is not linear With 0 V across the diode the diode

will not conduct the diode will not begin to conduct until a few tenths of a

volt are applied across it This is the voltage needed to overcome the

potential barrier It requires about 02 V to turn on a germanium diode and

about 06 V to turn on a silicon diode Fig 18 also shows what happens

when reverse bias is applied to a diode At increasing levels of reverse

voltage the curve shows some reverse current This leakage current is

caused by minority carries It is usually very small

Graph

Fig-14

Date____________

Pag

e37

Observation Table for Forward bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Date____________

Pag

e38

Observation Table for Reverse bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e39

Calculation for Forward bias 119877 = 119881

119868

Calculation for Reverse bias 119877 = 119881

119868

Date____________

Pag

e40

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e41

Zener Diode Reverse Bias Characteristics Experiment - 10

Aim To study the reverse bias characteristics of a Zener diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components Zener diode Resistors

Circuit Diagram

Procedure

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Theory

A diode which is heavily doped (Si or Ge) and which operates in the

reverse breakdown region with a sharp breakdown voltage is called a zener

diode The schematic symbol of a zener diode is shown in Fig-1 This is

similar to a normal diode except that the line (bar) representing the

cathode is bent at both ends like the letter Z for zener diode

Date____________

Pag

e42

A C Fig-1

In a simple diode the doping is light as a result the breakdown

voltage is high and not sharp But if doping is made heavy the depletion

layer becomes very narrow and even the breakdown voltage gets reduced

to a sharp value The zener diode is designed to operate in the breakdown

region without damage

The reverse breakdown of a zener diode may occur either due to

zener effect or avalanche effect But zener diode primarily depends on

zener effect for its working When the electric field across the junction is

sufficiently high due to the applied voltage the zener breakdown occurs

because of breaking of covalent bonds This produces a large number of

electrons and holes which constitute a steep rise in the reverse saturation

current (also called zener current 119868Z) This effect is called as zener effect

Zener current is independent of the applied voltage and depends only on

the external resistance

The V - 119868 characteristic of a zener diode is shown in Fig-2 The

forward characteristic is simply that of an ordinary forward biased junction

diode

Fig-2

Date____________

Pag

e43

Under reverse bias condition breakdown of junction occurs This

breakdown depends upon the amount of doping It can be seen from Fig-2

that as the reverse voltage is increased the reverse current remains

negligibly small up to the lsquokneersquo of the curve

At this lsquoknee pointrsquo the effect of breakdown process begins The

voltage corresponding to the lsquoknee pointrsquo in the figure is called the zener

breakdown voltage or simply zener voltage (VZ) which is very sharp

compared to a simle p-n junction diode Beyond this voltage the reverse

current (119868Z) increases sharply to a high value

The zener diode is not immediately burnt just because it has entered

the breakdown region As long as the external resistance connected to the

diode in the circuit limits the diode current to less than the burn out value

the diode will not burn out The zener voltage VZ remains constant even

when zener current 119868Z increases greatly This ability of a diode is called

regulating ability and it enables us to use zener diode for voltage

regulation

Date____________

Pag

e44

Observation Table

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e45

Graph 119868 V

Calculations 119877 = 119881

119868

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e46

Dispersive Power of The Prism Experiment - 11

Aim To find the dispersive power (D) of the prism by using spectrometer

Apparatus Mercury vapor lamp Spectrometer Prism

Procedure

Levelling and alignment of collimator and telescope

1 Switch on the mercury lamp Adjust the leveling screws on the chassis

Keep the spirit level on the chassis and do finer adjustments of these

screws to bring the bubble in the sprit level to the centre Repeat this

placing the sprit level along a direction perpendicular to the earlier

direction

2 Repeat this procedure for the prism table

3 Close the slit at the other end of the collimator using the drum screw DS1

Open it to a reasonable width Place the spectrometer in front of the

mercury lamp window and rotate the collimator so that the slit faces of

window View the slit through the telescope If it is not in the centre of the

view level collimator and the telescope so as to bring it to the centre

Setting the prism in the minimum deviation position

1 Rotate the prism table such that lines ruled on the table become

perpendicular to the axis of collimator

2 Place prism over the prism table such that its rough surface BA is

perpendicular to the line on prism table (See Fig-1(a))

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Observation Table

Sr

No

Inclination

of the

Plane (θ)

Effort required to start

the motion up (gm)

m=m1+m2

Avg Effort

m (gm)

Base of

the

Plane

b (cm)

Height

of the

Plane

h (cm)

Length

of the

Plane

l (cm)

cosθ=bl

sinθ=hl

Coefficient of

Kinetic Friction

μ = 119846119840 ndash 119820119840 119852119842119847 120521

119820119840 119836119848119852 120521

1

θ1 1

2

2

θ2 1

2

3

θ3 1

2

Here m2 = the weight put in the scale pan

Page18

Calculation

Coefficient of Kinetic Friction μ = mg ndash Mg sin θMg cos θ

(1) (2)

(3)

Average of Coefficient of Kinetic Friction

μ avg = μ 1 + μ 2 + μ 3

3

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Page19

Date____________

Pag

e20

Wattage of Bulb Experiment - 06

Aim To find the electrical energy consumed in a circuit (bulb)

Apparatus AC Ammeter(0-500 mA) AC Voltmeter(0-250 volt) Variac

Components Bulb

Circuit Diagram

Procedure

Connect the circuit as shown in the circuit diagram Now switch ON

the circuit and note down the reading shown by ammeter at 0 volt then

increase the voltage from 0 to 10 volt and note down the reading of

ammeter Now increase the voltage in order of 10 volts (up to 200 volts)

and note down the readings of the current shown by the ammeter Now

calculate the power consumed in a circuit at different stages

Theory

Experiments show that in stationary metallic conductors current does

work to increase their internal energy The heated conductor releases the

energy received to the surrounding bodies but this is done by means of

heat transfer This means that the quantity of heat released by a current

carrying conductor is equal to the total work done by the current

Date____________

Pag

e21

As we know that the work done by the current is given by 119830 = 119829119816119853helliphelliphelliphelliphelliphellip(1)

119830 = 119816120784119825119853 ( V = IR) helliphelliphelliphelliphelliphelliphellip (2)

The electrical power of a given device is simply the rate of doing

work or the amount of electric work done in one second

Therefore electric powerhellip

119823 =119830119848119851119844 119837119848119847119838 (119830)

119827119842119846119838 (119853)

119823 =119829119816119853

119853= 119829119816 helliphelliphelliphelliphelliphelliphellip (3)

Thus electric power is equal to the product of voltage by current

Watt is a unit of power Hence it can be expressed in terms of a volt

and an ampere by the formula for electric power Eqn (3)

Therefore

1 Watt = 1 volt ∙ 1 ampere

1 W = 1 V∙A

Thus if a potential difference of 1 volt causes a current of 1 ampere

to flow through a conductor (here a bulb) the electric power consumed is

1 watt and the electrical energy consumed is 1 joulesec this electrical

energy consumed in the bulb is converted into heat and light energy

Date____________

Pag

e22

Observation Table

Sr No Voltage V (volt) Current 119816 (mA) Power

119823 = 119829119816 (watt)

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

Date____________

Pag

e23

Calculation 119823 = 119829119816

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e24

Temperature of Tungsten Filament Experiment ndash 07

Aim To find the temperature of the tungsten filament of the bulb

Apparatus AC Ammeter(0-500 mA) AC Voltmeter(0-250 volt) Variac

Components Bulb

Circuit Diagram

Procedure

Connect the circuit as shown in the circuit diagram Now switch ON

the circuit and note down the reading shown by ammeter at 0 volt then

increase the voltage from 0 to 10 volt and note down the reading of

ammeter Now increase the voltage in order of 10 volts (up to 100 volts)

and note down the readings of the current shown by the ammeter Now

calculate the resistance and the temperature of the filament

Observations

(1) Room temperaturehellip t0 = _______ ˚C

(2) Resistance of the filament of the bulb at room temperaturehellip

R0 = _______ Ω

(3) Temperature coefficient of tungstenhellip α = 45times10-4 ˚C-1

Date____________

Pag

e25

Observation Table

Sr No Voltage V

(volt)

Current 119816

(mA)

Resistance of

The Filament

119825119853 =119829

119816 Ω

Temperature of The Filament

119853 =120783

120514[

119825119853

119825120782 120783 + 120514119853120782 minus 120783] ˚C

1

2

3

4

5

6

7

8

9

10

Graph Rt versus t

Date____________

Pag

e26

Calculations

(1) Resistance of The Filament Rt =V

I Ω

(2) Temperature of The Filament t =1

α[

Rt

R0 1 + αt0 minus 1] ˚C

Date____________

Pag

e27

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e28

Meldersquos Experiment - 08

Aim To find the frequency of the wave and the frequency of the tuning fork by

Meldersquos experiment

Apparatus Meldersquos experiment apparatus

Circuit Diagram

Transverse mode

Procedure

Set Meldersquos experiment apparatus as shown in circuit diagram in

longitudinal position and switch ON the power supply put some weight in

scale pan and adjust the length of the string in such a way that you find

some loops on the string (eg 2 loops) Now rotate the apparatus by 90˚ so

that it is set for lsquoBrsquo position for the same values of weight in pan and for

the same length of the string the number of loops created in lsquoBrsquo position

are double (eg 4 loops) than in lsquoArsquo position Note down these readings in

observation table Repeat the experiment for other values of weight in

scale pan

Date____________

Pag

e29

Theory

This is an easy and efficient method by which nodes and antinodes

formed on a string can be demonstrated

A tuning fork is fitted in a wooden block A long string or thread of

cotton is taken One end of this string is tied to one of the prongs of the

tuning fork and the second end of this string passes over a smooth pulley in

such a way that a small pan can be hang on it Small weights are put in the

pan to create tension in the string This arrangement is shown in the circuit

diagram

The fork is set into vibrations by lightly hitting the prong of the tuning

fork on which the string is not tied or by connecting an electric supply as

shown in the circuit diagram Thus the transverse vibrations are produced

in the string and by adjusting the length andor weights in the pan these

vibrations are reflected from the point of contact between the string and

the pulley and a number of loops appear on the string as shown in the

circuit diagram

When the prongs of the tuning fork vibrate in a plane parallel to the

direction of propagation of the waves it is called lsquoArsquo position or

longitudinal position

If the tuning fork along with the wooden block is rotated through

90˚ so that the plane of vibration of the tuning fork is normal (ie at right

angles) to the direction of propagation it is called lsquoBrsquo position or transverse

position

For the same length and same weight in the pan (ie for the same

tension) the number of loops in lsquoBrsquo position is double than in lsquoArsquo position

Thus either in lsquoArsquo position or in lsquoBrsquo position standing transverse

waves are generated in the string with a series of nodes and antinodes at

equal distances

The equation connecting number of loops (n or nrsquo) length of the

string (l) tension in the string (T) mass per unit length of the string (m) and

frequency of the string (f) is as follows

Date____________

Pag

e30

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position)

119943prime =119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

If the frequency of tuning fork is F then for lsquoArsquo position 119839 =119813

120784 and for lsquoBrsquo

position 119839prime = 119813

In the above equations if all the quantities on the RHS are known the

frequency of the tuning fork 119813 can be calculated

Observations

(1) Gravitational accelerationhellip g = 98 ms2

(2) Mass per unit length of the stringhellip m = _______ kgm

(3) Mass of the scale panhellip M1 = _______ kg

Observation Table

Sr

No

Total mass

suspended at

the end of the

stringhellip

M=M1+M2

(kg)

Tension

created

in the

stringhellip

T=Mg (N)

Length of the

vibrating string

Average

lengthhellip

119949 (m)

No of loops created on

the stringhellip

Frequency of the

vibrating stringhellip

Relation

between

f and frsquo 1199491 (m) 1199492 (m)

In

Longitudinal

Modehellip

n

In

Transverse

Modehellip

nrsquo

In

Longitudinal

Modehellip

119943 =119951

120784119949

119931

119950

In

Transverse

Modehellip

119943prime =119951prime

120784119949

119931

119950

1

2

3

4

Here M2 = the weight put in the scale pan

Page31

Date____________

Pag

e32

Calculations

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position) 119943prime =

119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e33

P-N Junction Diode Characteristics Experiment - 09

Aim To study the Forward and Reverse bias characteristics of a P-N junction

diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components P-N junction diode Resistors

Circuit Diagram

(Forward biased PN diode) (Reverse biased PN diode)

Procedure

For Forward Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 01 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 02 03 04hellip

volts and repeat the procedure Note down the knee voltage and

corresponding current in your observation table

For Reverse Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Date____________

Pag

e34

Theory

If donor (pentavalent) impurities are introduced on one side and

acceptors (trivalent) on the opposite side of a single crystal of an intrinsic

semiconductor like germanium or silicon a p-n junction is formed as shown

in Fig 11 In the figure a donor ion is indicated schematically by a plus sign

because after this impurity atom donates an electron it becomes a positive

ion

The acceptor ion is indicated by a minus sign because after this atom

accepts an electron it becomes a negative ion Initially there are only n-

type carriers to the right of the junction and only p-type carriers to the left

Because there is a density gradient across the junction holes will diffuse to

the right across the junction and electrons to the left As a result of the

displacement of these charges an electric field appears across the junction

Equilibrium is established when the field becomes large enough to restrain

the process of diffusion The positive holes which neutralize the acceptor

ions near the junction in p-type germanium disappear as a result of

combination with electrons which diffuse across the junction Similarly the

neutralizing electrons on the n side of the junction combine with holes

which cross the junction from the p side Since the region of the junction is

depleted of mobile charges it is called the depletion region or a potential

barrier

Forward Bias

An external voltage applied to the p-n junction with the polarity

shown in Fig 12 is known as forward bias The height of the potential

barrier at the junction is lowered by the applied forward voltage In other

words we can say that p-n junction diode is connected to an external

Date____________

Pag

e35

battery in such a way that depletion region is reduced in size or eliminated

altogether Which of these takes place is determined by the size of the

applied voltage The positive terminal of the battery repels the holes on the

p-side and pushes them towards the junction The negative terminal of the

battery repels the electrons and pushes them towards the junction This

collapses the depletion region With the depletion region gone the diode

can conduct

Reverse Bias

An external voltage applied with polarity in Fig 13 is called reverse

bias When reverse bias is applied to a junction diode the depletion region

does not collapse On the contrary it becomes wider The positive side of

battery is applied to the n-type material This attracts the free electrons

away from the junction The negative side of the battery attracts the holes

in p-type material away from the junction This makes the depletion region

wider than it was when no voltage is applied The depletion region is an

insulator and it will block the flow of current Actually a small current will

flow because of minority carriers The p-type material has a few minority

electrons These are pushed to the junction by the repulsion of the negative

side of the battery The n-type material has few minority holes These are

also pushed towards the junction Reverse bias forces the minority carriers

together and a small current - called leakage current - results

Diodes which are designed with adequate power dissipation

capability to operate in the breakdown region are none as Zener diodes

Two mechanisms of diode breakdown for increasing reverse voltage are

recognized In one mechanism the thermally generated electrons and

holes acquire sufficient energy from the applied potential to produce new

carriers by removing valence electrons from their bonds These new

carriers in turn produce additional carriers again through the process of

disrupting bonds This cumulative process is referred to as avalanche

breakdown Even if the initially available carriers do not acquire sufficient

energy to disrupt bonds it is possible to initiate breakdown through a

direct rupture of the bonds because of the existence of strong electric field

Under these conditions the breakdown is referred to as Zener breakdown

Date____________

Pag

e36

Zener breakdown occurs below 6 V Zener diodes are commonly used in

voltage-reference or constant-voltage devices

Characteristic curves of diode

Fig 14 shows V-I Characteristic curves for typical p-n junction diode

It is seen that the curve is not linear With 0 V across the diode the diode

will not conduct the diode will not begin to conduct until a few tenths of a

volt are applied across it This is the voltage needed to overcome the

potential barrier It requires about 02 V to turn on a germanium diode and

about 06 V to turn on a silicon diode Fig 18 also shows what happens

when reverse bias is applied to a diode At increasing levels of reverse

voltage the curve shows some reverse current This leakage current is

caused by minority carries It is usually very small

Graph

Fig-14

Date____________

Pag

e37

Observation Table for Forward bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Date____________

Pag

e38

Observation Table for Reverse bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e39

Calculation for Forward bias 119877 = 119881

119868

Calculation for Reverse bias 119877 = 119881

119868

Date____________

Pag

e40

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e41

Zener Diode Reverse Bias Characteristics Experiment - 10

Aim To study the reverse bias characteristics of a Zener diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components Zener diode Resistors

Circuit Diagram

Procedure

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Theory

A diode which is heavily doped (Si or Ge) and which operates in the

reverse breakdown region with a sharp breakdown voltage is called a zener

diode The schematic symbol of a zener diode is shown in Fig-1 This is

similar to a normal diode except that the line (bar) representing the

cathode is bent at both ends like the letter Z for zener diode

Date____________

Pag

e42

A C Fig-1

In a simple diode the doping is light as a result the breakdown

voltage is high and not sharp But if doping is made heavy the depletion

layer becomes very narrow and even the breakdown voltage gets reduced

to a sharp value The zener diode is designed to operate in the breakdown

region without damage

The reverse breakdown of a zener diode may occur either due to

zener effect or avalanche effect But zener diode primarily depends on

zener effect for its working When the electric field across the junction is

sufficiently high due to the applied voltage the zener breakdown occurs

because of breaking of covalent bonds This produces a large number of

electrons and holes which constitute a steep rise in the reverse saturation

current (also called zener current 119868Z) This effect is called as zener effect

Zener current is independent of the applied voltage and depends only on

the external resistance

The V - 119868 characteristic of a zener diode is shown in Fig-2 The

forward characteristic is simply that of an ordinary forward biased junction

diode

Fig-2

Date____________

Pag

e43

Under reverse bias condition breakdown of junction occurs This

breakdown depends upon the amount of doping It can be seen from Fig-2

that as the reverse voltage is increased the reverse current remains

negligibly small up to the lsquokneersquo of the curve

At this lsquoknee pointrsquo the effect of breakdown process begins The

voltage corresponding to the lsquoknee pointrsquo in the figure is called the zener

breakdown voltage or simply zener voltage (VZ) which is very sharp

compared to a simle p-n junction diode Beyond this voltage the reverse

current (119868Z) increases sharply to a high value

The zener diode is not immediately burnt just because it has entered

the breakdown region As long as the external resistance connected to the

diode in the circuit limits the diode current to less than the burn out value

the diode will not burn out The zener voltage VZ remains constant even

when zener current 119868Z increases greatly This ability of a diode is called

regulating ability and it enables us to use zener diode for voltage

regulation

Date____________

Pag

e44

Observation Table

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e45

Graph 119868 V

Calculations 119877 = 119881

119868

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e46

Dispersive Power of The Prism Experiment - 11

Aim To find the dispersive power (D) of the prism by using spectrometer

Apparatus Mercury vapor lamp Spectrometer Prism

Procedure

Levelling and alignment of collimator and telescope

1 Switch on the mercury lamp Adjust the leveling screws on the chassis

Keep the spirit level on the chassis and do finer adjustments of these

screws to bring the bubble in the sprit level to the centre Repeat this

placing the sprit level along a direction perpendicular to the earlier

direction

2 Repeat this procedure for the prism table

3 Close the slit at the other end of the collimator using the drum screw DS1

Open it to a reasonable width Place the spectrometer in front of the

mercury lamp window and rotate the collimator so that the slit faces of

window View the slit through the telescope If it is not in the centre of the

view level collimator and the telescope so as to bring it to the centre

Setting the prism in the minimum deviation position

1 Rotate the prism table such that lines ruled on the table become

perpendicular to the axis of collimator

2 Place prism over the prism table such that its rough surface BA is

perpendicular to the line on prism table (See Fig-1(a))

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Calculation

Coefficient of Kinetic Friction μ = mg ndash Mg sin θMg cos θ

(1) (2)

(3)

Average of Coefficient of Kinetic Friction

μ avg = μ 1 + μ 2 + μ 3

3

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Page19

Date____________

Pag

e20

Wattage of Bulb Experiment - 06

Aim To find the electrical energy consumed in a circuit (bulb)

Apparatus AC Ammeter(0-500 mA) AC Voltmeter(0-250 volt) Variac

Components Bulb

Circuit Diagram

Procedure

Connect the circuit as shown in the circuit diagram Now switch ON

the circuit and note down the reading shown by ammeter at 0 volt then

increase the voltage from 0 to 10 volt and note down the reading of

ammeter Now increase the voltage in order of 10 volts (up to 200 volts)

and note down the readings of the current shown by the ammeter Now

calculate the power consumed in a circuit at different stages

Theory

Experiments show that in stationary metallic conductors current does

work to increase their internal energy The heated conductor releases the

energy received to the surrounding bodies but this is done by means of

heat transfer This means that the quantity of heat released by a current

carrying conductor is equal to the total work done by the current

Date____________

Pag

e21

As we know that the work done by the current is given by 119830 = 119829119816119853helliphelliphelliphelliphelliphellip(1)

119830 = 119816120784119825119853 ( V = IR) helliphelliphelliphelliphelliphelliphellip (2)

The electrical power of a given device is simply the rate of doing

work or the amount of electric work done in one second

Therefore electric powerhellip

119823 =119830119848119851119844 119837119848119847119838 (119830)

119827119842119846119838 (119853)

119823 =119829119816119853

119853= 119829119816 helliphelliphelliphelliphelliphelliphellip (3)

Thus electric power is equal to the product of voltage by current

Watt is a unit of power Hence it can be expressed in terms of a volt

and an ampere by the formula for electric power Eqn (3)

Therefore

1 Watt = 1 volt ∙ 1 ampere

1 W = 1 V∙A

Thus if a potential difference of 1 volt causes a current of 1 ampere

to flow through a conductor (here a bulb) the electric power consumed is

1 watt and the electrical energy consumed is 1 joulesec this electrical

energy consumed in the bulb is converted into heat and light energy

Date____________

Pag

e22

Observation Table

Sr No Voltage V (volt) Current 119816 (mA) Power

119823 = 119829119816 (watt)

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

Date____________

Pag

e23

Calculation 119823 = 119829119816

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e24

Temperature of Tungsten Filament Experiment ndash 07

Aim To find the temperature of the tungsten filament of the bulb

Apparatus AC Ammeter(0-500 mA) AC Voltmeter(0-250 volt) Variac

Components Bulb

Circuit Diagram

Procedure

Connect the circuit as shown in the circuit diagram Now switch ON

the circuit and note down the reading shown by ammeter at 0 volt then

increase the voltage from 0 to 10 volt and note down the reading of

ammeter Now increase the voltage in order of 10 volts (up to 100 volts)

and note down the readings of the current shown by the ammeter Now

calculate the resistance and the temperature of the filament

Observations

(1) Room temperaturehellip t0 = _______ ˚C

(2) Resistance of the filament of the bulb at room temperaturehellip

R0 = _______ Ω

(3) Temperature coefficient of tungstenhellip α = 45times10-4 ˚C-1

Date____________

Pag

e25

Observation Table

Sr No Voltage V

(volt)

Current 119816

(mA)

Resistance of

The Filament

119825119853 =119829

119816 Ω

Temperature of The Filament

119853 =120783

120514[

119825119853

119825120782 120783 + 120514119853120782 minus 120783] ˚C

1

2

3

4

5

6

7

8

9

10

Graph Rt versus t

Date____________

Pag

e26

Calculations

(1) Resistance of The Filament Rt =V

I Ω

(2) Temperature of The Filament t =1

α[

Rt

R0 1 + αt0 minus 1] ˚C

Date____________

Pag

e27

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e28

Meldersquos Experiment - 08

Aim To find the frequency of the wave and the frequency of the tuning fork by

Meldersquos experiment

Apparatus Meldersquos experiment apparatus

Circuit Diagram

Transverse mode

Procedure

Set Meldersquos experiment apparatus as shown in circuit diagram in

longitudinal position and switch ON the power supply put some weight in

scale pan and adjust the length of the string in such a way that you find

some loops on the string (eg 2 loops) Now rotate the apparatus by 90˚ so

that it is set for lsquoBrsquo position for the same values of weight in pan and for

the same length of the string the number of loops created in lsquoBrsquo position

are double (eg 4 loops) than in lsquoArsquo position Note down these readings in

observation table Repeat the experiment for other values of weight in

scale pan

Date____________

Pag

e29

Theory

This is an easy and efficient method by which nodes and antinodes

formed on a string can be demonstrated

A tuning fork is fitted in a wooden block A long string or thread of

cotton is taken One end of this string is tied to one of the prongs of the

tuning fork and the second end of this string passes over a smooth pulley in

such a way that a small pan can be hang on it Small weights are put in the

pan to create tension in the string This arrangement is shown in the circuit

diagram

The fork is set into vibrations by lightly hitting the prong of the tuning

fork on which the string is not tied or by connecting an electric supply as

shown in the circuit diagram Thus the transverse vibrations are produced

in the string and by adjusting the length andor weights in the pan these

vibrations are reflected from the point of contact between the string and

the pulley and a number of loops appear on the string as shown in the

circuit diagram

When the prongs of the tuning fork vibrate in a plane parallel to the

direction of propagation of the waves it is called lsquoArsquo position or

longitudinal position

If the tuning fork along with the wooden block is rotated through

90˚ so that the plane of vibration of the tuning fork is normal (ie at right

angles) to the direction of propagation it is called lsquoBrsquo position or transverse

position

For the same length and same weight in the pan (ie for the same

tension) the number of loops in lsquoBrsquo position is double than in lsquoArsquo position

Thus either in lsquoArsquo position or in lsquoBrsquo position standing transverse

waves are generated in the string with a series of nodes and antinodes at

equal distances

The equation connecting number of loops (n or nrsquo) length of the

string (l) tension in the string (T) mass per unit length of the string (m) and

frequency of the string (f) is as follows

Date____________

Pag

e30

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position)

119943prime =119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

If the frequency of tuning fork is F then for lsquoArsquo position 119839 =119813

120784 and for lsquoBrsquo

position 119839prime = 119813

In the above equations if all the quantities on the RHS are known the

frequency of the tuning fork 119813 can be calculated

Observations

(1) Gravitational accelerationhellip g = 98 ms2

(2) Mass per unit length of the stringhellip m = _______ kgm

(3) Mass of the scale panhellip M1 = _______ kg

Observation Table

Sr

No

Total mass

suspended at

the end of the

stringhellip

M=M1+M2

(kg)

Tension

created

in the

stringhellip

T=Mg (N)

Length of the

vibrating string

Average

lengthhellip

119949 (m)

No of loops created on

the stringhellip

Frequency of the

vibrating stringhellip

Relation

between

f and frsquo 1199491 (m) 1199492 (m)

In

Longitudinal

Modehellip

n

In

Transverse

Modehellip

nrsquo

In

Longitudinal

Modehellip

119943 =119951

120784119949

119931

119950

In

Transverse

Modehellip

119943prime =119951prime

120784119949

119931

119950

1

2

3

4

Here M2 = the weight put in the scale pan

Page31

Date____________

Pag

e32

Calculations

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position) 119943prime =

119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e33

P-N Junction Diode Characteristics Experiment - 09

Aim To study the Forward and Reverse bias characteristics of a P-N junction

diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components P-N junction diode Resistors

Circuit Diagram

(Forward biased PN diode) (Reverse biased PN diode)

Procedure

For Forward Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 01 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 02 03 04hellip

volts and repeat the procedure Note down the knee voltage and

corresponding current in your observation table

For Reverse Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Date____________

Pag

e34

Theory

If donor (pentavalent) impurities are introduced on one side and

acceptors (trivalent) on the opposite side of a single crystal of an intrinsic

semiconductor like germanium or silicon a p-n junction is formed as shown

in Fig 11 In the figure a donor ion is indicated schematically by a plus sign

because after this impurity atom donates an electron it becomes a positive

ion

The acceptor ion is indicated by a minus sign because after this atom

accepts an electron it becomes a negative ion Initially there are only n-

type carriers to the right of the junction and only p-type carriers to the left

Because there is a density gradient across the junction holes will diffuse to

the right across the junction and electrons to the left As a result of the

displacement of these charges an electric field appears across the junction

Equilibrium is established when the field becomes large enough to restrain

the process of diffusion The positive holes which neutralize the acceptor

ions near the junction in p-type germanium disappear as a result of

combination with electrons which diffuse across the junction Similarly the

neutralizing electrons on the n side of the junction combine with holes

which cross the junction from the p side Since the region of the junction is

depleted of mobile charges it is called the depletion region or a potential

barrier

Forward Bias

An external voltage applied to the p-n junction with the polarity

shown in Fig 12 is known as forward bias The height of the potential

barrier at the junction is lowered by the applied forward voltage In other

words we can say that p-n junction diode is connected to an external

Date____________

Pag

e35

battery in such a way that depletion region is reduced in size or eliminated

altogether Which of these takes place is determined by the size of the

applied voltage The positive terminal of the battery repels the holes on the

p-side and pushes them towards the junction The negative terminal of the

battery repels the electrons and pushes them towards the junction This

collapses the depletion region With the depletion region gone the diode

can conduct

Reverse Bias

An external voltage applied with polarity in Fig 13 is called reverse

bias When reverse bias is applied to a junction diode the depletion region

does not collapse On the contrary it becomes wider The positive side of

battery is applied to the n-type material This attracts the free electrons

away from the junction The negative side of the battery attracts the holes

in p-type material away from the junction This makes the depletion region

wider than it was when no voltage is applied The depletion region is an

insulator and it will block the flow of current Actually a small current will

flow because of minority carriers The p-type material has a few minority

electrons These are pushed to the junction by the repulsion of the negative

side of the battery The n-type material has few minority holes These are

also pushed towards the junction Reverse bias forces the minority carriers

together and a small current - called leakage current - results

Diodes which are designed with adequate power dissipation

capability to operate in the breakdown region are none as Zener diodes

Two mechanisms of diode breakdown for increasing reverse voltage are

recognized In one mechanism the thermally generated electrons and

holes acquire sufficient energy from the applied potential to produce new

carriers by removing valence electrons from their bonds These new

carriers in turn produce additional carriers again through the process of

disrupting bonds This cumulative process is referred to as avalanche

breakdown Even if the initially available carriers do not acquire sufficient

energy to disrupt bonds it is possible to initiate breakdown through a

direct rupture of the bonds because of the existence of strong electric field

Under these conditions the breakdown is referred to as Zener breakdown

Date____________

Pag

e36

Zener breakdown occurs below 6 V Zener diodes are commonly used in

voltage-reference or constant-voltage devices

Characteristic curves of diode

Fig 14 shows V-I Characteristic curves for typical p-n junction diode

It is seen that the curve is not linear With 0 V across the diode the diode

will not conduct the diode will not begin to conduct until a few tenths of a

volt are applied across it This is the voltage needed to overcome the

potential barrier It requires about 02 V to turn on a germanium diode and

about 06 V to turn on a silicon diode Fig 18 also shows what happens

when reverse bias is applied to a diode At increasing levels of reverse

voltage the curve shows some reverse current This leakage current is

caused by minority carries It is usually very small

Graph

Fig-14

Date____________

Pag

e37

Observation Table for Forward bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Date____________

Pag

e38

Observation Table for Reverse bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e39

Calculation for Forward bias 119877 = 119881

119868

Calculation for Reverse bias 119877 = 119881

119868

Date____________

Pag

e40

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e41

Zener Diode Reverse Bias Characteristics Experiment - 10

Aim To study the reverse bias characteristics of a Zener diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components Zener diode Resistors

Circuit Diagram

Procedure

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Theory

A diode which is heavily doped (Si or Ge) and which operates in the

reverse breakdown region with a sharp breakdown voltage is called a zener

diode The schematic symbol of a zener diode is shown in Fig-1 This is

similar to a normal diode except that the line (bar) representing the

cathode is bent at both ends like the letter Z for zener diode

Date____________

Pag

e42

A C Fig-1

In a simple diode the doping is light as a result the breakdown

voltage is high and not sharp But if doping is made heavy the depletion

layer becomes very narrow and even the breakdown voltage gets reduced

to a sharp value The zener diode is designed to operate in the breakdown

region without damage

The reverse breakdown of a zener diode may occur either due to

zener effect or avalanche effect But zener diode primarily depends on

zener effect for its working When the electric field across the junction is

sufficiently high due to the applied voltage the zener breakdown occurs

because of breaking of covalent bonds This produces a large number of

electrons and holes which constitute a steep rise in the reverse saturation

current (also called zener current 119868Z) This effect is called as zener effect

Zener current is independent of the applied voltage and depends only on

the external resistance

The V - 119868 characteristic of a zener diode is shown in Fig-2 The

forward characteristic is simply that of an ordinary forward biased junction

diode

Fig-2

Date____________

Pag

e43

Under reverse bias condition breakdown of junction occurs This

breakdown depends upon the amount of doping It can be seen from Fig-2

that as the reverse voltage is increased the reverse current remains

negligibly small up to the lsquokneersquo of the curve

At this lsquoknee pointrsquo the effect of breakdown process begins The

voltage corresponding to the lsquoknee pointrsquo in the figure is called the zener

breakdown voltage or simply zener voltage (VZ) which is very sharp

compared to a simle p-n junction diode Beyond this voltage the reverse

current (119868Z) increases sharply to a high value

The zener diode is not immediately burnt just because it has entered

the breakdown region As long as the external resistance connected to the

diode in the circuit limits the diode current to less than the burn out value

the diode will not burn out The zener voltage VZ remains constant even

when zener current 119868Z increases greatly This ability of a diode is called

regulating ability and it enables us to use zener diode for voltage

regulation

Date____________

Pag

e44

Observation Table

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e45

Graph 119868 V

Calculations 119877 = 119881

119868

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e46

Dispersive Power of The Prism Experiment - 11

Aim To find the dispersive power (D) of the prism by using spectrometer

Apparatus Mercury vapor lamp Spectrometer Prism

Procedure

Levelling and alignment of collimator and telescope

1 Switch on the mercury lamp Adjust the leveling screws on the chassis

Keep the spirit level on the chassis and do finer adjustments of these

screws to bring the bubble in the sprit level to the centre Repeat this

placing the sprit level along a direction perpendicular to the earlier

direction

2 Repeat this procedure for the prism table

3 Close the slit at the other end of the collimator using the drum screw DS1

Open it to a reasonable width Place the spectrometer in front of the

mercury lamp window and rotate the collimator so that the slit faces of

window View the slit through the telescope If it is not in the centre of the

view level collimator and the telescope so as to bring it to the centre

Setting the prism in the minimum deviation position

1 Rotate the prism table such that lines ruled on the table become

perpendicular to the axis of collimator

2 Place prism over the prism table such that its rough surface BA is

perpendicular to the line on prism table (See Fig-1(a))

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e20

Wattage of Bulb Experiment - 06

Aim To find the electrical energy consumed in a circuit (bulb)

Apparatus AC Ammeter(0-500 mA) AC Voltmeter(0-250 volt) Variac

Components Bulb

Circuit Diagram

Procedure

Connect the circuit as shown in the circuit diagram Now switch ON

the circuit and note down the reading shown by ammeter at 0 volt then

increase the voltage from 0 to 10 volt and note down the reading of

ammeter Now increase the voltage in order of 10 volts (up to 200 volts)

and note down the readings of the current shown by the ammeter Now

calculate the power consumed in a circuit at different stages

Theory

Experiments show that in stationary metallic conductors current does

work to increase their internal energy The heated conductor releases the

energy received to the surrounding bodies but this is done by means of

heat transfer This means that the quantity of heat released by a current

carrying conductor is equal to the total work done by the current

Date____________

Pag

e21

As we know that the work done by the current is given by 119830 = 119829119816119853helliphelliphelliphelliphelliphellip(1)

119830 = 119816120784119825119853 ( V = IR) helliphelliphelliphelliphelliphelliphellip (2)

The electrical power of a given device is simply the rate of doing

work or the amount of electric work done in one second

Therefore electric powerhellip

119823 =119830119848119851119844 119837119848119847119838 (119830)

119827119842119846119838 (119853)

119823 =119829119816119853

119853= 119829119816 helliphelliphelliphelliphelliphelliphellip (3)

Thus electric power is equal to the product of voltage by current

Watt is a unit of power Hence it can be expressed in terms of a volt

and an ampere by the formula for electric power Eqn (3)

Therefore

1 Watt = 1 volt ∙ 1 ampere

1 W = 1 V∙A

Thus if a potential difference of 1 volt causes a current of 1 ampere

to flow through a conductor (here a bulb) the electric power consumed is

1 watt and the electrical energy consumed is 1 joulesec this electrical

energy consumed in the bulb is converted into heat and light energy

Date____________

Pag

e22

Observation Table

Sr No Voltage V (volt) Current 119816 (mA) Power

119823 = 119829119816 (watt)

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

Date____________

Pag

e23

Calculation 119823 = 119829119816

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e24

Temperature of Tungsten Filament Experiment ndash 07

Aim To find the temperature of the tungsten filament of the bulb

Apparatus AC Ammeter(0-500 mA) AC Voltmeter(0-250 volt) Variac

Components Bulb

Circuit Diagram

Procedure

Connect the circuit as shown in the circuit diagram Now switch ON

the circuit and note down the reading shown by ammeter at 0 volt then

increase the voltage from 0 to 10 volt and note down the reading of

ammeter Now increase the voltage in order of 10 volts (up to 100 volts)

and note down the readings of the current shown by the ammeter Now

calculate the resistance and the temperature of the filament

Observations

(1) Room temperaturehellip t0 = _______ ˚C

(2) Resistance of the filament of the bulb at room temperaturehellip

R0 = _______ Ω

(3) Temperature coefficient of tungstenhellip α = 45times10-4 ˚C-1

Date____________

Pag

e25

Observation Table

Sr No Voltage V

(volt)

Current 119816

(mA)

Resistance of

The Filament

119825119853 =119829

119816 Ω

Temperature of The Filament

119853 =120783

120514[

119825119853

119825120782 120783 + 120514119853120782 minus 120783] ˚C

1

2

3

4

5

6

7

8

9

10

Graph Rt versus t

Date____________

Pag

e26

Calculations

(1) Resistance of The Filament Rt =V

I Ω

(2) Temperature of The Filament t =1

α[

Rt

R0 1 + αt0 minus 1] ˚C

Date____________

Pag

e27

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e28

Meldersquos Experiment - 08

Aim To find the frequency of the wave and the frequency of the tuning fork by

Meldersquos experiment

Apparatus Meldersquos experiment apparatus

Circuit Diagram

Transverse mode

Procedure

Set Meldersquos experiment apparatus as shown in circuit diagram in

longitudinal position and switch ON the power supply put some weight in

scale pan and adjust the length of the string in such a way that you find

some loops on the string (eg 2 loops) Now rotate the apparatus by 90˚ so

that it is set for lsquoBrsquo position for the same values of weight in pan and for

the same length of the string the number of loops created in lsquoBrsquo position

are double (eg 4 loops) than in lsquoArsquo position Note down these readings in

observation table Repeat the experiment for other values of weight in

scale pan

Date____________

Pag

e29

Theory

This is an easy and efficient method by which nodes and antinodes

formed on a string can be demonstrated

A tuning fork is fitted in a wooden block A long string or thread of

cotton is taken One end of this string is tied to one of the prongs of the

tuning fork and the second end of this string passes over a smooth pulley in

such a way that a small pan can be hang on it Small weights are put in the

pan to create tension in the string This arrangement is shown in the circuit

diagram

The fork is set into vibrations by lightly hitting the prong of the tuning

fork on which the string is not tied or by connecting an electric supply as

shown in the circuit diagram Thus the transverse vibrations are produced

in the string and by adjusting the length andor weights in the pan these

vibrations are reflected from the point of contact between the string and

the pulley and a number of loops appear on the string as shown in the

circuit diagram

When the prongs of the tuning fork vibrate in a plane parallel to the

direction of propagation of the waves it is called lsquoArsquo position or

longitudinal position

If the tuning fork along with the wooden block is rotated through

90˚ so that the plane of vibration of the tuning fork is normal (ie at right

angles) to the direction of propagation it is called lsquoBrsquo position or transverse

position

For the same length and same weight in the pan (ie for the same

tension) the number of loops in lsquoBrsquo position is double than in lsquoArsquo position

Thus either in lsquoArsquo position or in lsquoBrsquo position standing transverse

waves are generated in the string with a series of nodes and antinodes at

equal distances

The equation connecting number of loops (n or nrsquo) length of the

string (l) tension in the string (T) mass per unit length of the string (m) and

frequency of the string (f) is as follows

Date____________

Pag

e30

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position)

119943prime =119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

If the frequency of tuning fork is F then for lsquoArsquo position 119839 =119813

120784 and for lsquoBrsquo

position 119839prime = 119813

In the above equations if all the quantities on the RHS are known the

frequency of the tuning fork 119813 can be calculated

Observations

(1) Gravitational accelerationhellip g = 98 ms2

(2) Mass per unit length of the stringhellip m = _______ kgm

(3) Mass of the scale panhellip M1 = _______ kg

Observation Table

Sr

No

Total mass

suspended at

the end of the

stringhellip

M=M1+M2

(kg)

Tension

created

in the

stringhellip

T=Mg (N)

Length of the

vibrating string

Average

lengthhellip

119949 (m)

No of loops created on

the stringhellip

Frequency of the

vibrating stringhellip

Relation

between

f and frsquo 1199491 (m) 1199492 (m)

In

Longitudinal

Modehellip

n

In

Transverse

Modehellip

nrsquo

In

Longitudinal

Modehellip

119943 =119951

120784119949

119931

119950

In

Transverse

Modehellip

119943prime =119951prime

120784119949

119931

119950

1

2

3

4

Here M2 = the weight put in the scale pan

Page31

Date____________

Pag

e32

Calculations

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position) 119943prime =

119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e33

P-N Junction Diode Characteristics Experiment - 09

Aim To study the Forward and Reverse bias characteristics of a P-N junction

diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components P-N junction diode Resistors

Circuit Diagram

(Forward biased PN diode) (Reverse biased PN diode)

Procedure

For Forward Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 01 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 02 03 04hellip

volts and repeat the procedure Note down the knee voltage and

corresponding current in your observation table

For Reverse Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Date____________

Pag

e34

Theory

If donor (pentavalent) impurities are introduced on one side and

acceptors (trivalent) on the opposite side of a single crystal of an intrinsic

semiconductor like germanium or silicon a p-n junction is formed as shown

in Fig 11 In the figure a donor ion is indicated schematically by a plus sign

because after this impurity atom donates an electron it becomes a positive

ion

The acceptor ion is indicated by a minus sign because after this atom

accepts an electron it becomes a negative ion Initially there are only n-

type carriers to the right of the junction and only p-type carriers to the left

Because there is a density gradient across the junction holes will diffuse to

the right across the junction and electrons to the left As a result of the

displacement of these charges an electric field appears across the junction

Equilibrium is established when the field becomes large enough to restrain

the process of diffusion The positive holes which neutralize the acceptor

ions near the junction in p-type germanium disappear as a result of

combination with electrons which diffuse across the junction Similarly the

neutralizing electrons on the n side of the junction combine with holes

which cross the junction from the p side Since the region of the junction is

depleted of mobile charges it is called the depletion region or a potential

barrier

Forward Bias

An external voltage applied to the p-n junction with the polarity

shown in Fig 12 is known as forward bias The height of the potential

barrier at the junction is lowered by the applied forward voltage In other

words we can say that p-n junction diode is connected to an external

Date____________

Pag

e35

battery in such a way that depletion region is reduced in size or eliminated

altogether Which of these takes place is determined by the size of the

applied voltage The positive terminal of the battery repels the holes on the

p-side and pushes them towards the junction The negative terminal of the

battery repels the electrons and pushes them towards the junction This

collapses the depletion region With the depletion region gone the diode

can conduct

Reverse Bias

An external voltage applied with polarity in Fig 13 is called reverse

bias When reverse bias is applied to a junction diode the depletion region

does not collapse On the contrary it becomes wider The positive side of

battery is applied to the n-type material This attracts the free electrons

away from the junction The negative side of the battery attracts the holes

in p-type material away from the junction This makes the depletion region

wider than it was when no voltage is applied The depletion region is an

insulator and it will block the flow of current Actually a small current will

flow because of minority carriers The p-type material has a few minority

electrons These are pushed to the junction by the repulsion of the negative

side of the battery The n-type material has few minority holes These are

also pushed towards the junction Reverse bias forces the minority carriers

together and a small current - called leakage current - results

Diodes which are designed with adequate power dissipation

capability to operate in the breakdown region are none as Zener diodes

Two mechanisms of diode breakdown for increasing reverse voltage are

recognized In one mechanism the thermally generated electrons and

holes acquire sufficient energy from the applied potential to produce new

carriers by removing valence electrons from their bonds These new

carriers in turn produce additional carriers again through the process of

disrupting bonds This cumulative process is referred to as avalanche

breakdown Even if the initially available carriers do not acquire sufficient

energy to disrupt bonds it is possible to initiate breakdown through a

direct rupture of the bonds because of the existence of strong electric field

Under these conditions the breakdown is referred to as Zener breakdown

Date____________

Pag

e36

Zener breakdown occurs below 6 V Zener diodes are commonly used in

voltage-reference or constant-voltage devices

Characteristic curves of diode

Fig 14 shows V-I Characteristic curves for typical p-n junction diode

It is seen that the curve is not linear With 0 V across the diode the diode

will not conduct the diode will not begin to conduct until a few tenths of a

volt are applied across it This is the voltage needed to overcome the

potential barrier It requires about 02 V to turn on a germanium diode and

about 06 V to turn on a silicon diode Fig 18 also shows what happens

when reverse bias is applied to a diode At increasing levels of reverse

voltage the curve shows some reverse current This leakage current is

caused by minority carries It is usually very small

Graph

Fig-14

Date____________

Pag

e37

Observation Table for Forward bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Date____________

Pag

e38

Observation Table for Reverse bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e39

Calculation for Forward bias 119877 = 119881

119868

Calculation for Reverse bias 119877 = 119881

119868

Date____________

Pag

e40

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e41

Zener Diode Reverse Bias Characteristics Experiment - 10

Aim To study the reverse bias characteristics of a Zener diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components Zener diode Resistors

Circuit Diagram

Procedure

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Theory

A diode which is heavily doped (Si or Ge) and which operates in the

reverse breakdown region with a sharp breakdown voltage is called a zener

diode The schematic symbol of a zener diode is shown in Fig-1 This is

similar to a normal diode except that the line (bar) representing the

cathode is bent at both ends like the letter Z for zener diode

Date____________

Pag

e42

A C Fig-1

In a simple diode the doping is light as a result the breakdown

voltage is high and not sharp But if doping is made heavy the depletion

layer becomes very narrow and even the breakdown voltage gets reduced

to a sharp value The zener diode is designed to operate in the breakdown

region without damage

The reverse breakdown of a zener diode may occur either due to

zener effect or avalanche effect But zener diode primarily depends on

zener effect for its working When the electric field across the junction is

sufficiently high due to the applied voltage the zener breakdown occurs

because of breaking of covalent bonds This produces a large number of

electrons and holes which constitute a steep rise in the reverse saturation

current (also called zener current 119868Z) This effect is called as zener effect

Zener current is independent of the applied voltage and depends only on

the external resistance

The V - 119868 characteristic of a zener diode is shown in Fig-2 The

forward characteristic is simply that of an ordinary forward biased junction

diode

Fig-2

Date____________

Pag

e43

Under reverse bias condition breakdown of junction occurs This

breakdown depends upon the amount of doping It can be seen from Fig-2

that as the reverse voltage is increased the reverse current remains

negligibly small up to the lsquokneersquo of the curve

At this lsquoknee pointrsquo the effect of breakdown process begins The

voltage corresponding to the lsquoknee pointrsquo in the figure is called the zener

breakdown voltage or simply zener voltage (VZ) which is very sharp

compared to a simle p-n junction diode Beyond this voltage the reverse

current (119868Z) increases sharply to a high value

The zener diode is not immediately burnt just because it has entered

the breakdown region As long as the external resistance connected to the

diode in the circuit limits the diode current to less than the burn out value

the diode will not burn out The zener voltage VZ remains constant even

when zener current 119868Z increases greatly This ability of a diode is called

regulating ability and it enables us to use zener diode for voltage

regulation

Date____________

Pag

e44

Observation Table

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e45

Graph 119868 V

Calculations 119877 = 119881

119868

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e46

Dispersive Power of The Prism Experiment - 11

Aim To find the dispersive power (D) of the prism by using spectrometer

Apparatus Mercury vapor lamp Spectrometer Prism

Procedure

Levelling and alignment of collimator and telescope

1 Switch on the mercury lamp Adjust the leveling screws on the chassis

Keep the spirit level on the chassis and do finer adjustments of these

screws to bring the bubble in the sprit level to the centre Repeat this

placing the sprit level along a direction perpendicular to the earlier

direction

2 Repeat this procedure for the prism table

3 Close the slit at the other end of the collimator using the drum screw DS1

Open it to a reasonable width Place the spectrometer in front of the

mercury lamp window and rotate the collimator so that the slit faces of

window View the slit through the telescope If it is not in the centre of the

view level collimator and the telescope so as to bring it to the centre

Setting the prism in the minimum deviation position

1 Rotate the prism table such that lines ruled on the table become

perpendicular to the axis of collimator

2 Place prism over the prism table such that its rough surface BA is

perpendicular to the line on prism table (See Fig-1(a))

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e21

As we know that the work done by the current is given by 119830 = 119829119816119853helliphelliphelliphelliphelliphellip(1)

119830 = 119816120784119825119853 ( V = IR) helliphelliphelliphelliphelliphelliphellip (2)

The electrical power of a given device is simply the rate of doing

work or the amount of electric work done in one second

Therefore electric powerhellip

119823 =119830119848119851119844 119837119848119847119838 (119830)

119827119842119846119838 (119853)

119823 =119829119816119853

119853= 119829119816 helliphelliphelliphelliphelliphelliphellip (3)

Thus electric power is equal to the product of voltage by current

Watt is a unit of power Hence it can be expressed in terms of a volt

and an ampere by the formula for electric power Eqn (3)

Therefore

1 Watt = 1 volt ∙ 1 ampere

1 W = 1 V∙A

Thus if a potential difference of 1 volt causes a current of 1 ampere

to flow through a conductor (here a bulb) the electric power consumed is

1 watt and the electrical energy consumed is 1 joulesec this electrical

energy consumed in the bulb is converted into heat and light energy

Date____________

Pag

e22

Observation Table

Sr No Voltage V (volt) Current 119816 (mA) Power

119823 = 119829119816 (watt)

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

Date____________

Pag

e23

Calculation 119823 = 119829119816

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e24

Temperature of Tungsten Filament Experiment ndash 07

Aim To find the temperature of the tungsten filament of the bulb

Apparatus AC Ammeter(0-500 mA) AC Voltmeter(0-250 volt) Variac

Components Bulb

Circuit Diagram

Procedure

Connect the circuit as shown in the circuit diagram Now switch ON

the circuit and note down the reading shown by ammeter at 0 volt then

increase the voltage from 0 to 10 volt and note down the reading of

ammeter Now increase the voltage in order of 10 volts (up to 100 volts)

and note down the readings of the current shown by the ammeter Now

calculate the resistance and the temperature of the filament

Observations

(1) Room temperaturehellip t0 = _______ ˚C

(2) Resistance of the filament of the bulb at room temperaturehellip

R0 = _______ Ω

(3) Temperature coefficient of tungstenhellip α = 45times10-4 ˚C-1

Date____________

Pag

e25

Observation Table

Sr No Voltage V

(volt)

Current 119816

(mA)

Resistance of

The Filament

119825119853 =119829

119816 Ω

Temperature of The Filament

119853 =120783

120514[

119825119853

119825120782 120783 + 120514119853120782 minus 120783] ˚C

1

2

3

4

5

6

7

8

9

10

Graph Rt versus t

Date____________

Pag

e26

Calculations

(1) Resistance of The Filament Rt =V

I Ω

(2) Temperature of The Filament t =1

α[

Rt

R0 1 + αt0 minus 1] ˚C

Date____________

Pag

e27

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e28

Meldersquos Experiment - 08

Aim To find the frequency of the wave and the frequency of the tuning fork by

Meldersquos experiment

Apparatus Meldersquos experiment apparatus

Circuit Diagram

Transverse mode

Procedure

Set Meldersquos experiment apparatus as shown in circuit diagram in

longitudinal position and switch ON the power supply put some weight in

scale pan and adjust the length of the string in such a way that you find

some loops on the string (eg 2 loops) Now rotate the apparatus by 90˚ so

that it is set for lsquoBrsquo position for the same values of weight in pan and for

the same length of the string the number of loops created in lsquoBrsquo position

are double (eg 4 loops) than in lsquoArsquo position Note down these readings in

observation table Repeat the experiment for other values of weight in

scale pan

Date____________

Pag

e29

Theory

This is an easy and efficient method by which nodes and antinodes

formed on a string can be demonstrated

A tuning fork is fitted in a wooden block A long string or thread of

cotton is taken One end of this string is tied to one of the prongs of the

tuning fork and the second end of this string passes over a smooth pulley in

such a way that a small pan can be hang on it Small weights are put in the

pan to create tension in the string This arrangement is shown in the circuit

diagram

The fork is set into vibrations by lightly hitting the prong of the tuning

fork on which the string is not tied or by connecting an electric supply as

shown in the circuit diagram Thus the transverse vibrations are produced

in the string and by adjusting the length andor weights in the pan these

vibrations are reflected from the point of contact between the string and

the pulley and a number of loops appear on the string as shown in the

circuit diagram

When the prongs of the tuning fork vibrate in a plane parallel to the

direction of propagation of the waves it is called lsquoArsquo position or

longitudinal position

If the tuning fork along with the wooden block is rotated through

90˚ so that the plane of vibration of the tuning fork is normal (ie at right

angles) to the direction of propagation it is called lsquoBrsquo position or transverse

position

For the same length and same weight in the pan (ie for the same

tension) the number of loops in lsquoBrsquo position is double than in lsquoArsquo position

Thus either in lsquoArsquo position or in lsquoBrsquo position standing transverse

waves are generated in the string with a series of nodes and antinodes at

equal distances

The equation connecting number of loops (n or nrsquo) length of the

string (l) tension in the string (T) mass per unit length of the string (m) and

frequency of the string (f) is as follows

Date____________

Pag

e30

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position)

119943prime =119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

If the frequency of tuning fork is F then for lsquoArsquo position 119839 =119813

120784 and for lsquoBrsquo

position 119839prime = 119813

In the above equations if all the quantities on the RHS are known the

frequency of the tuning fork 119813 can be calculated

Observations

(1) Gravitational accelerationhellip g = 98 ms2

(2) Mass per unit length of the stringhellip m = _______ kgm

(3) Mass of the scale panhellip M1 = _______ kg

Observation Table

Sr

No

Total mass

suspended at

the end of the

stringhellip

M=M1+M2

(kg)

Tension

created

in the

stringhellip

T=Mg (N)

Length of the

vibrating string

Average

lengthhellip

119949 (m)

No of loops created on

the stringhellip

Frequency of the

vibrating stringhellip

Relation

between

f and frsquo 1199491 (m) 1199492 (m)

In

Longitudinal

Modehellip

n

In

Transverse

Modehellip

nrsquo

In

Longitudinal

Modehellip

119943 =119951

120784119949

119931

119950

In

Transverse

Modehellip

119943prime =119951prime

120784119949

119931

119950

1

2

3

4

Here M2 = the weight put in the scale pan

Page31

Date____________

Pag

e32

Calculations

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position) 119943prime =

119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e33

P-N Junction Diode Characteristics Experiment - 09

Aim To study the Forward and Reverse bias characteristics of a P-N junction

diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components P-N junction diode Resistors

Circuit Diagram

(Forward biased PN diode) (Reverse biased PN diode)

Procedure

For Forward Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 01 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 02 03 04hellip

volts and repeat the procedure Note down the knee voltage and

corresponding current in your observation table

For Reverse Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Date____________

Pag

e34

Theory

If donor (pentavalent) impurities are introduced on one side and

acceptors (trivalent) on the opposite side of a single crystal of an intrinsic

semiconductor like germanium or silicon a p-n junction is formed as shown

in Fig 11 In the figure a donor ion is indicated schematically by a plus sign

because after this impurity atom donates an electron it becomes a positive

ion

The acceptor ion is indicated by a minus sign because after this atom

accepts an electron it becomes a negative ion Initially there are only n-

type carriers to the right of the junction and only p-type carriers to the left

Because there is a density gradient across the junction holes will diffuse to

the right across the junction and electrons to the left As a result of the

displacement of these charges an electric field appears across the junction

Equilibrium is established when the field becomes large enough to restrain

the process of diffusion The positive holes which neutralize the acceptor

ions near the junction in p-type germanium disappear as a result of

combination with electrons which diffuse across the junction Similarly the

neutralizing electrons on the n side of the junction combine with holes

which cross the junction from the p side Since the region of the junction is

depleted of mobile charges it is called the depletion region or a potential

barrier

Forward Bias

An external voltage applied to the p-n junction with the polarity

shown in Fig 12 is known as forward bias The height of the potential

barrier at the junction is lowered by the applied forward voltage In other

words we can say that p-n junction diode is connected to an external

Date____________

Pag

e35

battery in such a way that depletion region is reduced in size or eliminated

altogether Which of these takes place is determined by the size of the

applied voltage The positive terminal of the battery repels the holes on the

p-side and pushes them towards the junction The negative terminal of the

battery repels the electrons and pushes them towards the junction This

collapses the depletion region With the depletion region gone the diode

can conduct

Reverse Bias

An external voltage applied with polarity in Fig 13 is called reverse

bias When reverse bias is applied to a junction diode the depletion region

does not collapse On the contrary it becomes wider The positive side of

battery is applied to the n-type material This attracts the free electrons

away from the junction The negative side of the battery attracts the holes

in p-type material away from the junction This makes the depletion region

wider than it was when no voltage is applied The depletion region is an

insulator and it will block the flow of current Actually a small current will

flow because of minority carriers The p-type material has a few minority

electrons These are pushed to the junction by the repulsion of the negative

side of the battery The n-type material has few minority holes These are

also pushed towards the junction Reverse bias forces the minority carriers

together and a small current - called leakage current - results

Diodes which are designed with adequate power dissipation

capability to operate in the breakdown region are none as Zener diodes

Two mechanisms of diode breakdown for increasing reverse voltage are

recognized In one mechanism the thermally generated electrons and

holes acquire sufficient energy from the applied potential to produce new

carriers by removing valence electrons from their bonds These new

carriers in turn produce additional carriers again through the process of

disrupting bonds This cumulative process is referred to as avalanche

breakdown Even if the initially available carriers do not acquire sufficient

energy to disrupt bonds it is possible to initiate breakdown through a

direct rupture of the bonds because of the existence of strong electric field

Under these conditions the breakdown is referred to as Zener breakdown

Date____________

Pag

e36

Zener breakdown occurs below 6 V Zener diodes are commonly used in

voltage-reference or constant-voltage devices

Characteristic curves of diode

Fig 14 shows V-I Characteristic curves for typical p-n junction diode

It is seen that the curve is not linear With 0 V across the diode the diode

will not conduct the diode will not begin to conduct until a few tenths of a

volt are applied across it This is the voltage needed to overcome the

potential barrier It requires about 02 V to turn on a germanium diode and

about 06 V to turn on a silicon diode Fig 18 also shows what happens

when reverse bias is applied to a diode At increasing levels of reverse

voltage the curve shows some reverse current This leakage current is

caused by minority carries It is usually very small

Graph

Fig-14

Date____________

Pag

e37

Observation Table for Forward bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Date____________

Pag

e38

Observation Table for Reverse bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e39

Calculation for Forward bias 119877 = 119881

119868

Calculation for Reverse bias 119877 = 119881

119868

Date____________

Pag

e40

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e41

Zener Diode Reverse Bias Characteristics Experiment - 10

Aim To study the reverse bias characteristics of a Zener diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components Zener diode Resistors

Circuit Diagram

Procedure

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Theory

A diode which is heavily doped (Si or Ge) and which operates in the

reverse breakdown region with a sharp breakdown voltage is called a zener

diode The schematic symbol of a zener diode is shown in Fig-1 This is

similar to a normal diode except that the line (bar) representing the

cathode is bent at both ends like the letter Z for zener diode

Date____________

Pag

e42

A C Fig-1

In a simple diode the doping is light as a result the breakdown

voltage is high and not sharp But if doping is made heavy the depletion

layer becomes very narrow and even the breakdown voltage gets reduced

to a sharp value The zener diode is designed to operate in the breakdown

region without damage

The reverse breakdown of a zener diode may occur either due to

zener effect or avalanche effect But zener diode primarily depends on

zener effect for its working When the electric field across the junction is

sufficiently high due to the applied voltage the zener breakdown occurs

because of breaking of covalent bonds This produces a large number of

electrons and holes which constitute a steep rise in the reverse saturation

current (also called zener current 119868Z) This effect is called as zener effect

Zener current is independent of the applied voltage and depends only on

the external resistance

The V - 119868 characteristic of a zener diode is shown in Fig-2 The

forward characteristic is simply that of an ordinary forward biased junction

diode

Fig-2

Date____________

Pag

e43

Under reverse bias condition breakdown of junction occurs This

breakdown depends upon the amount of doping It can be seen from Fig-2

that as the reverse voltage is increased the reverse current remains

negligibly small up to the lsquokneersquo of the curve

At this lsquoknee pointrsquo the effect of breakdown process begins The

voltage corresponding to the lsquoknee pointrsquo in the figure is called the zener

breakdown voltage or simply zener voltage (VZ) which is very sharp

compared to a simle p-n junction diode Beyond this voltage the reverse

current (119868Z) increases sharply to a high value

The zener diode is not immediately burnt just because it has entered

the breakdown region As long as the external resistance connected to the

diode in the circuit limits the diode current to less than the burn out value

the diode will not burn out The zener voltage VZ remains constant even

when zener current 119868Z increases greatly This ability of a diode is called

regulating ability and it enables us to use zener diode for voltage

regulation

Date____________

Pag

e44

Observation Table

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e45

Graph 119868 V

Calculations 119877 = 119881

119868

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e46

Dispersive Power of The Prism Experiment - 11

Aim To find the dispersive power (D) of the prism by using spectrometer

Apparatus Mercury vapor lamp Spectrometer Prism

Procedure

Levelling and alignment of collimator and telescope

1 Switch on the mercury lamp Adjust the leveling screws on the chassis

Keep the spirit level on the chassis and do finer adjustments of these

screws to bring the bubble in the sprit level to the centre Repeat this

placing the sprit level along a direction perpendicular to the earlier

direction

2 Repeat this procedure for the prism table

3 Close the slit at the other end of the collimator using the drum screw DS1

Open it to a reasonable width Place the spectrometer in front of the

mercury lamp window and rotate the collimator so that the slit faces of

window View the slit through the telescope If it is not in the centre of the

view level collimator and the telescope so as to bring it to the centre

Setting the prism in the minimum deviation position

1 Rotate the prism table such that lines ruled on the table become

perpendicular to the axis of collimator

2 Place prism over the prism table such that its rough surface BA is

perpendicular to the line on prism table (See Fig-1(a))

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e22

Observation Table

Sr No Voltage V (volt) Current 119816 (mA) Power

119823 = 119829119816 (watt)

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

Date____________

Pag

e23

Calculation 119823 = 119829119816

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e24

Temperature of Tungsten Filament Experiment ndash 07

Aim To find the temperature of the tungsten filament of the bulb

Apparatus AC Ammeter(0-500 mA) AC Voltmeter(0-250 volt) Variac

Components Bulb

Circuit Diagram

Procedure

Connect the circuit as shown in the circuit diagram Now switch ON

the circuit and note down the reading shown by ammeter at 0 volt then

increase the voltage from 0 to 10 volt and note down the reading of

ammeter Now increase the voltage in order of 10 volts (up to 100 volts)

and note down the readings of the current shown by the ammeter Now

calculate the resistance and the temperature of the filament

Observations

(1) Room temperaturehellip t0 = _______ ˚C

(2) Resistance of the filament of the bulb at room temperaturehellip

R0 = _______ Ω

(3) Temperature coefficient of tungstenhellip α = 45times10-4 ˚C-1

Date____________

Pag

e25

Observation Table

Sr No Voltage V

(volt)

Current 119816

(mA)

Resistance of

The Filament

119825119853 =119829

119816 Ω

Temperature of The Filament

119853 =120783

120514[

119825119853

119825120782 120783 + 120514119853120782 minus 120783] ˚C

1

2

3

4

5

6

7

8

9

10

Graph Rt versus t

Date____________

Pag

e26

Calculations

(1) Resistance of The Filament Rt =V

I Ω

(2) Temperature of The Filament t =1

α[

Rt

R0 1 + αt0 minus 1] ˚C

Date____________

Pag

e27

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e28

Meldersquos Experiment - 08

Aim To find the frequency of the wave and the frequency of the tuning fork by

Meldersquos experiment

Apparatus Meldersquos experiment apparatus

Circuit Diagram

Transverse mode

Procedure

Set Meldersquos experiment apparatus as shown in circuit diagram in

longitudinal position and switch ON the power supply put some weight in

scale pan and adjust the length of the string in such a way that you find

some loops on the string (eg 2 loops) Now rotate the apparatus by 90˚ so

that it is set for lsquoBrsquo position for the same values of weight in pan and for

the same length of the string the number of loops created in lsquoBrsquo position

are double (eg 4 loops) than in lsquoArsquo position Note down these readings in

observation table Repeat the experiment for other values of weight in

scale pan

Date____________

Pag

e29

Theory

This is an easy and efficient method by which nodes and antinodes

formed on a string can be demonstrated

A tuning fork is fitted in a wooden block A long string or thread of

cotton is taken One end of this string is tied to one of the prongs of the

tuning fork and the second end of this string passes over a smooth pulley in

such a way that a small pan can be hang on it Small weights are put in the

pan to create tension in the string This arrangement is shown in the circuit

diagram

The fork is set into vibrations by lightly hitting the prong of the tuning

fork on which the string is not tied or by connecting an electric supply as

shown in the circuit diagram Thus the transverse vibrations are produced

in the string and by adjusting the length andor weights in the pan these

vibrations are reflected from the point of contact between the string and

the pulley and a number of loops appear on the string as shown in the

circuit diagram

When the prongs of the tuning fork vibrate in a plane parallel to the

direction of propagation of the waves it is called lsquoArsquo position or

longitudinal position

If the tuning fork along with the wooden block is rotated through

90˚ so that the plane of vibration of the tuning fork is normal (ie at right

angles) to the direction of propagation it is called lsquoBrsquo position or transverse

position

For the same length and same weight in the pan (ie for the same

tension) the number of loops in lsquoBrsquo position is double than in lsquoArsquo position

Thus either in lsquoArsquo position or in lsquoBrsquo position standing transverse

waves are generated in the string with a series of nodes and antinodes at

equal distances

The equation connecting number of loops (n or nrsquo) length of the

string (l) tension in the string (T) mass per unit length of the string (m) and

frequency of the string (f) is as follows

Date____________

Pag

e30

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position)

119943prime =119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

If the frequency of tuning fork is F then for lsquoArsquo position 119839 =119813

120784 and for lsquoBrsquo

position 119839prime = 119813

In the above equations if all the quantities on the RHS are known the

frequency of the tuning fork 119813 can be calculated

Observations

(1) Gravitational accelerationhellip g = 98 ms2

(2) Mass per unit length of the stringhellip m = _______ kgm

(3) Mass of the scale panhellip M1 = _______ kg

Observation Table

Sr

No

Total mass

suspended at

the end of the

stringhellip

M=M1+M2

(kg)

Tension

created

in the

stringhellip

T=Mg (N)

Length of the

vibrating string

Average

lengthhellip

119949 (m)

No of loops created on

the stringhellip

Frequency of the

vibrating stringhellip

Relation

between

f and frsquo 1199491 (m) 1199492 (m)

In

Longitudinal

Modehellip

n

In

Transverse

Modehellip

nrsquo

In

Longitudinal

Modehellip

119943 =119951

120784119949

119931

119950

In

Transverse

Modehellip

119943prime =119951prime

120784119949

119931

119950

1

2

3

4

Here M2 = the weight put in the scale pan

Page31

Date____________

Pag

e32

Calculations

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position) 119943prime =

119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e33

P-N Junction Diode Characteristics Experiment - 09

Aim To study the Forward and Reverse bias characteristics of a P-N junction

diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components P-N junction diode Resistors

Circuit Diagram

(Forward biased PN diode) (Reverse biased PN diode)

Procedure

For Forward Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 01 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 02 03 04hellip

volts and repeat the procedure Note down the knee voltage and

corresponding current in your observation table

For Reverse Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Date____________

Pag

e34

Theory

If donor (pentavalent) impurities are introduced on one side and

acceptors (trivalent) on the opposite side of a single crystal of an intrinsic

semiconductor like germanium or silicon a p-n junction is formed as shown

in Fig 11 In the figure a donor ion is indicated schematically by a plus sign

because after this impurity atom donates an electron it becomes a positive

ion

The acceptor ion is indicated by a minus sign because after this atom

accepts an electron it becomes a negative ion Initially there are only n-

type carriers to the right of the junction and only p-type carriers to the left

Because there is a density gradient across the junction holes will diffuse to

the right across the junction and electrons to the left As a result of the

displacement of these charges an electric field appears across the junction

Equilibrium is established when the field becomes large enough to restrain

the process of diffusion The positive holes which neutralize the acceptor

ions near the junction in p-type germanium disappear as a result of

combination with electrons which diffuse across the junction Similarly the

neutralizing electrons on the n side of the junction combine with holes

which cross the junction from the p side Since the region of the junction is

depleted of mobile charges it is called the depletion region or a potential

barrier

Forward Bias

An external voltage applied to the p-n junction with the polarity

shown in Fig 12 is known as forward bias The height of the potential

barrier at the junction is lowered by the applied forward voltage In other

words we can say that p-n junction diode is connected to an external

Date____________

Pag

e35

battery in such a way that depletion region is reduced in size or eliminated

altogether Which of these takes place is determined by the size of the

applied voltage The positive terminal of the battery repels the holes on the

p-side and pushes them towards the junction The negative terminal of the

battery repels the electrons and pushes them towards the junction This

collapses the depletion region With the depletion region gone the diode

can conduct

Reverse Bias

An external voltage applied with polarity in Fig 13 is called reverse

bias When reverse bias is applied to a junction diode the depletion region

does not collapse On the contrary it becomes wider The positive side of

battery is applied to the n-type material This attracts the free electrons

away from the junction The negative side of the battery attracts the holes

in p-type material away from the junction This makes the depletion region

wider than it was when no voltage is applied The depletion region is an

insulator and it will block the flow of current Actually a small current will

flow because of minority carriers The p-type material has a few minority

electrons These are pushed to the junction by the repulsion of the negative

side of the battery The n-type material has few minority holes These are

also pushed towards the junction Reverse bias forces the minority carriers

together and a small current - called leakage current - results

Diodes which are designed with adequate power dissipation

capability to operate in the breakdown region are none as Zener diodes

Two mechanisms of diode breakdown for increasing reverse voltage are

recognized In one mechanism the thermally generated electrons and

holes acquire sufficient energy from the applied potential to produce new

carriers by removing valence electrons from their bonds These new

carriers in turn produce additional carriers again through the process of

disrupting bonds This cumulative process is referred to as avalanche

breakdown Even if the initially available carriers do not acquire sufficient

energy to disrupt bonds it is possible to initiate breakdown through a

direct rupture of the bonds because of the existence of strong electric field

Under these conditions the breakdown is referred to as Zener breakdown

Date____________

Pag

e36

Zener breakdown occurs below 6 V Zener diodes are commonly used in

voltage-reference or constant-voltage devices

Characteristic curves of diode

Fig 14 shows V-I Characteristic curves for typical p-n junction diode

It is seen that the curve is not linear With 0 V across the diode the diode

will not conduct the diode will not begin to conduct until a few tenths of a

volt are applied across it This is the voltage needed to overcome the

potential barrier It requires about 02 V to turn on a germanium diode and

about 06 V to turn on a silicon diode Fig 18 also shows what happens

when reverse bias is applied to a diode At increasing levels of reverse

voltage the curve shows some reverse current This leakage current is

caused by minority carries It is usually very small

Graph

Fig-14

Date____________

Pag

e37

Observation Table for Forward bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Date____________

Pag

e38

Observation Table for Reverse bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e39

Calculation for Forward bias 119877 = 119881

119868

Calculation for Reverse bias 119877 = 119881

119868

Date____________

Pag

e40

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e41

Zener Diode Reverse Bias Characteristics Experiment - 10

Aim To study the reverse bias characteristics of a Zener diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components Zener diode Resistors

Circuit Diagram

Procedure

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Theory

A diode which is heavily doped (Si or Ge) and which operates in the

reverse breakdown region with a sharp breakdown voltage is called a zener

diode The schematic symbol of a zener diode is shown in Fig-1 This is

similar to a normal diode except that the line (bar) representing the

cathode is bent at both ends like the letter Z for zener diode

Date____________

Pag

e42

A C Fig-1

In a simple diode the doping is light as a result the breakdown

voltage is high and not sharp But if doping is made heavy the depletion

layer becomes very narrow and even the breakdown voltage gets reduced

to a sharp value The zener diode is designed to operate in the breakdown

region without damage

The reverse breakdown of a zener diode may occur either due to

zener effect or avalanche effect But zener diode primarily depends on

zener effect for its working When the electric field across the junction is

sufficiently high due to the applied voltage the zener breakdown occurs

because of breaking of covalent bonds This produces a large number of

electrons and holes which constitute a steep rise in the reverse saturation

current (also called zener current 119868Z) This effect is called as zener effect

Zener current is independent of the applied voltage and depends only on

the external resistance

The V - 119868 characteristic of a zener diode is shown in Fig-2 The

forward characteristic is simply that of an ordinary forward biased junction

diode

Fig-2

Date____________

Pag

e43

Under reverse bias condition breakdown of junction occurs This

breakdown depends upon the amount of doping It can be seen from Fig-2

that as the reverse voltage is increased the reverse current remains

negligibly small up to the lsquokneersquo of the curve

At this lsquoknee pointrsquo the effect of breakdown process begins The

voltage corresponding to the lsquoknee pointrsquo in the figure is called the zener

breakdown voltage or simply zener voltage (VZ) which is very sharp

compared to a simle p-n junction diode Beyond this voltage the reverse

current (119868Z) increases sharply to a high value

The zener diode is not immediately burnt just because it has entered

the breakdown region As long as the external resistance connected to the

diode in the circuit limits the diode current to less than the burn out value

the diode will not burn out The zener voltage VZ remains constant even

when zener current 119868Z increases greatly This ability of a diode is called

regulating ability and it enables us to use zener diode for voltage

regulation

Date____________

Pag

e44

Observation Table

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e45

Graph 119868 V

Calculations 119877 = 119881

119868

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e46

Dispersive Power of The Prism Experiment - 11

Aim To find the dispersive power (D) of the prism by using spectrometer

Apparatus Mercury vapor lamp Spectrometer Prism

Procedure

Levelling and alignment of collimator and telescope

1 Switch on the mercury lamp Adjust the leveling screws on the chassis

Keep the spirit level on the chassis and do finer adjustments of these

screws to bring the bubble in the sprit level to the centre Repeat this

placing the sprit level along a direction perpendicular to the earlier

direction

2 Repeat this procedure for the prism table

3 Close the slit at the other end of the collimator using the drum screw DS1

Open it to a reasonable width Place the spectrometer in front of the

mercury lamp window and rotate the collimator so that the slit faces of

window View the slit through the telescope If it is not in the centre of the

view level collimator and the telescope so as to bring it to the centre

Setting the prism in the minimum deviation position

1 Rotate the prism table such that lines ruled on the table become

perpendicular to the axis of collimator

2 Place prism over the prism table such that its rough surface BA is

perpendicular to the line on prism table (See Fig-1(a))

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e23

Calculation 119823 = 119829119816

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e24

Temperature of Tungsten Filament Experiment ndash 07

Aim To find the temperature of the tungsten filament of the bulb

Apparatus AC Ammeter(0-500 mA) AC Voltmeter(0-250 volt) Variac

Components Bulb

Circuit Diagram

Procedure

Connect the circuit as shown in the circuit diagram Now switch ON

the circuit and note down the reading shown by ammeter at 0 volt then

increase the voltage from 0 to 10 volt and note down the reading of

ammeter Now increase the voltage in order of 10 volts (up to 100 volts)

and note down the readings of the current shown by the ammeter Now

calculate the resistance and the temperature of the filament

Observations

(1) Room temperaturehellip t0 = _______ ˚C

(2) Resistance of the filament of the bulb at room temperaturehellip

R0 = _______ Ω

(3) Temperature coefficient of tungstenhellip α = 45times10-4 ˚C-1

Date____________

Pag

e25

Observation Table

Sr No Voltage V

(volt)

Current 119816

(mA)

Resistance of

The Filament

119825119853 =119829

119816 Ω

Temperature of The Filament

119853 =120783

120514[

119825119853

119825120782 120783 + 120514119853120782 minus 120783] ˚C

1

2

3

4

5

6

7

8

9

10

Graph Rt versus t

Date____________

Pag

e26

Calculations

(1) Resistance of The Filament Rt =V

I Ω

(2) Temperature of The Filament t =1

α[

Rt

R0 1 + αt0 minus 1] ˚C

Date____________

Pag

e27

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e28

Meldersquos Experiment - 08

Aim To find the frequency of the wave and the frequency of the tuning fork by

Meldersquos experiment

Apparatus Meldersquos experiment apparatus

Circuit Diagram

Transverse mode

Procedure

Set Meldersquos experiment apparatus as shown in circuit diagram in

longitudinal position and switch ON the power supply put some weight in

scale pan and adjust the length of the string in such a way that you find

some loops on the string (eg 2 loops) Now rotate the apparatus by 90˚ so

that it is set for lsquoBrsquo position for the same values of weight in pan and for

the same length of the string the number of loops created in lsquoBrsquo position

are double (eg 4 loops) than in lsquoArsquo position Note down these readings in

observation table Repeat the experiment for other values of weight in

scale pan

Date____________

Pag

e29

Theory

This is an easy and efficient method by which nodes and antinodes

formed on a string can be demonstrated

A tuning fork is fitted in a wooden block A long string or thread of

cotton is taken One end of this string is tied to one of the prongs of the

tuning fork and the second end of this string passes over a smooth pulley in

such a way that a small pan can be hang on it Small weights are put in the

pan to create tension in the string This arrangement is shown in the circuit

diagram

The fork is set into vibrations by lightly hitting the prong of the tuning

fork on which the string is not tied or by connecting an electric supply as

shown in the circuit diagram Thus the transverse vibrations are produced

in the string and by adjusting the length andor weights in the pan these

vibrations are reflected from the point of contact between the string and

the pulley and a number of loops appear on the string as shown in the

circuit diagram

When the prongs of the tuning fork vibrate in a plane parallel to the

direction of propagation of the waves it is called lsquoArsquo position or

longitudinal position

If the tuning fork along with the wooden block is rotated through

90˚ so that the plane of vibration of the tuning fork is normal (ie at right

angles) to the direction of propagation it is called lsquoBrsquo position or transverse

position

For the same length and same weight in the pan (ie for the same

tension) the number of loops in lsquoBrsquo position is double than in lsquoArsquo position

Thus either in lsquoArsquo position or in lsquoBrsquo position standing transverse

waves are generated in the string with a series of nodes and antinodes at

equal distances

The equation connecting number of loops (n or nrsquo) length of the

string (l) tension in the string (T) mass per unit length of the string (m) and

frequency of the string (f) is as follows

Date____________

Pag

e30

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position)

119943prime =119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

If the frequency of tuning fork is F then for lsquoArsquo position 119839 =119813

120784 and for lsquoBrsquo

position 119839prime = 119813

In the above equations if all the quantities on the RHS are known the

frequency of the tuning fork 119813 can be calculated

Observations

(1) Gravitational accelerationhellip g = 98 ms2

(2) Mass per unit length of the stringhellip m = _______ kgm

(3) Mass of the scale panhellip M1 = _______ kg

Observation Table

Sr

No

Total mass

suspended at

the end of the

stringhellip

M=M1+M2

(kg)

Tension

created

in the

stringhellip

T=Mg (N)

Length of the

vibrating string

Average

lengthhellip

119949 (m)

No of loops created on

the stringhellip

Frequency of the

vibrating stringhellip

Relation

between

f and frsquo 1199491 (m) 1199492 (m)

In

Longitudinal

Modehellip

n

In

Transverse

Modehellip

nrsquo

In

Longitudinal

Modehellip

119943 =119951

120784119949

119931

119950

In

Transverse

Modehellip

119943prime =119951prime

120784119949

119931

119950

1

2

3

4

Here M2 = the weight put in the scale pan

Page31

Date____________

Pag

e32

Calculations

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position) 119943prime =

119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e33

P-N Junction Diode Characteristics Experiment - 09

Aim To study the Forward and Reverse bias characteristics of a P-N junction

diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components P-N junction diode Resistors

Circuit Diagram

(Forward biased PN diode) (Reverse biased PN diode)

Procedure

For Forward Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 01 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 02 03 04hellip

volts and repeat the procedure Note down the knee voltage and

corresponding current in your observation table

For Reverse Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Date____________

Pag

e34

Theory

If donor (pentavalent) impurities are introduced on one side and

acceptors (trivalent) on the opposite side of a single crystal of an intrinsic

semiconductor like germanium or silicon a p-n junction is formed as shown

in Fig 11 In the figure a donor ion is indicated schematically by a plus sign

because after this impurity atom donates an electron it becomes a positive

ion

The acceptor ion is indicated by a minus sign because after this atom

accepts an electron it becomes a negative ion Initially there are only n-

type carriers to the right of the junction and only p-type carriers to the left

Because there is a density gradient across the junction holes will diffuse to

the right across the junction and electrons to the left As a result of the

displacement of these charges an electric field appears across the junction

Equilibrium is established when the field becomes large enough to restrain

the process of diffusion The positive holes which neutralize the acceptor

ions near the junction in p-type germanium disappear as a result of

combination with electrons which diffuse across the junction Similarly the

neutralizing electrons on the n side of the junction combine with holes

which cross the junction from the p side Since the region of the junction is

depleted of mobile charges it is called the depletion region or a potential

barrier

Forward Bias

An external voltage applied to the p-n junction with the polarity

shown in Fig 12 is known as forward bias The height of the potential

barrier at the junction is lowered by the applied forward voltage In other

words we can say that p-n junction diode is connected to an external

Date____________

Pag

e35

battery in such a way that depletion region is reduced in size or eliminated

altogether Which of these takes place is determined by the size of the

applied voltage The positive terminal of the battery repels the holes on the

p-side and pushes them towards the junction The negative terminal of the

battery repels the electrons and pushes them towards the junction This

collapses the depletion region With the depletion region gone the diode

can conduct

Reverse Bias

An external voltage applied with polarity in Fig 13 is called reverse

bias When reverse bias is applied to a junction diode the depletion region

does not collapse On the contrary it becomes wider The positive side of

battery is applied to the n-type material This attracts the free electrons

away from the junction The negative side of the battery attracts the holes

in p-type material away from the junction This makes the depletion region

wider than it was when no voltage is applied The depletion region is an

insulator and it will block the flow of current Actually a small current will

flow because of minority carriers The p-type material has a few minority

electrons These are pushed to the junction by the repulsion of the negative

side of the battery The n-type material has few minority holes These are

also pushed towards the junction Reverse bias forces the minority carriers

together and a small current - called leakage current - results

Diodes which are designed with adequate power dissipation

capability to operate in the breakdown region are none as Zener diodes

Two mechanisms of diode breakdown for increasing reverse voltage are

recognized In one mechanism the thermally generated electrons and

holes acquire sufficient energy from the applied potential to produce new

carriers by removing valence electrons from their bonds These new

carriers in turn produce additional carriers again through the process of

disrupting bonds This cumulative process is referred to as avalanche

breakdown Even if the initially available carriers do not acquire sufficient

energy to disrupt bonds it is possible to initiate breakdown through a

direct rupture of the bonds because of the existence of strong electric field

Under these conditions the breakdown is referred to as Zener breakdown

Date____________

Pag

e36

Zener breakdown occurs below 6 V Zener diodes are commonly used in

voltage-reference or constant-voltage devices

Characteristic curves of diode

Fig 14 shows V-I Characteristic curves for typical p-n junction diode

It is seen that the curve is not linear With 0 V across the diode the diode

will not conduct the diode will not begin to conduct until a few tenths of a

volt are applied across it This is the voltage needed to overcome the

potential barrier It requires about 02 V to turn on a germanium diode and

about 06 V to turn on a silicon diode Fig 18 also shows what happens

when reverse bias is applied to a diode At increasing levels of reverse

voltage the curve shows some reverse current This leakage current is

caused by minority carries It is usually very small

Graph

Fig-14

Date____________

Pag

e37

Observation Table for Forward bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Date____________

Pag

e38

Observation Table for Reverse bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e39

Calculation for Forward bias 119877 = 119881

119868

Calculation for Reverse bias 119877 = 119881

119868

Date____________

Pag

e40

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e41

Zener Diode Reverse Bias Characteristics Experiment - 10

Aim To study the reverse bias characteristics of a Zener diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components Zener diode Resistors

Circuit Diagram

Procedure

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Theory

A diode which is heavily doped (Si or Ge) and which operates in the

reverse breakdown region with a sharp breakdown voltage is called a zener

diode The schematic symbol of a zener diode is shown in Fig-1 This is

similar to a normal diode except that the line (bar) representing the

cathode is bent at both ends like the letter Z for zener diode

Date____________

Pag

e42

A C Fig-1

In a simple diode the doping is light as a result the breakdown

voltage is high and not sharp But if doping is made heavy the depletion

layer becomes very narrow and even the breakdown voltage gets reduced

to a sharp value The zener diode is designed to operate in the breakdown

region without damage

The reverse breakdown of a zener diode may occur either due to

zener effect or avalanche effect But zener diode primarily depends on

zener effect for its working When the electric field across the junction is

sufficiently high due to the applied voltage the zener breakdown occurs

because of breaking of covalent bonds This produces a large number of

electrons and holes which constitute a steep rise in the reverse saturation

current (also called zener current 119868Z) This effect is called as zener effect

Zener current is independent of the applied voltage and depends only on

the external resistance

The V - 119868 characteristic of a zener diode is shown in Fig-2 The

forward characteristic is simply that of an ordinary forward biased junction

diode

Fig-2

Date____________

Pag

e43

Under reverse bias condition breakdown of junction occurs This

breakdown depends upon the amount of doping It can be seen from Fig-2

that as the reverse voltage is increased the reverse current remains

negligibly small up to the lsquokneersquo of the curve

At this lsquoknee pointrsquo the effect of breakdown process begins The

voltage corresponding to the lsquoknee pointrsquo in the figure is called the zener

breakdown voltage or simply zener voltage (VZ) which is very sharp

compared to a simle p-n junction diode Beyond this voltage the reverse

current (119868Z) increases sharply to a high value

The zener diode is not immediately burnt just because it has entered

the breakdown region As long as the external resistance connected to the

diode in the circuit limits the diode current to less than the burn out value

the diode will not burn out The zener voltage VZ remains constant even

when zener current 119868Z increases greatly This ability of a diode is called

regulating ability and it enables us to use zener diode for voltage

regulation

Date____________

Pag

e44

Observation Table

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e45

Graph 119868 V

Calculations 119877 = 119881

119868

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e46

Dispersive Power of The Prism Experiment - 11

Aim To find the dispersive power (D) of the prism by using spectrometer

Apparatus Mercury vapor lamp Spectrometer Prism

Procedure

Levelling and alignment of collimator and telescope

1 Switch on the mercury lamp Adjust the leveling screws on the chassis

Keep the spirit level on the chassis and do finer adjustments of these

screws to bring the bubble in the sprit level to the centre Repeat this

placing the sprit level along a direction perpendicular to the earlier

direction

2 Repeat this procedure for the prism table

3 Close the slit at the other end of the collimator using the drum screw DS1

Open it to a reasonable width Place the spectrometer in front of the

mercury lamp window and rotate the collimator so that the slit faces of

window View the slit through the telescope If it is not in the centre of the

view level collimator and the telescope so as to bring it to the centre

Setting the prism in the minimum deviation position

1 Rotate the prism table such that lines ruled on the table become

perpendicular to the axis of collimator

2 Place prism over the prism table such that its rough surface BA is

perpendicular to the line on prism table (See Fig-1(a))

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e24

Temperature of Tungsten Filament Experiment ndash 07

Aim To find the temperature of the tungsten filament of the bulb

Apparatus AC Ammeter(0-500 mA) AC Voltmeter(0-250 volt) Variac

Components Bulb

Circuit Diagram

Procedure

Connect the circuit as shown in the circuit diagram Now switch ON

the circuit and note down the reading shown by ammeter at 0 volt then

increase the voltage from 0 to 10 volt and note down the reading of

ammeter Now increase the voltage in order of 10 volts (up to 100 volts)

and note down the readings of the current shown by the ammeter Now

calculate the resistance and the temperature of the filament

Observations

(1) Room temperaturehellip t0 = _______ ˚C

(2) Resistance of the filament of the bulb at room temperaturehellip

R0 = _______ Ω

(3) Temperature coefficient of tungstenhellip α = 45times10-4 ˚C-1

Date____________

Pag

e25

Observation Table

Sr No Voltage V

(volt)

Current 119816

(mA)

Resistance of

The Filament

119825119853 =119829

119816 Ω

Temperature of The Filament

119853 =120783

120514[

119825119853

119825120782 120783 + 120514119853120782 minus 120783] ˚C

1

2

3

4

5

6

7

8

9

10

Graph Rt versus t

Date____________

Pag

e26

Calculations

(1) Resistance of The Filament Rt =V

I Ω

(2) Temperature of The Filament t =1

α[

Rt

R0 1 + αt0 minus 1] ˚C

Date____________

Pag

e27

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e28

Meldersquos Experiment - 08

Aim To find the frequency of the wave and the frequency of the tuning fork by

Meldersquos experiment

Apparatus Meldersquos experiment apparatus

Circuit Diagram

Transverse mode

Procedure

Set Meldersquos experiment apparatus as shown in circuit diagram in

longitudinal position and switch ON the power supply put some weight in

scale pan and adjust the length of the string in such a way that you find

some loops on the string (eg 2 loops) Now rotate the apparatus by 90˚ so

that it is set for lsquoBrsquo position for the same values of weight in pan and for

the same length of the string the number of loops created in lsquoBrsquo position

are double (eg 4 loops) than in lsquoArsquo position Note down these readings in

observation table Repeat the experiment for other values of weight in

scale pan

Date____________

Pag

e29

Theory

This is an easy and efficient method by which nodes and antinodes

formed on a string can be demonstrated

A tuning fork is fitted in a wooden block A long string or thread of

cotton is taken One end of this string is tied to one of the prongs of the

tuning fork and the second end of this string passes over a smooth pulley in

such a way that a small pan can be hang on it Small weights are put in the

pan to create tension in the string This arrangement is shown in the circuit

diagram

The fork is set into vibrations by lightly hitting the prong of the tuning

fork on which the string is not tied or by connecting an electric supply as

shown in the circuit diagram Thus the transverse vibrations are produced

in the string and by adjusting the length andor weights in the pan these

vibrations are reflected from the point of contact between the string and

the pulley and a number of loops appear on the string as shown in the

circuit diagram

When the prongs of the tuning fork vibrate in a plane parallel to the

direction of propagation of the waves it is called lsquoArsquo position or

longitudinal position

If the tuning fork along with the wooden block is rotated through

90˚ so that the plane of vibration of the tuning fork is normal (ie at right

angles) to the direction of propagation it is called lsquoBrsquo position or transverse

position

For the same length and same weight in the pan (ie for the same

tension) the number of loops in lsquoBrsquo position is double than in lsquoArsquo position

Thus either in lsquoArsquo position or in lsquoBrsquo position standing transverse

waves are generated in the string with a series of nodes and antinodes at

equal distances

The equation connecting number of loops (n or nrsquo) length of the

string (l) tension in the string (T) mass per unit length of the string (m) and

frequency of the string (f) is as follows

Date____________

Pag

e30

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position)

119943prime =119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

If the frequency of tuning fork is F then for lsquoArsquo position 119839 =119813

120784 and for lsquoBrsquo

position 119839prime = 119813

In the above equations if all the quantities on the RHS are known the

frequency of the tuning fork 119813 can be calculated

Observations

(1) Gravitational accelerationhellip g = 98 ms2

(2) Mass per unit length of the stringhellip m = _______ kgm

(3) Mass of the scale panhellip M1 = _______ kg

Observation Table

Sr

No

Total mass

suspended at

the end of the

stringhellip

M=M1+M2

(kg)

Tension

created

in the

stringhellip

T=Mg (N)

Length of the

vibrating string

Average

lengthhellip

119949 (m)

No of loops created on

the stringhellip

Frequency of the

vibrating stringhellip

Relation

between

f and frsquo 1199491 (m) 1199492 (m)

In

Longitudinal

Modehellip

n

In

Transverse

Modehellip

nrsquo

In

Longitudinal

Modehellip

119943 =119951

120784119949

119931

119950

In

Transverse

Modehellip

119943prime =119951prime

120784119949

119931

119950

1

2

3

4

Here M2 = the weight put in the scale pan

Page31

Date____________

Pag

e32

Calculations

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position) 119943prime =

119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e33

P-N Junction Diode Characteristics Experiment - 09

Aim To study the Forward and Reverse bias characteristics of a P-N junction

diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components P-N junction diode Resistors

Circuit Diagram

(Forward biased PN diode) (Reverse biased PN diode)

Procedure

For Forward Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 01 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 02 03 04hellip

volts and repeat the procedure Note down the knee voltage and

corresponding current in your observation table

For Reverse Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Date____________

Pag

e34

Theory

If donor (pentavalent) impurities are introduced on one side and

acceptors (trivalent) on the opposite side of a single crystal of an intrinsic

semiconductor like germanium or silicon a p-n junction is formed as shown

in Fig 11 In the figure a donor ion is indicated schematically by a plus sign

because after this impurity atom donates an electron it becomes a positive

ion

The acceptor ion is indicated by a minus sign because after this atom

accepts an electron it becomes a negative ion Initially there are only n-

type carriers to the right of the junction and only p-type carriers to the left

Because there is a density gradient across the junction holes will diffuse to

the right across the junction and electrons to the left As a result of the

displacement of these charges an electric field appears across the junction

Equilibrium is established when the field becomes large enough to restrain

the process of diffusion The positive holes which neutralize the acceptor

ions near the junction in p-type germanium disappear as a result of

combination with electrons which diffuse across the junction Similarly the

neutralizing electrons on the n side of the junction combine with holes

which cross the junction from the p side Since the region of the junction is

depleted of mobile charges it is called the depletion region or a potential

barrier

Forward Bias

An external voltage applied to the p-n junction with the polarity

shown in Fig 12 is known as forward bias The height of the potential

barrier at the junction is lowered by the applied forward voltage In other

words we can say that p-n junction diode is connected to an external

Date____________

Pag

e35

battery in such a way that depletion region is reduced in size or eliminated

altogether Which of these takes place is determined by the size of the

applied voltage The positive terminal of the battery repels the holes on the

p-side and pushes them towards the junction The negative terminal of the

battery repels the electrons and pushes them towards the junction This

collapses the depletion region With the depletion region gone the diode

can conduct

Reverse Bias

An external voltage applied with polarity in Fig 13 is called reverse

bias When reverse bias is applied to a junction diode the depletion region

does not collapse On the contrary it becomes wider The positive side of

battery is applied to the n-type material This attracts the free electrons

away from the junction The negative side of the battery attracts the holes

in p-type material away from the junction This makes the depletion region

wider than it was when no voltage is applied The depletion region is an

insulator and it will block the flow of current Actually a small current will

flow because of minority carriers The p-type material has a few minority

electrons These are pushed to the junction by the repulsion of the negative

side of the battery The n-type material has few minority holes These are

also pushed towards the junction Reverse bias forces the minority carriers

together and a small current - called leakage current - results

Diodes which are designed with adequate power dissipation

capability to operate in the breakdown region are none as Zener diodes

Two mechanisms of diode breakdown for increasing reverse voltage are

recognized In one mechanism the thermally generated electrons and

holes acquire sufficient energy from the applied potential to produce new

carriers by removing valence electrons from their bonds These new

carriers in turn produce additional carriers again through the process of

disrupting bonds This cumulative process is referred to as avalanche

breakdown Even if the initially available carriers do not acquire sufficient

energy to disrupt bonds it is possible to initiate breakdown through a

direct rupture of the bonds because of the existence of strong electric field

Under these conditions the breakdown is referred to as Zener breakdown

Date____________

Pag

e36

Zener breakdown occurs below 6 V Zener diodes are commonly used in

voltage-reference or constant-voltage devices

Characteristic curves of diode

Fig 14 shows V-I Characteristic curves for typical p-n junction diode

It is seen that the curve is not linear With 0 V across the diode the diode

will not conduct the diode will not begin to conduct until a few tenths of a

volt are applied across it This is the voltage needed to overcome the

potential barrier It requires about 02 V to turn on a germanium diode and

about 06 V to turn on a silicon diode Fig 18 also shows what happens

when reverse bias is applied to a diode At increasing levels of reverse

voltage the curve shows some reverse current This leakage current is

caused by minority carries It is usually very small

Graph

Fig-14

Date____________

Pag

e37

Observation Table for Forward bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Date____________

Pag

e38

Observation Table for Reverse bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e39

Calculation for Forward bias 119877 = 119881

119868

Calculation for Reverse bias 119877 = 119881

119868

Date____________

Pag

e40

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e41

Zener Diode Reverse Bias Characteristics Experiment - 10

Aim To study the reverse bias characteristics of a Zener diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components Zener diode Resistors

Circuit Diagram

Procedure

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Theory

A diode which is heavily doped (Si or Ge) and which operates in the

reverse breakdown region with a sharp breakdown voltage is called a zener

diode The schematic symbol of a zener diode is shown in Fig-1 This is

similar to a normal diode except that the line (bar) representing the

cathode is bent at both ends like the letter Z for zener diode

Date____________

Pag

e42

A C Fig-1

In a simple diode the doping is light as a result the breakdown

voltage is high and not sharp But if doping is made heavy the depletion

layer becomes very narrow and even the breakdown voltage gets reduced

to a sharp value The zener diode is designed to operate in the breakdown

region without damage

The reverse breakdown of a zener diode may occur either due to

zener effect or avalanche effect But zener diode primarily depends on

zener effect for its working When the electric field across the junction is

sufficiently high due to the applied voltage the zener breakdown occurs

because of breaking of covalent bonds This produces a large number of

electrons and holes which constitute a steep rise in the reverse saturation

current (also called zener current 119868Z) This effect is called as zener effect

Zener current is independent of the applied voltage and depends only on

the external resistance

The V - 119868 characteristic of a zener diode is shown in Fig-2 The

forward characteristic is simply that of an ordinary forward biased junction

diode

Fig-2

Date____________

Pag

e43

Under reverse bias condition breakdown of junction occurs This

breakdown depends upon the amount of doping It can be seen from Fig-2

that as the reverse voltage is increased the reverse current remains

negligibly small up to the lsquokneersquo of the curve

At this lsquoknee pointrsquo the effect of breakdown process begins The

voltage corresponding to the lsquoknee pointrsquo in the figure is called the zener

breakdown voltage or simply zener voltage (VZ) which is very sharp

compared to a simle p-n junction diode Beyond this voltage the reverse

current (119868Z) increases sharply to a high value

The zener diode is not immediately burnt just because it has entered

the breakdown region As long as the external resistance connected to the

diode in the circuit limits the diode current to less than the burn out value

the diode will not burn out The zener voltage VZ remains constant even

when zener current 119868Z increases greatly This ability of a diode is called

regulating ability and it enables us to use zener diode for voltage

regulation

Date____________

Pag

e44

Observation Table

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e45

Graph 119868 V

Calculations 119877 = 119881

119868

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e46

Dispersive Power of The Prism Experiment - 11

Aim To find the dispersive power (D) of the prism by using spectrometer

Apparatus Mercury vapor lamp Spectrometer Prism

Procedure

Levelling and alignment of collimator and telescope

1 Switch on the mercury lamp Adjust the leveling screws on the chassis

Keep the spirit level on the chassis and do finer adjustments of these

screws to bring the bubble in the sprit level to the centre Repeat this

placing the sprit level along a direction perpendicular to the earlier

direction

2 Repeat this procedure for the prism table

3 Close the slit at the other end of the collimator using the drum screw DS1

Open it to a reasonable width Place the spectrometer in front of the

mercury lamp window and rotate the collimator so that the slit faces of

window View the slit through the telescope If it is not in the centre of the

view level collimator and the telescope so as to bring it to the centre

Setting the prism in the minimum deviation position

1 Rotate the prism table such that lines ruled on the table become

perpendicular to the axis of collimator

2 Place prism over the prism table such that its rough surface BA is

perpendicular to the line on prism table (See Fig-1(a))

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e25

Observation Table

Sr No Voltage V

(volt)

Current 119816

(mA)

Resistance of

The Filament

119825119853 =119829

119816 Ω

Temperature of The Filament

119853 =120783

120514[

119825119853

119825120782 120783 + 120514119853120782 minus 120783] ˚C

1

2

3

4

5

6

7

8

9

10

Graph Rt versus t

Date____________

Pag

e26

Calculations

(1) Resistance of The Filament Rt =V

I Ω

(2) Temperature of The Filament t =1

α[

Rt

R0 1 + αt0 minus 1] ˚C

Date____________

Pag

e27

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e28

Meldersquos Experiment - 08

Aim To find the frequency of the wave and the frequency of the tuning fork by

Meldersquos experiment

Apparatus Meldersquos experiment apparatus

Circuit Diagram

Transverse mode

Procedure

Set Meldersquos experiment apparatus as shown in circuit diagram in

longitudinal position and switch ON the power supply put some weight in

scale pan and adjust the length of the string in such a way that you find

some loops on the string (eg 2 loops) Now rotate the apparatus by 90˚ so

that it is set for lsquoBrsquo position for the same values of weight in pan and for

the same length of the string the number of loops created in lsquoBrsquo position

are double (eg 4 loops) than in lsquoArsquo position Note down these readings in

observation table Repeat the experiment for other values of weight in

scale pan

Date____________

Pag

e29

Theory

This is an easy and efficient method by which nodes and antinodes

formed on a string can be demonstrated

A tuning fork is fitted in a wooden block A long string or thread of

cotton is taken One end of this string is tied to one of the prongs of the

tuning fork and the second end of this string passes over a smooth pulley in

such a way that a small pan can be hang on it Small weights are put in the

pan to create tension in the string This arrangement is shown in the circuit

diagram

The fork is set into vibrations by lightly hitting the prong of the tuning

fork on which the string is not tied or by connecting an electric supply as

shown in the circuit diagram Thus the transverse vibrations are produced

in the string and by adjusting the length andor weights in the pan these

vibrations are reflected from the point of contact between the string and

the pulley and a number of loops appear on the string as shown in the

circuit diagram

When the prongs of the tuning fork vibrate in a plane parallel to the

direction of propagation of the waves it is called lsquoArsquo position or

longitudinal position

If the tuning fork along with the wooden block is rotated through

90˚ so that the plane of vibration of the tuning fork is normal (ie at right

angles) to the direction of propagation it is called lsquoBrsquo position or transverse

position

For the same length and same weight in the pan (ie for the same

tension) the number of loops in lsquoBrsquo position is double than in lsquoArsquo position

Thus either in lsquoArsquo position or in lsquoBrsquo position standing transverse

waves are generated in the string with a series of nodes and antinodes at

equal distances

The equation connecting number of loops (n or nrsquo) length of the

string (l) tension in the string (T) mass per unit length of the string (m) and

frequency of the string (f) is as follows

Date____________

Pag

e30

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position)

119943prime =119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

If the frequency of tuning fork is F then for lsquoArsquo position 119839 =119813

120784 and for lsquoBrsquo

position 119839prime = 119813

In the above equations if all the quantities on the RHS are known the

frequency of the tuning fork 119813 can be calculated

Observations

(1) Gravitational accelerationhellip g = 98 ms2

(2) Mass per unit length of the stringhellip m = _______ kgm

(3) Mass of the scale panhellip M1 = _______ kg

Observation Table

Sr

No

Total mass

suspended at

the end of the

stringhellip

M=M1+M2

(kg)

Tension

created

in the

stringhellip

T=Mg (N)

Length of the

vibrating string

Average

lengthhellip

119949 (m)

No of loops created on

the stringhellip

Frequency of the

vibrating stringhellip

Relation

between

f and frsquo 1199491 (m) 1199492 (m)

In

Longitudinal

Modehellip

n

In

Transverse

Modehellip

nrsquo

In

Longitudinal

Modehellip

119943 =119951

120784119949

119931

119950

In

Transverse

Modehellip

119943prime =119951prime

120784119949

119931

119950

1

2

3

4

Here M2 = the weight put in the scale pan

Page31

Date____________

Pag

e32

Calculations

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position) 119943prime =

119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e33

P-N Junction Diode Characteristics Experiment - 09

Aim To study the Forward and Reverse bias characteristics of a P-N junction

diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components P-N junction diode Resistors

Circuit Diagram

(Forward biased PN diode) (Reverse biased PN diode)

Procedure

For Forward Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 01 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 02 03 04hellip

volts and repeat the procedure Note down the knee voltage and

corresponding current in your observation table

For Reverse Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Date____________

Pag

e34

Theory

If donor (pentavalent) impurities are introduced on one side and

acceptors (trivalent) on the opposite side of a single crystal of an intrinsic

semiconductor like germanium or silicon a p-n junction is formed as shown

in Fig 11 In the figure a donor ion is indicated schematically by a plus sign

because after this impurity atom donates an electron it becomes a positive

ion

The acceptor ion is indicated by a minus sign because after this atom

accepts an electron it becomes a negative ion Initially there are only n-

type carriers to the right of the junction and only p-type carriers to the left

Because there is a density gradient across the junction holes will diffuse to

the right across the junction and electrons to the left As a result of the

displacement of these charges an electric field appears across the junction

Equilibrium is established when the field becomes large enough to restrain

the process of diffusion The positive holes which neutralize the acceptor

ions near the junction in p-type germanium disappear as a result of

combination with electrons which diffuse across the junction Similarly the

neutralizing electrons on the n side of the junction combine with holes

which cross the junction from the p side Since the region of the junction is

depleted of mobile charges it is called the depletion region or a potential

barrier

Forward Bias

An external voltage applied to the p-n junction with the polarity

shown in Fig 12 is known as forward bias The height of the potential

barrier at the junction is lowered by the applied forward voltage In other

words we can say that p-n junction diode is connected to an external

Date____________

Pag

e35

battery in such a way that depletion region is reduced in size or eliminated

altogether Which of these takes place is determined by the size of the

applied voltage The positive terminal of the battery repels the holes on the

p-side and pushes them towards the junction The negative terminal of the

battery repels the electrons and pushes them towards the junction This

collapses the depletion region With the depletion region gone the diode

can conduct

Reverse Bias

An external voltage applied with polarity in Fig 13 is called reverse

bias When reverse bias is applied to a junction diode the depletion region

does not collapse On the contrary it becomes wider The positive side of

battery is applied to the n-type material This attracts the free electrons

away from the junction The negative side of the battery attracts the holes

in p-type material away from the junction This makes the depletion region

wider than it was when no voltage is applied The depletion region is an

insulator and it will block the flow of current Actually a small current will

flow because of minority carriers The p-type material has a few minority

electrons These are pushed to the junction by the repulsion of the negative

side of the battery The n-type material has few minority holes These are

also pushed towards the junction Reverse bias forces the minority carriers

together and a small current - called leakage current - results

Diodes which are designed with adequate power dissipation

capability to operate in the breakdown region are none as Zener diodes

Two mechanisms of diode breakdown for increasing reverse voltage are

recognized In one mechanism the thermally generated electrons and

holes acquire sufficient energy from the applied potential to produce new

carriers by removing valence electrons from their bonds These new

carriers in turn produce additional carriers again through the process of

disrupting bonds This cumulative process is referred to as avalanche

breakdown Even if the initially available carriers do not acquire sufficient

energy to disrupt bonds it is possible to initiate breakdown through a

direct rupture of the bonds because of the existence of strong electric field

Under these conditions the breakdown is referred to as Zener breakdown

Date____________

Pag

e36

Zener breakdown occurs below 6 V Zener diodes are commonly used in

voltage-reference or constant-voltage devices

Characteristic curves of diode

Fig 14 shows V-I Characteristic curves for typical p-n junction diode

It is seen that the curve is not linear With 0 V across the diode the diode

will not conduct the diode will not begin to conduct until a few tenths of a

volt are applied across it This is the voltage needed to overcome the

potential barrier It requires about 02 V to turn on a germanium diode and

about 06 V to turn on a silicon diode Fig 18 also shows what happens

when reverse bias is applied to a diode At increasing levels of reverse

voltage the curve shows some reverse current This leakage current is

caused by minority carries It is usually very small

Graph

Fig-14

Date____________

Pag

e37

Observation Table for Forward bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Date____________

Pag

e38

Observation Table for Reverse bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e39

Calculation for Forward bias 119877 = 119881

119868

Calculation for Reverse bias 119877 = 119881

119868

Date____________

Pag

e40

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e41

Zener Diode Reverse Bias Characteristics Experiment - 10

Aim To study the reverse bias characteristics of a Zener diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components Zener diode Resistors

Circuit Diagram

Procedure

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Theory

A diode which is heavily doped (Si or Ge) and which operates in the

reverse breakdown region with a sharp breakdown voltage is called a zener

diode The schematic symbol of a zener diode is shown in Fig-1 This is

similar to a normal diode except that the line (bar) representing the

cathode is bent at both ends like the letter Z for zener diode

Date____________

Pag

e42

A C Fig-1

In a simple diode the doping is light as a result the breakdown

voltage is high and not sharp But if doping is made heavy the depletion

layer becomes very narrow and even the breakdown voltage gets reduced

to a sharp value The zener diode is designed to operate in the breakdown

region without damage

The reverse breakdown of a zener diode may occur either due to

zener effect or avalanche effect But zener diode primarily depends on

zener effect for its working When the electric field across the junction is

sufficiently high due to the applied voltage the zener breakdown occurs

because of breaking of covalent bonds This produces a large number of

electrons and holes which constitute a steep rise in the reverse saturation

current (also called zener current 119868Z) This effect is called as zener effect

Zener current is independent of the applied voltage and depends only on

the external resistance

The V - 119868 characteristic of a zener diode is shown in Fig-2 The

forward characteristic is simply that of an ordinary forward biased junction

diode

Fig-2

Date____________

Pag

e43

Under reverse bias condition breakdown of junction occurs This

breakdown depends upon the amount of doping It can be seen from Fig-2

that as the reverse voltage is increased the reverse current remains

negligibly small up to the lsquokneersquo of the curve

At this lsquoknee pointrsquo the effect of breakdown process begins The

voltage corresponding to the lsquoknee pointrsquo in the figure is called the zener

breakdown voltage or simply zener voltage (VZ) which is very sharp

compared to a simle p-n junction diode Beyond this voltage the reverse

current (119868Z) increases sharply to a high value

The zener diode is not immediately burnt just because it has entered

the breakdown region As long as the external resistance connected to the

diode in the circuit limits the diode current to less than the burn out value

the diode will not burn out The zener voltage VZ remains constant even

when zener current 119868Z increases greatly This ability of a diode is called

regulating ability and it enables us to use zener diode for voltage

regulation

Date____________

Pag

e44

Observation Table

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e45

Graph 119868 V

Calculations 119877 = 119881

119868

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e46

Dispersive Power of The Prism Experiment - 11

Aim To find the dispersive power (D) of the prism by using spectrometer

Apparatus Mercury vapor lamp Spectrometer Prism

Procedure

Levelling and alignment of collimator and telescope

1 Switch on the mercury lamp Adjust the leveling screws on the chassis

Keep the spirit level on the chassis and do finer adjustments of these

screws to bring the bubble in the sprit level to the centre Repeat this

placing the sprit level along a direction perpendicular to the earlier

direction

2 Repeat this procedure for the prism table

3 Close the slit at the other end of the collimator using the drum screw DS1

Open it to a reasonable width Place the spectrometer in front of the

mercury lamp window and rotate the collimator so that the slit faces of

window View the slit through the telescope If it is not in the centre of the

view level collimator and the telescope so as to bring it to the centre

Setting the prism in the minimum deviation position

1 Rotate the prism table such that lines ruled on the table become

perpendicular to the axis of collimator

2 Place prism over the prism table such that its rough surface BA is

perpendicular to the line on prism table (See Fig-1(a))

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e26

Calculations

(1) Resistance of The Filament Rt =V

I Ω

(2) Temperature of The Filament t =1

α[

Rt

R0 1 + αt0 minus 1] ˚C

Date____________

Pag

e27

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e28

Meldersquos Experiment - 08

Aim To find the frequency of the wave and the frequency of the tuning fork by

Meldersquos experiment

Apparatus Meldersquos experiment apparatus

Circuit Diagram

Transverse mode

Procedure

Set Meldersquos experiment apparatus as shown in circuit diagram in

longitudinal position and switch ON the power supply put some weight in

scale pan and adjust the length of the string in such a way that you find

some loops on the string (eg 2 loops) Now rotate the apparatus by 90˚ so

that it is set for lsquoBrsquo position for the same values of weight in pan and for

the same length of the string the number of loops created in lsquoBrsquo position

are double (eg 4 loops) than in lsquoArsquo position Note down these readings in

observation table Repeat the experiment for other values of weight in

scale pan

Date____________

Pag

e29

Theory

This is an easy and efficient method by which nodes and antinodes

formed on a string can be demonstrated

A tuning fork is fitted in a wooden block A long string or thread of

cotton is taken One end of this string is tied to one of the prongs of the

tuning fork and the second end of this string passes over a smooth pulley in

such a way that a small pan can be hang on it Small weights are put in the

pan to create tension in the string This arrangement is shown in the circuit

diagram

The fork is set into vibrations by lightly hitting the prong of the tuning

fork on which the string is not tied or by connecting an electric supply as

shown in the circuit diagram Thus the transverse vibrations are produced

in the string and by adjusting the length andor weights in the pan these

vibrations are reflected from the point of contact between the string and

the pulley and a number of loops appear on the string as shown in the

circuit diagram

When the prongs of the tuning fork vibrate in a plane parallel to the

direction of propagation of the waves it is called lsquoArsquo position or

longitudinal position

If the tuning fork along with the wooden block is rotated through

90˚ so that the plane of vibration of the tuning fork is normal (ie at right

angles) to the direction of propagation it is called lsquoBrsquo position or transverse

position

For the same length and same weight in the pan (ie for the same

tension) the number of loops in lsquoBrsquo position is double than in lsquoArsquo position

Thus either in lsquoArsquo position or in lsquoBrsquo position standing transverse

waves are generated in the string with a series of nodes and antinodes at

equal distances

The equation connecting number of loops (n or nrsquo) length of the

string (l) tension in the string (T) mass per unit length of the string (m) and

frequency of the string (f) is as follows

Date____________

Pag

e30

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position)

119943prime =119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

If the frequency of tuning fork is F then for lsquoArsquo position 119839 =119813

120784 and for lsquoBrsquo

position 119839prime = 119813

In the above equations if all the quantities on the RHS are known the

frequency of the tuning fork 119813 can be calculated

Observations

(1) Gravitational accelerationhellip g = 98 ms2

(2) Mass per unit length of the stringhellip m = _______ kgm

(3) Mass of the scale panhellip M1 = _______ kg

Observation Table

Sr

No

Total mass

suspended at

the end of the

stringhellip

M=M1+M2

(kg)

Tension

created

in the

stringhellip

T=Mg (N)

Length of the

vibrating string

Average

lengthhellip

119949 (m)

No of loops created on

the stringhellip

Frequency of the

vibrating stringhellip

Relation

between

f and frsquo 1199491 (m) 1199492 (m)

In

Longitudinal

Modehellip

n

In

Transverse

Modehellip

nrsquo

In

Longitudinal

Modehellip

119943 =119951

120784119949

119931

119950

In

Transverse

Modehellip

119943prime =119951prime

120784119949

119931

119950

1

2

3

4

Here M2 = the weight put in the scale pan

Page31

Date____________

Pag

e32

Calculations

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position) 119943prime =

119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e33

P-N Junction Diode Characteristics Experiment - 09

Aim To study the Forward and Reverse bias characteristics of a P-N junction

diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components P-N junction diode Resistors

Circuit Diagram

(Forward biased PN diode) (Reverse biased PN diode)

Procedure

For Forward Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 01 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 02 03 04hellip

volts and repeat the procedure Note down the knee voltage and

corresponding current in your observation table

For Reverse Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Date____________

Pag

e34

Theory

If donor (pentavalent) impurities are introduced on one side and

acceptors (trivalent) on the opposite side of a single crystal of an intrinsic

semiconductor like germanium or silicon a p-n junction is formed as shown

in Fig 11 In the figure a donor ion is indicated schematically by a plus sign

because after this impurity atom donates an electron it becomes a positive

ion

The acceptor ion is indicated by a minus sign because after this atom

accepts an electron it becomes a negative ion Initially there are only n-

type carriers to the right of the junction and only p-type carriers to the left

Because there is a density gradient across the junction holes will diffuse to

the right across the junction and electrons to the left As a result of the

displacement of these charges an electric field appears across the junction

Equilibrium is established when the field becomes large enough to restrain

the process of diffusion The positive holes which neutralize the acceptor

ions near the junction in p-type germanium disappear as a result of

combination with electrons which diffuse across the junction Similarly the

neutralizing electrons on the n side of the junction combine with holes

which cross the junction from the p side Since the region of the junction is

depleted of mobile charges it is called the depletion region or a potential

barrier

Forward Bias

An external voltage applied to the p-n junction with the polarity

shown in Fig 12 is known as forward bias The height of the potential

barrier at the junction is lowered by the applied forward voltage In other

words we can say that p-n junction diode is connected to an external

Date____________

Pag

e35

battery in such a way that depletion region is reduced in size or eliminated

altogether Which of these takes place is determined by the size of the

applied voltage The positive terminal of the battery repels the holes on the

p-side and pushes them towards the junction The negative terminal of the

battery repels the electrons and pushes them towards the junction This

collapses the depletion region With the depletion region gone the diode

can conduct

Reverse Bias

An external voltage applied with polarity in Fig 13 is called reverse

bias When reverse bias is applied to a junction diode the depletion region

does not collapse On the contrary it becomes wider The positive side of

battery is applied to the n-type material This attracts the free electrons

away from the junction The negative side of the battery attracts the holes

in p-type material away from the junction This makes the depletion region

wider than it was when no voltage is applied The depletion region is an

insulator and it will block the flow of current Actually a small current will

flow because of minority carriers The p-type material has a few minority

electrons These are pushed to the junction by the repulsion of the negative

side of the battery The n-type material has few minority holes These are

also pushed towards the junction Reverse bias forces the minority carriers

together and a small current - called leakage current - results

Diodes which are designed with adequate power dissipation

capability to operate in the breakdown region are none as Zener diodes

Two mechanisms of diode breakdown for increasing reverse voltage are

recognized In one mechanism the thermally generated electrons and

holes acquire sufficient energy from the applied potential to produce new

carriers by removing valence electrons from their bonds These new

carriers in turn produce additional carriers again through the process of

disrupting bonds This cumulative process is referred to as avalanche

breakdown Even if the initially available carriers do not acquire sufficient

energy to disrupt bonds it is possible to initiate breakdown through a

direct rupture of the bonds because of the existence of strong electric field

Under these conditions the breakdown is referred to as Zener breakdown

Date____________

Pag

e36

Zener breakdown occurs below 6 V Zener diodes are commonly used in

voltage-reference or constant-voltage devices

Characteristic curves of diode

Fig 14 shows V-I Characteristic curves for typical p-n junction diode

It is seen that the curve is not linear With 0 V across the diode the diode

will not conduct the diode will not begin to conduct until a few tenths of a

volt are applied across it This is the voltage needed to overcome the

potential barrier It requires about 02 V to turn on a germanium diode and

about 06 V to turn on a silicon diode Fig 18 also shows what happens

when reverse bias is applied to a diode At increasing levels of reverse

voltage the curve shows some reverse current This leakage current is

caused by minority carries It is usually very small

Graph

Fig-14

Date____________

Pag

e37

Observation Table for Forward bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Date____________

Pag

e38

Observation Table for Reverse bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e39

Calculation for Forward bias 119877 = 119881

119868

Calculation for Reverse bias 119877 = 119881

119868

Date____________

Pag

e40

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e41

Zener Diode Reverse Bias Characteristics Experiment - 10

Aim To study the reverse bias characteristics of a Zener diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components Zener diode Resistors

Circuit Diagram

Procedure

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Theory

A diode which is heavily doped (Si or Ge) and which operates in the

reverse breakdown region with a sharp breakdown voltage is called a zener

diode The schematic symbol of a zener diode is shown in Fig-1 This is

similar to a normal diode except that the line (bar) representing the

cathode is bent at both ends like the letter Z for zener diode

Date____________

Pag

e42

A C Fig-1

In a simple diode the doping is light as a result the breakdown

voltage is high and not sharp But if doping is made heavy the depletion

layer becomes very narrow and even the breakdown voltage gets reduced

to a sharp value The zener diode is designed to operate in the breakdown

region without damage

The reverse breakdown of a zener diode may occur either due to

zener effect or avalanche effect But zener diode primarily depends on

zener effect for its working When the electric field across the junction is

sufficiently high due to the applied voltage the zener breakdown occurs

because of breaking of covalent bonds This produces a large number of

electrons and holes which constitute a steep rise in the reverse saturation

current (also called zener current 119868Z) This effect is called as zener effect

Zener current is independent of the applied voltage and depends only on

the external resistance

The V - 119868 characteristic of a zener diode is shown in Fig-2 The

forward characteristic is simply that of an ordinary forward biased junction

diode

Fig-2

Date____________

Pag

e43

Under reverse bias condition breakdown of junction occurs This

breakdown depends upon the amount of doping It can be seen from Fig-2

that as the reverse voltage is increased the reverse current remains

negligibly small up to the lsquokneersquo of the curve

At this lsquoknee pointrsquo the effect of breakdown process begins The

voltage corresponding to the lsquoknee pointrsquo in the figure is called the zener

breakdown voltage or simply zener voltage (VZ) which is very sharp

compared to a simle p-n junction diode Beyond this voltage the reverse

current (119868Z) increases sharply to a high value

The zener diode is not immediately burnt just because it has entered

the breakdown region As long as the external resistance connected to the

diode in the circuit limits the diode current to less than the burn out value

the diode will not burn out The zener voltage VZ remains constant even

when zener current 119868Z increases greatly This ability of a diode is called

regulating ability and it enables us to use zener diode for voltage

regulation

Date____________

Pag

e44

Observation Table

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e45

Graph 119868 V

Calculations 119877 = 119881

119868

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e46

Dispersive Power of The Prism Experiment - 11

Aim To find the dispersive power (D) of the prism by using spectrometer

Apparatus Mercury vapor lamp Spectrometer Prism

Procedure

Levelling and alignment of collimator and telescope

1 Switch on the mercury lamp Adjust the leveling screws on the chassis

Keep the spirit level on the chassis and do finer adjustments of these

screws to bring the bubble in the sprit level to the centre Repeat this

placing the sprit level along a direction perpendicular to the earlier

direction

2 Repeat this procedure for the prism table

3 Close the slit at the other end of the collimator using the drum screw DS1

Open it to a reasonable width Place the spectrometer in front of the

mercury lamp window and rotate the collimator so that the slit faces of

window View the slit through the telescope If it is not in the centre of the

view level collimator and the telescope so as to bring it to the centre

Setting the prism in the minimum deviation position

1 Rotate the prism table such that lines ruled on the table become

perpendicular to the axis of collimator

2 Place prism over the prism table such that its rough surface BA is

perpendicular to the line on prism table (See Fig-1(a))

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e27

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e28

Meldersquos Experiment - 08

Aim To find the frequency of the wave and the frequency of the tuning fork by

Meldersquos experiment

Apparatus Meldersquos experiment apparatus

Circuit Diagram

Transverse mode

Procedure

Set Meldersquos experiment apparatus as shown in circuit diagram in

longitudinal position and switch ON the power supply put some weight in

scale pan and adjust the length of the string in such a way that you find

some loops on the string (eg 2 loops) Now rotate the apparatus by 90˚ so

that it is set for lsquoBrsquo position for the same values of weight in pan and for

the same length of the string the number of loops created in lsquoBrsquo position

are double (eg 4 loops) than in lsquoArsquo position Note down these readings in

observation table Repeat the experiment for other values of weight in

scale pan

Date____________

Pag

e29

Theory

This is an easy and efficient method by which nodes and antinodes

formed on a string can be demonstrated

A tuning fork is fitted in a wooden block A long string or thread of

cotton is taken One end of this string is tied to one of the prongs of the

tuning fork and the second end of this string passes over a smooth pulley in

such a way that a small pan can be hang on it Small weights are put in the

pan to create tension in the string This arrangement is shown in the circuit

diagram

The fork is set into vibrations by lightly hitting the prong of the tuning

fork on which the string is not tied or by connecting an electric supply as

shown in the circuit diagram Thus the transverse vibrations are produced

in the string and by adjusting the length andor weights in the pan these

vibrations are reflected from the point of contact between the string and

the pulley and a number of loops appear on the string as shown in the

circuit diagram

When the prongs of the tuning fork vibrate in a plane parallel to the

direction of propagation of the waves it is called lsquoArsquo position or

longitudinal position

If the tuning fork along with the wooden block is rotated through

90˚ so that the plane of vibration of the tuning fork is normal (ie at right

angles) to the direction of propagation it is called lsquoBrsquo position or transverse

position

For the same length and same weight in the pan (ie for the same

tension) the number of loops in lsquoBrsquo position is double than in lsquoArsquo position

Thus either in lsquoArsquo position or in lsquoBrsquo position standing transverse

waves are generated in the string with a series of nodes and antinodes at

equal distances

The equation connecting number of loops (n or nrsquo) length of the

string (l) tension in the string (T) mass per unit length of the string (m) and

frequency of the string (f) is as follows

Date____________

Pag

e30

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position)

119943prime =119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

If the frequency of tuning fork is F then for lsquoArsquo position 119839 =119813

120784 and for lsquoBrsquo

position 119839prime = 119813

In the above equations if all the quantities on the RHS are known the

frequency of the tuning fork 119813 can be calculated

Observations

(1) Gravitational accelerationhellip g = 98 ms2

(2) Mass per unit length of the stringhellip m = _______ kgm

(3) Mass of the scale panhellip M1 = _______ kg

Observation Table

Sr

No

Total mass

suspended at

the end of the

stringhellip

M=M1+M2

(kg)

Tension

created

in the

stringhellip

T=Mg (N)

Length of the

vibrating string

Average

lengthhellip

119949 (m)

No of loops created on

the stringhellip

Frequency of the

vibrating stringhellip

Relation

between

f and frsquo 1199491 (m) 1199492 (m)

In

Longitudinal

Modehellip

n

In

Transverse

Modehellip

nrsquo

In

Longitudinal

Modehellip

119943 =119951

120784119949

119931

119950

In

Transverse

Modehellip

119943prime =119951prime

120784119949

119931

119950

1

2

3

4

Here M2 = the weight put in the scale pan

Page31

Date____________

Pag

e32

Calculations

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position) 119943prime =

119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e33

P-N Junction Diode Characteristics Experiment - 09

Aim To study the Forward and Reverse bias characteristics of a P-N junction

diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components P-N junction diode Resistors

Circuit Diagram

(Forward biased PN diode) (Reverse biased PN diode)

Procedure

For Forward Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 01 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 02 03 04hellip

volts and repeat the procedure Note down the knee voltage and

corresponding current in your observation table

For Reverse Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Date____________

Pag

e34

Theory

If donor (pentavalent) impurities are introduced on one side and

acceptors (trivalent) on the opposite side of a single crystal of an intrinsic

semiconductor like germanium or silicon a p-n junction is formed as shown

in Fig 11 In the figure a donor ion is indicated schematically by a plus sign

because after this impurity atom donates an electron it becomes a positive

ion

The acceptor ion is indicated by a minus sign because after this atom

accepts an electron it becomes a negative ion Initially there are only n-

type carriers to the right of the junction and only p-type carriers to the left

Because there is a density gradient across the junction holes will diffuse to

the right across the junction and electrons to the left As a result of the

displacement of these charges an electric field appears across the junction

Equilibrium is established when the field becomes large enough to restrain

the process of diffusion The positive holes which neutralize the acceptor

ions near the junction in p-type germanium disappear as a result of

combination with electrons which diffuse across the junction Similarly the

neutralizing electrons on the n side of the junction combine with holes

which cross the junction from the p side Since the region of the junction is

depleted of mobile charges it is called the depletion region or a potential

barrier

Forward Bias

An external voltage applied to the p-n junction with the polarity

shown in Fig 12 is known as forward bias The height of the potential

barrier at the junction is lowered by the applied forward voltage In other

words we can say that p-n junction diode is connected to an external

Date____________

Pag

e35

battery in such a way that depletion region is reduced in size or eliminated

altogether Which of these takes place is determined by the size of the

applied voltage The positive terminal of the battery repels the holes on the

p-side and pushes them towards the junction The negative terminal of the

battery repels the electrons and pushes them towards the junction This

collapses the depletion region With the depletion region gone the diode

can conduct

Reverse Bias

An external voltage applied with polarity in Fig 13 is called reverse

bias When reverse bias is applied to a junction diode the depletion region

does not collapse On the contrary it becomes wider The positive side of

battery is applied to the n-type material This attracts the free electrons

away from the junction The negative side of the battery attracts the holes

in p-type material away from the junction This makes the depletion region

wider than it was when no voltage is applied The depletion region is an

insulator and it will block the flow of current Actually a small current will

flow because of minority carriers The p-type material has a few minority

electrons These are pushed to the junction by the repulsion of the negative

side of the battery The n-type material has few minority holes These are

also pushed towards the junction Reverse bias forces the minority carriers

together and a small current - called leakage current - results

Diodes which are designed with adequate power dissipation

capability to operate in the breakdown region are none as Zener diodes

Two mechanisms of diode breakdown for increasing reverse voltage are

recognized In one mechanism the thermally generated electrons and

holes acquire sufficient energy from the applied potential to produce new

carriers by removing valence electrons from their bonds These new

carriers in turn produce additional carriers again through the process of

disrupting bonds This cumulative process is referred to as avalanche

breakdown Even if the initially available carriers do not acquire sufficient

energy to disrupt bonds it is possible to initiate breakdown through a

direct rupture of the bonds because of the existence of strong electric field

Under these conditions the breakdown is referred to as Zener breakdown

Date____________

Pag

e36

Zener breakdown occurs below 6 V Zener diodes are commonly used in

voltage-reference or constant-voltage devices

Characteristic curves of diode

Fig 14 shows V-I Characteristic curves for typical p-n junction diode

It is seen that the curve is not linear With 0 V across the diode the diode

will not conduct the diode will not begin to conduct until a few tenths of a

volt are applied across it This is the voltage needed to overcome the

potential barrier It requires about 02 V to turn on a germanium diode and

about 06 V to turn on a silicon diode Fig 18 also shows what happens

when reverse bias is applied to a diode At increasing levels of reverse

voltage the curve shows some reverse current This leakage current is

caused by minority carries It is usually very small

Graph

Fig-14

Date____________

Pag

e37

Observation Table for Forward bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Date____________

Pag

e38

Observation Table for Reverse bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e39

Calculation for Forward bias 119877 = 119881

119868

Calculation for Reverse bias 119877 = 119881

119868

Date____________

Pag

e40

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e41

Zener Diode Reverse Bias Characteristics Experiment - 10

Aim To study the reverse bias characteristics of a Zener diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components Zener diode Resistors

Circuit Diagram

Procedure

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Theory

A diode which is heavily doped (Si or Ge) and which operates in the

reverse breakdown region with a sharp breakdown voltage is called a zener

diode The schematic symbol of a zener diode is shown in Fig-1 This is

similar to a normal diode except that the line (bar) representing the

cathode is bent at both ends like the letter Z for zener diode

Date____________

Pag

e42

A C Fig-1

In a simple diode the doping is light as a result the breakdown

voltage is high and not sharp But if doping is made heavy the depletion

layer becomes very narrow and even the breakdown voltage gets reduced

to a sharp value The zener diode is designed to operate in the breakdown

region without damage

The reverse breakdown of a zener diode may occur either due to

zener effect or avalanche effect But zener diode primarily depends on

zener effect for its working When the electric field across the junction is

sufficiently high due to the applied voltage the zener breakdown occurs

because of breaking of covalent bonds This produces a large number of

electrons and holes which constitute a steep rise in the reverse saturation

current (also called zener current 119868Z) This effect is called as zener effect

Zener current is independent of the applied voltage and depends only on

the external resistance

The V - 119868 characteristic of a zener diode is shown in Fig-2 The

forward characteristic is simply that of an ordinary forward biased junction

diode

Fig-2

Date____________

Pag

e43

Under reverse bias condition breakdown of junction occurs This

breakdown depends upon the amount of doping It can be seen from Fig-2

that as the reverse voltage is increased the reverse current remains

negligibly small up to the lsquokneersquo of the curve

At this lsquoknee pointrsquo the effect of breakdown process begins The

voltage corresponding to the lsquoknee pointrsquo in the figure is called the zener

breakdown voltage or simply zener voltage (VZ) which is very sharp

compared to a simle p-n junction diode Beyond this voltage the reverse

current (119868Z) increases sharply to a high value

The zener diode is not immediately burnt just because it has entered

the breakdown region As long as the external resistance connected to the

diode in the circuit limits the diode current to less than the burn out value

the diode will not burn out The zener voltage VZ remains constant even

when zener current 119868Z increases greatly This ability of a diode is called

regulating ability and it enables us to use zener diode for voltage

regulation

Date____________

Pag

e44

Observation Table

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e45

Graph 119868 V

Calculations 119877 = 119881

119868

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e46

Dispersive Power of The Prism Experiment - 11

Aim To find the dispersive power (D) of the prism by using spectrometer

Apparatus Mercury vapor lamp Spectrometer Prism

Procedure

Levelling and alignment of collimator and telescope

1 Switch on the mercury lamp Adjust the leveling screws on the chassis

Keep the spirit level on the chassis and do finer adjustments of these

screws to bring the bubble in the sprit level to the centre Repeat this

placing the sprit level along a direction perpendicular to the earlier

direction

2 Repeat this procedure for the prism table

3 Close the slit at the other end of the collimator using the drum screw DS1

Open it to a reasonable width Place the spectrometer in front of the

mercury lamp window and rotate the collimator so that the slit faces of

window View the slit through the telescope If it is not in the centre of the

view level collimator and the telescope so as to bring it to the centre

Setting the prism in the minimum deviation position

1 Rotate the prism table such that lines ruled on the table become

perpendicular to the axis of collimator

2 Place prism over the prism table such that its rough surface BA is

perpendicular to the line on prism table (See Fig-1(a))

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e28

Meldersquos Experiment - 08

Aim To find the frequency of the wave and the frequency of the tuning fork by

Meldersquos experiment

Apparatus Meldersquos experiment apparatus

Circuit Diagram

Transverse mode

Procedure

Set Meldersquos experiment apparatus as shown in circuit diagram in

longitudinal position and switch ON the power supply put some weight in

scale pan and adjust the length of the string in such a way that you find

some loops on the string (eg 2 loops) Now rotate the apparatus by 90˚ so

that it is set for lsquoBrsquo position for the same values of weight in pan and for

the same length of the string the number of loops created in lsquoBrsquo position

are double (eg 4 loops) than in lsquoArsquo position Note down these readings in

observation table Repeat the experiment for other values of weight in

scale pan

Date____________

Pag

e29

Theory

This is an easy and efficient method by which nodes and antinodes

formed on a string can be demonstrated

A tuning fork is fitted in a wooden block A long string or thread of

cotton is taken One end of this string is tied to one of the prongs of the

tuning fork and the second end of this string passes over a smooth pulley in

such a way that a small pan can be hang on it Small weights are put in the

pan to create tension in the string This arrangement is shown in the circuit

diagram

The fork is set into vibrations by lightly hitting the prong of the tuning

fork on which the string is not tied or by connecting an electric supply as

shown in the circuit diagram Thus the transverse vibrations are produced

in the string and by adjusting the length andor weights in the pan these

vibrations are reflected from the point of contact between the string and

the pulley and a number of loops appear on the string as shown in the

circuit diagram

When the prongs of the tuning fork vibrate in a plane parallel to the

direction of propagation of the waves it is called lsquoArsquo position or

longitudinal position

If the tuning fork along with the wooden block is rotated through

90˚ so that the plane of vibration of the tuning fork is normal (ie at right

angles) to the direction of propagation it is called lsquoBrsquo position or transverse

position

For the same length and same weight in the pan (ie for the same

tension) the number of loops in lsquoBrsquo position is double than in lsquoArsquo position

Thus either in lsquoArsquo position or in lsquoBrsquo position standing transverse

waves are generated in the string with a series of nodes and antinodes at

equal distances

The equation connecting number of loops (n or nrsquo) length of the

string (l) tension in the string (T) mass per unit length of the string (m) and

frequency of the string (f) is as follows

Date____________

Pag

e30

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position)

119943prime =119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

If the frequency of tuning fork is F then for lsquoArsquo position 119839 =119813

120784 and for lsquoBrsquo

position 119839prime = 119813

In the above equations if all the quantities on the RHS are known the

frequency of the tuning fork 119813 can be calculated

Observations

(1) Gravitational accelerationhellip g = 98 ms2

(2) Mass per unit length of the stringhellip m = _______ kgm

(3) Mass of the scale panhellip M1 = _______ kg

Observation Table

Sr

No

Total mass

suspended at

the end of the

stringhellip

M=M1+M2

(kg)

Tension

created

in the

stringhellip

T=Mg (N)

Length of the

vibrating string

Average

lengthhellip

119949 (m)

No of loops created on

the stringhellip

Frequency of the

vibrating stringhellip

Relation

between

f and frsquo 1199491 (m) 1199492 (m)

In

Longitudinal

Modehellip

n

In

Transverse

Modehellip

nrsquo

In

Longitudinal

Modehellip

119943 =119951

120784119949

119931

119950

In

Transverse

Modehellip

119943prime =119951prime

120784119949

119931

119950

1

2

3

4

Here M2 = the weight put in the scale pan

Page31

Date____________

Pag

e32

Calculations

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position) 119943prime =

119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e33

P-N Junction Diode Characteristics Experiment - 09

Aim To study the Forward and Reverse bias characteristics of a P-N junction

diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components P-N junction diode Resistors

Circuit Diagram

(Forward biased PN diode) (Reverse biased PN diode)

Procedure

For Forward Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 01 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 02 03 04hellip

volts and repeat the procedure Note down the knee voltage and

corresponding current in your observation table

For Reverse Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Date____________

Pag

e34

Theory

If donor (pentavalent) impurities are introduced on one side and

acceptors (trivalent) on the opposite side of a single crystal of an intrinsic

semiconductor like germanium or silicon a p-n junction is formed as shown

in Fig 11 In the figure a donor ion is indicated schematically by a plus sign

because after this impurity atom donates an electron it becomes a positive

ion

The acceptor ion is indicated by a minus sign because after this atom

accepts an electron it becomes a negative ion Initially there are only n-

type carriers to the right of the junction and only p-type carriers to the left

Because there is a density gradient across the junction holes will diffuse to

the right across the junction and electrons to the left As a result of the

displacement of these charges an electric field appears across the junction

Equilibrium is established when the field becomes large enough to restrain

the process of diffusion The positive holes which neutralize the acceptor

ions near the junction in p-type germanium disappear as a result of

combination with electrons which diffuse across the junction Similarly the

neutralizing electrons on the n side of the junction combine with holes

which cross the junction from the p side Since the region of the junction is

depleted of mobile charges it is called the depletion region or a potential

barrier

Forward Bias

An external voltage applied to the p-n junction with the polarity

shown in Fig 12 is known as forward bias The height of the potential

barrier at the junction is lowered by the applied forward voltage In other

words we can say that p-n junction diode is connected to an external

Date____________

Pag

e35

battery in such a way that depletion region is reduced in size or eliminated

altogether Which of these takes place is determined by the size of the

applied voltage The positive terminal of the battery repels the holes on the

p-side and pushes them towards the junction The negative terminal of the

battery repels the electrons and pushes them towards the junction This

collapses the depletion region With the depletion region gone the diode

can conduct

Reverse Bias

An external voltage applied with polarity in Fig 13 is called reverse

bias When reverse bias is applied to a junction diode the depletion region

does not collapse On the contrary it becomes wider The positive side of

battery is applied to the n-type material This attracts the free electrons

away from the junction The negative side of the battery attracts the holes

in p-type material away from the junction This makes the depletion region

wider than it was when no voltage is applied The depletion region is an

insulator and it will block the flow of current Actually a small current will

flow because of minority carriers The p-type material has a few minority

electrons These are pushed to the junction by the repulsion of the negative

side of the battery The n-type material has few minority holes These are

also pushed towards the junction Reverse bias forces the minority carriers

together and a small current - called leakage current - results

Diodes which are designed with adequate power dissipation

capability to operate in the breakdown region are none as Zener diodes

Two mechanisms of diode breakdown for increasing reverse voltage are

recognized In one mechanism the thermally generated electrons and

holes acquire sufficient energy from the applied potential to produce new

carriers by removing valence electrons from their bonds These new

carriers in turn produce additional carriers again through the process of

disrupting bonds This cumulative process is referred to as avalanche

breakdown Even if the initially available carriers do not acquire sufficient

energy to disrupt bonds it is possible to initiate breakdown through a

direct rupture of the bonds because of the existence of strong electric field

Under these conditions the breakdown is referred to as Zener breakdown

Date____________

Pag

e36

Zener breakdown occurs below 6 V Zener diodes are commonly used in

voltage-reference or constant-voltage devices

Characteristic curves of diode

Fig 14 shows V-I Characteristic curves for typical p-n junction diode

It is seen that the curve is not linear With 0 V across the diode the diode

will not conduct the diode will not begin to conduct until a few tenths of a

volt are applied across it This is the voltage needed to overcome the

potential barrier It requires about 02 V to turn on a germanium diode and

about 06 V to turn on a silicon diode Fig 18 also shows what happens

when reverse bias is applied to a diode At increasing levels of reverse

voltage the curve shows some reverse current This leakage current is

caused by minority carries It is usually very small

Graph

Fig-14

Date____________

Pag

e37

Observation Table for Forward bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Date____________

Pag

e38

Observation Table for Reverse bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e39

Calculation for Forward bias 119877 = 119881

119868

Calculation for Reverse bias 119877 = 119881

119868

Date____________

Pag

e40

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e41

Zener Diode Reverse Bias Characteristics Experiment - 10

Aim To study the reverse bias characteristics of a Zener diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components Zener diode Resistors

Circuit Diagram

Procedure

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Theory

A diode which is heavily doped (Si or Ge) and which operates in the

reverse breakdown region with a sharp breakdown voltage is called a zener

diode The schematic symbol of a zener diode is shown in Fig-1 This is

similar to a normal diode except that the line (bar) representing the

cathode is bent at both ends like the letter Z for zener diode

Date____________

Pag

e42

A C Fig-1

In a simple diode the doping is light as a result the breakdown

voltage is high and not sharp But if doping is made heavy the depletion

layer becomes very narrow and even the breakdown voltage gets reduced

to a sharp value The zener diode is designed to operate in the breakdown

region without damage

The reverse breakdown of a zener diode may occur either due to

zener effect or avalanche effect But zener diode primarily depends on

zener effect for its working When the electric field across the junction is

sufficiently high due to the applied voltage the zener breakdown occurs

because of breaking of covalent bonds This produces a large number of

electrons and holes which constitute a steep rise in the reverse saturation

current (also called zener current 119868Z) This effect is called as zener effect

Zener current is independent of the applied voltage and depends only on

the external resistance

The V - 119868 characteristic of a zener diode is shown in Fig-2 The

forward characteristic is simply that of an ordinary forward biased junction

diode

Fig-2

Date____________

Pag

e43

Under reverse bias condition breakdown of junction occurs This

breakdown depends upon the amount of doping It can be seen from Fig-2

that as the reverse voltage is increased the reverse current remains

negligibly small up to the lsquokneersquo of the curve

At this lsquoknee pointrsquo the effect of breakdown process begins The

voltage corresponding to the lsquoknee pointrsquo in the figure is called the zener

breakdown voltage or simply zener voltage (VZ) which is very sharp

compared to a simle p-n junction diode Beyond this voltage the reverse

current (119868Z) increases sharply to a high value

The zener diode is not immediately burnt just because it has entered

the breakdown region As long as the external resistance connected to the

diode in the circuit limits the diode current to less than the burn out value

the diode will not burn out The zener voltage VZ remains constant even

when zener current 119868Z increases greatly This ability of a diode is called

regulating ability and it enables us to use zener diode for voltage

regulation

Date____________

Pag

e44

Observation Table

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e45

Graph 119868 V

Calculations 119877 = 119881

119868

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e46

Dispersive Power of The Prism Experiment - 11

Aim To find the dispersive power (D) of the prism by using spectrometer

Apparatus Mercury vapor lamp Spectrometer Prism

Procedure

Levelling and alignment of collimator and telescope

1 Switch on the mercury lamp Adjust the leveling screws on the chassis

Keep the spirit level on the chassis and do finer adjustments of these

screws to bring the bubble in the sprit level to the centre Repeat this

placing the sprit level along a direction perpendicular to the earlier

direction

2 Repeat this procedure for the prism table

3 Close the slit at the other end of the collimator using the drum screw DS1

Open it to a reasonable width Place the spectrometer in front of the

mercury lamp window and rotate the collimator so that the slit faces of

window View the slit through the telescope If it is not in the centre of the

view level collimator and the telescope so as to bring it to the centre

Setting the prism in the minimum deviation position

1 Rotate the prism table such that lines ruled on the table become

perpendicular to the axis of collimator

2 Place prism over the prism table such that its rough surface BA is

perpendicular to the line on prism table (See Fig-1(a))

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e29

Theory

This is an easy and efficient method by which nodes and antinodes

formed on a string can be demonstrated

A tuning fork is fitted in a wooden block A long string or thread of

cotton is taken One end of this string is tied to one of the prongs of the

tuning fork and the second end of this string passes over a smooth pulley in

such a way that a small pan can be hang on it Small weights are put in the

pan to create tension in the string This arrangement is shown in the circuit

diagram

The fork is set into vibrations by lightly hitting the prong of the tuning

fork on which the string is not tied or by connecting an electric supply as

shown in the circuit diagram Thus the transverse vibrations are produced

in the string and by adjusting the length andor weights in the pan these

vibrations are reflected from the point of contact between the string and

the pulley and a number of loops appear on the string as shown in the

circuit diagram

When the prongs of the tuning fork vibrate in a plane parallel to the

direction of propagation of the waves it is called lsquoArsquo position or

longitudinal position

If the tuning fork along with the wooden block is rotated through

90˚ so that the plane of vibration of the tuning fork is normal (ie at right

angles) to the direction of propagation it is called lsquoBrsquo position or transverse

position

For the same length and same weight in the pan (ie for the same

tension) the number of loops in lsquoBrsquo position is double than in lsquoArsquo position

Thus either in lsquoArsquo position or in lsquoBrsquo position standing transverse

waves are generated in the string with a series of nodes and antinodes at

equal distances

The equation connecting number of loops (n or nrsquo) length of the

string (l) tension in the string (T) mass per unit length of the string (m) and

frequency of the string (f) is as follows

Date____________

Pag

e30

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position)

119943prime =119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

If the frequency of tuning fork is F then for lsquoArsquo position 119839 =119813

120784 and for lsquoBrsquo

position 119839prime = 119813

In the above equations if all the quantities on the RHS are known the

frequency of the tuning fork 119813 can be calculated

Observations

(1) Gravitational accelerationhellip g = 98 ms2

(2) Mass per unit length of the stringhellip m = _______ kgm

(3) Mass of the scale panhellip M1 = _______ kg

Observation Table

Sr

No

Total mass

suspended at

the end of the

stringhellip

M=M1+M2

(kg)

Tension

created

in the

stringhellip

T=Mg (N)

Length of the

vibrating string

Average

lengthhellip

119949 (m)

No of loops created on

the stringhellip

Frequency of the

vibrating stringhellip

Relation

between

f and frsquo 1199491 (m) 1199492 (m)

In

Longitudinal

Modehellip

n

In

Transverse

Modehellip

nrsquo

In

Longitudinal

Modehellip

119943 =119951

120784119949

119931

119950

In

Transverse

Modehellip

119943prime =119951prime

120784119949

119931

119950

1

2

3

4

Here M2 = the weight put in the scale pan

Page31

Date____________

Pag

e32

Calculations

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position) 119943prime =

119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e33

P-N Junction Diode Characteristics Experiment - 09

Aim To study the Forward and Reverse bias characteristics of a P-N junction

diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components P-N junction diode Resistors

Circuit Diagram

(Forward biased PN diode) (Reverse biased PN diode)

Procedure

For Forward Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 01 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 02 03 04hellip

volts and repeat the procedure Note down the knee voltage and

corresponding current in your observation table

For Reverse Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Date____________

Pag

e34

Theory

If donor (pentavalent) impurities are introduced on one side and

acceptors (trivalent) on the opposite side of a single crystal of an intrinsic

semiconductor like germanium or silicon a p-n junction is formed as shown

in Fig 11 In the figure a donor ion is indicated schematically by a plus sign

because after this impurity atom donates an electron it becomes a positive

ion

The acceptor ion is indicated by a minus sign because after this atom

accepts an electron it becomes a negative ion Initially there are only n-

type carriers to the right of the junction and only p-type carriers to the left

Because there is a density gradient across the junction holes will diffuse to

the right across the junction and electrons to the left As a result of the

displacement of these charges an electric field appears across the junction

Equilibrium is established when the field becomes large enough to restrain

the process of diffusion The positive holes which neutralize the acceptor

ions near the junction in p-type germanium disappear as a result of

combination with electrons which diffuse across the junction Similarly the

neutralizing electrons on the n side of the junction combine with holes

which cross the junction from the p side Since the region of the junction is

depleted of mobile charges it is called the depletion region or a potential

barrier

Forward Bias

An external voltage applied to the p-n junction with the polarity

shown in Fig 12 is known as forward bias The height of the potential

barrier at the junction is lowered by the applied forward voltage In other

words we can say that p-n junction diode is connected to an external

Date____________

Pag

e35

battery in such a way that depletion region is reduced in size or eliminated

altogether Which of these takes place is determined by the size of the

applied voltage The positive terminal of the battery repels the holes on the

p-side and pushes them towards the junction The negative terminal of the

battery repels the electrons and pushes them towards the junction This

collapses the depletion region With the depletion region gone the diode

can conduct

Reverse Bias

An external voltage applied with polarity in Fig 13 is called reverse

bias When reverse bias is applied to a junction diode the depletion region

does not collapse On the contrary it becomes wider The positive side of

battery is applied to the n-type material This attracts the free electrons

away from the junction The negative side of the battery attracts the holes

in p-type material away from the junction This makes the depletion region

wider than it was when no voltage is applied The depletion region is an

insulator and it will block the flow of current Actually a small current will

flow because of minority carriers The p-type material has a few minority

electrons These are pushed to the junction by the repulsion of the negative

side of the battery The n-type material has few minority holes These are

also pushed towards the junction Reverse bias forces the minority carriers

together and a small current - called leakage current - results

Diodes which are designed with adequate power dissipation

capability to operate in the breakdown region are none as Zener diodes

Two mechanisms of diode breakdown for increasing reverse voltage are

recognized In one mechanism the thermally generated electrons and

holes acquire sufficient energy from the applied potential to produce new

carriers by removing valence electrons from their bonds These new

carriers in turn produce additional carriers again through the process of

disrupting bonds This cumulative process is referred to as avalanche

breakdown Even if the initially available carriers do not acquire sufficient

energy to disrupt bonds it is possible to initiate breakdown through a

direct rupture of the bonds because of the existence of strong electric field

Under these conditions the breakdown is referred to as Zener breakdown

Date____________

Pag

e36

Zener breakdown occurs below 6 V Zener diodes are commonly used in

voltage-reference or constant-voltage devices

Characteristic curves of diode

Fig 14 shows V-I Characteristic curves for typical p-n junction diode

It is seen that the curve is not linear With 0 V across the diode the diode

will not conduct the diode will not begin to conduct until a few tenths of a

volt are applied across it This is the voltage needed to overcome the

potential barrier It requires about 02 V to turn on a germanium diode and

about 06 V to turn on a silicon diode Fig 18 also shows what happens

when reverse bias is applied to a diode At increasing levels of reverse

voltage the curve shows some reverse current This leakage current is

caused by minority carries It is usually very small

Graph

Fig-14

Date____________

Pag

e37

Observation Table for Forward bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Date____________

Pag

e38

Observation Table for Reverse bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e39

Calculation for Forward bias 119877 = 119881

119868

Calculation for Reverse bias 119877 = 119881

119868

Date____________

Pag

e40

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e41

Zener Diode Reverse Bias Characteristics Experiment - 10

Aim To study the reverse bias characteristics of a Zener diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components Zener diode Resistors

Circuit Diagram

Procedure

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Theory

A diode which is heavily doped (Si or Ge) and which operates in the

reverse breakdown region with a sharp breakdown voltage is called a zener

diode The schematic symbol of a zener diode is shown in Fig-1 This is

similar to a normal diode except that the line (bar) representing the

cathode is bent at both ends like the letter Z for zener diode

Date____________

Pag

e42

A C Fig-1

In a simple diode the doping is light as a result the breakdown

voltage is high and not sharp But if doping is made heavy the depletion

layer becomes very narrow and even the breakdown voltage gets reduced

to a sharp value The zener diode is designed to operate in the breakdown

region without damage

The reverse breakdown of a zener diode may occur either due to

zener effect or avalanche effect But zener diode primarily depends on

zener effect for its working When the electric field across the junction is

sufficiently high due to the applied voltage the zener breakdown occurs

because of breaking of covalent bonds This produces a large number of

electrons and holes which constitute a steep rise in the reverse saturation

current (also called zener current 119868Z) This effect is called as zener effect

Zener current is independent of the applied voltage and depends only on

the external resistance

The V - 119868 characteristic of a zener diode is shown in Fig-2 The

forward characteristic is simply that of an ordinary forward biased junction

diode

Fig-2

Date____________

Pag

e43

Under reverse bias condition breakdown of junction occurs This

breakdown depends upon the amount of doping It can be seen from Fig-2

that as the reverse voltage is increased the reverse current remains

negligibly small up to the lsquokneersquo of the curve

At this lsquoknee pointrsquo the effect of breakdown process begins The

voltage corresponding to the lsquoknee pointrsquo in the figure is called the zener

breakdown voltage or simply zener voltage (VZ) which is very sharp

compared to a simle p-n junction diode Beyond this voltage the reverse

current (119868Z) increases sharply to a high value

The zener diode is not immediately burnt just because it has entered

the breakdown region As long as the external resistance connected to the

diode in the circuit limits the diode current to less than the burn out value

the diode will not burn out The zener voltage VZ remains constant even

when zener current 119868Z increases greatly This ability of a diode is called

regulating ability and it enables us to use zener diode for voltage

regulation

Date____________

Pag

e44

Observation Table

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e45

Graph 119868 V

Calculations 119877 = 119881

119868

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e46

Dispersive Power of The Prism Experiment - 11

Aim To find the dispersive power (D) of the prism by using spectrometer

Apparatus Mercury vapor lamp Spectrometer Prism

Procedure

Levelling and alignment of collimator and telescope

1 Switch on the mercury lamp Adjust the leveling screws on the chassis

Keep the spirit level on the chassis and do finer adjustments of these

screws to bring the bubble in the sprit level to the centre Repeat this

placing the sprit level along a direction perpendicular to the earlier

direction

2 Repeat this procedure for the prism table

3 Close the slit at the other end of the collimator using the drum screw DS1

Open it to a reasonable width Place the spectrometer in front of the

mercury lamp window and rotate the collimator so that the slit faces of

window View the slit through the telescope If it is not in the centre of the

view level collimator and the telescope so as to bring it to the centre

Setting the prism in the minimum deviation position

1 Rotate the prism table such that lines ruled on the table become

perpendicular to the axis of collimator

2 Place prism over the prism table such that its rough surface BA is

perpendicular to the line on prism table (See Fig-1(a))

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e30

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position)

119943prime =119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

If the frequency of tuning fork is F then for lsquoArsquo position 119839 =119813

120784 and for lsquoBrsquo

position 119839prime = 119813

In the above equations if all the quantities on the RHS are known the

frequency of the tuning fork 119813 can be calculated

Observations

(1) Gravitational accelerationhellip g = 98 ms2

(2) Mass per unit length of the stringhellip m = _______ kgm

(3) Mass of the scale panhellip M1 = _______ kg

Observation Table

Sr

No

Total mass

suspended at

the end of the

stringhellip

M=M1+M2

(kg)

Tension

created

in the

stringhellip

T=Mg (N)

Length of the

vibrating string

Average

lengthhellip

119949 (m)

No of loops created on

the stringhellip

Frequency of the

vibrating stringhellip

Relation

between

f and frsquo 1199491 (m) 1199492 (m)

In

Longitudinal

Modehellip

n

In

Transverse

Modehellip

nrsquo

In

Longitudinal

Modehellip

119943 =119951

120784119949

119931

119950

In

Transverse

Modehellip

119943prime =119951prime

120784119949

119931

119950

1

2

3

4

Here M2 = the weight put in the scale pan

Page31

Date____________

Pag

e32

Calculations

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position) 119943prime =

119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e33

P-N Junction Diode Characteristics Experiment - 09

Aim To study the Forward and Reverse bias characteristics of a P-N junction

diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components P-N junction diode Resistors

Circuit Diagram

(Forward biased PN diode) (Reverse biased PN diode)

Procedure

For Forward Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 01 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 02 03 04hellip

volts and repeat the procedure Note down the knee voltage and

corresponding current in your observation table

For Reverse Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Date____________

Pag

e34

Theory

If donor (pentavalent) impurities are introduced on one side and

acceptors (trivalent) on the opposite side of a single crystal of an intrinsic

semiconductor like germanium or silicon a p-n junction is formed as shown

in Fig 11 In the figure a donor ion is indicated schematically by a plus sign

because after this impurity atom donates an electron it becomes a positive

ion

The acceptor ion is indicated by a minus sign because after this atom

accepts an electron it becomes a negative ion Initially there are only n-

type carriers to the right of the junction and only p-type carriers to the left

Because there is a density gradient across the junction holes will diffuse to

the right across the junction and electrons to the left As a result of the

displacement of these charges an electric field appears across the junction

Equilibrium is established when the field becomes large enough to restrain

the process of diffusion The positive holes which neutralize the acceptor

ions near the junction in p-type germanium disappear as a result of

combination with electrons which diffuse across the junction Similarly the

neutralizing electrons on the n side of the junction combine with holes

which cross the junction from the p side Since the region of the junction is

depleted of mobile charges it is called the depletion region or a potential

barrier

Forward Bias

An external voltage applied to the p-n junction with the polarity

shown in Fig 12 is known as forward bias The height of the potential

barrier at the junction is lowered by the applied forward voltage In other

words we can say that p-n junction diode is connected to an external

Date____________

Pag

e35

battery in such a way that depletion region is reduced in size or eliminated

altogether Which of these takes place is determined by the size of the

applied voltage The positive terminal of the battery repels the holes on the

p-side and pushes them towards the junction The negative terminal of the

battery repels the electrons and pushes them towards the junction This

collapses the depletion region With the depletion region gone the diode

can conduct

Reverse Bias

An external voltage applied with polarity in Fig 13 is called reverse

bias When reverse bias is applied to a junction diode the depletion region

does not collapse On the contrary it becomes wider The positive side of

battery is applied to the n-type material This attracts the free electrons

away from the junction The negative side of the battery attracts the holes

in p-type material away from the junction This makes the depletion region

wider than it was when no voltage is applied The depletion region is an

insulator and it will block the flow of current Actually a small current will

flow because of minority carriers The p-type material has a few minority

electrons These are pushed to the junction by the repulsion of the negative

side of the battery The n-type material has few minority holes These are

also pushed towards the junction Reverse bias forces the minority carriers

together and a small current - called leakage current - results

Diodes which are designed with adequate power dissipation

capability to operate in the breakdown region are none as Zener diodes

Two mechanisms of diode breakdown for increasing reverse voltage are

recognized In one mechanism the thermally generated electrons and

holes acquire sufficient energy from the applied potential to produce new

carriers by removing valence electrons from their bonds These new

carriers in turn produce additional carriers again through the process of

disrupting bonds This cumulative process is referred to as avalanche

breakdown Even if the initially available carriers do not acquire sufficient

energy to disrupt bonds it is possible to initiate breakdown through a

direct rupture of the bonds because of the existence of strong electric field

Under these conditions the breakdown is referred to as Zener breakdown

Date____________

Pag

e36

Zener breakdown occurs below 6 V Zener diodes are commonly used in

voltage-reference or constant-voltage devices

Characteristic curves of diode

Fig 14 shows V-I Characteristic curves for typical p-n junction diode

It is seen that the curve is not linear With 0 V across the diode the diode

will not conduct the diode will not begin to conduct until a few tenths of a

volt are applied across it This is the voltage needed to overcome the

potential barrier It requires about 02 V to turn on a germanium diode and

about 06 V to turn on a silicon diode Fig 18 also shows what happens

when reverse bias is applied to a diode At increasing levels of reverse

voltage the curve shows some reverse current This leakage current is

caused by minority carries It is usually very small

Graph

Fig-14

Date____________

Pag

e37

Observation Table for Forward bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Date____________

Pag

e38

Observation Table for Reverse bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e39

Calculation for Forward bias 119877 = 119881

119868

Calculation for Reverse bias 119877 = 119881

119868

Date____________

Pag

e40

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e41

Zener Diode Reverse Bias Characteristics Experiment - 10

Aim To study the reverse bias characteristics of a Zener diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components Zener diode Resistors

Circuit Diagram

Procedure

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Theory

A diode which is heavily doped (Si or Ge) and which operates in the

reverse breakdown region with a sharp breakdown voltage is called a zener

diode The schematic symbol of a zener diode is shown in Fig-1 This is

similar to a normal diode except that the line (bar) representing the

cathode is bent at both ends like the letter Z for zener diode

Date____________

Pag

e42

A C Fig-1

In a simple diode the doping is light as a result the breakdown

voltage is high and not sharp But if doping is made heavy the depletion

layer becomes very narrow and even the breakdown voltage gets reduced

to a sharp value The zener diode is designed to operate in the breakdown

region without damage

The reverse breakdown of a zener diode may occur either due to

zener effect or avalanche effect But zener diode primarily depends on

zener effect for its working When the electric field across the junction is

sufficiently high due to the applied voltage the zener breakdown occurs

because of breaking of covalent bonds This produces a large number of

electrons and holes which constitute a steep rise in the reverse saturation

current (also called zener current 119868Z) This effect is called as zener effect

Zener current is independent of the applied voltage and depends only on

the external resistance

The V - 119868 characteristic of a zener diode is shown in Fig-2 The

forward characteristic is simply that of an ordinary forward biased junction

diode

Fig-2

Date____________

Pag

e43

Under reverse bias condition breakdown of junction occurs This

breakdown depends upon the amount of doping It can be seen from Fig-2

that as the reverse voltage is increased the reverse current remains

negligibly small up to the lsquokneersquo of the curve

At this lsquoknee pointrsquo the effect of breakdown process begins The

voltage corresponding to the lsquoknee pointrsquo in the figure is called the zener

breakdown voltage or simply zener voltage (VZ) which is very sharp

compared to a simle p-n junction diode Beyond this voltage the reverse

current (119868Z) increases sharply to a high value

The zener diode is not immediately burnt just because it has entered

the breakdown region As long as the external resistance connected to the

diode in the circuit limits the diode current to less than the burn out value

the diode will not burn out The zener voltage VZ remains constant even

when zener current 119868Z increases greatly This ability of a diode is called

regulating ability and it enables us to use zener diode for voltage

regulation

Date____________

Pag

e44

Observation Table

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e45

Graph 119868 V

Calculations 119877 = 119881

119868

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e46

Dispersive Power of The Prism Experiment - 11

Aim To find the dispersive power (D) of the prism by using spectrometer

Apparatus Mercury vapor lamp Spectrometer Prism

Procedure

Levelling and alignment of collimator and telescope

1 Switch on the mercury lamp Adjust the leveling screws on the chassis

Keep the spirit level on the chassis and do finer adjustments of these

screws to bring the bubble in the sprit level to the centre Repeat this

placing the sprit level along a direction perpendicular to the earlier

direction

2 Repeat this procedure for the prism table

3 Close the slit at the other end of the collimator using the drum screw DS1

Open it to a reasonable width Place the spectrometer in front of the

mercury lamp window and rotate the collimator so that the slit faces of

window View the slit through the telescope If it is not in the centre of the

view level collimator and the telescope so as to bring it to the centre

Setting the prism in the minimum deviation position

1 Rotate the prism table such that lines ruled on the table become

perpendicular to the axis of collimator

2 Place prism over the prism table such that its rough surface BA is

perpendicular to the line on prism table (See Fig-1(a))

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Observation Table

Sr

No

Total mass

suspended at

the end of the

stringhellip

M=M1+M2

(kg)

Tension

created

in the

stringhellip

T=Mg (N)

Length of the

vibrating string

Average

lengthhellip

119949 (m)

No of loops created on

the stringhellip

Frequency of the

vibrating stringhellip

Relation

between

f and frsquo 1199491 (m) 1199492 (m)

In

Longitudinal

Modehellip

n

In

Transverse

Modehellip

nrsquo

In

Longitudinal

Modehellip

119943 =119951

120784119949

119931

119950

In

Transverse

Modehellip

119943prime =119951prime

120784119949

119931

119950

1

2

3

4

Here M2 = the weight put in the scale pan

Page31

Date____________

Pag

e32

Calculations

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position) 119943prime =

119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e33

P-N Junction Diode Characteristics Experiment - 09

Aim To study the Forward and Reverse bias characteristics of a P-N junction

diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components P-N junction diode Resistors

Circuit Diagram

(Forward biased PN diode) (Reverse biased PN diode)

Procedure

For Forward Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 01 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 02 03 04hellip

volts and repeat the procedure Note down the knee voltage and

corresponding current in your observation table

For Reverse Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Date____________

Pag

e34

Theory

If donor (pentavalent) impurities are introduced on one side and

acceptors (trivalent) on the opposite side of a single crystal of an intrinsic

semiconductor like germanium or silicon a p-n junction is formed as shown

in Fig 11 In the figure a donor ion is indicated schematically by a plus sign

because after this impurity atom donates an electron it becomes a positive

ion

The acceptor ion is indicated by a minus sign because after this atom

accepts an electron it becomes a negative ion Initially there are only n-

type carriers to the right of the junction and only p-type carriers to the left

Because there is a density gradient across the junction holes will diffuse to

the right across the junction and electrons to the left As a result of the

displacement of these charges an electric field appears across the junction

Equilibrium is established when the field becomes large enough to restrain

the process of diffusion The positive holes which neutralize the acceptor

ions near the junction in p-type germanium disappear as a result of

combination with electrons which diffuse across the junction Similarly the

neutralizing electrons on the n side of the junction combine with holes

which cross the junction from the p side Since the region of the junction is

depleted of mobile charges it is called the depletion region or a potential

barrier

Forward Bias

An external voltage applied to the p-n junction with the polarity

shown in Fig 12 is known as forward bias The height of the potential

barrier at the junction is lowered by the applied forward voltage In other

words we can say that p-n junction diode is connected to an external

Date____________

Pag

e35

battery in such a way that depletion region is reduced in size or eliminated

altogether Which of these takes place is determined by the size of the

applied voltage The positive terminal of the battery repels the holes on the

p-side and pushes them towards the junction The negative terminal of the

battery repels the electrons and pushes them towards the junction This

collapses the depletion region With the depletion region gone the diode

can conduct

Reverse Bias

An external voltage applied with polarity in Fig 13 is called reverse

bias When reverse bias is applied to a junction diode the depletion region

does not collapse On the contrary it becomes wider The positive side of

battery is applied to the n-type material This attracts the free electrons

away from the junction The negative side of the battery attracts the holes

in p-type material away from the junction This makes the depletion region

wider than it was when no voltage is applied The depletion region is an

insulator and it will block the flow of current Actually a small current will

flow because of minority carriers The p-type material has a few minority

electrons These are pushed to the junction by the repulsion of the negative

side of the battery The n-type material has few minority holes These are

also pushed towards the junction Reverse bias forces the minority carriers

together and a small current - called leakage current - results

Diodes which are designed with adequate power dissipation

capability to operate in the breakdown region are none as Zener diodes

Two mechanisms of diode breakdown for increasing reverse voltage are

recognized In one mechanism the thermally generated electrons and

holes acquire sufficient energy from the applied potential to produce new

carriers by removing valence electrons from their bonds These new

carriers in turn produce additional carriers again through the process of

disrupting bonds This cumulative process is referred to as avalanche

breakdown Even if the initially available carriers do not acquire sufficient

energy to disrupt bonds it is possible to initiate breakdown through a

direct rupture of the bonds because of the existence of strong electric field

Under these conditions the breakdown is referred to as Zener breakdown

Date____________

Pag

e36

Zener breakdown occurs below 6 V Zener diodes are commonly used in

voltage-reference or constant-voltage devices

Characteristic curves of diode

Fig 14 shows V-I Characteristic curves for typical p-n junction diode

It is seen that the curve is not linear With 0 V across the diode the diode

will not conduct the diode will not begin to conduct until a few tenths of a

volt are applied across it This is the voltage needed to overcome the

potential barrier It requires about 02 V to turn on a germanium diode and

about 06 V to turn on a silicon diode Fig 18 also shows what happens

when reverse bias is applied to a diode At increasing levels of reverse

voltage the curve shows some reverse current This leakage current is

caused by minority carries It is usually very small

Graph

Fig-14

Date____________

Pag

e37

Observation Table for Forward bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Date____________

Pag

e38

Observation Table for Reverse bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e39

Calculation for Forward bias 119877 = 119881

119868

Calculation for Reverse bias 119877 = 119881

119868

Date____________

Pag

e40

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e41

Zener Diode Reverse Bias Characteristics Experiment - 10

Aim To study the reverse bias characteristics of a Zener diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components Zener diode Resistors

Circuit Diagram

Procedure

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Theory

A diode which is heavily doped (Si or Ge) and which operates in the

reverse breakdown region with a sharp breakdown voltage is called a zener

diode The schematic symbol of a zener diode is shown in Fig-1 This is

similar to a normal diode except that the line (bar) representing the

cathode is bent at both ends like the letter Z for zener diode

Date____________

Pag

e42

A C Fig-1

In a simple diode the doping is light as a result the breakdown

voltage is high and not sharp But if doping is made heavy the depletion

layer becomes very narrow and even the breakdown voltage gets reduced

to a sharp value The zener diode is designed to operate in the breakdown

region without damage

The reverse breakdown of a zener diode may occur either due to

zener effect or avalanche effect But zener diode primarily depends on

zener effect for its working When the electric field across the junction is

sufficiently high due to the applied voltage the zener breakdown occurs

because of breaking of covalent bonds This produces a large number of

electrons and holes which constitute a steep rise in the reverse saturation

current (also called zener current 119868Z) This effect is called as zener effect

Zener current is independent of the applied voltage and depends only on

the external resistance

The V - 119868 characteristic of a zener diode is shown in Fig-2 The

forward characteristic is simply that of an ordinary forward biased junction

diode

Fig-2

Date____________

Pag

e43

Under reverse bias condition breakdown of junction occurs This

breakdown depends upon the amount of doping It can be seen from Fig-2

that as the reverse voltage is increased the reverse current remains

negligibly small up to the lsquokneersquo of the curve

At this lsquoknee pointrsquo the effect of breakdown process begins The

voltage corresponding to the lsquoknee pointrsquo in the figure is called the zener

breakdown voltage or simply zener voltage (VZ) which is very sharp

compared to a simle p-n junction diode Beyond this voltage the reverse

current (119868Z) increases sharply to a high value

The zener diode is not immediately burnt just because it has entered

the breakdown region As long as the external resistance connected to the

diode in the circuit limits the diode current to less than the burn out value

the diode will not burn out The zener voltage VZ remains constant even

when zener current 119868Z increases greatly This ability of a diode is called

regulating ability and it enables us to use zener diode for voltage

regulation

Date____________

Pag

e44

Observation Table

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e45

Graph 119868 V

Calculations 119877 = 119881

119868

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e46

Dispersive Power of The Prism Experiment - 11

Aim To find the dispersive power (D) of the prism by using spectrometer

Apparatus Mercury vapor lamp Spectrometer Prism

Procedure

Levelling and alignment of collimator and telescope

1 Switch on the mercury lamp Adjust the leveling screws on the chassis

Keep the spirit level on the chassis and do finer adjustments of these

screws to bring the bubble in the sprit level to the centre Repeat this

placing the sprit level along a direction perpendicular to the earlier

direction

2 Repeat this procedure for the prism table

3 Close the slit at the other end of the collimator using the drum screw DS1

Open it to a reasonable width Place the spectrometer in front of the

mercury lamp window and rotate the collimator so that the slit faces of

window View the slit through the telescope If it is not in the centre of the

view level collimator and the telescope so as to bring it to the centre

Setting the prism in the minimum deviation position

1 Rotate the prism table such that lines ruled on the table become

perpendicular to the axis of collimator

2 Place prism over the prism table such that its rough surface BA is

perpendicular to the line on prism table (See Fig-1(a))

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e32

Calculations

119943 =119951

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoArsquo position) 119943prime =

119951prime

120784119949

119931

119950 helliphelliphelliphelliphellip (For lsquoBrsquo position)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e33

P-N Junction Diode Characteristics Experiment - 09

Aim To study the Forward and Reverse bias characteristics of a P-N junction

diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components P-N junction diode Resistors

Circuit Diagram

(Forward biased PN diode) (Reverse biased PN diode)

Procedure

For Forward Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 01 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 02 03 04hellip

volts and repeat the procedure Note down the knee voltage and

corresponding current in your observation table

For Reverse Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Date____________

Pag

e34

Theory

If donor (pentavalent) impurities are introduced on one side and

acceptors (trivalent) on the opposite side of a single crystal of an intrinsic

semiconductor like germanium or silicon a p-n junction is formed as shown

in Fig 11 In the figure a donor ion is indicated schematically by a plus sign

because after this impurity atom donates an electron it becomes a positive

ion

The acceptor ion is indicated by a minus sign because after this atom

accepts an electron it becomes a negative ion Initially there are only n-

type carriers to the right of the junction and only p-type carriers to the left

Because there is a density gradient across the junction holes will diffuse to

the right across the junction and electrons to the left As a result of the

displacement of these charges an electric field appears across the junction

Equilibrium is established when the field becomes large enough to restrain

the process of diffusion The positive holes which neutralize the acceptor

ions near the junction in p-type germanium disappear as a result of

combination with electrons which diffuse across the junction Similarly the

neutralizing electrons on the n side of the junction combine with holes

which cross the junction from the p side Since the region of the junction is

depleted of mobile charges it is called the depletion region or a potential

barrier

Forward Bias

An external voltage applied to the p-n junction with the polarity

shown in Fig 12 is known as forward bias The height of the potential

barrier at the junction is lowered by the applied forward voltage In other

words we can say that p-n junction diode is connected to an external

Date____________

Pag

e35

battery in such a way that depletion region is reduced in size or eliminated

altogether Which of these takes place is determined by the size of the

applied voltage The positive terminal of the battery repels the holes on the

p-side and pushes them towards the junction The negative terminal of the

battery repels the electrons and pushes them towards the junction This

collapses the depletion region With the depletion region gone the diode

can conduct

Reverse Bias

An external voltage applied with polarity in Fig 13 is called reverse

bias When reverse bias is applied to a junction diode the depletion region

does not collapse On the contrary it becomes wider The positive side of

battery is applied to the n-type material This attracts the free electrons

away from the junction The negative side of the battery attracts the holes

in p-type material away from the junction This makes the depletion region

wider than it was when no voltage is applied The depletion region is an

insulator and it will block the flow of current Actually a small current will

flow because of minority carriers The p-type material has a few minority

electrons These are pushed to the junction by the repulsion of the negative

side of the battery The n-type material has few minority holes These are

also pushed towards the junction Reverse bias forces the minority carriers

together and a small current - called leakage current - results

Diodes which are designed with adequate power dissipation

capability to operate in the breakdown region are none as Zener diodes

Two mechanisms of diode breakdown for increasing reverse voltage are

recognized In one mechanism the thermally generated electrons and

holes acquire sufficient energy from the applied potential to produce new

carriers by removing valence electrons from their bonds These new

carriers in turn produce additional carriers again through the process of

disrupting bonds This cumulative process is referred to as avalanche

breakdown Even if the initially available carriers do not acquire sufficient

energy to disrupt bonds it is possible to initiate breakdown through a

direct rupture of the bonds because of the existence of strong electric field

Under these conditions the breakdown is referred to as Zener breakdown

Date____________

Pag

e36

Zener breakdown occurs below 6 V Zener diodes are commonly used in

voltage-reference or constant-voltage devices

Characteristic curves of diode

Fig 14 shows V-I Characteristic curves for typical p-n junction diode

It is seen that the curve is not linear With 0 V across the diode the diode

will not conduct the diode will not begin to conduct until a few tenths of a

volt are applied across it This is the voltage needed to overcome the

potential barrier It requires about 02 V to turn on a germanium diode and

about 06 V to turn on a silicon diode Fig 18 also shows what happens

when reverse bias is applied to a diode At increasing levels of reverse

voltage the curve shows some reverse current This leakage current is

caused by minority carries It is usually very small

Graph

Fig-14

Date____________

Pag

e37

Observation Table for Forward bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Date____________

Pag

e38

Observation Table for Reverse bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e39

Calculation for Forward bias 119877 = 119881

119868

Calculation for Reverse bias 119877 = 119881

119868

Date____________

Pag

e40

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e41

Zener Diode Reverse Bias Characteristics Experiment - 10

Aim To study the reverse bias characteristics of a Zener diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components Zener diode Resistors

Circuit Diagram

Procedure

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Theory

A diode which is heavily doped (Si or Ge) and which operates in the

reverse breakdown region with a sharp breakdown voltage is called a zener

diode The schematic symbol of a zener diode is shown in Fig-1 This is

similar to a normal diode except that the line (bar) representing the

cathode is bent at both ends like the letter Z for zener diode

Date____________

Pag

e42

A C Fig-1

In a simple diode the doping is light as a result the breakdown

voltage is high and not sharp But if doping is made heavy the depletion

layer becomes very narrow and even the breakdown voltage gets reduced

to a sharp value The zener diode is designed to operate in the breakdown

region without damage

The reverse breakdown of a zener diode may occur either due to

zener effect or avalanche effect But zener diode primarily depends on

zener effect for its working When the electric field across the junction is

sufficiently high due to the applied voltage the zener breakdown occurs

because of breaking of covalent bonds This produces a large number of

electrons and holes which constitute a steep rise in the reverse saturation

current (also called zener current 119868Z) This effect is called as zener effect

Zener current is independent of the applied voltage and depends only on

the external resistance

The V - 119868 characteristic of a zener diode is shown in Fig-2 The

forward characteristic is simply that of an ordinary forward biased junction

diode

Fig-2

Date____________

Pag

e43

Under reverse bias condition breakdown of junction occurs This

breakdown depends upon the amount of doping It can be seen from Fig-2

that as the reverse voltage is increased the reverse current remains

negligibly small up to the lsquokneersquo of the curve

At this lsquoknee pointrsquo the effect of breakdown process begins The

voltage corresponding to the lsquoknee pointrsquo in the figure is called the zener

breakdown voltage or simply zener voltage (VZ) which is very sharp

compared to a simle p-n junction diode Beyond this voltage the reverse

current (119868Z) increases sharply to a high value

The zener diode is not immediately burnt just because it has entered

the breakdown region As long as the external resistance connected to the

diode in the circuit limits the diode current to less than the burn out value

the diode will not burn out The zener voltage VZ remains constant even

when zener current 119868Z increases greatly This ability of a diode is called

regulating ability and it enables us to use zener diode for voltage

regulation

Date____________

Pag

e44

Observation Table

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e45

Graph 119868 V

Calculations 119877 = 119881

119868

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e46

Dispersive Power of The Prism Experiment - 11

Aim To find the dispersive power (D) of the prism by using spectrometer

Apparatus Mercury vapor lamp Spectrometer Prism

Procedure

Levelling and alignment of collimator and telescope

1 Switch on the mercury lamp Adjust the leveling screws on the chassis

Keep the spirit level on the chassis and do finer adjustments of these

screws to bring the bubble in the sprit level to the centre Repeat this

placing the sprit level along a direction perpendicular to the earlier

direction

2 Repeat this procedure for the prism table

3 Close the slit at the other end of the collimator using the drum screw DS1

Open it to a reasonable width Place the spectrometer in front of the

mercury lamp window and rotate the collimator so that the slit faces of

window View the slit through the telescope If it is not in the centre of the

view level collimator and the telescope so as to bring it to the centre

Setting the prism in the minimum deviation position

1 Rotate the prism table such that lines ruled on the table become

perpendicular to the axis of collimator

2 Place prism over the prism table such that its rough surface BA is

perpendicular to the line on prism table (See Fig-1(a))

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e33

P-N Junction Diode Characteristics Experiment - 09

Aim To study the Forward and Reverse bias characteristics of a P-N junction

diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components P-N junction diode Resistors

Circuit Diagram

(Forward biased PN diode) (Reverse biased PN diode)

Procedure

For Forward Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 01 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 02 03 04hellip

volts and repeat the procedure Note down the knee voltage and

corresponding current in your observation table

For Reverse Bias

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Date____________

Pag

e34

Theory

If donor (pentavalent) impurities are introduced on one side and

acceptors (trivalent) on the opposite side of a single crystal of an intrinsic

semiconductor like germanium or silicon a p-n junction is formed as shown

in Fig 11 In the figure a donor ion is indicated schematically by a plus sign

because after this impurity atom donates an electron it becomes a positive

ion

The acceptor ion is indicated by a minus sign because after this atom

accepts an electron it becomes a negative ion Initially there are only n-

type carriers to the right of the junction and only p-type carriers to the left

Because there is a density gradient across the junction holes will diffuse to

the right across the junction and electrons to the left As a result of the

displacement of these charges an electric field appears across the junction

Equilibrium is established when the field becomes large enough to restrain

the process of diffusion The positive holes which neutralize the acceptor

ions near the junction in p-type germanium disappear as a result of

combination with electrons which diffuse across the junction Similarly the

neutralizing electrons on the n side of the junction combine with holes

which cross the junction from the p side Since the region of the junction is

depleted of mobile charges it is called the depletion region or a potential

barrier

Forward Bias

An external voltage applied to the p-n junction with the polarity

shown in Fig 12 is known as forward bias The height of the potential

barrier at the junction is lowered by the applied forward voltage In other

words we can say that p-n junction diode is connected to an external

Date____________

Pag

e35

battery in such a way that depletion region is reduced in size or eliminated

altogether Which of these takes place is determined by the size of the

applied voltage The positive terminal of the battery repels the holes on the

p-side and pushes them towards the junction The negative terminal of the

battery repels the electrons and pushes them towards the junction This

collapses the depletion region With the depletion region gone the diode

can conduct

Reverse Bias

An external voltage applied with polarity in Fig 13 is called reverse

bias When reverse bias is applied to a junction diode the depletion region

does not collapse On the contrary it becomes wider The positive side of

battery is applied to the n-type material This attracts the free electrons

away from the junction The negative side of the battery attracts the holes

in p-type material away from the junction This makes the depletion region

wider than it was when no voltage is applied The depletion region is an

insulator and it will block the flow of current Actually a small current will

flow because of minority carriers The p-type material has a few minority

electrons These are pushed to the junction by the repulsion of the negative

side of the battery The n-type material has few minority holes These are

also pushed towards the junction Reverse bias forces the minority carriers

together and a small current - called leakage current - results

Diodes which are designed with adequate power dissipation

capability to operate in the breakdown region are none as Zener diodes

Two mechanisms of diode breakdown for increasing reverse voltage are

recognized In one mechanism the thermally generated electrons and

holes acquire sufficient energy from the applied potential to produce new

carriers by removing valence electrons from their bonds These new

carriers in turn produce additional carriers again through the process of

disrupting bonds This cumulative process is referred to as avalanche

breakdown Even if the initially available carriers do not acquire sufficient

energy to disrupt bonds it is possible to initiate breakdown through a

direct rupture of the bonds because of the existence of strong electric field

Under these conditions the breakdown is referred to as Zener breakdown

Date____________

Pag

e36

Zener breakdown occurs below 6 V Zener diodes are commonly used in

voltage-reference or constant-voltage devices

Characteristic curves of diode

Fig 14 shows V-I Characteristic curves for typical p-n junction diode

It is seen that the curve is not linear With 0 V across the diode the diode

will not conduct the diode will not begin to conduct until a few tenths of a

volt are applied across it This is the voltage needed to overcome the

potential barrier It requires about 02 V to turn on a germanium diode and

about 06 V to turn on a silicon diode Fig 18 also shows what happens

when reverse bias is applied to a diode At increasing levels of reverse

voltage the curve shows some reverse current This leakage current is

caused by minority carries It is usually very small

Graph

Fig-14

Date____________

Pag

e37

Observation Table for Forward bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Date____________

Pag

e38

Observation Table for Reverse bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e39

Calculation for Forward bias 119877 = 119881

119868

Calculation for Reverse bias 119877 = 119881

119868

Date____________

Pag

e40

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e41

Zener Diode Reverse Bias Characteristics Experiment - 10

Aim To study the reverse bias characteristics of a Zener diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components Zener diode Resistors

Circuit Diagram

Procedure

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Theory

A diode which is heavily doped (Si or Ge) and which operates in the

reverse breakdown region with a sharp breakdown voltage is called a zener

diode The schematic symbol of a zener diode is shown in Fig-1 This is

similar to a normal diode except that the line (bar) representing the

cathode is bent at both ends like the letter Z for zener diode

Date____________

Pag

e42

A C Fig-1

In a simple diode the doping is light as a result the breakdown

voltage is high and not sharp But if doping is made heavy the depletion

layer becomes very narrow and even the breakdown voltage gets reduced

to a sharp value The zener diode is designed to operate in the breakdown

region without damage

The reverse breakdown of a zener diode may occur either due to

zener effect or avalanche effect But zener diode primarily depends on

zener effect for its working When the electric field across the junction is

sufficiently high due to the applied voltage the zener breakdown occurs

because of breaking of covalent bonds This produces a large number of

electrons and holes which constitute a steep rise in the reverse saturation

current (also called zener current 119868Z) This effect is called as zener effect

Zener current is independent of the applied voltage and depends only on

the external resistance

The V - 119868 characteristic of a zener diode is shown in Fig-2 The

forward characteristic is simply that of an ordinary forward biased junction

diode

Fig-2

Date____________

Pag

e43

Under reverse bias condition breakdown of junction occurs This

breakdown depends upon the amount of doping It can be seen from Fig-2

that as the reverse voltage is increased the reverse current remains

negligibly small up to the lsquokneersquo of the curve

At this lsquoknee pointrsquo the effect of breakdown process begins The

voltage corresponding to the lsquoknee pointrsquo in the figure is called the zener

breakdown voltage or simply zener voltage (VZ) which is very sharp

compared to a simle p-n junction diode Beyond this voltage the reverse

current (119868Z) increases sharply to a high value

The zener diode is not immediately burnt just because it has entered

the breakdown region As long as the external resistance connected to the

diode in the circuit limits the diode current to less than the burn out value

the diode will not burn out The zener voltage VZ remains constant even

when zener current 119868Z increases greatly This ability of a diode is called

regulating ability and it enables us to use zener diode for voltage

regulation

Date____________

Pag

e44

Observation Table

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e45

Graph 119868 V

Calculations 119877 = 119881

119868

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e46

Dispersive Power of The Prism Experiment - 11

Aim To find the dispersive power (D) of the prism by using spectrometer

Apparatus Mercury vapor lamp Spectrometer Prism

Procedure

Levelling and alignment of collimator and telescope

1 Switch on the mercury lamp Adjust the leveling screws on the chassis

Keep the spirit level on the chassis and do finer adjustments of these

screws to bring the bubble in the sprit level to the centre Repeat this

placing the sprit level along a direction perpendicular to the earlier

direction

2 Repeat this procedure for the prism table

3 Close the slit at the other end of the collimator using the drum screw DS1

Open it to a reasonable width Place the spectrometer in front of the

mercury lamp window and rotate the collimator so that the slit faces of

window View the slit through the telescope If it is not in the centre of the

view level collimator and the telescope so as to bring it to the centre

Setting the prism in the minimum deviation position

1 Rotate the prism table such that lines ruled on the table become

perpendicular to the axis of collimator

2 Place prism over the prism table such that its rough surface BA is

perpendicular to the line on prism table (See Fig-1(a))

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e34

Theory

If donor (pentavalent) impurities are introduced on one side and

acceptors (trivalent) on the opposite side of a single crystal of an intrinsic

semiconductor like germanium or silicon a p-n junction is formed as shown

in Fig 11 In the figure a donor ion is indicated schematically by a plus sign

because after this impurity atom donates an electron it becomes a positive

ion

The acceptor ion is indicated by a minus sign because after this atom

accepts an electron it becomes a negative ion Initially there are only n-

type carriers to the right of the junction and only p-type carriers to the left

Because there is a density gradient across the junction holes will diffuse to

the right across the junction and electrons to the left As a result of the

displacement of these charges an electric field appears across the junction

Equilibrium is established when the field becomes large enough to restrain

the process of diffusion The positive holes which neutralize the acceptor

ions near the junction in p-type germanium disappear as a result of

combination with electrons which diffuse across the junction Similarly the

neutralizing electrons on the n side of the junction combine with holes

which cross the junction from the p side Since the region of the junction is

depleted of mobile charges it is called the depletion region or a potential

barrier

Forward Bias

An external voltage applied to the p-n junction with the polarity

shown in Fig 12 is known as forward bias The height of the potential

barrier at the junction is lowered by the applied forward voltage In other

words we can say that p-n junction diode is connected to an external

Date____________

Pag

e35

battery in such a way that depletion region is reduced in size or eliminated

altogether Which of these takes place is determined by the size of the

applied voltage The positive terminal of the battery repels the holes on the

p-side and pushes them towards the junction The negative terminal of the

battery repels the electrons and pushes them towards the junction This

collapses the depletion region With the depletion region gone the diode

can conduct

Reverse Bias

An external voltage applied with polarity in Fig 13 is called reverse

bias When reverse bias is applied to a junction diode the depletion region

does not collapse On the contrary it becomes wider The positive side of

battery is applied to the n-type material This attracts the free electrons

away from the junction The negative side of the battery attracts the holes

in p-type material away from the junction This makes the depletion region

wider than it was when no voltage is applied The depletion region is an

insulator and it will block the flow of current Actually a small current will

flow because of minority carriers The p-type material has a few minority

electrons These are pushed to the junction by the repulsion of the negative

side of the battery The n-type material has few minority holes These are

also pushed towards the junction Reverse bias forces the minority carriers

together and a small current - called leakage current - results

Diodes which are designed with adequate power dissipation

capability to operate in the breakdown region are none as Zener diodes

Two mechanisms of diode breakdown for increasing reverse voltage are

recognized In one mechanism the thermally generated electrons and

holes acquire sufficient energy from the applied potential to produce new

carriers by removing valence electrons from their bonds These new

carriers in turn produce additional carriers again through the process of

disrupting bonds This cumulative process is referred to as avalanche

breakdown Even if the initially available carriers do not acquire sufficient

energy to disrupt bonds it is possible to initiate breakdown through a

direct rupture of the bonds because of the existence of strong electric field

Under these conditions the breakdown is referred to as Zener breakdown

Date____________

Pag

e36

Zener breakdown occurs below 6 V Zener diodes are commonly used in

voltage-reference or constant-voltage devices

Characteristic curves of diode

Fig 14 shows V-I Characteristic curves for typical p-n junction diode

It is seen that the curve is not linear With 0 V across the diode the diode

will not conduct the diode will not begin to conduct until a few tenths of a

volt are applied across it This is the voltage needed to overcome the

potential barrier It requires about 02 V to turn on a germanium diode and

about 06 V to turn on a silicon diode Fig 18 also shows what happens

when reverse bias is applied to a diode At increasing levels of reverse

voltage the curve shows some reverse current This leakage current is

caused by minority carries It is usually very small

Graph

Fig-14

Date____________

Pag

e37

Observation Table for Forward bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Date____________

Pag

e38

Observation Table for Reverse bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e39

Calculation for Forward bias 119877 = 119881

119868

Calculation for Reverse bias 119877 = 119881

119868

Date____________

Pag

e40

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e41

Zener Diode Reverse Bias Characteristics Experiment - 10

Aim To study the reverse bias characteristics of a Zener diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components Zener diode Resistors

Circuit Diagram

Procedure

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Theory

A diode which is heavily doped (Si or Ge) and which operates in the

reverse breakdown region with a sharp breakdown voltage is called a zener

diode The schematic symbol of a zener diode is shown in Fig-1 This is

similar to a normal diode except that the line (bar) representing the

cathode is bent at both ends like the letter Z for zener diode

Date____________

Pag

e42

A C Fig-1

In a simple diode the doping is light as a result the breakdown

voltage is high and not sharp But if doping is made heavy the depletion

layer becomes very narrow and even the breakdown voltage gets reduced

to a sharp value The zener diode is designed to operate in the breakdown

region without damage

The reverse breakdown of a zener diode may occur either due to

zener effect or avalanche effect But zener diode primarily depends on

zener effect for its working When the electric field across the junction is

sufficiently high due to the applied voltage the zener breakdown occurs

because of breaking of covalent bonds This produces a large number of

electrons and holes which constitute a steep rise in the reverse saturation

current (also called zener current 119868Z) This effect is called as zener effect

Zener current is independent of the applied voltage and depends only on

the external resistance

The V - 119868 characteristic of a zener diode is shown in Fig-2 The

forward characteristic is simply that of an ordinary forward biased junction

diode

Fig-2

Date____________

Pag

e43

Under reverse bias condition breakdown of junction occurs This

breakdown depends upon the amount of doping It can be seen from Fig-2

that as the reverse voltage is increased the reverse current remains

negligibly small up to the lsquokneersquo of the curve

At this lsquoknee pointrsquo the effect of breakdown process begins The

voltage corresponding to the lsquoknee pointrsquo in the figure is called the zener

breakdown voltage or simply zener voltage (VZ) which is very sharp

compared to a simle p-n junction diode Beyond this voltage the reverse

current (119868Z) increases sharply to a high value

The zener diode is not immediately burnt just because it has entered

the breakdown region As long as the external resistance connected to the

diode in the circuit limits the diode current to less than the burn out value

the diode will not burn out The zener voltage VZ remains constant even

when zener current 119868Z increases greatly This ability of a diode is called

regulating ability and it enables us to use zener diode for voltage

regulation

Date____________

Pag

e44

Observation Table

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e45

Graph 119868 V

Calculations 119877 = 119881

119868

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e46

Dispersive Power of The Prism Experiment - 11

Aim To find the dispersive power (D) of the prism by using spectrometer

Apparatus Mercury vapor lamp Spectrometer Prism

Procedure

Levelling and alignment of collimator and telescope

1 Switch on the mercury lamp Adjust the leveling screws on the chassis

Keep the spirit level on the chassis and do finer adjustments of these

screws to bring the bubble in the sprit level to the centre Repeat this

placing the sprit level along a direction perpendicular to the earlier

direction

2 Repeat this procedure for the prism table

3 Close the slit at the other end of the collimator using the drum screw DS1

Open it to a reasonable width Place the spectrometer in front of the

mercury lamp window and rotate the collimator so that the slit faces of

window View the slit through the telescope If it is not in the centre of the

view level collimator and the telescope so as to bring it to the centre

Setting the prism in the minimum deviation position

1 Rotate the prism table such that lines ruled on the table become

perpendicular to the axis of collimator

2 Place prism over the prism table such that its rough surface BA is

perpendicular to the line on prism table (See Fig-1(a))

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e35

battery in such a way that depletion region is reduced in size or eliminated

altogether Which of these takes place is determined by the size of the

applied voltage The positive terminal of the battery repels the holes on the

p-side and pushes them towards the junction The negative terminal of the

battery repels the electrons and pushes them towards the junction This

collapses the depletion region With the depletion region gone the diode

can conduct

Reverse Bias

An external voltage applied with polarity in Fig 13 is called reverse

bias When reverse bias is applied to a junction diode the depletion region

does not collapse On the contrary it becomes wider The positive side of

battery is applied to the n-type material This attracts the free electrons

away from the junction The negative side of the battery attracts the holes

in p-type material away from the junction This makes the depletion region

wider than it was when no voltage is applied The depletion region is an

insulator and it will block the flow of current Actually a small current will

flow because of minority carriers The p-type material has a few minority

electrons These are pushed to the junction by the repulsion of the negative

side of the battery The n-type material has few minority holes These are

also pushed towards the junction Reverse bias forces the minority carriers

together and a small current - called leakage current - results

Diodes which are designed with adequate power dissipation

capability to operate in the breakdown region are none as Zener diodes

Two mechanisms of diode breakdown for increasing reverse voltage are

recognized In one mechanism the thermally generated electrons and

holes acquire sufficient energy from the applied potential to produce new

carriers by removing valence electrons from their bonds These new

carriers in turn produce additional carriers again through the process of

disrupting bonds This cumulative process is referred to as avalanche

breakdown Even if the initially available carriers do not acquire sufficient

energy to disrupt bonds it is possible to initiate breakdown through a

direct rupture of the bonds because of the existence of strong electric field

Under these conditions the breakdown is referred to as Zener breakdown

Date____________

Pag

e36

Zener breakdown occurs below 6 V Zener diodes are commonly used in

voltage-reference or constant-voltage devices

Characteristic curves of diode

Fig 14 shows V-I Characteristic curves for typical p-n junction diode

It is seen that the curve is not linear With 0 V across the diode the diode

will not conduct the diode will not begin to conduct until a few tenths of a

volt are applied across it This is the voltage needed to overcome the

potential barrier It requires about 02 V to turn on a germanium diode and

about 06 V to turn on a silicon diode Fig 18 also shows what happens

when reverse bias is applied to a diode At increasing levels of reverse

voltage the curve shows some reverse current This leakage current is

caused by minority carries It is usually very small

Graph

Fig-14

Date____________

Pag

e37

Observation Table for Forward bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Date____________

Pag

e38

Observation Table for Reverse bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e39

Calculation for Forward bias 119877 = 119881

119868

Calculation for Reverse bias 119877 = 119881

119868

Date____________

Pag

e40

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e41

Zener Diode Reverse Bias Characteristics Experiment - 10

Aim To study the reverse bias characteristics of a Zener diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components Zener diode Resistors

Circuit Diagram

Procedure

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Theory

A diode which is heavily doped (Si or Ge) and which operates in the

reverse breakdown region with a sharp breakdown voltage is called a zener

diode The schematic symbol of a zener diode is shown in Fig-1 This is

similar to a normal diode except that the line (bar) representing the

cathode is bent at both ends like the letter Z for zener diode

Date____________

Pag

e42

A C Fig-1

In a simple diode the doping is light as a result the breakdown

voltage is high and not sharp But if doping is made heavy the depletion

layer becomes very narrow and even the breakdown voltage gets reduced

to a sharp value The zener diode is designed to operate in the breakdown

region without damage

The reverse breakdown of a zener diode may occur either due to

zener effect or avalanche effect But zener diode primarily depends on

zener effect for its working When the electric field across the junction is

sufficiently high due to the applied voltage the zener breakdown occurs

because of breaking of covalent bonds This produces a large number of

electrons and holes which constitute a steep rise in the reverse saturation

current (also called zener current 119868Z) This effect is called as zener effect

Zener current is independent of the applied voltage and depends only on

the external resistance

The V - 119868 characteristic of a zener diode is shown in Fig-2 The

forward characteristic is simply that of an ordinary forward biased junction

diode

Fig-2

Date____________

Pag

e43

Under reverse bias condition breakdown of junction occurs This

breakdown depends upon the amount of doping It can be seen from Fig-2

that as the reverse voltage is increased the reverse current remains

negligibly small up to the lsquokneersquo of the curve

At this lsquoknee pointrsquo the effect of breakdown process begins The

voltage corresponding to the lsquoknee pointrsquo in the figure is called the zener

breakdown voltage or simply zener voltage (VZ) which is very sharp

compared to a simle p-n junction diode Beyond this voltage the reverse

current (119868Z) increases sharply to a high value

The zener diode is not immediately burnt just because it has entered

the breakdown region As long as the external resistance connected to the

diode in the circuit limits the diode current to less than the burn out value

the diode will not burn out The zener voltage VZ remains constant even

when zener current 119868Z increases greatly This ability of a diode is called

regulating ability and it enables us to use zener diode for voltage

regulation

Date____________

Pag

e44

Observation Table

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e45

Graph 119868 V

Calculations 119877 = 119881

119868

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e46

Dispersive Power of The Prism Experiment - 11

Aim To find the dispersive power (D) of the prism by using spectrometer

Apparatus Mercury vapor lamp Spectrometer Prism

Procedure

Levelling and alignment of collimator and telescope

1 Switch on the mercury lamp Adjust the leveling screws on the chassis

Keep the spirit level on the chassis and do finer adjustments of these

screws to bring the bubble in the sprit level to the centre Repeat this

placing the sprit level along a direction perpendicular to the earlier

direction

2 Repeat this procedure for the prism table

3 Close the slit at the other end of the collimator using the drum screw DS1

Open it to a reasonable width Place the spectrometer in front of the

mercury lamp window and rotate the collimator so that the slit faces of

window View the slit through the telescope If it is not in the centre of the

view level collimator and the telescope so as to bring it to the centre

Setting the prism in the minimum deviation position

1 Rotate the prism table such that lines ruled on the table become

perpendicular to the axis of collimator

2 Place prism over the prism table such that its rough surface BA is

perpendicular to the line on prism table (See Fig-1(a))

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e36

Zener breakdown occurs below 6 V Zener diodes are commonly used in

voltage-reference or constant-voltage devices

Characteristic curves of diode

Fig 14 shows V-I Characteristic curves for typical p-n junction diode

It is seen that the curve is not linear With 0 V across the diode the diode

will not conduct the diode will not begin to conduct until a few tenths of a

volt are applied across it This is the voltage needed to overcome the

potential barrier It requires about 02 V to turn on a germanium diode and

about 06 V to turn on a silicon diode Fig 18 also shows what happens

when reverse bias is applied to a diode At increasing levels of reverse

voltage the curve shows some reverse current This leakage current is

caused by minority carries It is usually very small

Graph

Fig-14

Date____________

Pag

e37

Observation Table for Forward bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Date____________

Pag

e38

Observation Table for Reverse bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e39

Calculation for Forward bias 119877 = 119881

119868

Calculation for Reverse bias 119877 = 119881

119868

Date____________

Pag

e40

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e41

Zener Diode Reverse Bias Characteristics Experiment - 10

Aim To study the reverse bias characteristics of a Zener diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components Zener diode Resistors

Circuit Diagram

Procedure

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Theory

A diode which is heavily doped (Si or Ge) and which operates in the

reverse breakdown region with a sharp breakdown voltage is called a zener

diode The schematic symbol of a zener diode is shown in Fig-1 This is

similar to a normal diode except that the line (bar) representing the

cathode is bent at both ends like the letter Z for zener diode

Date____________

Pag

e42

A C Fig-1

In a simple diode the doping is light as a result the breakdown

voltage is high and not sharp But if doping is made heavy the depletion

layer becomes very narrow and even the breakdown voltage gets reduced

to a sharp value The zener diode is designed to operate in the breakdown

region without damage

The reverse breakdown of a zener diode may occur either due to

zener effect or avalanche effect But zener diode primarily depends on

zener effect for its working When the electric field across the junction is

sufficiently high due to the applied voltage the zener breakdown occurs

because of breaking of covalent bonds This produces a large number of

electrons and holes which constitute a steep rise in the reverse saturation

current (also called zener current 119868Z) This effect is called as zener effect

Zener current is independent of the applied voltage and depends only on

the external resistance

The V - 119868 characteristic of a zener diode is shown in Fig-2 The

forward characteristic is simply that of an ordinary forward biased junction

diode

Fig-2

Date____________

Pag

e43

Under reverse bias condition breakdown of junction occurs This

breakdown depends upon the amount of doping It can be seen from Fig-2

that as the reverse voltage is increased the reverse current remains

negligibly small up to the lsquokneersquo of the curve

At this lsquoknee pointrsquo the effect of breakdown process begins The

voltage corresponding to the lsquoknee pointrsquo in the figure is called the zener

breakdown voltage or simply zener voltage (VZ) which is very sharp

compared to a simle p-n junction diode Beyond this voltage the reverse

current (119868Z) increases sharply to a high value

The zener diode is not immediately burnt just because it has entered

the breakdown region As long as the external resistance connected to the

diode in the circuit limits the diode current to less than the burn out value

the diode will not burn out The zener voltage VZ remains constant even

when zener current 119868Z increases greatly This ability of a diode is called

regulating ability and it enables us to use zener diode for voltage

regulation

Date____________

Pag

e44

Observation Table

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e45

Graph 119868 V

Calculations 119877 = 119881

119868

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e46

Dispersive Power of The Prism Experiment - 11

Aim To find the dispersive power (D) of the prism by using spectrometer

Apparatus Mercury vapor lamp Spectrometer Prism

Procedure

Levelling and alignment of collimator and telescope

1 Switch on the mercury lamp Adjust the leveling screws on the chassis

Keep the spirit level on the chassis and do finer adjustments of these

screws to bring the bubble in the sprit level to the centre Repeat this

placing the sprit level along a direction perpendicular to the earlier

direction

2 Repeat this procedure for the prism table

3 Close the slit at the other end of the collimator using the drum screw DS1

Open it to a reasonable width Place the spectrometer in front of the

mercury lamp window and rotate the collimator so that the slit faces of

window View the slit through the telescope If it is not in the centre of the

view level collimator and the telescope so as to bring it to the centre

Setting the prism in the minimum deviation position

1 Rotate the prism table such that lines ruled on the table become

perpendicular to the axis of collimator

2 Place prism over the prism table such that its rough surface BA is

perpendicular to the line on prism table (See Fig-1(a))

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e37

Observation Table for Forward bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Date____________

Pag

e38

Observation Table for Reverse bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e39

Calculation for Forward bias 119877 = 119881

119868

Calculation for Reverse bias 119877 = 119881

119868

Date____________

Pag

e40

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e41

Zener Diode Reverse Bias Characteristics Experiment - 10

Aim To study the reverse bias characteristics of a Zener diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components Zener diode Resistors

Circuit Diagram

Procedure

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Theory

A diode which is heavily doped (Si or Ge) and which operates in the

reverse breakdown region with a sharp breakdown voltage is called a zener

diode The schematic symbol of a zener diode is shown in Fig-1 This is

similar to a normal diode except that the line (bar) representing the

cathode is bent at both ends like the letter Z for zener diode

Date____________

Pag

e42

A C Fig-1

In a simple diode the doping is light as a result the breakdown

voltage is high and not sharp But if doping is made heavy the depletion

layer becomes very narrow and even the breakdown voltage gets reduced

to a sharp value The zener diode is designed to operate in the breakdown

region without damage

The reverse breakdown of a zener diode may occur either due to

zener effect or avalanche effect But zener diode primarily depends on

zener effect for its working When the electric field across the junction is

sufficiently high due to the applied voltage the zener breakdown occurs

because of breaking of covalent bonds This produces a large number of

electrons and holes which constitute a steep rise in the reverse saturation

current (also called zener current 119868Z) This effect is called as zener effect

Zener current is independent of the applied voltage and depends only on

the external resistance

The V - 119868 characteristic of a zener diode is shown in Fig-2 The

forward characteristic is simply that of an ordinary forward biased junction

diode

Fig-2

Date____________

Pag

e43

Under reverse bias condition breakdown of junction occurs This

breakdown depends upon the amount of doping It can be seen from Fig-2

that as the reverse voltage is increased the reverse current remains

negligibly small up to the lsquokneersquo of the curve

At this lsquoknee pointrsquo the effect of breakdown process begins The

voltage corresponding to the lsquoknee pointrsquo in the figure is called the zener

breakdown voltage or simply zener voltage (VZ) which is very sharp

compared to a simle p-n junction diode Beyond this voltage the reverse

current (119868Z) increases sharply to a high value

The zener diode is not immediately burnt just because it has entered

the breakdown region As long as the external resistance connected to the

diode in the circuit limits the diode current to less than the burn out value

the diode will not burn out The zener voltage VZ remains constant even

when zener current 119868Z increases greatly This ability of a diode is called

regulating ability and it enables us to use zener diode for voltage

regulation

Date____________

Pag

e44

Observation Table

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e45

Graph 119868 V

Calculations 119877 = 119881

119868

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e46

Dispersive Power of The Prism Experiment - 11

Aim To find the dispersive power (D) of the prism by using spectrometer

Apparatus Mercury vapor lamp Spectrometer Prism

Procedure

Levelling and alignment of collimator and telescope

1 Switch on the mercury lamp Adjust the leveling screws on the chassis

Keep the spirit level on the chassis and do finer adjustments of these

screws to bring the bubble in the sprit level to the centre Repeat this

placing the sprit level along a direction perpendicular to the earlier

direction

2 Repeat this procedure for the prism table

3 Close the slit at the other end of the collimator using the drum screw DS1

Open it to a reasonable width Place the spectrometer in front of the

mercury lamp window and rotate the collimator so that the slit faces of

window View the slit through the telescope If it is not in the centre of the

view level collimator and the telescope so as to bring it to the centre

Setting the prism in the minimum deviation position

1 Rotate the prism table such that lines ruled on the table become

perpendicular to the axis of collimator

2 Place prism over the prism table such that its rough surface BA is

perpendicular to the line on prism table (See Fig-1(a))

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e38

Observation Table for Reverse bias

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e39

Calculation for Forward bias 119877 = 119881

119868

Calculation for Reverse bias 119877 = 119881

119868

Date____________

Pag

e40

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e41

Zener Diode Reverse Bias Characteristics Experiment - 10

Aim To study the reverse bias characteristics of a Zener diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components Zener diode Resistors

Circuit Diagram

Procedure

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Theory

A diode which is heavily doped (Si or Ge) and which operates in the

reverse breakdown region with a sharp breakdown voltage is called a zener

diode The schematic symbol of a zener diode is shown in Fig-1 This is

similar to a normal diode except that the line (bar) representing the

cathode is bent at both ends like the letter Z for zener diode

Date____________

Pag

e42

A C Fig-1

In a simple diode the doping is light as a result the breakdown

voltage is high and not sharp But if doping is made heavy the depletion

layer becomes very narrow and even the breakdown voltage gets reduced

to a sharp value The zener diode is designed to operate in the breakdown

region without damage

The reverse breakdown of a zener diode may occur either due to

zener effect or avalanche effect But zener diode primarily depends on

zener effect for its working When the electric field across the junction is

sufficiently high due to the applied voltage the zener breakdown occurs

because of breaking of covalent bonds This produces a large number of

electrons and holes which constitute a steep rise in the reverse saturation

current (also called zener current 119868Z) This effect is called as zener effect

Zener current is independent of the applied voltage and depends only on

the external resistance

The V - 119868 characteristic of a zener diode is shown in Fig-2 The

forward characteristic is simply that of an ordinary forward biased junction

diode

Fig-2

Date____________

Pag

e43

Under reverse bias condition breakdown of junction occurs This

breakdown depends upon the amount of doping It can be seen from Fig-2

that as the reverse voltage is increased the reverse current remains

negligibly small up to the lsquokneersquo of the curve

At this lsquoknee pointrsquo the effect of breakdown process begins The

voltage corresponding to the lsquoknee pointrsquo in the figure is called the zener

breakdown voltage or simply zener voltage (VZ) which is very sharp

compared to a simle p-n junction diode Beyond this voltage the reverse

current (119868Z) increases sharply to a high value

The zener diode is not immediately burnt just because it has entered

the breakdown region As long as the external resistance connected to the

diode in the circuit limits the diode current to less than the burn out value

the diode will not burn out The zener voltage VZ remains constant even

when zener current 119868Z increases greatly This ability of a diode is called

regulating ability and it enables us to use zener diode for voltage

regulation

Date____________

Pag

e44

Observation Table

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e45

Graph 119868 V

Calculations 119877 = 119881

119868

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e46

Dispersive Power of The Prism Experiment - 11

Aim To find the dispersive power (D) of the prism by using spectrometer

Apparatus Mercury vapor lamp Spectrometer Prism

Procedure

Levelling and alignment of collimator and telescope

1 Switch on the mercury lamp Adjust the leveling screws on the chassis

Keep the spirit level on the chassis and do finer adjustments of these

screws to bring the bubble in the sprit level to the centre Repeat this

placing the sprit level along a direction perpendicular to the earlier

direction

2 Repeat this procedure for the prism table

3 Close the slit at the other end of the collimator using the drum screw DS1

Open it to a reasonable width Place the spectrometer in front of the

mercury lamp window and rotate the collimator so that the slit faces of

window View the slit through the telescope If it is not in the centre of the

view level collimator and the telescope so as to bring it to the centre

Setting the prism in the minimum deviation position

1 Rotate the prism table such that lines ruled on the table become

perpendicular to the axis of collimator

2 Place prism over the prism table such that its rough surface BA is

perpendicular to the line on prism table (See Fig-1(a))

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e39

Calculation for Forward bias 119877 = 119881

119868

Calculation for Reverse bias 119877 = 119881

119868

Date____________

Pag

e40

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e41

Zener Diode Reverse Bias Characteristics Experiment - 10

Aim To study the reverse bias characteristics of a Zener diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components Zener diode Resistors

Circuit Diagram

Procedure

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Theory

A diode which is heavily doped (Si or Ge) and which operates in the

reverse breakdown region with a sharp breakdown voltage is called a zener

diode The schematic symbol of a zener diode is shown in Fig-1 This is

similar to a normal diode except that the line (bar) representing the

cathode is bent at both ends like the letter Z for zener diode

Date____________

Pag

e42

A C Fig-1

In a simple diode the doping is light as a result the breakdown

voltage is high and not sharp But if doping is made heavy the depletion

layer becomes very narrow and even the breakdown voltage gets reduced

to a sharp value The zener diode is designed to operate in the breakdown

region without damage

The reverse breakdown of a zener diode may occur either due to

zener effect or avalanche effect But zener diode primarily depends on

zener effect for its working When the electric field across the junction is

sufficiently high due to the applied voltage the zener breakdown occurs

because of breaking of covalent bonds This produces a large number of

electrons and holes which constitute a steep rise in the reverse saturation

current (also called zener current 119868Z) This effect is called as zener effect

Zener current is independent of the applied voltage and depends only on

the external resistance

The V - 119868 characteristic of a zener diode is shown in Fig-2 The

forward characteristic is simply that of an ordinary forward biased junction

diode

Fig-2

Date____________

Pag

e43

Under reverse bias condition breakdown of junction occurs This

breakdown depends upon the amount of doping It can be seen from Fig-2

that as the reverse voltage is increased the reverse current remains

negligibly small up to the lsquokneersquo of the curve

At this lsquoknee pointrsquo the effect of breakdown process begins The

voltage corresponding to the lsquoknee pointrsquo in the figure is called the zener

breakdown voltage or simply zener voltage (VZ) which is very sharp

compared to a simle p-n junction diode Beyond this voltage the reverse

current (119868Z) increases sharply to a high value

The zener diode is not immediately burnt just because it has entered

the breakdown region As long as the external resistance connected to the

diode in the circuit limits the diode current to less than the burn out value

the diode will not burn out The zener voltage VZ remains constant even

when zener current 119868Z increases greatly This ability of a diode is called

regulating ability and it enables us to use zener diode for voltage

regulation

Date____________

Pag

e44

Observation Table

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e45

Graph 119868 V

Calculations 119877 = 119881

119868

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e46

Dispersive Power of The Prism Experiment - 11

Aim To find the dispersive power (D) of the prism by using spectrometer

Apparatus Mercury vapor lamp Spectrometer Prism

Procedure

Levelling and alignment of collimator and telescope

1 Switch on the mercury lamp Adjust the leveling screws on the chassis

Keep the spirit level on the chassis and do finer adjustments of these

screws to bring the bubble in the sprit level to the centre Repeat this

placing the sprit level along a direction perpendicular to the earlier

direction

2 Repeat this procedure for the prism table

3 Close the slit at the other end of the collimator using the drum screw DS1

Open it to a reasonable width Place the spectrometer in front of the

mercury lamp window and rotate the collimator so that the slit faces of

window View the slit through the telescope If it is not in the centre of the

view level collimator and the telescope so as to bring it to the centre

Setting the prism in the minimum deviation position

1 Rotate the prism table such that lines ruled on the table become

perpendicular to the axis of collimator

2 Place prism over the prism table such that its rough surface BA is

perpendicular to the line on prism table (See Fig-1(a))

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e40

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e41

Zener Diode Reverse Bias Characteristics Experiment - 10

Aim To study the reverse bias characteristics of a Zener diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components Zener diode Resistors

Circuit Diagram

Procedure

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Theory

A diode which is heavily doped (Si or Ge) and which operates in the

reverse breakdown region with a sharp breakdown voltage is called a zener

diode The schematic symbol of a zener diode is shown in Fig-1 This is

similar to a normal diode except that the line (bar) representing the

cathode is bent at both ends like the letter Z for zener diode

Date____________

Pag

e42

A C Fig-1

In a simple diode the doping is light as a result the breakdown

voltage is high and not sharp But if doping is made heavy the depletion

layer becomes very narrow and even the breakdown voltage gets reduced

to a sharp value The zener diode is designed to operate in the breakdown

region without damage

The reverse breakdown of a zener diode may occur either due to

zener effect or avalanche effect But zener diode primarily depends on

zener effect for its working When the electric field across the junction is

sufficiently high due to the applied voltage the zener breakdown occurs

because of breaking of covalent bonds This produces a large number of

electrons and holes which constitute a steep rise in the reverse saturation

current (also called zener current 119868Z) This effect is called as zener effect

Zener current is independent of the applied voltage and depends only on

the external resistance

The V - 119868 characteristic of a zener diode is shown in Fig-2 The

forward characteristic is simply that of an ordinary forward biased junction

diode

Fig-2

Date____________

Pag

e43

Under reverse bias condition breakdown of junction occurs This

breakdown depends upon the amount of doping It can be seen from Fig-2

that as the reverse voltage is increased the reverse current remains

negligibly small up to the lsquokneersquo of the curve

At this lsquoknee pointrsquo the effect of breakdown process begins The

voltage corresponding to the lsquoknee pointrsquo in the figure is called the zener

breakdown voltage or simply zener voltage (VZ) which is very sharp

compared to a simle p-n junction diode Beyond this voltage the reverse

current (119868Z) increases sharply to a high value

The zener diode is not immediately burnt just because it has entered

the breakdown region As long as the external resistance connected to the

diode in the circuit limits the diode current to less than the burn out value

the diode will not burn out The zener voltage VZ remains constant even

when zener current 119868Z increases greatly This ability of a diode is called

regulating ability and it enables us to use zener diode for voltage

regulation

Date____________

Pag

e44

Observation Table

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e45

Graph 119868 V

Calculations 119877 = 119881

119868

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e46

Dispersive Power of The Prism Experiment - 11

Aim To find the dispersive power (D) of the prism by using spectrometer

Apparatus Mercury vapor lamp Spectrometer Prism

Procedure

Levelling and alignment of collimator and telescope

1 Switch on the mercury lamp Adjust the leveling screws on the chassis

Keep the spirit level on the chassis and do finer adjustments of these

screws to bring the bubble in the sprit level to the centre Repeat this

placing the sprit level along a direction perpendicular to the earlier

direction

2 Repeat this procedure for the prism table

3 Close the slit at the other end of the collimator using the drum screw DS1

Open it to a reasonable width Place the spectrometer in front of the

mercury lamp window and rotate the collimator so that the slit faces of

window View the slit through the telescope If it is not in the centre of the

view level collimator and the telescope so as to bring it to the centre

Setting the prism in the minimum deviation position

1 Rotate the prism table such that lines ruled on the table become

perpendicular to the axis of collimator

2 Place prism over the prism table such that its rough surface BA is

perpendicular to the line on prism table (See Fig-1(a))

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e41

Zener Diode Reverse Bias Characteristics Experiment - 10

Aim To study the reverse bias characteristics of a Zener diode

Apparatus Regulated dc power supply (0-15 V) Voltmeter Ammeter

Components Zener diode Resistors

Circuit Diagram

Procedure

First connect the circuit as shown in the circuit diagram Now switch

on the regulated power supply and start increasing the voltage Set the

voltage shown by volt meter at 1 volt and note down the value of current

shown by ammeter in observation table Set the voltage at 2 3 4hellip volts

and repeat the procedure Note down the break down voltage and

corresponding current in your observation table

Theory

A diode which is heavily doped (Si or Ge) and which operates in the

reverse breakdown region with a sharp breakdown voltage is called a zener

diode The schematic symbol of a zener diode is shown in Fig-1 This is

similar to a normal diode except that the line (bar) representing the

cathode is bent at both ends like the letter Z for zener diode

Date____________

Pag

e42

A C Fig-1

In a simple diode the doping is light as a result the breakdown

voltage is high and not sharp But if doping is made heavy the depletion

layer becomes very narrow and even the breakdown voltage gets reduced

to a sharp value The zener diode is designed to operate in the breakdown

region without damage

The reverse breakdown of a zener diode may occur either due to

zener effect or avalanche effect But zener diode primarily depends on

zener effect for its working When the electric field across the junction is

sufficiently high due to the applied voltage the zener breakdown occurs

because of breaking of covalent bonds This produces a large number of

electrons and holes which constitute a steep rise in the reverse saturation

current (also called zener current 119868Z) This effect is called as zener effect

Zener current is independent of the applied voltage and depends only on

the external resistance

The V - 119868 characteristic of a zener diode is shown in Fig-2 The

forward characteristic is simply that of an ordinary forward biased junction

diode

Fig-2

Date____________

Pag

e43

Under reverse bias condition breakdown of junction occurs This

breakdown depends upon the amount of doping It can be seen from Fig-2

that as the reverse voltage is increased the reverse current remains

negligibly small up to the lsquokneersquo of the curve

At this lsquoknee pointrsquo the effect of breakdown process begins The

voltage corresponding to the lsquoknee pointrsquo in the figure is called the zener

breakdown voltage or simply zener voltage (VZ) which is very sharp

compared to a simle p-n junction diode Beyond this voltage the reverse

current (119868Z) increases sharply to a high value

The zener diode is not immediately burnt just because it has entered

the breakdown region As long as the external resistance connected to the

diode in the circuit limits the diode current to less than the burn out value

the diode will not burn out The zener voltage VZ remains constant even

when zener current 119868Z increases greatly This ability of a diode is called

regulating ability and it enables us to use zener diode for voltage

regulation

Date____________

Pag

e44

Observation Table

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e45

Graph 119868 V

Calculations 119877 = 119881

119868

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e46

Dispersive Power of The Prism Experiment - 11

Aim To find the dispersive power (D) of the prism by using spectrometer

Apparatus Mercury vapor lamp Spectrometer Prism

Procedure

Levelling and alignment of collimator and telescope

1 Switch on the mercury lamp Adjust the leveling screws on the chassis

Keep the spirit level on the chassis and do finer adjustments of these

screws to bring the bubble in the sprit level to the centre Repeat this

placing the sprit level along a direction perpendicular to the earlier

direction

2 Repeat this procedure for the prism table

3 Close the slit at the other end of the collimator using the drum screw DS1

Open it to a reasonable width Place the spectrometer in front of the

mercury lamp window and rotate the collimator so that the slit faces of

window View the slit through the telescope If it is not in the centre of the

view level collimator and the telescope so as to bring it to the centre

Setting the prism in the minimum deviation position

1 Rotate the prism table such that lines ruled on the table become

perpendicular to the axis of collimator

2 Place prism over the prism table such that its rough surface BA is

perpendicular to the line on prism table (See Fig-1(a))

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e42

A C Fig-1

In a simple diode the doping is light as a result the breakdown

voltage is high and not sharp But if doping is made heavy the depletion

layer becomes very narrow and even the breakdown voltage gets reduced

to a sharp value The zener diode is designed to operate in the breakdown

region without damage

The reverse breakdown of a zener diode may occur either due to

zener effect or avalanche effect But zener diode primarily depends on

zener effect for its working When the electric field across the junction is

sufficiently high due to the applied voltage the zener breakdown occurs

because of breaking of covalent bonds This produces a large number of

electrons and holes which constitute a steep rise in the reverse saturation

current (also called zener current 119868Z) This effect is called as zener effect

Zener current is independent of the applied voltage and depends only on

the external resistance

The V - 119868 characteristic of a zener diode is shown in Fig-2 The

forward characteristic is simply that of an ordinary forward biased junction

diode

Fig-2

Date____________

Pag

e43

Under reverse bias condition breakdown of junction occurs This

breakdown depends upon the amount of doping It can be seen from Fig-2

that as the reverse voltage is increased the reverse current remains

negligibly small up to the lsquokneersquo of the curve

At this lsquoknee pointrsquo the effect of breakdown process begins The

voltage corresponding to the lsquoknee pointrsquo in the figure is called the zener

breakdown voltage or simply zener voltage (VZ) which is very sharp

compared to a simle p-n junction diode Beyond this voltage the reverse

current (119868Z) increases sharply to a high value

The zener diode is not immediately burnt just because it has entered

the breakdown region As long as the external resistance connected to the

diode in the circuit limits the diode current to less than the burn out value

the diode will not burn out The zener voltage VZ remains constant even

when zener current 119868Z increases greatly This ability of a diode is called

regulating ability and it enables us to use zener diode for voltage

regulation

Date____________

Pag

e44

Observation Table

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e45

Graph 119868 V

Calculations 119877 = 119881

119868

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e46

Dispersive Power of The Prism Experiment - 11

Aim To find the dispersive power (D) of the prism by using spectrometer

Apparatus Mercury vapor lamp Spectrometer Prism

Procedure

Levelling and alignment of collimator and telescope

1 Switch on the mercury lamp Adjust the leveling screws on the chassis

Keep the spirit level on the chassis and do finer adjustments of these

screws to bring the bubble in the sprit level to the centre Repeat this

placing the sprit level along a direction perpendicular to the earlier

direction

2 Repeat this procedure for the prism table

3 Close the slit at the other end of the collimator using the drum screw DS1

Open it to a reasonable width Place the spectrometer in front of the

mercury lamp window and rotate the collimator so that the slit faces of

window View the slit through the telescope If it is not in the centre of the

view level collimator and the telescope so as to bring it to the centre

Setting the prism in the minimum deviation position

1 Rotate the prism table such that lines ruled on the table become

perpendicular to the axis of collimator

2 Place prism over the prism table such that its rough surface BA is

perpendicular to the line on prism table (See Fig-1(a))

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e43

Under reverse bias condition breakdown of junction occurs This

breakdown depends upon the amount of doping It can be seen from Fig-2

that as the reverse voltage is increased the reverse current remains

negligibly small up to the lsquokneersquo of the curve

At this lsquoknee pointrsquo the effect of breakdown process begins The

voltage corresponding to the lsquoknee pointrsquo in the figure is called the zener

breakdown voltage or simply zener voltage (VZ) which is very sharp

compared to a simle p-n junction diode Beyond this voltage the reverse

current (119868Z) increases sharply to a high value

The zener diode is not immediately burnt just because it has entered

the breakdown region As long as the external resistance connected to the

diode in the circuit limits the diode current to less than the burn out value

the diode will not burn out The zener voltage VZ remains constant even

when zener current 119868Z increases greatly This ability of a diode is called

regulating ability and it enables us to use zener diode for voltage

regulation

Date____________

Pag

e44

Observation Table

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e45

Graph 119868 V

Calculations 119877 = 119881

119868

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e46

Dispersive Power of The Prism Experiment - 11

Aim To find the dispersive power (D) of the prism by using spectrometer

Apparatus Mercury vapor lamp Spectrometer Prism

Procedure

Levelling and alignment of collimator and telescope

1 Switch on the mercury lamp Adjust the leveling screws on the chassis

Keep the spirit level on the chassis and do finer adjustments of these

screws to bring the bubble in the sprit level to the centre Repeat this

placing the sprit level along a direction perpendicular to the earlier

direction

2 Repeat this procedure for the prism table

3 Close the slit at the other end of the collimator using the drum screw DS1

Open it to a reasonable width Place the spectrometer in front of the

mercury lamp window and rotate the collimator so that the slit faces of

window View the slit through the telescope If it is not in the centre of the

view level collimator and the telescope so as to bring it to the centre

Setting the prism in the minimum deviation position

1 Rotate the prism table such that lines ruled on the table become

perpendicular to the axis of collimator

2 Place prism over the prism table such that its rough surface BA is

perpendicular to the line on prism table (See Fig-1(a))

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e44

Observation Table

Sr No Voltage V

(volt) Current 119868

(mA)

Resistance

119877 = 119881

119868 Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Date____________

Pag

e45

Graph 119868 V

Calculations 119877 = 119881

119868

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e46

Dispersive Power of The Prism Experiment - 11

Aim To find the dispersive power (D) of the prism by using spectrometer

Apparatus Mercury vapor lamp Spectrometer Prism

Procedure

Levelling and alignment of collimator and telescope

1 Switch on the mercury lamp Adjust the leveling screws on the chassis

Keep the spirit level on the chassis and do finer adjustments of these

screws to bring the bubble in the sprit level to the centre Repeat this

placing the sprit level along a direction perpendicular to the earlier

direction

2 Repeat this procedure for the prism table

3 Close the slit at the other end of the collimator using the drum screw DS1

Open it to a reasonable width Place the spectrometer in front of the

mercury lamp window and rotate the collimator so that the slit faces of

window View the slit through the telescope If it is not in the centre of the

view level collimator and the telescope so as to bring it to the centre

Setting the prism in the minimum deviation position

1 Rotate the prism table such that lines ruled on the table become

perpendicular to the axis of collimator

2 Place prism over the prism table such that its rough surface BA is

perpendicular to the line on prism table (See Fig-1(a))

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e45

Graph 119868 V

Calculations 119877 = 119881

119868

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e46

Dispersive Power of The Prism Experiment - 11

Aim To find the dispersive power (D) of the prism by using spectrometer

Apparatus Mercury vapor lamp Spectrometer Prism

Procedure

Levelling and alignment of collimator and telescope

1 Switch on the mercury lamp Adjust the leveling screws on the chassis

Keep the spirit level on the chassis and do finer adjustments of these

screws to bring the bubble in the sprit level to the centre Repeat this

placing the sprit level along a direction perpendicular to the earlier

direction

2 Repeat this procedure for the prism table

3 Close the slit at the other end of the collimator using the drum screw DS1

Open it to a reasonable width Place the spectrometer in front of the

mercury lamp window and rotate the collimator so that the slit faces of

window View the slit through the telescope If it is not in the centre of the

view level collimator and the telescope so as to bring it to the centre

Setting the prism in the minimum deviation position

1 Rotate the prism table such that lines ruled on the table become

perpendicular to the axis of collimator

2 Place prism over the prism table such that its rough surface BA is

perpendicular to the line on prism table (See Fig-1(a))

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e46

Dispersive Power of The Prism Experiment - 11

Aim To find the dispersive power (D) of the prism by using spectrometer

Apparatus Mercury vapor lamp Spectrometer Prism

Procedure

Levelling and alignment of collimator and telescope

1 Switch on the mercury lamp Adjust the leveling screws on the chassis

Keep the spirit level on the chassis and do finer adjustments of these

screws to bring the bubble in the sprit level to the centre Repeat this

placing the sprit level along a direction perpendicular to the earlier

direction

2 Repeat this procedure for the prism table

3 Close the slit at the other end of the collimator using the drum screw DS1

Open it to a reasonable width Place the spectrometer in front of the

mercury lamp window and rotate the collimator so that the slit faces of

window View the slit through the telescope If it is not in the centre of the

view level collimator and the telescope so as to bring it to the centre

Setting the prism in the minimum deviation position

1 Rotate the prism table such that lines ruled on the table become

perpendicular to the axis of collimator

2 Place prism over the prism table such that its rough surface BA is

perpendicular to the line on prism table (See Fig-1(a))

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e47

Fig-1(a)

3 Rotate the prism slightly about point A such that the prism is in slightly

tilted position ABC

4 View the spectrum through the telescope It will contain red yellow green

blue and violet lines The spectral lines will in general be broad and blurred

5 Rotate the telescope and prism table together in clockwise direction

watching the spectrum all the time through the telescope so as to keep the

spectrum in view The spectrum will rotate in any one direction (to the right

or to the left) Continue this till the spectrum starts retracing its path ie it

starts moving opposite to the earlier direction This position is called the

minimum deviation position

6 Tighten screw FS2 to fix the telescope

Collimator adjustment for parallel rays (Schusters method)

1 Rotate the prism table slightly so that the refracting edge moves towards

the spectral lines will appear a little blurred Adjust the collimator screw till

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e48

you see the spectral lines as best as possible Keep the lines in the best

focus all the time adjusting the focusing screw of the telescope

2 Now rotate the prism table slightly in the opposite direction so that the

refracting edge moves away from the telescope You should cross the

minimum deviation position and go slightly beyond it The spectral lines will

again appear a little blurred Now adjust the collimator screw to make the

lines as well defined as possible

3 Repeat steps 1 and 2 three to four times so that the spectrum remains

sharp and well-illuminated around the minimum deviation position This

ensures that the configuration of collimator lenses is adjusted to send out

parallel rays The rays are then parallel also to the axis of the collimator

The spectrometer is now adjusted for parallel rays After this do not disturb

the adjustment of the collimator screw throughout the experiment

4 Adjust the prism table to bring the spectrum exactly to the minimum

deviation position Tighten the screw FS1 so that the prism table is fixed

Take care that you do not disturb the prism throughout

Measurement of the angles of minimum deviation

1 Once the minimum deviation position is obtained adjust the vertical cross

wire of the telescope slightly beyond the violet (or if violet is not seen then

the blue) line Fix FS2 Using M1 bring the cross wire on the violet line or if

this is not visible on the blue line Note down the readings in the window

2 Now set the telescope cross wire on line of the red color in the spectrum

using fine adjustment screw M Note down same windowrsquos reading

Theory

Dispersion of light

The process of splitting of a white light (polychromatic light) into its

constitute colors is known as dispersion

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e49

When different colors or wavelengths are present in incident light

then these colors are deviated to different extent This is because the

refractive index (120578) of any material is different for different colors of light

All colors ie all wavelengths have the same velocity in air or in vacuum

Thus in any medium other than air or vacuum the velocity of red

color is more than that of violet color

Now refractive index (120578) of a medium is the ratio of the velocity of

light in air (c) to the velocity of light in that medium (119907) ie

120578 =119888

119907

Therefore for any medium other than air or vacuum the refractive

index of violet color is maximum and that of red color is minimum The

refractive indices of other colors lie in between

Hence violet color for which the refractive index is maximum is

deviated to the greatest extent while the red color for which refractive

index is minimum is deviated to the least extent The deviations of the

other colors lie between those of red and violet

In short violet color deviates most and red color deviates least

Dispersive Powerhellip 119915 =120633119933minus120633119929

120633119950

The dispersive power of any object is depends on its material

The dispersive power for a flint glass is more than that for the

ordinary crown glass because the value of 120575119881 minus 120575119877 for flint glass is

more than the value of 120575119881 minus 120575119877 for ordinary crown glass

Thus the colors in the spectrum obtained by flint glass prism

are dispersed to larger extent

Observations

Least count of the spectrometer = 1rsquo

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e50

Observation Table

Sr No

Color of the Spectral line

Reading of Spectrometer Angle of minimum

deviation 120575119898 = θ1~ θ2

In minimum deviation Position

θ1

Direct Reading

θ2

1 Red 120575119877 = ___________

2 Violet 120575119881 = ___________

Calculations

(1) Angle of minimum deviation 120575119898 = θ1~ θ2

(i) 120575119877 = θ1~ θ2 (ii) 120575119881 = θ1~ θ2

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________

Date____________

Pag

e51

(2) Dispersive power of the prism

119863 =120575119881minus120575119877

120575119898 where

120575119898 =120575119881+120575119877

2 (Angle of minimum deviation

for mean wavelength)

Result ___________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Sign __________________