completed edc

UFY12209CDP CIRCUITS AND DEVICES LABORATORY L T P C (For B.E- ECE only) 0 0 3 2

SYLLABUS

1. Verification of KVL and KCL

2. Verification of Thevenin and Norton Theorems.

3. Verification of superposition Theorem.

4. Verification of Maximum power transfer and reciprocity theorems.

5. Frequency response of series and parallel resonance circuits.

6. Characteristics of PN and Zener diode

7. Characteristics of CE configuration

8. Characteristics of CB configuration

9. Characteristics of UJT and SCR

10. Characteristics of JFET and MOSFET II.

11. Characteristics of Diac and Triac.

12. Characteristics of Photodiode and Phototransistor.

TOTAL: 45 PERIODS

2

2

List & cycle of Experiments

Cycle-I

1. Characteristics of PN Diode

2. Characteristics of Zener diode

3. Transistor Characteristics – Common Emitter mode

4. Transistor Characteristics – Common Base mode

5. Characteristics of UJT

6. Characteristics of SCR

7. Characteristics of JFET and MOSFET

8. Characteristics of Photodiode and Phototransistor

9. Characteristics of Diac and Triac

Cycle-II

9. Verification of KVL and KCL

10. Verification of Thevenin‟s and Norton‟s Theorems

11. Verification of Reciprocity Theorem

12. Verification of Superposition Theorem

13. Verification of Maximum power transfer theorem

14. Frequency Response of series resonance circuits

15. Frequency Response of Parallel resonance circuits.

Experiments Beyond Anna University Syllabus

16. Zener Diode as Voltage Regulator

3

3

General Instructions to students for ECE Lab courses

Acquire a good knowledge of the surrounding of your worktable. Know where the

various live points are situated in your table.

In case of any unwanted things happening, immediately switch off the mains in the

worktable.

This must be done when there is a power break during the experiment being carried

out.

Before entering into the lab class, you must be well prepared for the experiment

that you are going to do on that day.

Get the circuit diagram approved.

Prepare the list of equipments and components required for the experiment and get the

indent approved.

Plan well the disposition of the various equipments on the worktable so that the

experiment can be carried out.

Make connections as per the approved circuit diagram and get the same verified.

After getting the approval only supply must be switched on.

You must get the observation note corrected within two days from the date of

completion of experiment.

Submit the record notebook for the experiment completed, in the next class.

If you miss any practical class due to unavoidable reasons, intimate the staff in charge

and do the missed experiment in the repetition class.

Such of those students who fail to put in a minimum of 75% attendance in the

laboratory class will run the risk of not being allowed for the University Practical

Examination. They will have to repeat the lab course in subsequent semester after

paying prescribed fee.

4

4

Guide lines for preparation of Observation & Record

On the Left Side On the Right Side Circuit Diagram:

(With suitable title for each diagram)

Device Details:

(With pin diagram)

Observation:

(Separate tabular columns for

observations part and calculation

parts)

(Suitable title for each tabular

column)

Model graphs if any:

Model calculation if any:

Aim :

Apparatus Required :

Precautions (if any):

Procedure:

(Brief procedure in observation)

(Detailed procedure in Record note

book)

Theory:

(Brief theory about the experiment)

(In record, theory should cover the

answers for discussion questions)

Result:

Discussion Questions:

(Answer for discussion question in

observation only)

(In record, include the answers in the

theory itself)

5

5

P-N JUNCTION DIODE

Circuit Diagram

Forward bias

Reverse bias

Circuit Model

P-N Junction Diode

.

6

6

Objective

To obtain the forward and reverse bias characteristics of semiconductor diode

Reference

1 “ Electronic Devices and circuits” by Salivahanan, Suresh kumar, Vallavaraj.

2 “ Principles of Electronics” by V.K. Mehta.

3 “ Basic Electronics” – A Text Lab Manual by Paul. B. Zbar and Malvino.

Knowledge Required

P-N Junction, depletion layer, barrier potential, forward bias, reverse bias, break

down voltage, Avalanche breakdown.

Precaution

Voltage level should not exceed the value specified for the device.

Procedure

For various values of forward and reverse biased voltages, tabulate the values of

currents.

1. Characteristics of PN Diode

7

7

Observation

Forward Bias Reverse Bias

Vf (V) If (mA) Vr (V) Ir (A)

Formulae Used

Forward Resistance(Rf) = Change in forward Voltage/Change in forward Current

Reverse Resistance(Rr) = Change in Reverse Voltage/Change in Reverse Current

Model Graphs:-

V-I Characteristics

Diode forward resistance

8

8

Result

The forward and reverse bias characteristics of semiconductor diode are plotted.

Forward Resistance = ______________

Discussion Questions

1. What are Intrinsic and Extrinsic Semiconductors?

2. Define Peak Inverse Voltage.

3. What do you mean by potential barrier in a PN Junction?

4. What are N – type and P – type semiconductors?

5. What are the applications of semiconductor diode?

6. What are Donors and Acceptors in semiconductors?

7. Define doping.

********************************************************************

9

9

Circuit Diagram

ZENER DIODE

Forward bias

Reverse bias

10

10

Objective

To obtain the forward and reverse bias characteristics of zener diode

Reference

1.“ Electronic Devices and circuits” by Salivahanan, Suresh kumar, Vallavaraj.

2.“ Principles of Electronics” by V.K. Mehta.

3.“ Basic Electronics” – A Text Lab Manual by Paul. B. Zbar and Malvino.

Knowledge Required

P-N Junction, depletion layer, barrier potential, forward bias, reverse bias, break

down voltage, zener breakdown, Avalanche breakdown.

Precaution

Voltage level should not exceed the value specified for the device.

Procedure

For various values of forward and reverse biased voltages, tabulate the values of

currents.

2. Characteristics of Zener Diode

11

11

Observation

Forward Bias Reverse Bias

Formulae Used

Forward Resistance(Rf) = Change in forward Voltage/Change in forward Current

Reverse Resistance(Rr) = Change in Reverse Voltage/Change in Reverse Current

Model Graphs

V-I Characteristics

.

Vf (V) If (mA) Vr (V) Ir (A)

12

12

Result

The forward and reverse bias characteristics of Zener diode is plotted.

Forward Resistance = ______________

Reverse Resistance = ______________


1. What are the applications of Zener diode?

2. How does a Zener diode act as voltage regulator?

3. In What way Zener Diode is different from PN junction Diode?

4. What do you mean by avalanche breakdown voltage?

5. What do you mean by Leakage current?

***********************************************************

13

13

Circuit Diagram

Observation

Input Characteristics

VCE (V) VCE (V) VCE (V)

VBE (V) IB (A) VBE (V) IB (A) VBE (V) IB (A)

Output Characteristics

IB (A) IB (A) IB (A)

VCE (V) IC (mA) VCE (V) IC (mA) VCE (V) IC (mA)

14

14

Objective

To obtain the characteristic curves for a transistor in common emitter mode

and hence to determine the h-parameters.

Reference

1. “Electronic devices and circuits” by Salivahanan, Suresh kumar, Vallavaraj

2. “Principles of Electronics” by V.K.Mehta

Knowledge required

Composition of transistor, types of transistors, transistor biasing, Working of

transistor, types of circuit connections for operating a transistor, forward biased

diode characteristic, knee voltage.

Precautions

1. Polarities of the bias voltage should be correct.

2. Voltage and current levels should not exceed the values specified for the device.

3. Both rheostats should be kept in minimum position at the time of switching on

the supply.

Procedure


Keeping the voltage across Collector to Emitter (VCE) as constant, tabulate the

values of base current for various values of Base-Emitter voltage (VBE).

Repeat the same procedure for various constant values of VCE.


Keeping the base current as constant, tabulate the values of collector current

(IC) for various values of Collector-Emitter voltage (VCE).

Repeat the same procedure for various constant values of base current (IB).

3. Transistor Characteristics-Common Emitter Mode

15

15

Formulae Used

1. Input impedance „hie‟ = ∆VBE/∆IB

2. Reverse Voltage gain „hre‟ = ∆VBE/∆VCE

3. Output admittance „hoe‟ = ∆IC/∆VCE

4. Forward Current gain „hfe‟ = ∆IC/∆IB

Model Graphs

Input Characteristics Output Characteristics

Pin Diagram

VCE3 < VCE2

VCE1

VCE2 < VCE1

VBE

IB IB3 > IB2

IB1

IB2 > IB1

VCE

IC

16

16

Result

The input and output characteristics of CE transistor configuration are drawn.

Parameters Practical value

hie

hfe

hoe

hre


1. What is mean by biasing?

2. Why the BJT is called as current controlled device?

3. What are the different operating regions?

4. Define the base width modulation or early effect.

5. What is secondary breakdown?

******************************************************************

17

17

Circuit Diagram

Observation


VCB (V) VCB (V) VCB (V)

IE (mA) VEB (V) IE (mA) VEB (V) IE (mA) VEB (V)


IE (mA) IE (mA) IE (mA)

IC (mA) VCB (V) IC (mA) VCB (V) IC (mA) VCB (V)

(0-30)V (0-30)V

18

18

Objective

To obtain the characteristic curves for a transistor in common base mode and

hence to determine the h-parameters.

Reference

1. “Electronic devices and circuits” by Salivahanan, Suresh kumar, Vallavaraj

2. “Principles of Electronics” by V.K.Mehta

Knowledge required

Composition of transistor, types of transistors, transistor biasing, working of

transistor, types of circuit connections for operating a transistor, forward biased diode

characteristic, knee voltage.

Precautions

1. Polarities of the bias voltage should be correct.

2. Voltage and current levels should not exceed the values specified for the

device.

3. Both rheostats should be kept in minimum position at the time of switching on

the supply.

Procedure


Keeping the voltage across Collector to Base (VCB) as constant, tabulate the

values of emitter current IE, for various values of Emitter- Base voltage (VEB).

Repeat the same procedure for various constant values of VCB.


Keeping the emitter current IE as constant, tabulate the values of collector

current IC, for various values of Collector-Base voltage (VCB).

Repeat the same procedure for various constant values of emitter current IE.

4. Transistor Characteristics-Common Base Mode

19

19

Formulae Used

1. Input impedance „hib‟ = ∆VEB/∆IE

2. Reverse Voltage gain „hrb‟ = ∆VEB/∆VCB

3. Output admittance „hob‟ = ∆IC/∆VCB

4. Forward Current gain „hfb‟ = ∆IC/∆IE

Model Graphs

Input characteristics Output characteristics

Pin Diagram

VCB3 > VCB2

VCB1

VCB2 > VCB1

VEB

IE

20

20

Result

The input and output characteristics of CB transistor configuration are drawn.

Parameters Practical value

hib

hfb

hob

hrb


1. Compare the various configurations of transistor based on the following headings

(a) voltage gain

(b) input resistance

(c) output resistance

(d) application

2. What is the main advantage of CE over CB configuration?

3. Write the relationship between , , .

************************************************************************

21

21

Circuit Diagram

Observation

VB1B2 = VB1B2= VB1B2 =

IE (mA) VE (V) IE (mA) VE (V) IE (mA) VE (V)

Model Graphs

Characteristics of UJT

22

22

Objective

To obtain the characteristics of uni junction transistor and hence to determine the UJT

parameters.

Reference

1. “Electronic Devices and Circuits” by Salivahanan, Suresh kumar, Vallavaraj.

2. “Principles of Electronics” by V.K.Mehta.

3. “Basic Electronics” – A Text Lab Manual by Paul.B.Zbar and Malvino.

Knowledge Required

Construction details of UJT, cut off region, negative resistance region, saturation

region, valley point.

Precaution

Voltage and Current levels should not exceed the values specified for the device.

Procedure

1. Keeping the voltage between the bases VBB as constant, tabulate the values of emitter

current (IE) for various values of emitter voltage VE by adjusting the potential divider

arrangements.

2. Repeat the same procedure for various constant values of VB1B2.

η = VEB1 – VBE

------------

VB1B2

Result

The input and output characteristics of Uni junction transistor are drawn.

The intrinsic stand off ratio ( η ) =


1. Draw the equivalent circuit of UJT.

2. What are Valley point and Peak point?

3. What are the factors affecting the frequency of the pulses produced by UJT?

4. What is the difference between UJT and PUT?

5. State the applications of UJT.

6. What do you mean by Negative Resistance region?

5. Characteristics of UJT

23

23

24

24

Objective

To find the latching and holding current of a given SCR

Reference

1.“Electronic Devices and Circuits” by Salivahanan, Suresh kumar,

Vallavaraj.



Knowledge Required

Construction details of SCR, gate current and breakover voltage.

Precaution


Procedure

1. Check the RPS connecting the circuit.

2. Connect the circuit as per the circuit diagram

3. Set the gate current Ig equal to firing current vary anode the cathode voltage.

VAK in steps of 1V and note down the corresponding anode current IA.

4. VBRF is the point where voltage (VAK) suddenly drops and hence there is a sudden

increase in anode current IA.

5. Increase the VAK in steps and note down the IA.

6. Open the gate and decrease VAK.

6. Characteristics of SCR

25

25

Tabulation

IG= ----- (mA)

Sl.No. VAK.(v) IA (mA)

26

26

Result

The Characteristics of SCR is drawn.

Forward break over voltage(VBRF ) =

Latching current (IL ) =

Holding current (IH) =


1.What is the purpose of gate current in SCR?

2.Define Holding current

3.Specify the methods of turning on SCR.

4.What is the difference between SCR & Diode?

5.Define Latching current.

******************************************************************

27

27

Circuit Diagram

Observation

Drain Characteristics

VGS = --V VGS =--V VGS =--V

VDS(V) ID(mA) VDS(V) ID(mA) VDS(V) ID(mA)

Transfer Characteristics

VDS =-- V VDS =--V VDS =--V

VGS (V) ID(mA) VGS (V) ID(mA) VGS (V) ID(mA)

28

28

Objective

To obtain the characteristics of junction field effect transistor and hence to

determine the FET parameters.

Reference




Knowledge Required

Pinch off voltage, Gate-source cut off voltage.

Precaution


Procedure


1. Keeping the values of Gate-source voltage VGS, as constant, tabulate the

values of drain current (ID), for various values of drain-source voltage VDS.

2. Repeat the same procedure for various constant values of VGS.


1. Keeping the values of Drain-source voltage VDS, as constant, tabulate the

values of drain current (ID) for various values of VGS.

2. Repeat the same procedure for various constant values of VDS.

7(a). Characteristics of JFET

29

29

Model Graphs

Drain Characteristics Transfer Characteristics

Formulae Used

1. Drain Resistance(Rd) = ∆VDS/∆ID

2. Amplification factor(µ ) = ∆VDS/∆VGS

3. Mutual Conductance(gm) = ∆ID/∆VGS

30

30

Result

The drain and transfer characteristics of Junction field effect Transistor are

drawn and the parameters obtained are

(i) Dynamic drain resistance (Rd) =

(ii) Mutual conductance(gm) =

(iii) Amplification factor(µ ) =


1. What are the differences between JFET and MOSFET?

2. Define pinch off voltage.

3. What are the modes of operation available in JFET?

4. Why JFET is called as a voltage controlled device?

5. What is the difference between FET and BJT?

************************************************************************

31

31

Circuit Diagram:

Observation


VGS = --V VGS =--V VGS =--V

VDS(V) ID(mA) VDS(V) ID(mA) VDS(V) ID(mA)


VDS =-- V VDS =--V VDS =--V

VGS (V) ID(mA) VGS (V) ID(mA) VGS (V) ID(mA)

32

32

Objective

To obtain the characteristics of junction Metal Oxide Semiconductor field effect

transistor and hence to determine the MOSFET parameters.

Reference




Knowledge Required

Pinch off voltage, Gate-source cut off voltage.

Precaution


Procedure


3. Keeping the values of Gate-source voltage VGS, as constant, tabulate the

values of drain current (ID), for various values of drain-source voltage VDS.

4. Repeat the same procedure for various constant values of VGS.


3. Keeping the values of Drain-source voltage VDS, as constant, tabulate the

values of drain current (ID) for various values of VGS.

4. Repeat the same procedure for various constant values of VDS.

7(b). Characteristics of MOSFET

33

33

Symbol:

Model Graphs

Transfer Characteristics Output Characteristics

Formulae Used

1. Drain Resistance(Rd) = ∆VDS/∆ID

2. Amplification factor(µ ) = ∆VDS/∆VGS

3. Mutual Conductance(gm) = ∆ID/∆VGS

34

34

Result

The drain and transfer characteristics of Metal Oxide Semiconductor field

effect Transistor are drawn and the parameters obtained are

(iv) Dynamic drain resistance (Rd) =

(v) Mutual conductance(gm) =

(vi) Amplification factor(µ ) =


1. What are the differences between JFET and MOSFET?

2. Define pinch off voltage.

3. What are the modes of operation available in MOSFET?

4. Why MOSFET is called as a voltage controlled device?

5. What is the difference between MOSFET and BJT?

6. Why MOSFET is called insulated gate FET?

7. What is N-channel and P-channel MOSFET?

8. Differentiate Enhancement and Depletion types of MOSFETs.

9. Is it possible for a Depletion type of MOSFET to operate in both modes?

10. What are the disadvantages of MOSFET type and why V-MOS is developed?

************************************************************************

35

35

Circuit Diagram:

Characteristics of Phototransistor

Characteristics of Photodiode:

Model Graph:

36

36

Objective

To obtain the characteristics of Photodiode

Reference




Knowledge Required

Construction and operation of Photodiode.

Precaution 1.Polarities of the bias voltage should be correct.

2.Volatge and current levels should not exceed the values specified for the device.

Procedure

1.Select Photodiode.

2.Connect the circuit as per the circuit diagram.

3.For different values of voltage, note the corresponding current.

4. The same procedure is repeated for Dark, Dim and Bright conditions.

8. Characteristics of Photodiode and Phototransistor

37

37

Observation :( Phototransistor)

DARK DIM BRIGHT

VD(V) ID(µA) VD(V) ID(µA) VD(V) ID(µA)

Observation :( Photodiode)

DARK DIM BRIGHT

VD(V) ID(µA) VD(V) ID(µA) VD(V) ID(µA)

38

38

Result

The characteristics of photodiode and phototransistor were plotted.


1. What is meant by Photodiode?

2. What is meant by dark current?

3. What are the applications of Dark current?

4. What are the differences between photodiode and transistor?

5. What are the applications of Photo Transistor?

********************************************************************

39

39

DIAC:

Circuit Symbol:

Circuit Diagram:

Forward Bias:

Reverse Bias:

40

40

Objective

To obtain the characteristics of DIAC and TRIAC

Reference




Knowledge Required

Bidirectional Trigger Diode, Holding Current,Thyristor

Precaution


Procedure

DIAC:

1.Connections are given as per the circuit diagram.

1. The power supply is varied in constant steps and the corresponding voltage

and current readings are noted down.

2. For particular values of applied forward voltage , the current increases. Then

the voltage across DIAC decreases with increase in current.

3. The same procedure is repeated for reverse voltage of DIAC.

4. The VI characteristics is drawn from the tabulated readings.

TRIAC:

1. Connections are given as per the circuit diagram.

2. Set the value of IG to be constant by adjusting the power supply.

3. The terminal voltage is varied in steps and the corresponding readings are

noted down.

4. The same procedure is repeated for reverse polarity of TRIAC.

5. The voltage and current readings are noted down.

6. The characteristics curve is plotted for the tabulated readings.

9. Characteristics of DIAC and TRIAC

41

41

Tabulation:

Forward Bias:

Reverse Bias:

Forward Voltage

Vf (V)

Forward Current

If (mA)

Model Graph:

Reverse Voltage

Vr (V)

Reverse Current

Ir (mA)

42

42

43

43

TRIAC:

Circuit Diagram:

Forward Bias:

Reverse Bias:

44

44

45

45

Tabulation:

Forward Bias: Reverse Bias:

IG = 2.5 mA

Forward Voltage

Vf (V)

Forward Current

If (mA)

Model Graph:

IG = 6 mA

Reverse Voltage

Vr (V)

Reverse Current

Ir (mA)

46

46

Result

The forward and reverse bias characteristics of DIAC and TRIAC are plotted.

Questions for Discussion:

1. Why the DIAC is said to be a symmetrical trigger diode?

2. Draw the SCR equivalent circuit of TRIAC.

3. How can you control the phase using TRIAC?

4. Give few applications of DIAC.

5. Give few applications of TRIAC

47

47

Circuit diagram

Kirchoff’s Voltage Law

Kirchoff’s Current Law

48

48

9.Verification of Kirchoff’s Voltage and Current Laws

Objective

To verify the Kirchoff‟s laws with the help of simple D.C series and parallel

circuits.

Reference

1. Electric circuit Theory, M.Arumugam and N.Premkumar

1. Electric circuits, Joseph A.Edminister

2. “Basic Electricity” Text Lab Manual, Paul .B Zhar and Gordon Rockmaker

Knowledge Required

Basic circuit laws [Ohm‟s law & Kirchoff‟s laws]

Concept of series and parallel circuits

Use of double tube rheostats, other equipments and meters

Selection of meter ranges, fuse rating

Precautions

The branch currents should not exceed the device ratings.

The ammeter and voltmeter ranges should be properly chosen.

LAWS

i) Kirchoff‟s Voltage Law

Kirchoff‟s voltage law states that the algebraic sum of all branch voltages around a closed

loop of a network is zero at all instant of time. Kirchoff‟s voltage law deals with the

element voltages in a loop. A loop is a closed path formed by two or more circuit

elements. While applying KVL to a particular loop first assign a reference direction to

each element voltage for example, assign +ve sign to the voltages if they correspond to

voltage drops and assign –ve sign to the voltages if they correspond to voltage rises.

ii) Kirchoff‟s Current Law

Kirchoff‟s current law states that the algebraic sum of the branch currents at the node is

zero at all instants of time. It deals with the element currents meeting at a node. While

applying KCL to a particular node, first assign a reference direction to each element

current for example, assign +ve sign to those currents whose direction points away from

the node. Similarly assign –ve sign to those currents whose direction points towards the

node.

49

49

Theoretical calculations

Kirchoff’s Voltage Law

Kirchoff’s Current Law

Comparison tabulation

Kirchoff‟s Voltage Law

VS1

(volts)

VS2

(volts)

VS1 –

VS2

(volts)

V1

(volts)

V2

(volts)

V3

(volts)

V = V1 + V2 + V3

(volts)

Kirchoff‟s Current Law

VS (volts) I (mA) I1 (mA) I2 (mA) I = I1 + I2 (mA)

Req = R1 + R2 + R3

It=Vt/ Req

VR1= It* R1

VR2= It* R2

VR3= It* R3

Req = (1/R1) +(1/ R2 )

It=Vt/ Req

IR1= Vt/R1

IR2= Vt/R1

50

50

Procedure

(a) To verify KVL

1. The circuit connections are made as shown in figure.

2. Keep the rheostat at a particular position and switch on the supply voltage. Now, note

down the voltages across each element using the voltmeters namely V1, V2 and V3

with proper sign. Now the algebraic sum of the three voltages can be verified to be

equal to zero.

3. Next, change the resistance of the rheostats to some other value and repeat the above

process.

(b) To verify KCL

1. The circuit connections are made as shown in figure.

2. Keep the rheostat at a particular position and switch on the supply voltage. Now, note

down the currents through each element using the ammeters namely I1, I2 and I3 with

proper sign. Now the algebraic sum of the currents at node B can be verified to be

equal to zero.

3. Next, change the resistance of the rheostats to some other value and repeat the above

process.

51

51

Result Comparing the observed values and the theoretical values, we infer that they are

almost equal. Thus Kirchoff‟s law is verified both theoretically and practically.


1. State Ohm‟s law and Kirchoff‟s laws.

2. Distinguish between mesh and loop.

3. What are active and passive elements?

4. Can we use MI meters in d.c. circuits? Justify your answer.

5. What will happen on reversing the polarities of the MC meter terminals?

**********************************************************

52

52

Circuit Diagram: (Thevenin’s)

Equivalent circuit

Rth

Tabulation

Sl.no V1

(volts)

V2

(volts)

IL(mA) Vth(V) Rth(Ω)

the pra the pra the pra

53

53

10. Thevenin’s and Norton’s Theorems

Objective

To obtain the Thevenin‟s and Norton‟s equivalent of the given circuit and hence

to verify these theorems with the equivalent circuits.

References

“Electric Circuit Theory” by Arumugam & Premkumar

“Electric Circuits” by Joseph A. Edminister

“Basic Electricity - A Text Lab Manual” by Paul B. Zbar and Gordon Rockmaker

Knowledge Required

Theorems – statement and their explanation.

Basic circuit laws

Selection of meter ranges, fuse ratings

THEVENIN‟S Theorem An linear active network containing linear impedances and voltage sources can be

replaced by an equivalent circuit consisting of voltage source (Vth) acting in series with an

impedance (Zth). The voltage source is the Thevenin‟s voltage (Vth) at open circuit

condition and hence also called open circuit voltage and impedance is the driving point

impedance at the terminals when all the voltage sources are removed and called as

Thevenin‟s impedance (Zth).

It is used to find the current through a particular element in a general network which

may consists of several elements along with the number of voltage and current sources.

Procedure 1. The circuit connections are given as shown in figure. The variable resistances

are initially adjusted to some suitable values. The supply voltages are

adjusted to some values V1&V2 and the current through the branch BE is

measured using the ammeter present in that branch.

2. Next, the load RL is removed from the circuit. The open circuit voltage

between B&E is measured using the proper voltage range of the multimeter.

This reading gives the value of the Thevenin‟s voltage (Vth).

3. In order to find Thevenin‟s resistance Rth, the branch BE is shorted through

an ammeter and

the short circuit current ISC is measured. Now, Rth = Vth/ISC. The value of the

current through RL is calculated as

Lth

thL

RR

VI

54

54

Circuit diagram (Norton‟s)

Equivalent circuit

Tabulation

Sl.no V1

(volts)

V2

(volts)

IL(mA) Isc (mA) Rth(Ω)

the pra the pra the pra

55

55

Now, this value can be verified to be equal to the one which was measured using

the ammeter.

4. The experiment is repeated for different values of the variable resistance and

also by changing the supply voltage

NORTAN‟S Theorem

Any two terminal linear network consisting of voltage sources and impedances

can be replaced with an equivalent circuit consisting of current source (Isc) in parallel with

an impedance (Rth). The current source (ISC) is the short circuit current and the impedance

(Rth) is the Thevenin‟s resistance. Norton‟s theorem is useful to find the current through a

particular element, in general which may consists of several elements along with the

number of voltage and current sources.

Procedure

1.The circuit connections are given as shown in figure. The variable resistances

are initially adjusted to some suitable values. The supply voltages are adjusted to

some values say V1 and V2. In order to find the Thevenin‟s resistance,(Rth) all the

voltage sources are removed and then the resistance between B&E is measured

using the proper resistance range of the multimeter. This reading gives the value

of Thevenin‟s resistance.

2. The branch BE is shorted through an ammeter and short circuit current Isc is

measured.

3. The value of current flowing through RL is measured using the formula.

Lth

thscL

RR

RII

4. The experiment is repeated for different values of the variable resistance and

also by changing the supply voltage.

56

56

57

57

Result

Comparing the observed values and the theoretical values, we infer that they are

almost equal. Thus both theorems are verified both theoretically and practically


1. Prove that Norton‟s theorem is the converse of Thevenin‟s theorem.

2. What are the practical applications of Thevenin‟s theorem?

3. Are these theorems applicable for AC circuits? If so, give the statements.

4. What is the internal resistance of an ideal voltage and ideal current sources?

58

58

Circuit diagram

Before interchanging(Fig 1)

Tabulation

Before interchanging voltage and current source

Sl.no Voltage(V) Current(A) V/I (Ω)

59

59

Objective To verify reciprocity theorem experimentally for the given circuit.

References




Knowledge Required

Theorem – statement and their explanation.

Basic circuit laws

Theorem

According to Reciprocity theorem, if we apply some input to a circuit which

consists of resistors, inductors ,capacitors and transformers including coupled circuits, the

ratio of response(o/p) in any element to the input is constant even when the input and

output are interchanged .

Procedure

1. The connections are given as per the circuit diagram as shown in fig.1

2. Switch on the power supply and the rheostat is adjusted to vary the input supply

voltage.

3. For each values of voltage, corresponding current in the short circuited terminal is

noted.

4. The voltage and current sources are interchanged as shown in fig.2.

5. The rheostat is adjusted and the values of current and voltage are noted.

6. The reciprocity theorem was verified by obtaining equal values of ratios of

response to input before and after interchanging the sources.

11. VERIFICATION OF RECIPROCITY

THEOREM

60

60

After interchanging(Fig 2)

After interchanging voltage and current source

Sl.no Voltage(V) Current(A) V/I (Ω)

61

61

Result

Thus the reciprocity theorem was verified both theoretically and practically for the given circuit.


1.What are the practical applications of this theorem?

2. Are this theorem applicable for AC circuits? If so, give the statements

****************************************************

62

62

Circuit Diagram:

CIRCUIT TO FIND IL1 :

CIRCUIT TO FIND IL2 :

63

63

Objective To verify superposition theorem experimentally using DC network.

References




Knowledge Required

Theorem – statement and their explanation.

Basic circuit laws

Theorem

Superposition theorem states that in a linear network containing several sources,

the overall response at any point in the network equals the sum of, the responses of each

individual source considered separately replacing the other source by their equivalents.

Procedure

1.Theoretically calculate the value of current IL flowing through RL by

including V1 &V2.

2.Theoretically calculate the value of IL(1) by including V1and S.C.V2.

Also find the value of IL(2) by including V2 alone and S.C.V1.

3.The connections are made as per the given circuit.

4.Find the value of IL(1) with V1 alone.

5.Find the value of IL(2) with V2 alone.

6.Verify theoretically & practically that, IL= IL(1) + IL(2)

12 .VERIFICATION OF SUPERPOSITION

THEOREM

64

64

Tabulation

Parameters

Theoretical values(V)

Practical value(V)

V1 acting alone

V2 acting alone

Both are acting

Design:

65

65

Result

From the tabulated results, super position theorem is verified theoretically &

practically.


1. At what situation this theorem can be applicable?

2. What do you mean by linear & bilateral networks?

***********************************************

66

66

CIRCUIT DIAGRAM:

Tabulation:

Sl.

No

.

Observations Calculations Value of Rs (Ohms)

P max (watts) Current IL

( m.A ) Voltage

VL

(Volt)

Power VL IL

(watts)

RL = VL /

IL

(Ohms) Th Pr

67

67

13. Verification of Maximum Power Transfer theorem

Onjective:

To verify the Maximum Power transfer theorem by conducting suitable test.

REFERENCS:

1).“Engineering circuit Analysis” ,6th

Edition Tata McGraw-Hill publishing

company ltd Author-WH Hayt,J E Kemmerly,S M Durbin

2).“Electrical Engineering Fundamentals”,-Second Edition, Prentice Hall of

India Author-Vincent Del Toro

PROCEDURE:

1. Connections are made as per circuit diagram.

2. Keep the variable point of Rs in a suitable position.

3. Start with maximum resistance adjusted for RL. Note the current through & voltage

across RL.

4. Vary the RL and note the current & voltage. Take a number of readings upto a low

value of RL.

5. Change Rs and repeat steps 3 & 4

6. For every Rs plot RL & power consumed, and find out the value of RL for

maximum power from the graph.

THEORETICAL CALCULATIONS FOR PRESENT CIRCUIT:

Theoretical calculation for circuit diagram 1

The source delivers the maximum power when the load resistance is equal to the source

resistance.

RL= 25Ω

The current I = 50 / (25 + RL ) = 50 /50 =1A

The maximum power delivered to the load P= I2 RL

=1* 25 = 25W

68

68

FORMULAE USED:

PL= IL2 * RL

PL = Power in the Load resistance (RL) in watts.

IL = Load current in amps.

RESULT:

Maximum Power Transfer Theorem was verified for the given circuit


1. When will a circuit deliver maximum power to the load?

2. State Maximum power transfer theorem.

3. State the formula for maximum power delivered to the load?

69

69

Circuit Diagram

Tabulation

Frequency

F (Hz)

Output Voltage,

V0 (volts)

Current,

I (mA)

Model Graph

70

70

14. Resonant frequency and frequency response of a series RLC Circuit

Objective

To obtain the frequency response characteristic of RLC series circuit.

Reference

1) “Electric Circuit Theory” by Arumugam and Prem Kumaran.

2) “Basic Electricity – A text lab Manual” by Paul B.Zbar and Gordon

Rockmaker

3) “Electricity – Principles and Applications” by Fowler.

Knowledge Required

Series Circuit, resonance, frequency response.

Precautions:

1) Keep the beam intensity down to the minimum required for a particular

setting. Take care to turn down the glare on slow sweep speeds.

2) While making measurements, it should be ensured that time base and vertical

amplifier control are in their calibrated positions.

3) Ensure that the vertical gain control is set above the voltage of the signal to be

measured.

Procedure

Set up inductance value in the DIB using an LCR meter. Connect resistor R, DIB

and capacitor C in series with a signal generator. Adjust the signal generator such that

five volt peak magnitude is achieved on the CRO. Vary the frequency from 100Hz to

100kHz and note down the corresponding voltage across R with the help of the CRO.

Formula used

At resonance, XC = XL

where

1

2C

r

Xf C

2L rX f L

1

2rf

LC

71

71

Result

Thus the frequency response characteristic of RLC series circuit is drawn.


1. What is resonance in ac circuits?

2. Write the formula for resonant frequency in RLC series circuit?

3. What are half power frequencies?

4. Define Q factor of a circuit.

5. Prove that resonant frequency is the geometric mean of half power

frequencies.

72

72

Circuit Diagram

Tabulation

Frequency

F (Hz)

Output Voltage,

V0 (volts)

Current,

I (mA)

Model Graph

73

73

15. Frequency response of a Parallel Resonant Circuit

Objective

To obtain the frequency response characteristic of. Parallel Resonant Circuit

Reference “Principles of Electrical Engineering and Electronics” by V.K.Mehta.

Knowledge Required:

Resonant frequency of a parallel circuit

Frequency Response curve

Precautions:

1. Keep the beam intensity down to the minimum required for a particular setting.

2.Take care to turn down the glare on slow sweep speeds.

3.While making measurements, it should be ensured that time base and vertical

amplifier control are in their calibrated positions.

4.Ensure that the vertical gain control is set above the voltage of the signal to be

measured.

Procedure

1. Make the connections as shown in the circuit diagram.

2. Turn on the signal generator and the CRO and increase the output voltage of the

signal generator to 10 volts.

3. Maintain this voltage throughout the experiment and adjust if necessary.

4. Vary the Generator frequency above and below the resonant frequency in a wide

range and measure the current through the multimeter.

5. Calculate the impedance of the circuit at each frequency and record it in a tabular

column.

6. Plot the frequency vs current and frequency vs impedance curves on a semi-log

graph sheet and indicate the resonant frequency.

Result

Thus the frequency response characteristic of Parallel Resonant circuit is drawn.


1. What is the condition for parallel resonance?

2. Explain the effects of changes in frequency on the impedance of a parallel RLC

circuit.

3. Explain the effects of changes in frequency on the total current of a parallel RLC

circuit.

4. Compare series and parallel resonant circuit and

5. Define Q-factor in a parallel resonant circuit.

74

74

Circuit Diagram

Line Regulation Vin= -----(v)

Load Regulation IL =----(mA)

Sl.No IL(mA) Vd(v)

Sl.No Voltage(v) Vd(v)

75

75

Objective

To regulate the output voltage using Zener diode.

Theory

The key feature of a zener diode remain that it maintains reverse voltage across its

terminals constant. So it is used in voltage regulators. There are two ways: 1) Zener

diode as a voltage regulator with a input voltage (line regulation)

2) Zener diode as a voltage regulator with a changing load (Load regulation).

Procedure

1.Connect the circuit as shown in figure.

2.Line regulation :

Vary the input voltage slowly in steps and note down input voltage, output voltage

and ammeter readings corresponding to each setting. Take care that the maximum

current rating is not exceeded. Here the load current IL is maintained constant.

3.Plot a graph between input voltage and diode voltage

4.Load regulation: Vary the values of load current by adjusting the load

resistance and measure the diode voltage. Here input voltage is maintained

constant.

5.Plot a graph between load current and diode voltage.

Result

Thus the line &load regulation were checked using Zener diode.

16. Zener Diode as voltage Regulator

completed edc

Documents