electromagnetic induction c

8/6/2019 Electromagnetic Induction c

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I ntroductory ElectronicsI ntroductory Electronics

Unit22C

Unit22C

Th e e l ec t r o n i cs in d u s t r y i n Si n g a p o r e i s t h e co u n t r y s l a rg e s t m a n u f a ct u r i n g i n d u s t r y . Go o d s l ik e ca l cu l a t o r s ,

c o m p u t e r s an d c o m p a c t d i s c p l a y e r s a s w e l l as e l ect r o n i c co m p o n e n t s e ar n e d $ 6 1 . 2 b i ll i o n i n 1 9 9 8 a n d e m p l o y e d

n e a r l y 1 3 0 0 0 0 p e o p l e in t h e ir m a n u f a ct u r e .

Th e e l ec t r o n i cs in d u s t r y i n Si n g a p o r e i s t h e co u n t r y s l a rg e s t m a n u f a ct u r i n g i n d u s t r y. Go o d s l ik e ca l cu l a t o r s ,

co m p u t e r s a n d co m p a c t d i s c p l a y e r s a s w e l l as el e ct r o n i c co m p o n e n t s e ar n e d $ 6 1 . 2 b i ll i o n i n 1 9 9 8 a n d e m p l o y e d

n e a r l y 1 3 0 0 0 0 p e o p le in t h e i r m a n u f a ct u r e .


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c o n t e n t s c o n t e n t s

Use of Cathode-Ray OscilloscopeAction and Use of Circuit Components

Chapter Review

Use of Cathode-Ray Oscilloscope

Action and Use of Circuit Components

Chapter Review


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A cathode ray oscilloscope (C.R.O) is an instrument thatshows how voltage drop across a device varies with time.

A cathode ray oscilloscope (C.R.O) is an instrument thatshows how voltage drop across a device varies with time.

u se o f ca t h od e - r ay o sci l l o scop e u se o f ca t h od e - r ay o sci l l o scop e when the electron beam strikes the screen, it creates a bright dot

an evacuated glass tube

works on the principle of the deflection of an electron

beam by an electric field

works on the principle of the deflection of an electron

beam by an electric field

a. filamen t

b._____c d. e. f.

g.


4/23

Functions of the parts

a. Filament: Produces heat when current flows through it.

b. Cathode: Absorbs heat from filament. Emits electrons.

c. Grid: Controls the rate of electrons reaching the screen.Hence, it controls the intensity of light spot on the screen.

d. Anode: Focuses and accelerates electrons into a fine beamthat moves at high speed.


5/23

Functions of the parts

e. Y-plates: Voltage connected to the Y-plates; deflects theelectron beam vertically.

f. X-plates: Voltage connected to the X-plates; deflects theelectron beam horizontally.

g. Fluorescent screen: Light is produced when electron beam

hits the screen.


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CRO

On/off switch: Switch on andadjust intensity of light spot. Focus : Turn to focus light spot. X-shift/Yshift : Turn the X-shift

and Y-shift to move the lightspot to the centre of the screen. Y-gain : Fix the sensitivity of Y-

plates marked in volts per

division. Time base : When on, light spotmoves repeatedly across thescreen. Marked in millisecondper division.

Y-input : Connect input voltageto Y-plates.

on/off switch

focusX-shift

Y-shift

+

Y-input

Y-gainTime-base

Time-basefine tuning


7/23

spot is deflected by different steady voltages on the Y-plates

m ea su r i n g v o l t a g es m ea su r i n g v o l t a g es

u se o f ca t h od e - r ay o sci l l o scop e u se o f ca t h od e - r ay o sci l l o scop e

Effect of a d.c. voltage applied to the Y-plates:Effect of a d.c. voltage applied to the Y-plates:


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CRO: To measure Potential Difference Switch off time base.

Connect potentialdifference to bemeasured to Y-input.

Set Y-gain to asuitable value, e.g. 2.0V per division.

a. To measure e.m.f. of acell.E.m.f. of cell= deflection x gain=

on/off switch

focus

X-shift

Y-shift

+

Y-gain

2.0 V per division

Time-base:off Time-base

fine tuning:off


9/23

CRO: To measure Potential Difference Switch off time base.


Set Y-gain to asuitable value, e.g. 1.5V per division.

a. To measure p.d. acrossa bulbp.d. of bulb=

on/off switch

focus

X-shift

Y-shift

+

Y-gain

1.5 V per division


fine tuning:off


10/23

CRO : To measure Potential Difference Switch off time base.


Set Y-gain to asuitable value, e.g.1.0V per division.

a. To measure a.c. voltagepeak voltage Vo= (vertical length) x Y-gain=

on/off switch

focusX-shift

Y-shift

+

Y-gain

1.0 V per division


fine tuning:off


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pr epa r in g t h e C.R.O fo r u se p r epa r in g t h e C.R.O fo r u se


very low frequency low frequency high frequency

time basetime baseo effects of different time base settingso effects of different time base settings

o as the distance moved by the spot is proportional to time,the horizontal deflection is a measure of time

o as the distance moved by the spot is proportional to time,the horizontal deflection is a measure of time


12/23

CRO : To display waveform of a voltage The waveform of a

voltage is the graph of voltage against time.

Connect voltage to theY-input.

Select a suitable valueof Y-gain, e.g. 1.0Vper division.

Switch time-base onand adjust the finetuning until a steadytrace is obtained onthe screen.

on/off switch

focus

X-shift

Y-shift

+

Y-gain

1.0 V per division

Time-base:onTime-base

fine tuning:on


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when an alternating voltage is applied to the Y-plates,the spot will move up and down along the vertical axisat the same frequency as the alternating voltage

when an alternating voltage is applied to the Y-plates,the spot will move up and down along the vertical axisat the same frequency as the alternating voltage



5. Effect of an a.c. voltage applied to the Y-plates:5. Effect of an a.c. voltage applied to the Y-plates:

A

B


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length of the vertical line AB gives the peak-to-peak

voltage (V pp ) applied to the Y-platespeak voltage:

length of the vertical line AB gives the peak-to-peak

voltage (V pp ) applied to the Y-platespeak voltage:

Vp =Vp = 2

Vpp

A

B

m ea su r i n g v o l t a g es m ea su r i n g v o l t a g es u se o f ca t h od e - r ay o sci l l o scop e u se o f ca t h od e - r ay o sci l l o scop e

Effect of an a.c. voltage applied to the Y-plates:Effect of an a.c. voltage applied to the Y-plates:

Voltage /V


15/23

CRO : To display waveform of an a.c. supply The waveform of a

voltage is the graph of voltage against time.

Connect voltage to theY-input.

Select a suitable valueof Y-gain, e.g. 1.0Vper division.

Peak voltage =

Switch time-base onand adjust the finetuning until a steady

Period =

Frequency =

on/off switch

focus

X-shift

Y-shift

+

Y-gain

1.0 V per

division

Time-base on: 5 ms per division


16/23

A C.R.O can be used as a d.c. or a.c. voltmeter when:the time base is off

the voltage to be measured is applied to the Y-plates bythe Y-input terminalsthe deflection of the spot is proportional to the voltageapplied

A C.R.O can be used as a d.c. or a.c. voltmeter when:the time base is off

the voltage to be measured is applied to the Y-plates bythe Y-input terminalsthe deflection of the spot is proportional to the voltageapplied




17/23


18/23

d i sp l ay i n g w av e f or m s d i sp l ay i n g w av e f or m s


A microphone is connected to the Y-input terminals,waveform of sounds from different musical instruments

can be seen on the screen.

A microphone is connected to the Y-input terminals,waveform of sounds from different musical instrumentscan be seen on the screen.

violin

trumpet

clarinet


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m easu r i n g sh o r t t i m e i n t er v a l s m easu r i n g sh o r t t im e in t er v a ls


A C.R.O. can be used to measure short time intervals.A C.R.O. can be used to measure short time intervals.

a sharp noise like a whistle or a clap will produce a peaka sharp noise like a whistle or a clap will produce a peak


20/23

m easu r i n g sh o r t t i m e i n t er v a l s m easu r i n g sh o r t t im e in t er v a ls


The C.R.O. can be used to find a more accurate value forthe speed of sound (recall chapter 15).The C.R.O. can be used to find a more accurate value forthe speed of sound (recall chapter 15).

highsmooth

wall

d

echo

person whistles

distance between the peaks will give the time for thereflection to come back off the wall; therefore the speedof sound can be calculated

distance between the peaks will give the time for thereflection to come back off the wall; therefore the speedof sound can be calculated


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e.g. To measure short time interval

on/off switch

focus

X-shift

Y-shift

+

Y-gain

1.0 V per division

Time-base on: 10 ms per division

7.5 m

Determine the speedof sound.


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t h e t e l ev i si o n t u b e t h e t e l ev i si o n t u b e


In a televisionset, magneticcoils instead of electric fieldplates are usedto deflect the

electron beamsbecause theygive a muchwider angle of

deflection.Relatively shorttubes are ableto give bigpictures.

In a televisionset, magneticcoils instead of electric fieldplates are usedto deflect theelectron beamsbecause theygive a muchwider angle of

deflection.Relatively shorttubes are ableto give bigpictures.


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t h e t e l ev i si o n t u b e t h e t e l ev i si o n t u b e


two time base circuits are used to trace out the wholescreen of the television:two time base circuits are used to trace out the wholescreen of the television:

o one moves the electron beam vertically down the screeno another moves it acrosso one moves the electron beam vertically down the screeno another moves it across

colour pictures are produced by adding differentphosphors to the fluorescent screencolour pictures are produced by adding differentphosphors to the fluorescent screen

electromagnetic induction c

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