phylabmanual2013-14

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MGM’s

Jawaharlal Nehru Engineering College,

Aurangabad.

Laboratory Manual of Engineering Physics

FE- 2012-13 (Part-II)

Laboratory : - Physics Dept: - Applied Science

Principal HOD Lab Incharge

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MGM’s

Jawaharlal Nehru Engineering College,

Aurangabad.

Laboratory Manual

Engineering Physics

For

First Year Students

© Author JNEC , Aurangabad

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FORWARD

It is my great pleasure to present this laboratory manual for first year engineering

students for the subject of Engineering Physics keeping in view the vast coverage

required for visualization of concepts of basic Physics with simple language.

As a student, many of you may be wondering with some of the questions in your mind

regarding the subject and exactly what has been tried is to answer through this manual.

As you may be aware that MGM has already been awarded with ISO 9000 certification

and it is our endure to technically equip our students taking the advantage of the

procedural aspects of ISO 9000 Certification.

Faculty members are also advised that covering these aspects in initial stage itself, will

greatly relieve them in future, as much of the load will be taken care by the enthusiasm

and energy of the students once they are conceptually clear.

Dr.S.D.Deshmukh

Principal

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LABORATORY MANUAL CONTENTS

This manual is intended for the first year students of engineering branches in the subject

of Engineering Physics. This manual typically contains practical / Lab sessions related

Physics covering various aspects related the subject to enhanced understanding.

Although , as per the syllabus , only diagrams , circuits are prescribed , we have made

the efforts to cover various aspects of EP subject covering electronic aspects ,

Construction and working of CRT, Laurent’s half shade polarimeter ,Theory of

diffraction grating ,R.P. of telescope ,Transistor characteristics ,diode characteristics

will be complete in itself to make it meaningful , elaborative understandable concepts

and conceptual visualization .

Students are advised to thoroughly go though this manual rather than only topics

mentioned in the syllabus as practical aspects are the key to understanding and

conceptual visualization of theoretical aspects covered in the books.

Good Luck for your Enjoyable Laboratory Sessions

Dr.V.M.Arole Ms.K.R.Zakde

Ms.R.R.Choudhari

HOD,Applied Science Mr.A.B.Itolikar

Ms.S.N.Wankhede

Lecturer,Applied Science Dept

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DOs and DON’Ts in Laboratory

1. Make entry in the Log Book as soon as you enter the Laboratory.

2. All the student should sit according to their roll numbers starting from their left to

right.

3. All the students are supposed to enter the terminal number in the log book.

4. Do not change the terminal on which you are working.

5. All the students are expected to get non-programmable calculators / log tables.

6. Strictly observe the instructions given by the teacher .

Instruction for Laboratory Teachers :

1. Submission related to whatever lab work has been completed should be done

during the next lab session.

2. The promptness of submission should be encouraged by way of marking and

evaluation patterns that will benefit the sincere students.

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SUBJECT INDEX

1) To determine e/m of an electron by Thomson bar magnet method.

2) To determine radius of curvature of a Plano convex lens using Newton’s ring.

3) To determine the specific rotation of sugar using Laurent’s half shade Polarimeter.

4) To determine the wavelength of light by means of plane diffraction grating.

5) To determine the resolving power (R.P.) of a telescope.

6) To study the forward and reverse bias characteristics of a semiconductor diode and zener

diode.

7) To Plot the input and output characteristics of NPN transistor in the common emitter

connection.

8) To determine of α and β of PNP transistor.

9) Study of application of Cathode Ray Oscilloscope (CRO) for Frequency and Amplitude

measurements.

10) To determine the wavelength of LASER source.

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EXPERIMENT NO. 1EXPERIMENT NO. 1EXPERIMENT NO. 1EXPERIMENT NO. 1

Aim: To determine e/m of an electron by Thomson bar magnet method.

Apparatus: Cathode ray tube, wooden stand with graduated scale to mount Cathode ray tube, power

supply, magnetometer, bar magnets.

Theory: An electron is deflected in electric and magnetic fields. However the deflection depends upon

charge ‘e’, mass ‘m’ and velocity ‘v’ of the electron. By arranging crossed electric and magnetic fields,

the electrostatic deflection is counter balanced by magnetic deflection. This condition enables one to

determine the specific charge ‘e/m’ Diagram:

Procedure: The experimental set up is shown in the figure. The cathode ray tube (C.R.T.) is mounted on

a centimetre marked wooden frame having platform length parallel to flight of electron beam. In the

region of deflecting plates CD, the frame carries cross arms on either side on which two bar magnets with

opposite poles facing each other can be placed and suitably displaced.

Thus C.R.T. is placed in magnetic meridian and bar magnet N-S in East-West direction. The

power supply provides necessary voltages to C.R.T. The deflecting voltage between plates CD is

measured by an inbuilt voltmeter. The screen S of C.R.T. has ‘cm’ marks to measure deflection. Line of

flight of electron beam represents X-direction while vertical deflection on fluorescent screen represents

Y-direction.

Set up the apparatus as described above, switch on the power pack , allow warm-up time,

use X and Y deflection knobs to get a point spot at the origin on the fluorescent screen. Note the un-

deflected position of spot.

Now place the bar magnets with opposite poles facing each other on East-West arms on

both sides at an identical distance of ‘5 cm’. Note down the deflection (y cm) on the screen. Now adjust

the Y-deflection voltage so that the deflected spot returns back to its initial position i.e. the un-deflected

position of the spot. Note the deflecting voltage ‘V’ volt.

Repeat the above procedure for magnet position at 7cm.

Switch off the power supply and remove the tube. Place the wooden stand in the same

position as that of the tube. Place the magnetometer and adjust its position for (0-0) i.e. Null Deflection.

Now place the magnets again at 5 cm as in first part and note the deflection at different points along the

axes of the tube. For each reading H=H’tanθ is calculated. A graph of h(l-x) vs x is drawn . The area

under the curve between x=0 and x=l gives the value of the integral in the expression for e/m. Substituting

values of the other quantities p,d,l,H,V and y the specific charge can be calculated.

Transfer the final readings from observation table A to observation table B and complete

the calculations.

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Observation Table : (Part – I )

Sr.No. Dist.of near end of each magnet

from tube ‘x cm’

Deflection on the

screen ‘y cm’

Potential difference between the

plate to bring spot to zero ‘V volts’

E = V/d

Volts/cm

1. 5

2. 7

(Part-II) __

H’=0. 38 Gauss H = mean H

x cm. θ deg.

tanθ

__

H = H’tanθ

Gauss

__

h=H – H

Gauss

λ – x

cm.

h(λ – x)

6

8

10

12

.

.

.

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Calculations : Formula

= emu/gm

Tube constants ( type 8C 2P31):-

i. Length of deflecting plates p=2.0cm.

ii. Distance between deflecting plates d=0.2cm

iii. Distance between edge of deflecting plate and fluorescent screen L=10cm.

iv. p/2+L=11cm.= λ

Result : The specific charge e/m of an electron = emu / gm

QUESTIONS:

1. Write important parts of cathode Ray Tube.

2. Describe working of cathode Ray Tube.

3. Write function of deflecting plates in CRT.

4. What is the experimental arrangement for the determination of specific

charge ‘e/m’ ?

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EXPERIMENT NO. EXPERIMENT NO. EXPERIMENT NO. EXPERIMENT NO. 2222 Aim: To determine radius of curvature of a Plano convex lens using Newton’s ring method.

Apparatus : Travelling microscope sodium lamp, Plano convex lens , optically plane glass plate

inclined at 450 in wooden box, magnifying lens.

Theory : Circular interference fringes produce by enclosing a thin air film of varying thickness

between the surface of the Plano convex lens of large radius of curvature and a plane glass plate

are known as Newton’s ring.

Procedure : Calculate the least count of travelling microscope using following formula.

L.C. of travelling microscope = Value of smallest division on main scale

Total No. of division on vernier scale

The experimental arrangement used is as shown in the figure. A parallel beam of light

from sodium source is reflected down on the Plano convex lens by a glass plate inclined at an

angle of 450 to the horizontal . Newton’s ring are viewed by means of a travelling microscope.

Circular dark and bright rings are observed along with the centre of dark.

Adjust the position of the microscope till the point of intersection of cross wire

coincides with the centre of ring pattern.

Now shift the travelling microscope to the left side till the vertical cross wire become

tangential at the centre of the 10th bright ring . Note the travelling microscope reading i.e. main

scale reading (M.S.R.) and vernier scale reading (V.S.R.) as given in the format.

Shift t the microscope in the reverse direction till the vertical cross wire become

tangential to the 8th,6th,4th ,2nd bright ring and note down (M.S.R.) &

(V.S.R.) every time.

By rotating the travelling microscope screw in the same direction, cross over the

centre of the rings and note down the (M.S.R.) &(V.S.R.) readings for 10th, 8

th,6th,4th ,2nd bright

rings to the right side.The travelling microscope screw should always be rotated in one direction

to avoid any error due to backlash. Transfer the final reading from observation table A to

Observation table B and complete the calculations. Plot a graph of the square of the diameter (

Light source (S)

Microscope (M)

Glass

Plate(G)

Plano-convex Lens

Glass

plate

Figure 1: Newton’s ring apparatus

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Dn2) and the No. of rings (n). The graph should be a straight line, radius of curvature of the plano

convex lens ( R ) is calculated from the graph.

Observation table –A

Sr.No. Position Ring No.(n) M.S.R.

(a)

V.S.R.

V.S.R.×

L.C.(b)

Final

reading

(a+b)

1

2

3

4

5

Left side

(A)

10

08

06

04

02

6

7

8

9

10

Right side

(B)

02

04

06

08

10

Observation table –B

Ring (n) Microscope reading Diameter

Dn=|A-B|

Diameter 2

Dn2 Left side(A) Right side(B)

10

08

06

04

02

Formula :

Dn22 – Dn1

2

Radius of curvature( R) = ----------------------

4λ(n2-n1)

Where , λ = 5980 A0

RESULT : By Newton’s rings experiment radius of curvature of a Plano convex lens is calculated and is

found out to be (R) =..................cm.

QUESTIONS :

1.Define interference phenomenon.

2.Give theory of formation of Newton’s rings.

3.What will be the nature of Newton’s rings if sodium source is replaced by white light merqury source ?

4.State any four applications of Interference in Science and Engineering.

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5. Choose the correct option of the following

(i)A phase difference pi between two interfering beam is equal to path difference

a)twice the wavelength b)equal to wavelength c)half of wavelength d)none of them

(ii). Newton’s rings illustrate the phenomenon of

a) Interference b)Diffraction c) Polarization d) Dispersion

EXPERIMENT NO. EXPERIMENT NO. EXPERIMENT NO. EXPERIMENT NO. 3333

Aim: To determine the specific rotation of sugar using Laurent’z half shade

polarimeter.

Apparatus : Laurent’z half shade polarimeter, source of light , sugar, distilled

water, measuring cylinder, beakers.

Theory : If θ is the optical rotation produced by ‘l’ decimetres of a solution and c

is the concentration in gm/cc, then specific rotation S can be given as ,

S = θ / l c

Diagram:

Procedure : Find out the least count of analyser scale using following formula



Place the polarimeter tube so that the aperture of the tube is in the front

of light. Look through the eye-piece so that the two halves of the half shade device

are clearly visible . Fill the polarimeter tube with distilled water taking care of that

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either there is no air bubble in the tube or if it is there, it remains at the centre part

of the tube.

Place the tube in the polarimeter and observe through the eyepiece-E . In

general we find two semi circles of different colours. By rotating the analyser

eyepiece system, the colour pair gets changed. Let us select a pair of different

colour, say red and blue. By rotating the analyser scale, the colour pair can be

interchange. By rotating the analyser scale, the two colours can be mixed so that

circular field of view appears gray instead of two semicircle of red and blue.

Record the reading of analyser scale at this position.

Prepare a sugar solution by dissolving 10 gm., 8gm, 6gm, and 4gm of sugar

in 100ml of distilled water separately. Fill the polarimeter tube with 10gm

concentration of sugar solution. Adjust the analyser scale until the field of view

appears gray. Note down the analyser reading . Repeat the same procedure for

other sugar concentrations i.e. 8gm,6gm,and 4gm. Adjust the analyser scale until

the field of view appears gray everytime.

Calculate the values of angle of rotation θ for different sugar concentrations

with respect to distilled water. Plot the graph of angle of rotation θ against mass of

sugar n. Graph is straight line, find out its slope.

Calculations :

S = 1000θ / Lm

Where , L= length of polarimeter tube = 20cm

θ = Angle of rotation

m= mass of sugar

Obsrevations:

Length of polarimeter tube = 20cm

Least count of analyser scale=_______

Observation table:

Sr.No. Mass of sugar in water (m) Analyser reading Angle of rotation (θ)

1 Distilled water

2 10gm sugar in 100ml water




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Result : Specific rotation S = __________

0/gm cc

QUESTIONS:

1.What is a Polarimeter ?

2.What are quarter wave plate and half wave plate?

3.Define Specific rotation.

4.What is optical activity ?

5.Optically active substances are those which

a)rotate the plane of polarization b)cause double refraction

c)polarise light d)none of the above


Aim: To determine the wavelength of light by means of plane diffraction grating .

Apparatus : Spectrometer, plane diffraction grating , sodium lamp, magnifying

lens.

Theory: When a parallel beam of monochromatic light is incident normally on a

grating , the transmitted light gives rise to primary maxima in certain specific

direction .

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Procedure : Calculate the least count of spectrometer using following formula

L.C. of spectrometer = Value of smallest division on main scale


Adjust the collimeter and telescope for parallel rays the slit of collimeter is

illuminated by monochromatic sodium light and the position of the telescope is

adjusted such that the image of the slit is obtain at the centre of the field of view of

telescope. Note the position of the telescope on the circular scale and add 900 to

this reading .The telescope is turn to this position. Now the axis of the collimeter

and telescope are at right angle to each other .

Set the diffraction grating on the prism table such that the grating surface is

perpendicular to the prism table . Rotate the prism table and then turn the prism

table a further 450 so that the grating surface is normal to incident light. Now,

rotate the telescope again so as to observe the image of the slit.

Move the telescope till the first order diffracted image is visible on both

sides of the line of direct vision and note the spectrometer reading as window A

and window B. Calculate the angle of diffraction.

Observation Table :

Sr.

No

Order

of

spectrum

Telescope reading at 2θ1= |||| A1-A2|||| 2θ2= |||| B1-B2|||| Mean

2θ

Mean

θ T1 T2 Window

A1

Window

B1

Window

A2

Window

B2

1. n=1

Calculations :

(a+b) sin θ = nλ

Where, a is the width of transparency.

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B is the width of opacity

(a+b) is called width of grating element.

θ is the angle of diffraction

λ is the wavelength of light used.

No. of lines on grating per inch = 15000

Grating element ( a+b ) = 2.54/15000 cm

Result: Wavelength of given sodium monochromatic source is = ………..A0

Questions :

1. What is diffraction of light?

2. Discuss Fraunhofer and Fresnel’s diffraction.

3. What is diffraction grating ?

4. Give the difference between diffraction and interference .

5. Choose the correct option of the following.

(i) The diffraction phenomenon is

a.Bending of light around an obstacle

b.rectilinear propagation of light

c.Oscillation of light in one direction

d.None of them

(ii) To observed diffraction ,the size of the obstacle

a. Should be much larger than the wavelength

b.Has no relation to wavelength

c.Should be of the same order as the wavelength

d.Should be exactly half of the wavelength

(iii) The diffraction property of light confine

a.Wave nature

b.Transverse wave nature

c.Longitudinal wave nature

d.Quantum nature


Aim: To determine the resolving power (R.P.) of a telescope.

Apparatus : Telescope, wire gauge, travelling microscope, adjustable slit,

monochromatic source (sodium light).

Theory: Resolving power of a telescope is defined as the reciprocal of the smallest

angle subtended at the objective of the telescope by two point objects which can be

just distinguished as separate.

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Diagram :

Procedure : Find out the least count of travelling microscope using following

formula.



Find distance between two consecutive wires on given wire gauge using

travelling microscope. Now place the wire guage in front of the source of

monochromatic light as shown. Adjust the telescope so as to observe clear image

of wire gauge. Now attach given adjustable slit on objective of telescope in open

mode.

Continuously observing through the telescope, reduce the slit width

gradually so that the image seen through the telescope just cease to be resolved.

Measure the critical width at this position. Also measure the distance (D) of wire

gauge from the objective of telescope as shown in the figure.

Observation Table :

(A) : To determine the distance between two wires on wire gauge (d) :

Sr.

No

No. of

wire

M.S.R.

(A)

V.S.R. V.S.R.×××× L.C.

(B)

A+B Distance between

two wires (d)

1 00

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2 01

3 02

4 03

5 04

6 05

(B) : To determine critical width (a) :

Sr.No M.S.R.

(A)

V.S.R. V.S.R.×××× L.C.

(B)

A+B = a

1

Formula :

Resolving power (R.P.) of telescope = D/d = a/1.22λ

Where , λ = 5890 A0

D is distance from wire guage till the objective of telescope

d is distance between two consecutive wires on wire guage

a is critical width.

RESULT: Resolving power (R.P.) of telescope is ....................

QUESTIONS:

1.Define Resolving power.

2.Explain the limit of resolution of a telescope.

3.What is Rayleigh’s criterion of resolution ?

4.Find the expression for the Resolving power (R.P.) of telescope.

5.To increase the resolving power of telescope

(i)the focal length of objective has to be increased

(ii)both focal length and aperture of the objective has to be increased

(iii)the wavelength of light has to be increased

(iv)the aperture of the objective has to be increased


SEMICONDUCTOR DIODE AND ZENER DIODE CHARACHTERISTICS

AIM: To study the forward and reverse bias characteristics of a semiconductor diode and

zener diode.

APPARATUS: D.C.Power supply, circuit board, voltmeter, ammeter, semiconductor diode and zener

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diode.

PROCEDURE: Connect the circuit as shown in the diagram. Initially, the connections are made for

forward bias. The positive terminal of the low voltage power pack is connected in series with the

milliammeter to the semiconductor diode. Apply a very small voltage, e.g. 0.1V to the semiconductor

diode and note the reading of milliammeter. Increase the applied voltage gradually and note the

corresponding forward current.

The characteristics for the reverse bias conditions are plotted in a similar way but the positive of the

power pack is connected to the diode in the reverse direction of conduction. Compared to forward

bias, the value of reverse bias voltage is greater. The conduction current is quite small of the order of

microamperes.

For zener diode, the procedure for forward and reverse bias characteristics is the same as above.

OBSERVATION TABLE:

Semiconductor diode Zener diode

Forward bias Reverse bias

Voltage

(V) Vf

Current

(mA) If

Voltage

(V) Vr

Current

(µµµµA)Ir

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0.1 1

0.2 2

0.3 3

0.4 4

0.5 5

0.6 6

0.7 7

0.8 8

0.9 9

1.0 10

GRAPH: Plot the characteristics of the semiconductor diode and zener diode on separate papers. The

forward and reverse bias characteristics are on the same graph paper.

1. Take a graph sheet and divide it into 4 equal parts. Mark origin at the center of the

graph sheet.

2. Now mark +ve x-axis as Vf , -ve x-axis as Vr , +ve y-axis as If, -ve y-axis as Ir.

3. Mark the readings tabulated for diode forward biased condition in first Quadrant and

diode reverse biased condition in third Quadrant for both semiconductor and zener diode

Figure 1-Semiconductor diode Figure 2- Zener diode

Figure 2-

CONCLUSION: Thus the forward and reverse bias characteristics of a semiconductor diode and

zener diode are verified.

QUESTIONS : 1.Explain forward bias and reverse bias conditions of a semiconductor diode.

2.What is a deplation layer?

3.A semiconductor diode is used as

a) an amplifier b)a rectifier c)an oscillator d)a voltage regulator

4. A semiconductor diode utilises ........................ characteristic for rectification.

a)reverse b) forward c) forward or reverse d)none of the above

5. Explain forward bias and reverse bias conditions of Zener diode.


TRANSISTOR INPUT AND OUTPUT CHARACHTERISTICS

Forward bias Reverse bias

Voltage

(V)Vf

Current

(mA)If

Voltage

(V)Vr

Current

(mA)Ir 0.1 01

0.2 02

0.3 03

0.4 04

0.5 05

0.6 06

0.7 6.4

0.8 6.8

0.9 7.2

1.0

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AIM: To Plot the input and output characteristics of NPN transistor in the common emitter

connection.

APPARATUS: Circuit board, D.C. power supply, voltmeter, mill ammeter, micro ammeter, NPN

transistor.

PROCEDURE: Make the connections as shown in the circuit diagram. For input characteristics, the

collector - emitter voltage VCE is kept constant i.e. VCE = 0.6 V and gradually VBE from 0.1 V and

note down corresponding values of IB . The procedure is also repeated for VCE = 1 V .

For output characteristics, the base current IB is kept constant by adjusting base– emitter voltage .

Then VCE is increased gradually and the collector current Ic is noted for each value of VCE . The

procedure is repeated for different values of IB .

OBSERVATION TABLE: Input Characteristics

VCE = 0.6 V VCE = 1 V

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VBE (v) IB (mA) VBE (v) IB (mA)

0.1 0.1

0.2 0.2

0.3 0.3

0.4 0.4

0.5 0.5

0.6 0.6

0.7 0.7

Output Characteristics

IB =0.4mA IB =0.6mA

VCE (v) IC (mA) VCE (v) IC (mA)

1 1

2 2

3 3

4 4

5 5

6 6

7 7

8 8

9 9

10 10

GRAPH: Input characteristics are drawn by plotting VBE versus IB for constant value of VCE.

Output characteristics are drawn by plotting VCE versus IC for constant value of IB.

Input Characteristics Output Characteristics

CONCLUSION: Thus the input and output characteristics of NPN transistor in the common emitter

connection are verified.

QUESTIONS :

1. Define transistor.

2. How transistor represents symbolically?

3. Explain input and output characteristics of npn transistor in CE configuration.

4. Describe working of npn transistor.


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DETERMINATION OF αααα AND ββββ OF PNP TRANSISTOR

AIM: To determine of α and β of PNP transistor

APPARATUS: DC power supply , circuit board, voltmeter, milliammeter, micro ammeter.

CIRCUIT DIAGRAM:

PROCEDURE:

First make the connections for common base circuit. The collector base voltage, VCB is

kept constant at a suitable value. The emitter current IE is increased in equal steps. For each setting of

IE, corresponding value of collector current i.e. IC is noted down. Since IC is nearly independent of VCB,

it is not necessary to repeat the procedure for various values of VCB. Plot transfer characteristics, i.e. IC

v/s IE for constant value of VCB.

In the second part connections are made for common emitter circuit. Keep collector

emitter voltage VCE, constant at a suitable value. Increase IB in equal steps and note the corresponding

IC. Plot IC v/s IB for constant value of VCE.

CALCULATIONS:

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1. Current amplification factor for transistor in common base connections.

∆ IC

α = −−−

∆ IE 2. Current amplification factor for transistor in common emitter connections.

∆ IC

ββββ = −−−

∆ IB

OBSERVATION TABLE:

PART-I : Common base configuration PART-II : Common emitter configuration

VCB = 1.5 V

IE (mA) IC (mA)

1

2

3

4

5

6

7

8

9

10

VCE =1.5 V

IB(µA) IC (mA)

10

20

30

40

50

60

70

80

90

100

CONCLUSION: 1. Current amplification factor for transistor in common base connections is __________

2. Current amplification factor for transistor in common emitter connections is ________

QUESTIONS :

1. Write a short note on p-n-p transistor.

2. Expalin important applications of transistor.

3. What are α and β ?

24


USE OF CRO FOR MEASERMENT OF ELECTRICAL PARAMETER

AIM: Study of application of Cathode Ray Oscilloscope (CRO) for Frequency and Amplitude measurements.

APPARATUS: Function generator, CRO.

PROCEDURE: CRO is used in voltage measurements and waveform observation to highly specialised

applications in all areas of science, engineering and technology. Voltage measured by CRO is peak to peak value.

To measure voltage from the Cathode Ray Tube display we must observe vertical knob expressed in volt /division

and peak to peak deflection of beam i.e. number of division. The peak to peak voltage is

V= (volt /division)×(number of division per cycle)

Time period and frequency can also be measured by CRO. A waveform must be displayed on CRT. Accuracy is

improved if single cycle display fills much of horizontal distance across screen. Time Period is given by

T= (Time / division) × (number of division per cycle)

And frequency is given by

F= 1/T

OBSERVATIONS:

A) Frequency measurements

1) Number of division covered by one cycle (x) = …………..div.

2) Time per division factor (y) = …………….sec.

3) Time for one cycle (T) = (x) × (y) = …………sec.

4) Frequency = 1/T = ………….KHz

B) Amplitude measurements

1) Peak to peak distance covered by waveform = p = ………div.

2) Volt per division factor ( µ ) = ………volt

3) Peak to peak voltage ( A ) = p × µ = ……….volt

4) Amplitude of oscillations = A/2 = ……….volt

CONCLUSION:

QUESTIONS:

1.What is Cathode Ray Oscilloscope ( CRO) ?

2.What is relation between path difference and phase differences?

3. Write in short working of CRT.

4.What is superposition principle?

5.Define frequency .

25


DETERMINATION OF WAVELENGTH OF LASER SOURCE

AIM: To determine the wavelength of LASER source

APPARATUS: LASER source (diode Laser, 5 mW power), diffraction grating of various orders, stand, etc.

PROCEDURE: Keep the laser source and stand for grating as shown in the diagram. Focus the laser beam so as

to get a fine spot on the screen.

Following characteristics are to be studied in case of laser source.

I) Intensity

II) Beam of divergence

III) Change in diffraction pattern obtained on the screen as a function of various gratings.

By measuring distance ‘x’ and ‘y’ (refer diagram), angle θ can be determined.

Using relation (a+b) sinθ = nλ, the wavelength of given laser source can be determined.

CALCULATIONS:

(a+b) sinθ = nλ

where,

(a+b)= width of grating = 2.54/15000

θ = angle of diffraction

n = order of diffraction

λ = wavelength of given laser source

Number of line per inch =15000

CONCLUSION: The wavelength of given LASER source is ...........................A0

QUESTIONS:

26

1.What do you mean by LASERs ?

2.Define spontaneous emission and stimulated emission.

3.How does metastable state act in laser media?

4.What are different uses to which laser beams are put?

5.Which of the following is not a laser property ?

a)Coherence b)Highly directional c)Extreme brightness d)Divergence

List of Experiments

Subject: - Engineering Physics

11) To determine e/m of an electron by Thomson bar magnet method.

12) To determine radius of curvature of a Plano convex lens using Newton’s ring.

13) To determine the specific rotation of sugar using Laurent’z half shade Polarimeter.

14) To determine the wavelength of light by means of plane diffraction grating.

15) To determine the resolving power (R.P.) of a telescope.

16) To study the forward and reverse bias characteristics of a semiconductor diode and zener diode.

17) To Plot the input and output characteristics of NPN transistor in the common emitter connection.

18) To determine of α and β of PNP transistor.

19) Study of application of Cathode Ray Oscilloscope (CRO) for Frequency and Amplitude

measurements.

20) To determine the wavelength of LASER source

phylabmanual2013-14

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