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QMP 7.1 D/F

Channabasaveshwara Institute of Technology (An ISO 9001:2015 Certified Institution)

NH 206 (B.H. Road), Gubbi, Tumakuru – 572 216. Karnataka.

Department of Physics

Engineering Physics Laboratory

17 PHYL 17/27

Bachelor of Engineering – 1st / 2nd Semester

All Engineering Branches

Laboratory Manual

2017-18

Prepared by Approved by

Mr.Vageesh V.Kantli Dr.Shivaprakash M.C

Assistant Professor Asso.Prof, and HOD.

Engineering Physics Laboratory 17 PHYL 17/27 2017-18

Department of Physics, C.I.T, Gubbi. 2

Diagram:

Observations:

Diffraction Order

m

Distance 2Xm

in cm

Xm

in cm

Diffraction angle

1tan mm

x

R

in degree

Wavelength sin md

m

in metre

1 θ1 = λ1 =

2 θ2 = λ2 =

3 θ3 = λ3 =

4 θ4 = λ4 =

5 θ5 = λ5 =

av = …………………. m

av = …………………. nm

Calculations: Evaluation:

2X1 =

X1 =

θ1=

λ1 =

Department of

Physics

Particulars Max

Marks Marks

Obtained

Observation 05

Conduction 10

Viva -Voce 05

Total 20

Signature of Staff with date

Signature of Student with date



Experiment No. : 1 Diffraction Date: Aim: To determine the wavelength of the laser by diffraction using grating. Apparatus: Diode laser source, grating (2500 LPI) with holder, scale, screen and thread. Principle: Diffraction of light occurs when the width of the obstacle is comparable to the

wavelength of the source. The light from the laser source is allowed to fall normally on the

grating, by measuring the distance between the diffracted spots, the wavelength of laser

light is determined.

Formula:

Wavelength of the laser source, λ = m

d msin metre

Where θm is the angle of diffraction corresponding to mth order principal maximum.

m = 1, 2, 3… is called order of diffraction, d is the grating constant

For 2500 lines per inch of a grating; ‘d’ can be calculated as below

m10m10X01.198425.19/m

1

/0.0254m2500

1

inch/ 2500

1

inch / linesofNumber

1d 55

1tan mm

x

R

Where Xm is the distance of mth order diffraction maximum from the central

maximum measured in cm, R=distance between screen and grating = 100cm

Procedure:

1. Place the grating in its holder and the screen is placed at a distance of 100cm

2. The grating is kept between the laser source and the screen.

3. The laser beam after passing through the grating undergoes diffraction. The

diffraction spots are observed on the screen.

4. The distances 2Xm between the symmetrical spots on either side of 0th order are

measured and entered in the tabular column.

5. The angle of diffraction θm is calculated using1tan m

m

x

R

.

6. is calculated using the formula sin md

m

Result:

The wavelength of the given Laser light source λ = ………..…nm.



Circuit diagram: Nature of graph:

Observations:

Voltage V

in volts

Current

I in mA

Power

P=VI in watts

Resistance

R=V / I in Ω

log10 P log10R

1.8

2.0

2.2

2.4

2.6

2.8

3.0

3.2

3.4

3.6

3.8

Calculations: Evaluation:

V = I=

P = V I =

log10P =

R = V / I =

log10R =

Department of

Physics

Particulars Max

Marks Marks

Obtained

Observation 05

Conduction 10

Viva -Voce 05

Total 20

Signature of

Staff with date

Signature of

Student with date

Log10 P

C

A

B B

B Log10 R

Slope = AB/BC



Experiment No. : 2 Stefan’s law Date: Aim: To verify the Stefan’s fourth power law of radiation by electrical method.

Apparatus: 6V Electric bulb, voltmeter (multimeter), DC milliammeter, resistance coil

(50E/10W), power supply (20/30V) and connecting wires.

Principle and Formula: Stefan’s law states that the energy radiated by a perfect black

body is directly proportional to fourth power of absolute temperature.

E α T4 i.e. E = T4

Where = Stefan’s constant = 5.67x10-8 W/m2K4 4= Stefan’s index

The power dissipated from the bulb is given by P = VI in watts

VR

I Where V= voltage across the bulb in volts

I = current through the bulb in mA Procedure:

1. Electrical connections are made as shown in the circuit diagram.

2. The battery is switched on, the voltage across the bulb is increased as 1.8 volts, 2.0,

2.2, 2.4,…………………….4.0 Volts.

3. At each stage the voltmeter reading(V) and milliammeter reading I (in amperes) are

noted and power dissipated in the filament of the bulb Power P=VI in watts is

calculated.

4. The resistance of the filament R=V/I , log10P and log10R are calculated .

5. A graph is drawn by plotting log10 P along the Y-axis and log10R along the X-axis.

6. The value of the slope of the straight line graph gives the Stefan’s index. Result:

The value of Stefan’s index = ……….



Observations:

Nature of graph Evaluation:

Capacity of a capacitor C = R

t

693.0 farads

Dielectric constant of a capacitor Calculations: C= Єr=

C= Єr=

Time t

in sec

Voltage ‘V’ across the capacitor in volts

During Charging

During Discharging

0 0.00

10

20

30

40

50

60

70

80

90

100

110

120

Department of

Physics

Particulars Max

Marks Marks

Obtained

Observations 05

Conduction 10

Viva -Voce 05

Total 20

Signature of

Staff with date

Signature of

Student with date

.

693.0

10

0

6

RBL

dtr

Circuit Diagram:



Experiment No. : 3 Dielectric Constant Date:

Aim: To determine the dielectric constant of a capacitor.

Apparatus: Electrolytic capacitor of 2200 F, Voltmeter (multimeter), a resistor (10 K),

two-way key, power supply (20/30V), Stop clock and connecting wires.

Formula: t t C = = farads Rloge2 0.693R Where t = time corresponding to intersection of the two curves Dielectric constant of a capacitor = Where Єo = 8.854x10-12 F/m, L: length of capacitor strip =0.55m, B : Breadth of capacitor strip=1.5x10-2 m, d: distance of separation of capacitor strips=100x10-6m ,

R: resistance=10x103. Procedure:

1. Electrical connections are made as shown in the circuit diagram and the voltage in

power supply is set to 8V.

2. A stop-clock is started and circuit is closed (by closing the plug key K1) simultaneously.

3. The potential difference V across the terminals of capacitor is noted at every 10

seconds interval, till 120 seconds during the charging of capacitor and reading are

entered in the tabular column. R=10K.

4. The stop clock is stopped and reset, the plug key is removed.

5. The plug key is transferred from K1 to K2 and stop clock is started simultaneously

6. The potential difference V across the terminals of capacitor is noted at every 10

seconds interval, till 120 seconds during the discharging of capacitor and reading are

entered in the tabular column.

7. A graph of time t versus potential difference V is plotted for both charging and

discharging of the capacitor in the same graph

8. The time t corresponding to the intersection of the curves is determined.

Result: t Capacity of a capacitor C = =……………farads 0.693R C =…………..μf

Dielectric constant of a capacitor Єr=……………………

RBL

dtr

0

6

693.0

10



Circuit diagram: Observations:

Sl. No.

Low intensity of bulb

(For I=4A)

Moderate intensity of bulb

(For I=8A)

High intensity of bulb

(For I= 12A) Biasing voltage

in volts Current

in A Biasing voltage

in volts Current

in A Biasing voltage

in volts Current

in A 1 0 0 0 2 1 1 1 3 2 2 2 4 3 3 3 5 4 4 4 6 5 5 5

Nature of graph: Evaluation:

Department of

Physics

Particulars Max

Marks Marks

Obtained

Observation 05

Conduction 10

Viva -Voce 05

Total 20

Signature of

Staff with date

Signature of

Student with date

in Volts

in μA



Experiment No. : 4 Photodiode Characteristics Date:

Aim: To study the I – V characteristics of the given Photodiode in reverse bias and

variation of photocurrent as a function of reverse voltage and intensity.

Apparatus: Photodiode, bulb, power supply and microammeter. Principle:

Photodiode is a two terminal junction diode in which the reverse saturation current

changes when it’s reverse biased junction is illuminated by suitable wavelength of light.

When a p-n junction is reverse biased, a small amount of reverse saturation current

is due to thermally generated electron-hole pairs. The number of these minority charge

carriers depends on the intensity of light incident on the junction. When the diode is in a

glass package, light can reach the junction and thus changes the reverse current.

Procedure:

1. The electrical connections are made as shown in the circuit diagram; taking care that

photodiode is reverse biased.

2. Battery is switched on, the voltage across the bulb is increased till the micro

ammeter reads photocurrent of 4μA

3. For this fixed intensity of the bulb the reverse bias voltage across the photodiode is

varied as 0, 1, 2, 3, 4 and 5 volts and the corresponding microammeter reading is

recorded in the tabular column.

4. The experiment is repeated by varying the intensity of the bulb for 8 μA and 12 μA

5. The graph is plotted between current versus voltage for different intensity of the bulb.

6. The characteristics of photodiode in reverse bias condition are obtained as shown in

the nature of graph.

Result:

The I-V characteristics of the given photodiode for different intensity of light

as represented in the graph.



Circuit diagram:

Observations: Forward Bias Characteristics Reverse Bias Characteristics

Evaluation: Calculations:

Forward voltage VF in volts

Forward current IF in mA

0.00

0.10

0.20

0.30

0.40

0.50

0.60

Reverse voltage VR in volts

Reverse current IR in mA

0.0

2.0

4.0

6.0

8.0

10.0

11.0

Department of

Physics

Particulars Max

Marks Marks

Obtained

Observations 05

Conduction 10

Viva -Voce 05

Total 20

Signature of

Staff with date

Signature of

Student with date

Slope= AB/BC

VF VR

IF

IR

Vz

VK



Experiment No. : 5 I-V Characteristics of Zener Diode Date:

Aim: To study the I-V characteristics of the given zener diode and hence to determine

the knee voltage, forward resistance of the diode under forward biased condition and zener (breakdown) voltage under reverse biased condition.

Apparatus: Zener diode, resistor (100Ω), milliammeter, voltmeter (multimeter), power supply (20/30V) and connecting wires. Procedure: Forward bias characteristics: 1. The electrical connections are made as shown in the circuit diagram (1). Taking care

that P side of the diode is connected to positive terminal of the battery through the

resistance R=100. 2. The voltage VF across the diode is varied in steps of 0.1V, till the milliammeter reads

IF = 0.5mA. (Use only fine knob) 3. After that vary the voltage VF in the interval of 0.02V till milliammeter reads IF = 20 mA

readings IF and VF are entered in the tabular column 4. A graph of IF along Y-axis verses VF along X-axis is plotted which gives the forward

bias characteristics of the zener diode. 5. Draw a tangent to the curve at which the current suddenly increases and the point of

intersection of the tangent with the X-axis gives the knee voltage. 6. Construct a triangle ABC by drawing tangent AB to curved portion. 7. The reciprocal of the slope of the tangent 1/Slope = BC/AB gives the forward

resistance (RF) of the zener diode. Reverse bias characteristics:

1. The polarity of the Zener diode is reversed as shown in diagram (2). 2. The voltage VR across the diode is varied in steps of 2V till milliammeter reads

0.5mA.(Use course knob up to 11V) 3. Thereafter the voltage VR is varied in the interval of 0.02V till milliammter reads 20mA.

Using fine knob. 4. At each stage voltage VR and the current IR through the zener diode is noted. 5. A graph of IR along –ve Y-axis versus VR along –ve X-axis is plotted on the same

graph which gives the reverse bias characteristic of the zener diode. 6. A tangent is drawn to the curve at the point current increases suddenly and the

interception of the tangent with the –ve X-axis gives the zener (breakdown) voltage (VZ)

Result:

The I-V characteristics of the given Zener diode are drawn.

The Knee Voltage VK = ……………V

The zener (breakdown) voltage VZ =…………V

Forward Resistance of a diode RF = ……………



Circuit diagram: Observations: C = 1 µF, R = 100 Ω, L = 1 H

Series Resonance circuit:

The series resonance frequency fr=……….Hz

Bandwidth =……….Hz

Quality factor Q = …….

Frequency ‘f’

In Hz

Ammeter reading

‘I’ in mA

40

80

120

160

200

240

280

320

360

400 Nature of Graph:



Experiment No. : 6 Series and Parallel LCR Circuits Date:

Aim: To study the frequency response characteristics of a series and parallel resonance circuits and hence to determine the resonance frequency, bandwidth and the quality factor of the circuits. Apparatus: Audio frequency oscillator, Copper ballast /choke (Inductor), L = 1 H, Capacitor C=1μF, Resistance box R = 100 Ω, AC milliammeter and connecting wires. Formula: Bandwidth = (f2 - f1 ) Hz

Where f2 = Upper cut-off frequency in Hz.

f1 = Lower cut-off frequency in Hz.

fr = Resonance frequency in Hz

The quality factor of the circuit is given by

r

2 1

fQ=

f f

Common procedure for both series and parallel:

1. The electrical connections are made as shown in the circuit diagram.

2. The frequency generator is switched on and frequency is set at 40 Hz, the milliammeter

reading is noted.

3. The frequency is increased in steps of 20Hz up to 400Hz and in each time

corresponding milliammeter reading is noted.

a. Series resonance circuit:

1. A graph is plotted by taking frequency along the X-axis and current along the Y- axis.

2. The frequency corresponding to the maximum value of current (Imax) which is

called resonance frequency ( fr ) is noted from the graph.

3. The maximum value of current (Imax) of a resonance curve for a particular value is

noted.

4. A straight line parallel to X - axis corresponding to the value of (Imax / √2) is drawn

on the curve such that the line cuts the curve at two points on either side of the

resonance frequency.

5. The frequencies f1 and f2 corresponding to these points are noted from the graph and

the band width (f2 - f1) Hz is calculated.

6. The quality factor of the circuit is then calculated using the relation. r

2 1

fQ=

f f



Circuit diagram: Observations:

C =1 µF, R =100 Ω , L = 1 H

Parallel Resonance Circuit:

The parallel resonance frequency fr=……….Hz Evaluation:



Frequency ‘f’

In Hz

Ammeter reading

‘I’

in mA

40

80

120

160

200

240

280

320

360

400

Department of Physics

Particulars Max

Marks Marks

Obtained

Observations 05

Conduction 10

Viva -Voce 05

Total 20

Signature of

Staff with date

Signature of

Student with date

Nature of Graph:



b. Parallel Resonance Circuit: 1. A graph is plotted by taking frequency along the x- axis and current along the Y- axis.

2. In this case the resonance occurs when the current in the circuit is minimum.

3. Hence the frequency corresponding to Imin gives the resonance frequency fr of the

circuit.

4. A straight line parallel to X- axis corresponding to the value of (Imin X √2) is drawn on

the curve such that the line cuts the curve at two points on both side of resonance

frequency.

5. The frequencies f1 and f2 are noted from the graph and the band width (f2 - f1) Hz is

calculated

6. The quality factor of circuit is calculated using the relation

.

r

2 1

fQ=

f f

Result:

Series Resonance circuit:

The series resonance frequency fr=……….Hz



Parallel Resonance Circuit:

The parallel resonance frequency fr=……….Hz





Circuit diagrams: Identification of circuit elements L, C and R:

Measurement of C:

Capacity of the capacitor, C = µFarads.

Calculations:

C = f2

1

rv

v

c

r

=

Trail no. Terminals Current

in mA Component

1 1 2

2 3 4

3 5 6

Trail No.

Resistance in the Resistance Box

‘r’

in Ω

Voltage across

Resistance Box ‘r’

Vr in volts

Voltage across ‘C’

‘Vc’ in volts

C=f2

1

rv

v

c

r

In µFarads

1 3000

2 4000

3 5000

1 2

3 4

5 6

-

1.5V

mA

+ +

+

Ba P1

P2

C

Vc Vr

Resistance Box

Transformer Output

r



Experiment No. : 7 Black box experiment Date:

Aim: Identification of unknown passive electrical components and determine the value of Inductance and capacitance. Apparatus: The circuit elements L, C and R are enclosed inside a box. Each element is connected between two terminals. Power supply, DC milliammeter, step-down transformer, decade resistance box and voltmeter (multimeter). Procedure: Identification of circuit elements L, C and R:

1. Electrical connections are made as shown in the circuit diagram and the voltage in power supply is set to 1.5V

2. A power supply, a DC milliammeter are connected in series between the P1 and P2.

3. The probes P1 and P2 are connected between each pair of terminals 1 2, 3 4 and

5 6. In each case the current is noted and entered in the tabular column.

4. Current is maximum when inductor is connected. Current is zero when capacitor is

connected. Current is intermediate when resistor is connected.

Measurement of C:

1. The terminals of the capacitor, a resistance box and the terminals of the transformer

output are connected in series as shown in fig.

2. A high resistance of the order of 3000Ω is introduced in the resistance box. The

circuit is switched on.

3. The voltages across capacitor Vc, resistor Vr are noted down using AC voltmeter.

4. The experiment is repeated with two more trials. Readings are entered in the tabular

column.

5. The capacity of the capacitor is calculated using the formula,

C= f2

1

rv

v

c

r

Farad Where f = Frequency of the transformer output= 50 Hz.

6. The average value of ‘C’ is calculated.

Measurement of L:

1. The circuit connections are made as shown in fig. by connecting terminals of the

inductor in series with resistance ‘r’ and transformer output.

2. A resistance of 300Ω is introduced in ‘r’. Circuit is switched on.

3. Using AC voltmeter the voltages across ‘L’ and ‘r’ are noted.

4. Experiment is repeated for r= 400 Ω and 500 Ω.

5. Readings are entered in the tabular column.

6. ‘L’ is calculated using the formula, and Average value of ‘L’ is calculated

L= f2V

rV

r

L

H f=50Hz in each case.

Result: The circuit elements are identified and their values are determined.

L=…………H C=…………µF



Measurement of L:

Trail no.

Resistance in the

Resistance Box ‘r’ in Ω

Voltage across L VL in volts

Voltage across resistance box ‘r’

Vr in volts

L= f2V

rV

r

L

in Henry 1 300

2 400

3 500

Inductance L= Henry

Calculations:

L = f2V

rV

r

L

=

Evaluation:

Department of

Physics

Particulars Max

Marks Marks

Obtained

Observations 05

Conduction 10

Viva -Voce 05

Total 20

Signature of

Staff with date

Signature of

Student with date

L

VL Vr

Resistance Box

Transformer Output

r



Screw Gauge

0

0

95

5

0

(a)

No zero error

i.e Z.E. = 0

Z.C. = 0

(b)

-ve zero error

Z.E. = -ve

Z.C. = +ve

(c)

+ve zero error

Z.E. = +ve

Z.C. = -ve

Observations: No. of rotations given to the screw head =2

No of divisions uncovered on the pitch scale = 2mm

No of divisions uncovered on the pitch scalePitch =

No. of complete rotations given to the head scale =2/2 =1 mm

Pitch

Least Count (L.C) = mmTotal no. of head scale divisions

=1/100=0.01mm

Zero error =…………….divisions. Zero correction = ………… divisions. To find radius of the thin wire for Fermi energy experiment:

Tabular Column:

Trial No.

PSR

in mm HSD

Corrected HSD CHSD = HSD + ZC

Diameter ‘d’ in mm

d = PSR + (CHSD X LC)

1

2

3

Mean diameter d =………….mm Radius r = d/2 =………….mm

To find the thickness of the specimen material for young’s modulus experiment:

Tabular Column:

Zero error =…………….divisions Zero correction = ………… divisions

Trial No.

PSR in mm

HSD Corrected HSD

CHSD = HSD + ZC Thickness ‘d’ in mm


1

2

3

Mean thickness d =………………..mm



Observations:

Tr. no.

Object and

Dimensions

Axis of suspension with figure

Moment of

Inertia I in Kgm2

Time for 10 Oscillations

in sec

Period T T=t /10

in sec 2T

I

kgm2s-2 t1 t2 Avg t

1

Rectangular slab

Mass

M =…….g

=

=……kg

=

Length

l =…..cm

=

=……….m

=

Breadth

B =……cm

=

=………m

=

Passes through the centre

perpendicular to the plane

I1= M(l2+B2)

12

I1=

T1=

2

1

1

T

I

=

2

Passes through centre and

parallel to the breadth

I2 = 12

2Ml

I2=

T2 =

2

2

2

T

I

=

3

Passes through the centre and parallel to the

length

I3 = 12

MB2

I3=

T3 =

2

3

3

T

I

=

4

Circular disc

Diameter D =….cm

= =……m =

R = D/2

=…..m =

Mass M =…….g

=

=……kg

=

Passes through the centre and

perpendicular to the plane

I4 = 2

MR 2

I4=

T4 =

2

4

4

T

I

=

5

Passes through the centre along

a diameter.

I5 = 4

MR 2

I5=

T5 =

2

5

5

T

I

=

6 Irregular

body Any axis

I0 = T0 = =

---------



Experiment No. : 8 Torsional Pendulum Date:

Aim: Determination of moment of inertia of irregular body and rigidity modulus of the

material of the suspension wire (steel) using Torsional pendulum.

Apparatus: Rectangular slab, circular disc, irregular slab, chucks nuts with wire, iron stand,

stop clock, metre scale and Screw gauge.

Procedure: Case A:

1. The length ‘l’ and breadth ‘B’ of the rectangular slab are measured.

2. The rectangular slab is suspended using chuck nuts, wire and stand so that the axis

passes through the centre perpendicular to the plane.

3. It is set to torsional oscillations and time for 10 oscillations is determined and

repeated with one more trials.

4. Average‘t’ and Period ‘T1’ is determined.

5. The moment of inertia I1= )(12

22 BlM

is calculated.

6. 2

1

1

T

I is calculated. And readings are entered in the tabular column.

Case B:

1. The rectangular slab is suspended about an axis passing through centre and parallel

to the breadth.

2. It is set to torsional oscillations, Average‘t’ and Period ‘T2’ is determined The

moment of inertia I2 =12

2Ml is calculated.

3. 2

2

2

T

I is calculated. And readings are entered in the tabular column

Case C:

1. The rectangular slab is suspended so that its axis passes through its centre and

parallel to the length.

2. It is set to torsional oscillations, Average‘t’ and Period ‘T3’ is determined The moment

of inertia I3 =12

MB2

is calculated.

3. 2

3

3

T

Iis calculated. And readings are entered in the tabular column



To find radius of the wire: Zero error =…………….divisions Zero correction = ………… divisions

Trial No.

PSR in mm

HSD Corrected HSD

CHSD = HSD + ZC Diameter ‘d’ in mm


1

2

3

Mean diameter d =………….mm

Radius r = d/2 =………….mm

Length of the Wire L = ………….cm

L= ………………m

Calculations:

meanT

I2

2

1

1T

I

2

2

2T

I

2

3

3T

I

2

4

4T

I2

5

5T

I

mean

2

2

00T

ITI

=

I0 =…………………. Kgm2

n =

24

8

T

I

r

L

Mean

n =………………….. N/m2 Evaluation:

Department of

Physics

Particulars Max

Marks Marks

Obtained

Observations 05

Conduction 10

Viva -Voce 05

Total 20



=

5 =



Case D:

1. The circular disc is suspended about an axis passing through its centre and

perpendicular to the plane.

2. It is set to torsional oscillations, Average‘t’ and Period ‘T4’ is determined The

moment of inertia of the circular disc I4 = 2

MR 2

is calculated.

Where ‘R’ is the radius of the disc.

3. 2

4

4

T

I is calculated. And Readings are entered in the tabular column

Case E:

1. The circular disc is suspended about an axis passing through its centre along a

diameter and set to torsional oscillations.

2. Average‘t’ and Period ‘T5’ is determined

3. The moment of inertia of the circular disc, I5 =4

MR 2

is calculated.

4. 2

5

5

T

I is calculated. And Readings are entered in the tabular column

Case F: 1. The irregular body is suspended about an axis its period of oscillation, ‘T0’ is

determined.

2. Moment of inertia I0 of the irregular body can be determined using the formula

meanT

ITI

2

2

00

3. The rigidity modulus of the wire is calculated using the formula

n =

24

8

T

I

r

L

Mean

where r is the radius of the wire to be determined using screw gauge.

L is the length of the wire. Result:

1. Moment of inertia of irregular body I0= …………….. Kgm2

2. Rigidity modulus of the wire n = …………….. N/m2



Circuit diagram:

Observations: For input characteristics: Nature of Graph:

VCE = 4V

VBE in volts

IB

in µA

0.00

0.10

0.20

0.30

0.40

0.50

V in VoltsBE

IBV = 4VCE

A

A

B

C

Input Resistance Ri = BC/AB



Experiment No. : 9 Characteristics of Transistor Date:

Aim: To study of Input and Output Characteristics of a given NPN Transistor in common emitter (CE) mode configuration and hence to determine the Input

resistance (Ri), Output resistance (R0), Amplification factor (β) and Current gain (α) of

the transistor. Apparatus: Transistor (NPN), DC milli ammeter, DC micro ammeter, DC voltmeter, resistor

(66K), dual regulated DC power supply and connecting wires.

Formula: The amplification factor β in Common Emitter (CE) mode is given by

1B2B

1C2C

II

II

Current gain in CE mode

Procedure: 1. The electrical connections are made as shown in the circuit diagram. Taking care the

terminals of the transistor, micro ammeter, milliammeter and multimeter

2. See that voltage knobs are at minimum position and Input battery and out battery is

switched on the power supply.

Input characteristics:

1. The voltage between the collector-emitter VCE = 4 V is set constant, by varying the

voltage knob of the output battery.

2. The voltage between Base-Emitter VBE is varied in the input battery, in the interval of

0.1V, till the micro ammeter starts showing 1 µA.

3. Thereafter VBE is varied in the interval 0.02 V till micro ammeter reads about 20µA, at

each stage base current IB is recorded.

4. The graph is drawn by taking VBE along X-axis and IB along Y-axis, which gives the

input characteristics.

5. The input resistance of the transistor is calculated using the formula Ri = BC/AB in Ω



For output characteristics:

IB1= 50µA IB2 = 100µA IB3 = 150 µA

VCE

in volts

IC1 in mA

VCE in volts

IC2

in mA VCE

in volts IC3

in mA

0 0 0

1 1 1

2 2 2

3 3 3

4 4 4

5 5 5

Nature of graph:

IB1 =30µA

Evaluation:

Department of

Physics

Particulars Max

Marks Marks

Obtained

Observations 05

Conduction 10

Viva -Voce 05

Total 20

Signature of

Staff with date

Signature of

Student with date

VCE in volts

IB1 =50µA

IB3 =150µA

IB2 =100µA

IC in mA

Output Resistance Ro =BC/AB Ω



Output characteristics: 1. The base current IB1 = 50 µA is set constant by varying the input battery voltage knob.

2. The Collector-Emitter voltage VCE is varied as 0,1, 2, 3, 4 and 5V, at each stage the

Collector current IC is noted

3. The experiment is repeated by keeping IB2 = 100µA and IB3 =150 µA

4. The graph is plotted by taking VCE along X-axis and IC along Y-axis which gives the

output characteristics

5. The amplification factor is calculated using the formula

1B2B

1C2C

II

II

and Current gain in CE mode is calculated using the formula

Results: The input, output characteristics of the given transistor are drawn.

The input resistance of the transistor Ri= ……………..Ω

The output resistance of the transistor Ro= ……………Ω

The amplification factor of a transistor in CE mode β = …….

The current gain α= ……………..



Observations:

50

20/1

V.SinDivisionsTotal

MSD1ofValueMicroscope TravellingofcountLeast =0.001cm

Tabular column for recording MSR and CVD readings

Load on the hanger

in gm

Load increasing (LI) Load decreasing(LD)

MSR in cm

CVD TR

in cm MSR in cm

CVD TR

in cm

0

50

100

150

200

250

Load in

the

weight

hanger

in gm

Travelling Microscope

reading Mean

2

LDLI

in cm

Load

in the

weight

hanger

in gm

Travelling Microscope

reading Mean

2

LDLI

in cm

Elevation

for 150 gm

in cm

Load increasing (LI)in cm

Load decreasing (LD) in cm

Load increasing (LI)in cm

Load decreasing (LD) in cm

0 150

50 200

100 250

Mean Elevation (mean) =……….......cm

=…………..m

Young’s modulus 3

2

2

3

bd

xmgLY in N/m2

Calculations:

m = 150gm=150x10-3Kg, g=9.8 m/s2, L=60cm=60x10-2m, x=15cm=15x10-2m

Diagram:



Experiment No. : 10 Uniform Bending Experiment Date:

Aim: To determine the young’s modulus of a material bar.

Apparatus: A thin bar of material whose young’s modulus is required, two knife-edges

fixed in rigid supports, travelling microscope and set of 50gm weights. Formula:

3

2

2

3

bd

xmgLY in N/m2

Where ‘Y’ is young’s modulus for the material, ‘L’ is the distance between the knife edges in m, ‘X’ is the distance between knife edge and load in m, ‘b’ is the breadth in m and‘d’ is

the thickness of the bar in m, ‘g’ is the acceleration due to gravity in m/s2 and ‘’ is the

elevation of the bar due to a load in metre. m is Elevation for the mass m = 150gm Procedure: 1. The thickness‘d’ of the meter scale is measured using screw gauge.(see page no.19) 2. The breadth ‘b’ of the meter scale is measured using slide calipers. (see page no.34) 3. The meter scale is set horizontally with the support of knife edges K1 and K2. 4. L is the distance between K1 and K2. i.e. L=60cm=60x10-2m 5. A needle is fixed vertically at the centre of the scale using wax. 6. Weight hangers are attached downwards at the ends of the scale 7. Travelling Microscope is focused to the tip of the needle, MSR & CVD are noted and the

total reading is calculated. 8. Readings are recorded in the tabular column with the regular intervals of weights of

50 gm in the hangers. 9. The depression of the scale for 150 gm (m = 150gm=150x10-3Kg) and mean depression

is calculated.

10. The young’s modulus of the material of the scale is calculated using the formula

Result: - The Young’s modulus for the material of the bar is Y=……………N/m2.

Evaluation:

Department of

Physics

Particulars Max

Marks Marks

Obtained

Observations 05

Conduction 10

Viva -Voce 05

Total 20





Diagram: Observations:

50

20/1

V.SinDivisionsTotal

MSD1ofValueTMofcountLeast = 0.001cm

Tabular column for recording MSR and CVD readings

Ring No. Left side readings Right side readings MSR in cm CVD TR in cm MSR in cm CVD TR in cm

12

10

08

06

04

02

Ring

No.

Travelling

Microscope

reading

Diameter

Dm

in cm

Dm2

in cm2

Ring

No.

Travelling

Microscope

reading

Diameter

Dn

in cm

Dn2

in cm2

Dm2 - Dn

2

in cm2 Left side (L) in cm

Right side (R) in cm

Left side (L) in cm

Right side (R) in cm

12 06

10 04

08 02

mean

2

n

2

m DD =…….......... cm2

mean

2

n

2

m DD =…………...x10-4m2

Calculations:

)nm(4

DDR mean

2

n

2

m

R =……………..m



Experiment No. :11 Newton’s Rings Date:

Aim: To determine the radius of curvature of planoconvex lens surface by forming

Newton's rings with it.

Apparatus: Optical arrangement for Newton’s rings, travelling microscope, sodium vapor

lamp, short focus convex lens, reading lens. Formula:

Radius of curvature of the lens R = )(4

22

nm

DD nm

m

Where λ is the wavelength of the monochromatic light, = 5893Å. = 5893 × 10-10m;

Dm and Dn are the diameters of mth and nth order dark rings;(m-n)=6 Procedure:

1. The Least count of travelling microscope(TM) is calculated. 2. The experimental setup is arranged as shown in figure. 3. The TM is focused for the Newton’s rings system. 4. The intersection of the cross wires of TM is focused successively for different rings from

left to right of the rings system. 5. The MSR and CVD are noted and total readings are calculated. 6. The readings are entered in the tabular column. 7. The diameters and squares of the diameters of the rings are calculated.

8. The difference in squares of the diameters 2

n

2

m DD is calculated.

9. The average value of 2

n

2

m DD is calculated.

10. By knowing the value of the of sodium light, radius of curvature of the plano convex lens is calculated using the formula.

Result: The radius of curvature of given Plano convex lens surface is R = ………..m.

R =…………cm Evaluation:

Department of

Physics

Particulars Max

Marks Marks

Obtained

Observations 05

Conduction 10

Viva -Voce 05

Total 20

Signature of

Staff with date

Signature of

Student with date

P



Observations:

Nature of graph:

A R

In Ω C B

O Temp in 0C Evaluation:

Calculations:

Temperature in 0C

V in mV I in mA R=V/I in Ω

80°

75°

70°

65°

60°

55°

50°

45°

Department of

Physics

Particulars Max

Marks Marks

Obtained

Observations 05

Conduction 10

Viva -Voce 05

Total 20

Signature of

Staff with date

Signature of

Student with date

Circuit diagram:

Slope=AB/BC



Experiment No. :12 Fermi energy Date:

Aim: To determine the Fermi energy of copper wire (metal).

Apparatus: A copper wire coil, battery, milliammeter, millivoltmeter (multimeter), beaker

with hot water, thermometer, screw gauge, connecting wires.

Formula:

eVL

SAE

F

19

15

106.1

10437.1

Where A is area of cross section of copper wire A=π r2

in m2 r is the radius (Determine r using Screw gauge) in m ρ is the density of copper wire=8.94 x 103 Kg/m3 S is the slope L is Length of the copper wire (~19.8m) Procedure:

1. The circuit connection is made as shown in the circuit diagram by taking care the

polarities of the milliammeter and multimeter.

2. The coil is immersed in cold water, a thermometer is immersed, 100 resistor is

used the battery is switched on; the voltage is set for 2V.

3. Now the copper wire immersed in hot water, At about 85°C the voltage V in millivolt

and the current I in milliamps are noted and the temperature are noted.

4. The experiment is repeated for every 5°C fall in temperature till 45 °C

5. The resistance R=V/I Ω of the coil for each temperature is calculated.

6. The graph is plotted by taking R along Y-axis and temperature along X-axis

Slope S = AB/BC =…. …………../ 0C is calculated.

Result:

Fermi energy of copper EF= ……..…eV



Vernier Calipers Observations:

cmcm

cm

01.010

1.0

10

10

1

scaleverniertheindivisionsofnumberTotal

readingScaleMain1ofValuecountLeast

To find breadth of the specimen material for Young’s modulus experiment:

Trial No.

MSR in cm

CVD b = MSR + (CVD X LC)

in cm

1

2

3

Mean ‘b’ =………….cm

b =………….x 10-2

m

Definitions and Viva-Voce Questions with Answers

1. WAVELENGTH OF LASER LIGHT USING A SEMICONDUCTOR LASER

1. Diffraction of light: The phenomenon of bending of light around the corners of small obstacles

and hence its encroachment into the region of geometrical shadow. Prof Grimaldi discovered

diffraction of light in 1665.

2. Grating: A grating is a device consists of a large number of parallel slits of the same width

separated by equal opaque spaces. It is used in the field of spectroscopy and determining the

wavelength. Joseph Fraunhoffer was the first to construct a grating.

A grating is made by ruling equidistant fine and parallel lines on an optically flat glass plate by

using a diamond point.

3. Grating element and grating constant: Grating element or grating constant is the sum of the

width of an interspaces and the width of a line. The distance between two adjacent opaque lines in

the grating.

4. LASER: Light amplification by stimulated emission of radiation. It is a process by which a

coherent, highly monochromatic and perfectly parallel beam is obtained.

5. Basic principle of Laser: Radiation interacts with matter under appropriate conditions. The

interaction leads to an abrupt transition of the quantum system such as an atom or a molecule from

one energy state to another. If the transition is from higher state to lower state is through stimulated

emission then it gives rise to highly coherent light, which is the basic principle.

6. Induced absorption: In induced absorption incident photon is absorbed as a result the system is

elevated from a lower energy state to a higher energy state.

7. Spontaneous emission: Spontaneous emission is the emission of a photon, when a system transits

from a higher energy state to lower energy state without the aid of any external agency.



8. Stimulated emission: It is the emission of a photon by a system, under the influence of passing

photon of just the right energy due to which the system transits from higher energy states to a lower

energy state. The photon thus emitted is called a stimulated photon and will have same phase, energy

and direction of movement as that of the passing photon called the stimulated photon.

9. Population inversion: It is an assembly of atoms in a system in which majority of the atoms are

in the excited state. ie., there exists more number of atoms in the excited state than in the ground

state.

10. Pumping: It is the process of rising atoms from the ground state to an excited sate by incidenting

a photon of right energy on the system. 11. What is the difference between interference and diffraction?

Interference is the result of interaction of light coming from two different wave fronts originating

from the same source. While diffraction is the result of interaction of light coming from different

parts of the same wave front.

12. What are the different types of diffractions?

Fresnel diffraction: Here the distance between source and screen is finite. The wave fronts are

spherical. Fraunhofer diffraction: The distance between the source and the screen is infinite. The

wave fronts travelling through the grating are parallel.

13. What is the Condition required for diffraction?

The size of the obstacle must be of the size of the wavelength of laser light.

2. STEFAN’S LAW 1. Stefan’s law: The amount of thermal radiation emitted per second per unit area of the surface of a

black body is directly proportional to the fourth power of the absolute temperature.

2. Perfect black body: A perfect black body is one which absorbs completely the radiations of all

wavelength incidents on it. Circuit’s absorptance is equal to 1.

3. Black body radiation: A perfect black body is heated to a high temperature it emits radiation

consisting of all possible wavelengths. The radiation thus emitted is called the black body radiation.

It is also called full or total radiation.

4. Emissive power of a body: Emissive power of a body at a particular temperature is defined as the

total energy radiated per second. 5. Emissivity: Emissivity is defined as the ratio of the emissive

power of a body to the emissive power of a black body at the same temperature.

6. Radiation of heat: The process of transfer of heat from one place to another along a straight line

without affecting an intervening medium is called radiation.

7. Thermal radiation: The energy emitted by body in the form of radiation by virtue of its

temperature is called thermal radiation of energy.

8. Absorptive power of a body: It is the ratio of the amount of thermal radiation absorbed by the

body in a certain time to the total amount of thermal radiation incident in it in the same time,

9. Transmission coefficient of a body: It is the ratio of amount of thermal radiation transmitted by

the body in certain time to the total amount of thermal radiation incident on it in the same time.

10. Reflection coefficient of the body: It is the ratio of amount of thermal radiation reflected by the

body in certain time to the total amount of thermal radiation incident on it in the same time.

11. What is the theory of Planck’s, regarding radiation?

Radiation can be emitted or absorbed only in discrete units corresponds to an energy E given by

E=h, is the frequency of radiation, h is Planck’s constant. h = 6.625 x 10-34 J-s.

12. Which is the black body in your experiment? Ans: Tungsten filament of the bulb

3. DIELECTRIC CONSTANT OF A CAPACITOR

1. Dielectrics: Dielectrics are insulators. They do not have free electrons and hence do not conduct

electricity. The dielectric material shows the polarization of charges. Ex: air, glass, plastic, water etc



2. Polar molecules: The molecules of a dielectric which act like tiny electric dipoles and possess a

permanent dipole moment but get induced with dipole moment are called polar molecules.

3. Non polar molecules: The molecules of a dielectric which do not possess a permanent dipole

moment but get induced with dipole moment in an electric field are called non polar molecules.

4. Give the two examples of polar and non polar molecules? Water (H2O) & carbon monoxide (CO) are polar molecules and Oxygen (O2) & carbon dioxide

(CO2) non polar molecules.

5. Polarization of charges: When a dielectric slab is placed in an electric field, the positive &

negative charges induced on the opposite faces of a dielectric due to the electric polarization is called

polarization of charges.

6. Dipole: Two equal and unlike charges separated by a finite distance constitute a couple

7. Dielectric break down: The phenomenon due to which dielectric loses its insulating property and

behaves like a conductor is called dielectric break down.

8. Dielectric strength of a dielectric: The maximum value of applied electric field above which

dielectric break down occurs is called the dielectric strength of a dielectric.

9. When can a dielectric be strongly polarized?

A dielectric can be strongly polarized at lower temperature with stronger applied electric field.

10. Capacitor: A capacitor is device which cans stores electric energy by storing electric charges.

11. Capacitance: It represents the charge storing ability of the capacitor. It is equal to the charge

stored in the capacitor under a potential difference of 1 volt.

12. Dipole moment: Product of magnitude of either charge or the distance between the charges.

13. Charging of a capacitor: When a capacitor is in a closed circuit with a dc source and a resistor,

the charge on the capacitor increases with time and reaches saturation.

14. Discharging of a capacitor: When a charged capacitor is in a closed circuit with a resistor, the

charges on the capacitor leak through its dielectric and the resistor. The charge on capacitor

decreases with time and reaches zero. This process is called discharging.

15. Define 1 Farad. Ans: It is the capacitance of a capacitor which holds 1Colomb of charge under a

potential difference of 1Volt.

16. Define Dielectric constant?

It is the ratio of permittivity of any medium to the permittivity of vacuum.

4. PHOTODIODE CHARACTERISTICS

1. Photodiode: Photodiode is a two terminal junction diode in which the reverse saturation current

changes when it’s reverse biased junction is illuminated by suitable wavelength of light.

2. Working principle the photodiode: When a p-n junction is reverse biased, a small amount of

reverse saturation current is due to thermally generated electron-hole pairs. The number of these

minority charge carriers, depends on the intensity of light incident on the junction.

3. How photodiode is different from LED?

In Photodiode the illuminated light produce a reverse saturation current but in LED’s a suitable

biasing current produce a photons of suitable frequency.

4. Factors we must consider while selecting photodiode: Wavelength of light which it is sensitive,

Operating voltage, switching time and mounting.

5. Applications: Photodiodes are used in detection, demodulation, switching, logic circuits,

character recognition, optical communication equipments, encoders etc.

6. Optoelectronics: It is the technology that makes use of the principles of optics and electronics.

Ex: A light emitting diode and photo diode.

7. Why is photodiode not used in forward bias? In forward bias, knee voltage is small (<1V).

Above this voltage, current increases sharply (continuously). But, in reverse bias, current remains

constant up to a large biasing voltage. When light is incident, current increases to a different but

constant value.



5. ZENER DIODE

1. Diode: The diode is a semiconductor device having p-n junction it allows unidirectional flow of

current. 2. Zener diode: A heavily doped P-N junction which has a sharp breakdown voltage is

called as a zener diode.

3. Factor does the breakdown voltage of a zener diode depends: The breakdown voltage of a

zener diode depends upon the amount of doping. If the diode is heavily doped, the depletion layer

will be thin and consequently the breakdown of the junction will occur at a lower reverse voltage.

4. Knee voltage :The forward bias voltage after which there is a sharp increase in current

5. Breakdown voltage: When the reverse bias of a zener diode is increased, a critical voltage is

reached at which the reverse current increases sharply to a high value is called breakdown voltage.

6. What is the difference between an ordinary diode and a zener diode?

Ordinary diode: Operated under forward bias. No extreme doping on either side. Reverse break

down is large. Used in rectifiers and gates.

Zener diode: Operated under reverse bias (in general). doping is extremely high, Both small and

large breakdown types. Used in Voltage stabilizers

7. Uses: It is used as a voltage regulator to provide a constant voltage from a source whose voltage

vary over sufficient range.

8. Characteristics of a Zener Diode: A Graph showing the variation of voltage applied across the

terminals of a diode to the corresponding current is called characteristics of a diode. In case of

junction diodes, there are two types of characteristics, forward and reverse characteristics.

9. Doping : The process of introducing the impurity in a semiconductor is called doping.

10. Zener effect: The effect due to which a large reverse current flow is observed in a heavily doped

diode as a result of tunneling of electrons from p-side to n-side when the diode is under reverse

biased condition.

11. Semiconductor: It is material whose characteristics lei between that of conductor and

insulator. Biasing: Supplying external voltage to the particular diode is called biasing.

6. SERIES AND PARALLEL RESONANCE CIRCUIT 1. Series resonance circuit : A circuit containing an inductor, a capacitor and a resistor in series

with an AC source. 2. Function of Audio Frequency oscillator: An A.F oscillator is a device which can produce

sinusoidal waveforms of any desired frequency ranging from 20Hz to 20 KHz.

3. Resonance in an LCR circuit: The condition in which frequency of the applied current from the

AC source matches the natural frequency of the LCR circuit. When the inductive reactance matches

with the capacitive reactance the resonance occur

4. What is the Impedance of a series LCR circuit under resonance?

Impedance = resistance at resonance. Z = R.

5. Resonance frequency: The frequency at which the resonance occurs is called

6. Bandwidth: The range of frequencies between the cutoff frequencies is called bandwidth.

7. Quality factor: The ratio of a resonant frequency of a circuit to its bandwidth is called

8. Series circuit called as acceptor circuit : Because it accept one frequency component out of the

input signals having different frequencies. The accepted frequency is equal to its own resonance

frequency.

9. Parallel resonance circuit is called a rejecter circuit: Because it rejects the signal having same

frequency as its own frequency.

10. Importance of series resonance circuits: For high frequency A.C in radio communications, a

series resonance circuit is used. LCR circuits are used in frequency filter circuits like high pass

filter, low pass filter and band pass filter.

11. Resistance: The opposition offered to the flow of DC by an element or by a circuit.



12. Capacitor: It is a passive circuit component which stores energy in its electrostatic field.. It

consists of the plates separated by a distance

13. Alternating current: The current which varies periodically with time (in both magnitude and

direction).

14. Why do you need a frequency generator (AC) in this experiment? Why cannot you use DC?

The very aim is to study how the LCR circuit allows / stops the current of a particular frequency

stopping / allowing currents of other frequencies. Hence there is a need for the variable frequency

AC source. Here DC is of no use as it has no frequency.

15. Define frequency and period of AC?

Number of cycles generated per second is called frequency and Time taken to generate one complete

cycle is called period.

16. Uses of an LCR circuit: In radio and TV receivers to select a particular station (frequency).

In communication devices like RADARs, Radio Signal Communication. etc.

17. Define self induction (phenomenon of self inductance).

The phenomenon by which an EMF is induced in a coil (or in a closed circuit) due to change in

magnetic flux linked with the same coil (circuit).

18. Define the self inductance.

It is the emf induced in the coil when rate of change of current (or magnetic flux) in the coil is unity.

19. When is the self inductance said to be 1 Henry?

It is the self inductance of a coil if a pd of 1V is induced in the coil when the current through it varies

at the rate of 1ampere per second (or flux linked with it varies at 1Wb/s).

20. Define phenomenon of mutual inductance?

The phenomenon of inducing an emf in one coil (secondary) by changing current in another coil

(primary) near it.

21. Where is the principle of mutual induction used? Ans: In transformers.

22. Choke: It is an inductance coil used in AC circuits to bring down the value of current without

appreciable power loss.

23. What is rms value of AC?

Square root of the sum of the squares of the instantaneous values taken over a complete cycle. It is

that DC value which produces the same heating effect (power dissipation) in a resistor as the AC

passed through the same resistor.

24. Significance of Quality factor: It measures the sharpness of the allowed frequency.

25. Why current increases till resonance and decreases after resonance in a series LCR circuit?

As frequency increases, the inductive reactance increases and capacitive reactance decreases. The

decrease in the capacitive reactance is very much larger than the increase in the inductive reactance

till resonance. After resonance the increase in the inductive reactance is very much larger than the

decrease in the capacitive reactance.

.

7. TRANSISTOR CHARACTERISTICS

1. Transistor: A transistor is a semiconductor device consisting of two P-N junctions back to back.

It has 3 doped regions and its main action is amplification.

2. Transistor is so named: Transistor term is derived from the combination of two words “transfer”

and “resistor”. When transistors are used in circuits the variations in the low resistance input circuit

are transferred to high resistance output circuit.

3. Name the three regions in a transistor. They are emitter, base and collector .

4. Which region of the transistor is very highly doped?

Emitter of the transistor is very highly doped.

5. How is emitter region different from collector?

Emitter is more heavily doped than the collector.

6. What is the role of emitter, base and collector of a transistor?



Emitter supplies a large number of majority charge carriers of current through the device. Base

controls the flow of charges through the device. Collector collects the majority charge carriers

supplied by the emitter.

7. What is the significance of arrow mark in the symbol of a transistor?

The arrow mark is always on the emitter and it signifies the direction of conventional currents.

8. What is the relation between transistor currents?

The emitter current (IE) is always equal to the sum of base current (IB) and collector current (Ic).

9. Transistor is current control device: By controlling the base current, the outgoing collector

current can be controlled for the given emitter current. Hence a transistor is current control device.

10. Applications of the transistor: In amplification of ac signals and switching (gates) devices of

radio, TV and other communication systems.

11. npn transistor : The transistor in which a p-type sc is sandwiched between two n-type scs.

12. pnp transistor : The transistor in which an n-type sc is sandwiched between two p-type scs.

13. Amplification: The process of increasing the amplitude of weak AC signal (voltage or current)

Without altering the other characteristics (like frequency) of the signal.

14. Mention the three modes in which transistor is operated.

Common base mode, Common collector mode , Common Emitter mode

15. Why CE mode is more often used in the transistor circuit? Ans: CE mode is used more often

because of high input impedance, high voltage gain, high current gain, and power gain.

16. Explain the input and output characteristics.

Input characteristics relate the input voltage with input current at a constant output voltage. In this

experiment the base current IB is the input current, VBE is the input voltage and VCE is the output

voltage. The input characteristics are the curves obtained by plotting IB verses VBE at constant VCE.

Output characteristics relate the output voltage with output current at a constant input current. In this

experiment the collector current IC is the output current, VCE is the output voltage and IB is the input

current. The o/p characteristics are the curves obtained by plotting IC verses VCE at constant IB.

17. What are the three regions of output characteristics curve?

a. Cut off region: It is the region below the curve when the base current is zero.

b. Saturation region: It is a region till the collector current increases sharply.

c. Active region: It is the region where the collector current remains steady.

18. In which region the transistor is operating? Ans: Active region

8. UNIFORM BENDING EXPERIMENT 1. Define stress and strain and state their units?

The magnitude of the attractive or repulsive forces between molecules of a body per unit area is

called stress. It is measured in N/m2.The change of shape or the fractional change of size of a body

by a given set of forces or couples is called strain. Strain has no unit.

2. State Hooke’s law and define Modulus of Elasticity? The stress is proportional to the strain within the elastic limits is called Hooke’s law.

The ratio of any stress to the strain is called modulus of elasticity. It is measured in N/m2.

There are three moduli in use.

Young’s modulus:- The ratio of longitudinal stress to longitudinal strain, within the elastic limits is

called young’s modulus of the material. Its unit is N/m2.

Bulk modulus:-When a uniform pressure is applied over the whole surface of a body, it produces a

Uniform compression. The compression is proportional to the pressure, and the ratio of pressure to

the volume strain is called bulk modulus. It is measured in N/m2.

Rigidity modulus: It is the ratio of shear stress to the shear strain. Its unit is N/m2.

3. List the different stages of elastic properties of matter?

When a load is continuously increased in the case of wire, it reaches different elastic stages like: i.

Elastic limit ii. Permanent set iii. Breaking stress and iv. Yield point.



4. What is Poisson’s ratio? What is its unit? Within elastic limits there is a complete proportionality between the lateral strain and the

longitudinal strain is called Poisson’s ratio. It has no unit.

5. How is bending of a beam related to young’s modulus?

When a beam is bent by an applied couple, its longitudinal filaments are lengthened on the convex

side and shortened on the concave, and thus the resistance which the beam offers to bending, will

depend upon young’s modulus for the material.

6. What is a cantilever?

When one end of a horizontal beam is fixed and the other end is free, it is called a cantilever.

7. Elasticity: The property by virtue of which a body tends to regain its original shape and size

(Original configuration or dimensions) when the deforming forces are removed.

8. Elastic limit: It is the upper limit of the deforming force up to which if the deforming force is

removed, the body completely regains its original condition, and beyond which the body loses its

elasticity and becomes permanently deformed.

9. How is a uniform bending produced?

The pure bending shown in the diagram can be produced by applying four forces to the beam, two

opposite directions in each end. This configuration is known as four point bending and produces a

uniform bending moment over the centre section.

9. NEWTON’S RINGS 1. Interference of light: The modification in the distribution of light energy due to the superposition

of two or more waves of light is called interference of light.

2. Conditions for sustained interference: The light waves superposing at a point must have the

same wavelength or same frequency. The amplitude of superposing light waves should be equal or

almost equal. The waves superposing should either have the same phase or constant phase difference.

Light sources must be very narrow and very close to each other.

3. Coherent sources: Any two sources of light continuously emitting light waves having zero or

constant phase difference are called coherent sources.

4. How Newton’s rings are formed?

When a monochromatic light falls normally on Plano convex lens and glass plate set, the light

reflected by the lower surface of the lens and upper surface of the glass plate superpose to produce

Interference pattern. This circular interference pattern is called Newton’s rings.

5. Why is the central ring is dark? The path difference of (/2) is introduced between the two rays

as a result of the phase change of for ray reflects from glass plate and no phase change for the ray

reflects from plano convex lens. The central ring is dark because the two interfering rays have a path

difference (/2) in spite of the fact that the thickness is zero.

6. How to obtain central bright spot in Newton’s rings? By interpose a film of refractive index

less than that of the material of the lens and greater than that of the material of the plate. Then the

path difference between the two rays becomes produces central bright spot.

7. On what factors does the diameter of a ring depend?

It depends on the wavelength of the light and the radius of curvature of the plano-convex lens.

8. What are the applications of Newton’s rings?

It is used to determine wavelength of unknown light source and radius of curvature of given lens

.

10. FERMI ENERGY

1. Fermi level: The highest energy level in the valence band occupied by electrons in a crystal at

absolute zero of temperature is called Fermi level.

2. Fermi energy: The energy corresponding to the Fermi level is called Fermi energy.

3. What is the importance of Fermi energy?



Electrical conduction takes place only when electrons acquire energy above the Fermi energy.

4. Fermi factor: Fermi factor is the probability of occupation of a given energy state for a material

in thermal equilibrium.

5. Fermi temperature (TF) : It is the temperature at which the average thermal energy of the free

electrons in a solid becomes equal to the Fermi energy at 00K. At this temperature gas can be

considered degenerate. It depends on mass of fermions and energy.

6 Fermi velocity: The velocity of the electrons which occupy the Fermi level is called the Fermi

velocity VF. It is measured by VF = mEF /2

7 . What is the unit for Fermi energy?

Its unit is eV. 1eV is the energy possessed by electron when unit charge is accelerated

through a potential of 1Volts. 1eV = 1.6 x 10-19Cx1V = 1.6x10-19J.12. Fermi Dirac distribution: It is

the representation which depicts the details of distribution of electrons among the various available

energy levels of a material under thermal equilibrium conditions. Fermi factor is called a Fermi

Dirac distribution function.

8. Factors on which EF depends: EF depends on the material and the temperature.

9. How many electrons are there in each energy level? According to Paul’s exclusion principle,

there are 2 electrons are there in each energy level.

10. Paul’s exclusion principle: It states that no two electrons having same quantum number can

occupy the same energy levels in same time.

11. Mean free path (): It is the average distance traveled by the conduction electrons between

successive collisions with lattice ions. It is measured in m.

12. What is meant by collision time () :The average time that elapse between two successive

collisions of an electron with the lattice points is called mean collision time.

13. Relaxation time (r) :Due to sudden disappearance of an electric field across a metal the

average velocity of its conduction electrons decays exponentially to zero. And the time required in

this process for the average velocity to reduce to l/e times its value just when the field is turned off,

is known as relaxation time.

14. Drift velocity: The velocity of the electron in the steady state in an applied electric field is

called the drift velocity (m/s).

15. What is the importance of Fermi energy?

It helps to understand electrical & thermal properties of solids. It explains why electrons do not

contribute significantly to the specific heat of solids at room temperature T. it gives information

about the velocity of electrons which participate in ordinary electrical conduction.

11. TORSIONAL PENDULUM

1. Inertia: Every object continues to be in its state of rest or uniform motion along a straight line

unless compelled by an external agency, is called inertia.

2. Moment of inertia: It is the product of the rotating mass and square of its distance from the axis

of rotation. unit of moment of inertia is Kgm2

3. Rigidity modulus: Within the elastic limit, the ratio of tangential stress to tangential strain.

4. Torsional oscillation: One end of wire fixed to rigid support other end carrying an object is

twisted and released. It execute torsional oscillations.

5. Inertia of rest: Inertia of rest is the tendency of a body at rest to remain at rest. i.e., a body at rest

cannot start moving on its own. Inertia of rest depends on the mass of the body.

6. Inertia of motion: Inertia of motion is the tendency of a body to continue in the state of uniform

motion along a straight line i.e. on its own; the body cannot change either the magnitude or the

direction of its velocity. The inertia of motion of a body depends on the mass as well as the velocity

of the body.



7. Rigid body: A rigid body is one in which the particles of the body remain at fixed distance from

one another. Therefore, the size and shape is not altered by the application of external forces.

8. Translational motion: The motion of a body along a straight or curved path is translational

motion. In translational motion, each particle of the body covers the same distance in a given time.

9. Rotational motion: During the motion of the body if a line of points of the body remain at rest,

the motion is called rotational motion. In rotational motion different particles describe different

distances. Example: spinning top, motion of earth about its own axis, merry go round of a giant

wheel, etc.

10. Factors on which the moment inertia of a body depends: Axis of rotation, distribution of the

mass of the body, shape and size.

11. Torsion of a body: A body is said to be under torsion if it is fixed at one end and is twisted at the

other end bout its axis by means of a torque (couple).

12. Torsional pendulum: A rigid body attached to one end of the wire whose other end is fixed to a

support is capable of oscillating when the rigid body is given torque or rotating effect. This

arrangement is called a torsional pendulum.

13. Torque: A force F acting at a distance r from the axis of a body has a rotational effect on the

body. This rotational effect of a force is called moment of the force or torque.

12. BLACK BOX EXPERIMENT 1. Inductor: It is a passive circuit component which stores energy in its magnetic field.

2. Where do the charges resides in the capacitor? Charges reside on the surface of capacitor plates.

3. Define surface density of charge? Charge per unit area is called surface density.

4. Where does the dielectric material placed in the capacitor? It is placed between the plates.

5. What is the effect of dielectric between the plates of the capacitor? It increases the capacity.

6. What is a resistor?

A resistor is a circuit component which offers a definite amount of opposition to the current flow

7. What is electromagnetic induction?

The phenomenon in which an EMF and hence a current is induced in a circuit due to change in

magnetic flux linked with it.

Scheme of Evaluation

Subject: Engineering Physics Laboratory Subject Code: 15PHYL17

The student has to perform TWO experiments during the practical examination of THREE hours duration. The scheme of valuation shall be as follows:

Description Marks for First

experiment Marks for Second

experiment

Write up: Formula, Tabular column and Circuit diagram / Ray Diagram

3+3+3 = 09 3+3+3 = 09

Experimental set up / Circuit connection 06 06

Conduction and reading 12 12

Graph, Calculations, Results and accuracy 2+2+1+1 = 06 2+2+1+1 = 06

Viva-Voce 07 07

Total = 40 + 40 = 80 Marks Note: The student is required to obtain a minimum of 30 Marks in the practical examination

to pass.

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