PHYSICS LABORATORY MANUAL I B.Sc., II SEMESTER

Department of Physics, GFGC, Thirthahalli.

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PHYSICS LABORATORY MANUAL

I B.Sc., II SEMESTER

DEPARTMENT OF PHYSICS

GOVERNMENT FIRST GRADE COLLEGE

THIRTHAHALLI


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LIST OF EXPERIMENTS

1. ‘q’ by uniform bending

2. ‘q’ by single cantilever

3. Sonometer

4. Torsional pendulum

5. Viscosity of water

6. Volume resonator

7. Surface tension by drop weight method

8. Surface tension of water by capillary rise method


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Expt. Name: ‘q’ BY UNIFORM BENDING

AIM: To determine young’s modulus (q) of the material of the given bar by

method of uniform bending.

APPARATUS: Bar, two knife edges, two scale pans, slotted weight of 50

grams, travelling microscope, slide calipers, screw gauge, a bright pin.

PROCEDURE: The experimental arrangements are made as shown in figure.

Bright pin is fixed vertically at the center of the bar. Care is taken to see that

knife edges and scale pans are symmetrically placed from the two edges of the

bar.

Some dead load is added to the scale pan. A travelling microscope is set in front

of the arrangement and eyepiece is focused and its height is adjusted such that

the tip of the pin coincides with a horizontal cross wire.

The reading on the vertical scale is noted. Equal weights in steps of 50 g are

added equally to the scale pan in increasing steps. In each case microscope is

adjusted by increasing in height in one direction only and the corresponding

reading for the tip of the pin is noted. The experiment is repeated for different

loads. Observations are tabulated. The elevation (y) for different loads (m) are

noted.

A graph of the load against elevation is plotted. The slope of the straight line is

found. Using the meter scale, the distance between the knife edges and scale is

measured. Using a screw gauge, the thickness (d) of the bar is determined.

Using vernier calipers, the average breadth of the bar is measured.

The young’s modulus of the material of the bar is calculated using the formula,

RESULT: Young’s modulus of the material of the given bar, q = ______ Nm-2

.


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OBSERVATIONS:

FORMULA USED:

Where, g = acceleration due to gravity in m/s2.

x = distance between knife edge and scale pan in m.

= distance between two knife edges in m.

b = mean breadth of bar in m.

d = mean thickness of bar in m.

EXPERIMENTAL SET UP:

NATURE OF GRAPH:


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TABLE-1: To determine elevation for different loads:

L.C. of travelling microscope =

= -------cm

Distance between two knife edges, l = _______________m.

Distance between knife edge & scale pan, x = _____________m.

TABULAR COLUMN:

Load in

Kg

Reading in cm Mean reading

in cm

Elevation y in

cm Load increasing Load decreasing

TABLE-2: To determine the thickness of bar:

Pitch of screw gauge, P =

= ---------

L.C. of screw gauge, LC =

= ----------mm.

Zero error with sign, ZE = ___

TABULAR COLUMN:

Trial

no.

PSR in mm HSR in

division

TR=PSR+(HSR-Z)LC in mm Mean [d] in

mm

Mean thickness, d=__________m.

CALCULATIONS:


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Expt. Name: ‘q’ BY SINGLE CANTILIVER

AIM: To determine young’s modulus (q) of the material of the cantilever by

graphical method.

APPARATUS: Cantilever, rigid support, slotted weight of 50 grams, travelling

microscope, slide calipers, screw gauge, a bright pin.

PROCEDURE: One end of the given material in the form of a thin bar is fixed

firmly by means of a given clamp on a support, so that cantilever is projected.

At the other end of the cantilever bar, a scale pan is attached. A bright pin is

fixed vertically at the position of the scale pan by means of wax. A travelling

microscope is set in front of the cantilever and its eyepiece is focused to the tip

of the pin, so that horizontal cross wire coincide with the tip of the pin.

A convenient dead load is placed on the scale pan. The sight of the eyepiece is

carefully decreased only in the one direction and tip of the pin is made to

coincide with the horizontal cross wire, the reading is noted.

Next, convenient slotted weights are added to the scale pan in equal steps and in

each step the reading of the tip of the pin is noted by decreasing the height of

the microscope.

The experiment is repeated by decreasing the load in steps. The average reading

for a particular load is calculated. From these observations, the depression of the

cantilever is calculated for different loads.

Using a meter scale, the length of the cantilever (l), the distance between the

fixed end to the point of suspension of scale pan is measured. Using a screw

gauge, the average thickness (d) of the bar is measured. Using a vernier calipers,

the average breadth (b) is measured. A graph of load vs depression is plotted.

The slope of the straight line is calculated. Young’s modulus of the material of

the cantilever is calculated using the relation,

RESULT: Young’s modulus of the material of the cantilever, q = _____ Nm-2

.


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OBSERVATIONS:

FORMULA USED:

Young’s modulus,

Where, g = acceleration due to gravity in ms-2.

= length of cantilever in m.

b = mean breadth of cantilever in m.

d = mean thickness of cantilever in m.


NATURE OF GRAPH:

TABLE-1: To determine depression for different loads (M):

L.C. of travelling microscope, L.C. =

= -------- cm.

Length of the cantilever, l = __________m.


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TABULAR COLUMN:

Load in

Kg

Reading in cm Mean reading

in cm

Depression y

in cm Load increasing Load decreasing

TABLE-2: To determine the thickness of bar:


= --------- mm.


= ---------- mm.

Zero error with sign, Z = ____

TABULAR COLUMN:

Trial

no.

PSR in mm HSR in

division

TR=PSR+(HSR-Z)LC in mm Mean (d) in

mm

Mean thickness, d= ________m.

Breadth of the cantilever, b = ________m.

CALCULATIONS:


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Expt. Name: SONOMETER

AIM: To determine the frequency of AC by using sonometer.

APPARATUS: Sonometer, electromagnets, step down transformer, weight

hanger, slotted weights etc.

PROCEDURE: The sonometer is set on the experimental table. Weight of 1Kg

is placed on the hanger, the tension T on the hanger is calculated using the

formula, T = (W+x)g in Newton. Where, x is the weight of the hanger and W is

the weight added to the hanger.

The electromagnet is held at the center position of sonometer wire between the

two bridges, such that flat surface of the electromagnet is about one centimeter

above the wire. The terminals of the electromagnet are connected to the output

terminals of the transformer and transformer is connected to the mains.The

circuit is closed. The wire of the sonometer vibrates. The movable bridges are

adjusted on either side, such that the wire is made to vibrate in a single loop

having maximum amplitude.

At this stage, the frequency of wire is equal to frequency of electromagnet so

that resonance occurs. The resonating length (L) of the wire is measured. The

experiment is repeated by increasing tension by 0.5Kg weight for four trials. A

graph of T against l2 is plotted. The slope of the straight line is calculated.

About 1 meter length of a sonometer wire is weighed using a physical balance.

If M is the mass of the wire of length L, the mass per unit length of the wire is

calculated using the formula,

Kgm

-1 and Frequency of AC is calculated

using the formula,

√

.

Observations are tabulated as shown.

RESULT: Frequency of AC, n = ____ Hz.


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OBSERVATIONS:

FORMULA USED:

Frequency of AC,

√

Where, N = frequency of wire in resonance with electromagnet.

T = Tension in Newton.

l = resonating length in m.

m = linear density in Kgm-1

.


NATURE OF GRAPH:


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Observations:

Mass of the L meter length (sonometer wire), M = ________Kg.

Length of the sonometer wire, L = _____m.

Mass per unit length, m =

= _________Kgm

-1.

Weight of hanger, x = _______Kg.

TABULAR COLUMN:

Trial

no.

Weight in

hanger in Kg (x)

Tension

T=(W+x)g in N

Resonating

length ‘l’ in m

in

CALCULATIONS:

Frequency of AC,

√


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Expt. Name: TORSIONAL PENDULUM

AIM: (a) to determine moment of inertia of an irregular body using a regular

body. (b) To determine rigidity modulus of the wire used.

APPARATUS: Irregular body, circular disc, steel wire with chuck nut, stop

clock, screw gauge etc.

PROCEDURE: The Torsional pendulum with circular disc, the axis being

passing at its center is set on experimental table as shown in figure. The circular

disc is set into free Torsional oscillations using the index. 20 oscillations are

counted and time for 20 oscillations is noted using a stop clock. Experiment is

repeated for 3 trials and average time for 20 oscillations is calculated.

Next the circular disc is replaced by the given irregular body and again the

period of oscillations of Torsional pendulum is determined. Using a thread,

circumference of circular disc and hence its radius R is determined. The mass of

circular disc M is found using a balance.

Then, moment of inertia of the disc is calculated using the formula,

in

Kgm2

about an axes passing through its center.

The moment of inertia of an irregular body is then calculated using the formula,

in Kgm2.

Using a screw gauge, the average radius of the suspension wire of the Torsional

pendulum is determined. Using a meter scale, the length ‘l’ of the wire is

determined.

The rigidity modulus of the material of the wire is given by,

Nm-2

RESULT: Moment of inertia of regular body, I = ________ kgm2.

Moment of inertia of an irregular body, = ________ kgm2.

Rigidity modulus of material of wire, = ________Nm-2

.


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OBSERVATIONS:

FORMULA:

(a) Moment of inertia of circular body,

in Kgm

2

Where, M = Mass of disc in Kg.

R = Radius of circular disc in m.

(b) Moment of inertia of irregular body,

in Kgm

2

Where, Tx = Period for irregular body in sec.

T = Period for circular body in sec.

(c) Rigidity modulus of wire,

Nm-2

.

Where, l = length of the wire in m.

r = radius of the wire in m.


Mass of the circular disc, M = _______ Kg.

Radius of the circular disc, R = ________ m.

Length of the wire, l = __________m.


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Table-1: To determine period of regular body about its centre:

TABULAR COLUMN:

No. of

oscillations

Time in

sec.

No. of

oscillations

Time in sec.

Time for 20

oscillations

Mean

0

5

10

15

20

25

30

35

Period, T =

= ------------- sec.

TABLE-2; To determine period of irregular body about its centre:

TABULAR COLUMN:

No. of

oscillations

Time in

sec.

No. of

oscillations

Time in

sec.

Time for 20

oscillations

Mean

0

5

10

15

20

25

30

35

Period, =

= ---------------- sec.


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TABLE-3: To determine the radius of given wire:


= ---------


= ---------- mm.

Zero error with sign, ZE = ____

TABULAR COLUMN:

Trial

no.

PSR in mm HSR in

division


mm

Mean radius,

= ------ = _________m.

CALCULATIONS:


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Expt. Name: VISCOSITY OF WATER

AIM: To determine the co-efficient of viscosity of water by capillary flow

method.

APPARATUS: Aspirator bottle with side hole, a fine capillary tube, stop

clock, measuring jar, beaker etc.

PROCEDURE: The experimental setup is made as shown in the figure. An

aspirator bottle is graduated vertically by means of a graph. A capillary tube of

length l is introduced inside the hole horizontally. The bottle is filled with water

to a considerable level. To preset the water running along the tube, a piece of

thread is tied at the end of the tube and hanging from it.

The free end of capillary is closed by the thumb and height of the water level of

the bottle is noted.

A beaker is placed just below the free end of the tube. Water is collected in the

beaker say for 5 minutes. The height of the water level in the bottle is noted.

The volume of the water ‘v’ collected in the beaker is measured using a

measuring jar.

The experiment is repeated for different time ‘t’ in seconds. Observations are

tabulated and in each case [

] are calculated. The length ‘l’ of capillary tube is

measured. The inner radius of the capillary tube is measured using vernier

calipers. The viscosity of water is calculated using the formula,

[

]

in N sec/m2.

RESULT: Viscosity of water, = ______ Nsm-2

.


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OBSERVATIONS:

FORMULA USED:

Viscosity of water,

[

]

in N sec/m2

Where, g = acceleration due to gravity in m/s2

= density of water in Kg/m3.

r = radius of tube (inner) in m.

t = time of flow of water in sec.

h = height of water above tube in m.

v = volume of water collected in t sec in m3.


Acceleration due to gravity, g = _______m/sec2

Density of water, = _________Kg/m3.

Length of capillary tube, l = _______m.

Radius of capillary tube, r = _______m.


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TABLE-1: To find [

] :

TABULAR COLUMN:

[

]

= ______sec/m2

TABLE-2: To find the radius of the capillary tube:

TABULAR COLUMN:

Trial

no.

Reading in cm Mean diameter d in m

R1 R2 R1 R2

Mean radius,

= ------- = _________m.

CALCULATIONS:

The Coefficient of viscosity of water is,

[

]

in N sec/m2.

Trial

no.

Time

of flow

in sec

Initial height

of water h1 in

m

Final height

of water h2

in m

Mean in m

Volume of

water in

m3

[

] in

sec/m2


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Expt. Name: VOLUME RESONATOR

AIM: To determine the velocity of sound at lab temperature and at 00C using

volume resonator.

APPARATUS: Volume resonator, tuning fork, beaker, measuring jar, vernier

calipers, thermometer etc.

PROCEDURE: The volume resonator is set on the experimental table as

shown in the figure. Water is poured into the resonator up to the base of the

neck. A tuning fork of known frequency is set into vibration by striking it on

the rubber pad and held just above the mouth of the volume resonator

horizontally such that vibrations are parallel to the air column in the neck. Using

pinch cork little water is allowed to fall into a clean beaker till a loud resonance

sound is observed.

The volume of the water V is collected in the beaker is measured using a

measuring cylinder. The experiment is repeated for different tuning forks and

observations are noted.

A graph of f 2

verses 1/v is plotted. The slope of straight line is calculated. The

length ‘l’ of the neck of aspirator bottle is measured. Using vernier calipers, the

inner diameter ‘d’ of the neck is measured. Then the velocity of sound in air at

lab temperature is calculated using the formula,

√

m/s.

If t0C is the lab temperature then, velocity of sound at 0

0C is V0 and is

calculated using the formula, √

.

RESULT: Velocity of sound at lab temperature, V = _______ms-1

.

Velocity of sound at 00C temperature, V0 = _______ms

-1.


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OBSERVATIONS:

FORMULA USED:

(a) Area of the neck,

Where, d = inner diameter of neck in m.

(b) The velocity of sound in air at laboratory temperature,

√

m/sec.

Where, a = area of neck in m2.

l = length of neck in m.

(c) If T0 C is a lab temperature then, velocity of sound at 0

0 C is and is

calculated by the formula, √

Where, f = frequency of tuning fork in Hz.

V = volume of water collected at resonance in m3.

a = area of neck.



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NATURE OF GRAPH:

Observations:

Lab temperature, t = ____ 0 C.

Length of the neck of the bottle, l = ________ m.

Inner diameter of the neck, d = _________ m.

TABULAR COLUMN:

Trial

no.

Frequency of

tuning fork in Hz

Volume of

water v in m3

f 2 in Hz

in m

-3

CALCULATIONS:


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Expt. Name: SURFACE TENSION BY DROP WEIGHT METHOD

AIM: To determine surface tension of water by drop weight method.

APPARATUS: Funnel glass tube, rubber tube, pinch cork, beaker, water,

physical balance, weight box, stop clock etc.

PROCEDURE: The experimental setup is made as shown in the figure. Water

is filled in the funnel by releasing the pinch cork. The air bubbles are removed

which are present in the rubber tube and glass tube.

The pinch cork is tightened and is now adjusted such that about to 8 to 10 drops

are formed at the end of the glass tube per minute. With this adjustment, 30

drops of water are collected in a clean dry weighted beaker.

The beaker with collected water is weighed again. From these observations, the

weight of single drop is calculated. Using screw gauge, the external diameter of

the glass tube at which the drops are formed is determined. Then the surface

tension ‘T’ of water is calculated using the formula,

in Nm

-1. Where, r

is the outer radius of glass tube.

RESULT: Surface tension of water, T = _______Nm-1

.


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OBSERVATIONS:

FORMULA USED:

Surface tension ‘T’ of water,

in Nm

-1

Where, g = acceleration due to gravity in ms-2

.

m = mass of single drop formed in air in kg.

r = the outer radius of glass tube in m.


TABLE-1: To find the mass of a single water drop:

TABULAR COLUMN:

Mass of dry

beaker, m1 in

Kg

Mass of beaker + 30

drops of water, m2 in

Kg

Mass of 30 drops

of water, (m2- m1)

in Kg

Mass of single drop,

in Kg

Mass of a single water drop, m = _________ Kg.


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Table-2: To find the outer radius of the glass tube using screw gauge:


= --------- mm.


= ---------- mm.

Zero error with sign, Z = ____

TABULAR COLUMN:

Trial

no.

PSR in mm HSR in

division


mm

Mean diameter, d= ________mm.

Radius,

= ---- = _________m

CALCULATIONS:


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Expt. Name: SURFACE TENSION OF WATER BY CAPILLARY RISE

METHOD

AIM: To determine surface tension of water by capillary rise method.

APPARATUS: Capillary tube, small beaker, pure water, travelling

microscope, a pin etc.

PROCEDURE: A small beaker containing sufficient water where surface

tension is to be measured is placed on the screw motion adjusted stand.

Capillary tube is held vertically by a stand in such a way that, its lower end is

dipped in the water. A pin is attached to the capillary tube and the stand is

adjusted such that the tip of the pin just touches the surface of water in a beaker.

Due to the surface tension, water raises to a certain height in the capillary tube.

Care is taken to see that, there is no air bubble inside the capillary tube. The

arrangement may be examined with an electrical bulb.

A travelling microscope is arranged in front of the capillary tube. The

microscope is focused such that the horizontal cross wire is made to coincide

with the image of the upper meniscus of water in the capillary tube. The stand

is lowered and beaker with water is removed. The microscope is lowered and is

focused to the tip of the pin and readings are noted. The experiment is repeated

and average height of water in the capillary tube is noted.

The capillary tube is held horizontally. The microscope is focused to the free

end of the tip and the internal diameter and hence internal radius of the capillary

tube is measured.

Observations are tabulated as shown. The surface tension of the water is

calculated using the formula,

[

]

RESULT: Surface tension of water, T = _______Nm-1

.


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OBSERVATIONS:

FORMULA USED: Surface tension of the water,

[

]

Where, g = acceleration due to gravity in m/s2.

d = density of water in Kgm-3

= _______ Kgm-3

r = inner radius of the capillary of the capillary tube in m.

h = capillary rise in m.


TABLE-1: To determine capillary rise:

L.C. of travelling microscope, L.C. =

= -------- cm.

TABULAR COLUMN:

Trial

no.

Reading of the

meniscus h1 in cm

Reading against tip of the

pin h2 in cm

Capillary rise h1-h2

in cm

Mean, h = __________ m


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TABLE-1: To determine the inner radius of the tube:

TABULAR COLUMN:

Position Reading in cm Mean diameter in

cm

Radius in cm

Rl R

ll R

l - R

ll

Horizontal

Vertical

CALCULATIONS:

PHYSICS LABORATORY MANUAL I B.Sc., II SEMESTER

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