Investigatory Project-Tangent Galvanometer.docx

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PHYSICS

INVESTIGATORY

PROJECT

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PHYSICS PROJECT

ON:-TAN

GEN

T

GAL

VAN

OM

ETE

R

2016-17

NAME : CLASS :XII ROLL NO : SCHOOL :

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CERTIFICATE

This is to certify that ___________ of

class XII-A has completed the physics

project entitled: ‘Study on Earth’s

Magnetic Field Using a Tangent

Galvanometer, himself and under

the guidance of Mr/s.___________.

All the work related to the thesis had

been done by the candidate himself.

The approach was sincere and

scientific.

Mr/s. __________ Examiner

(Subject teacher)

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ACKNOWLEDGEMENT

I am grateful to the Almighty to give

me strength to successfully complete

my project.

This project wouldn’t have been

feasible without the proper and

rigorous guidance of my Physics

teacher Mr/s.__________, who guided

me throughout this project in every

possible way.

I am deeply indebted to my school for

providing the best of facilities and

environment to bring out our

innovation and spirit of inquiry

through this venture. This report is

being submitted as a part of practical

examination conducted as per the

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INDEX

SL.N

O

TOPIC

PAGE NO.

1.

Introduction

2.

Aim

3.

Apparatus

4.

Theory

5.

Procedure

6.

Observations

7.

Calculations

8.

Results

9.

Precautions

10. Sources of Error

11. Bibliography

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INTRODUCTION

Tangent Galvanometer is an

early measuring instrument for

small electric currents. It

consists of a coil of insulated

copper wire wound on a

circular non-magnetic frame.

Its working is based on the

principle of the tangent law of

magnetism.

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AIM

To study the earth’s magnetic

field using a Tangent

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Tangent galvanometer (TG),

Rheostat (R),

Battery (E),

Ammeter (A),

Key (k)

Reversing key

Connecting wires

Meter scale

PRINCIPLE

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The working of the tangent Galvanometer is based on the tangent law.

When a bar magnet is suspended in two

Magnetic fields B and Bh, it comes to rest

making an angle θ with the direction of Bh.

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DIAGRAM

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THEORY

Tangent galvanometer is an early

measuring instrument for small electric currents. It consists of a coil of insulated copper wire wound on a circular

non-magnetic frame. Its working is based on the principle of the tangent law of

magnetism.

STATEMENT: When a magnet is suspended freely in two mutually

perpendicular uniform magnetic fields F

and BH , the magnet comes to rest

making an angle θ with the direction H such that

F = BH tan θ

Let a current I be passed through the coil of radius R, having turns N. Then

magnetic field produced at the centre of the coil is

F = 4 πμ

2 πIN

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Let BH is the horizontal component of

earth’s magnetic field and the magnetic needle comes to rest at an angle θ with the direction of BH then Eq. (1) and (2)

BH tan θ = μ 4 π 2 πIN R BH tan θ = 10−7 2 πINR BH = 10 −7 2 πIN R tan θ

By substituting the value of current I, from Eq. (3) tan θ I = μo 2 πN 4 π RH BH = μo Nk 2 R K = tan θI

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radius of coil of galvanometer R,

deflection θ and N, the value of H can be calculated.

PROCEDURE

For performing in real life

Connections are made as shown in the figure, where K is the key, E the battery, A the ammeter, R the rheostat, C the

commutator, and T.G the tangent galvanometer.

The commutator can reverse the current through the T.G coil without changing the current in the rest of the circuit.

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The magnetic field can be

calculated as follows:

1. Make the circuit connections in

accordance with the circuit diagram.

2. Using a spirit level, level the base

and compass needle in compass box of tangent galvanometer by

adjusting the leveling screw.

3. Now rotate the coil of the

galvanometer about its vertical axis, till the magnetic needle, its image in the plane of the mirror fixed at the base of the compass box and the coil i.e., all these three lie in the same vertical plane. In this setting, the ends of aluminum pointer should

read zero-zero. If this is not so, rotate the box without disturbing the

position of the coil till at least one of the ends of the pointer stands at the zero mark.

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4. Note the number of turns in the coil. 5. A suitable amount of current is

passed through the coil.

6. Note down the current as well as the

deflection in the TG.

7. Reverse the current and note the

deflection again.

8. Repeat for different values of

current.

9. Measure the radius of coil from

perimeter.

10. By changing the value of current,

take four or more set of reading and

plot the graph between I and tan.

The graph will be a straight line.

11. Determine the reduction factor and

the horizontal intensity of Earth’s magnetic field.

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OBSERVATIONS

Number of turns in the coil = 300 Outer radius of the coil =16 cm Inner radius of the coil =14 cm Radius of the coil = 15 cm

Table for Variation of



with I.

S. N o. Ammeter Reading (A) Value of deflection, Mea n Tan BH=μ . nK 2. a For direct current For revers e curren t Bh× 107 Observ ed Corre cted1234 1. 0.5 0.5 10 10 10 10 10 0.17 63 3.5630 2. 1 1 25 25 25 25 25 0.46 63 2.690 3. 1.5 1.5 35 35 35 35 35 0.70 02 2.637 4. 2 2 45 45 45 45 45 1.00 0 2.510

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OBSERVATIONS

Number of turns in the coil = ____ Outer radius of the coil = ___ cm Inner radius of the coil = ___ cm Radius of the coil = ___ cm

Table for Variation of



with I.

S. N o. Ammeter Reading (A) Value of deflection, Mea n Tan BH=μ . nK 2. a For direct current For revers e curren t Bh× 107 Observ ed Corre cted1234 1. 2. 3. 4.

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CALCULATIONS

Horizontal intensity of Earth’s magnetic field,

Bh is, Bh=

μ . n . K

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Reduction factor K can be determined from the graph as

, K=

BCAB

RESULT

Reduction factor of the given Tangent Galvanometer,

K=2.448 A

Horizontal component of Earth’s magnetic field,

Bh = 2.8 ×10−7

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RESULT

Reduction factor of the given Tangent Galvanometer,

K= ______ A

Horizontal component of Earth’s magnetic field,

Bh = _____ ¿¿

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PRECAUTIONS

1. The battery should be freshly charged. 2. The magnetic needle should swing freely

in the horizontal plane.

3. The plane of coil must be set in magnetic meridian.

4. All the readings must be adjusted between 30o and 600.

5. There should be no parallax in noting

down the reading of ammeter and defletion.

SOURCES OF ERROR

1. There may be a magnetic material around the apparatus.

2.The plane of the coil will not be exactly in

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BIBLIOGRAPHY

NCERT Physics Text Book for Class

XII

Comprehensive Physics Practical

Book

www.wikipedia.org/wiki/Galvanome

ter

www.icbse.com

Figure

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References