Investigatory Project-Tangent Galvanometer.docx

PHYSICS INVESTIGATORY PROJECT

PHYSICS PROJECT ON:-

TAN GEN T GAL VAN: NAME CLASS :XII OM ROLL NO : SCHOOL ETE : R

2016-17

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. __________ (Subject teacher)

Examiner

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 guidelines issued by CBSE.

INDEX

SL.N O 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11.

TOPIC Introduction Aim Apparatus Theory Procedure Observations Calculations Results Precautions Sources of Error Bibliography

PAGE NO.

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.

AIM To study the earth’s magnetic field using a Tangent Galvanometer.

APPARATUS

 Tangent galvanometer (TG),  Rheostat (R),  Battery (E),  Ammeter (A),  Key (k)  Reversing key  Connecting wires  Meter scale

PRINCIPLE

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.

DIAGRAM

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 nonmagnetic 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 B , the magnet comes to rest making an angle θ with the direction H such that H

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=

μ 4π

2 πIN R

Let B 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) H

BH

tan θ

BH

tan θ

BH

=

μ 4π

2 πIN R

=

10−7

2 πIN R

10−7

=

2 πIN R tan θ

By substituting the value of current I, from Eq. (3) tan θ I BH

μo 2 πN 4 π RH

= =

K=

μo Nk 2R I tan θ

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.

 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.

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.

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,  For direct current

Mea n 

Tan 

0.17 63 0.46 63 0.70 02 1.00 0

1

2

1.

Observ Corre ed cted 0.5 0.5

For revers e curren t 3 4

10

10

10 10

10

2.

1

1

25

25

25

25

25

3.

1.5

1.5

35

35

35

35

35

4.

2

2

45

45

45

45

45

BH=

μ . nK 2. a

B h × 107

3.5630 2.690 2.637 2.510

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,  For direct current

Observ Corre ed cted 1. 2. 3. 4.

1

2

For revers e curren t 3 4

Mea n 

Tan 

BH=

μ . nK 2. a

B h × 107

CALCULATIONS Horizontal intensity of Earth’s magnetic field, Bh

is,

B h=

μ.n. K 2. a

Reduction factor K can be determined from the graph as,

K=

AB BC

RESULT Reduction factor of the given Tangent Galvanometer, K=2.448 A Horizontal component of Earth’s magnetic field, Bh

= 2.8

×10−7

T

RESULT Reduction factor of the given Tangent Galvanometer, K= ______ A Horizontal component of Earth’s magnetic field, Bh

= _____

¿¿ ×10¿

T

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 the magnetic meridian.

BIBLIOGRAPHY  NCERT Physics Text Book for Class XII  Comprehensive Physics Practical Book  www.wikipedia.org/wiki/Galvanome ter  www.icbse.com  www.cbse.nic.in