Physics investigatory report - vanasthalischool.invanasthalischool.in/pdfs/physics-XII.pdf · The tangent galvanometer is an early measuring instrument for Current The magnetic field

Prepared by: Amit sh (XII-B/A/C ) Roll No:

PHYSICS INVESTIGATORY REPORT

EARTH MAGNETIC FIELD’S MAGNETIC FIELD USING TANGENT

GALVANOMETER

Amit sh | Vanasthali public School | XII- B/A/C

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PHYSICS

INVESTIGATORY

REPORT

EARTH MAGNETIC FIELD

Although historically ancient travelers made abundant use of the

earth’s magnetic field for the exploration of the earth, they were

ignorant of its origin. In many respects the earth’s magnetic field

exhibits characteristics similar to those of a bar magnet; nonetheless,

the mechanisms responsible for generating each are vastly different.

Magnetic field lines appear to originate near the south geographic pole,

i.e. magnetic north pole, and terminate near the north geographic pole,

i.e. magnetic south pole. It is interesting to note that in the vicinity of

Wilmington, North Carolina the magnetic field lines enter the earth at a

relatively steep angle. The angle of inclination or dip angle, which is the

angle that a compass

needle makes with respect to the plane of the horizon, is approximately

60. In this experiment principles of magnetostatics and elementary

vector analysis are used to determine the earth’s magnetic field in the

vicinity of Wilmington, North Carolina.

A tangent galvanometer

is an early measuring

instrument used for the

measurement of electric

current. It works by using

a compass needle to

compare a magnetic field

generated by the

unknown current to the

magnetic field of the

Earth. It gets its name

from its operating

principle, the tangent law

of magnetism, which

states that the tangent of

the angle a compass

needle makes is

proportional to the ratio

of the strengths of the

two perpendicular

magnetic fields. It was

first described by Claude

Pouillet in 1837.Who

later employed this

sensitive form of

galvanometer to verify

Ohm’s law.


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vanasthali public School Vasundhara, Ghaziabad

Certificate

2016-17

This is to certify that Amit of Class XII-B/A/C has completed

the Physics Project entitled “To determine Earth Magnetic

Field using Tangent Galvanometer” himself and under my

guidance. The progress of the project has been continuously

reported and has been in my knowledge consistently.

…………….………. …………….……….

Internal Examiner External Examiner


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Acknowledgement

I would like to express my sincere gratitude to my Physics teacher,

Mr. Nitin Jassal for giving us the wonderful opportunity to do a case

study and providing vital support, guidance and encouragement

throughout the project. Without his motivation and help,the successful

completion of this project would not be possible. Secondly i would also

like to thank my friends who helped me a lot in finalizing this project

within the limited time frame.


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TABLE OF CONTENTS

Overview................................................................................................................................................ 5

Aim of the Project .................................................................................................................................. 5

Apparatus and Materials required .......................................................................................................... 6

Theory ................................................................................................................................................... 7

Applications .................................................................................................................................... 8

Procedure .............................................................................................................................................. 8

The initial ADJUSTMENTS .............................................................. Error! Bookmark not defined.

Procedure for performing simulator ................................................................................................. 9

Observations and Graph ...................................................................................................................... 10

To determine the horizontal component of earth’s magnetic field (Bh) ........................................... 10

To determine the reduction factor of T.G ...................................................................................... 10

From graph ................................................................................................................................... 11

Result .................................................................................................................................................. 11

Facts ............................................................................................................................................. 11

Applications ......................................................................................................................................... 11

Bibliography ......................................................................................................................................... 12

The Tangent galvanometer .................................................................................................................. 12


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OVERVIEW

The tangent galvanometer was first described in an 1837 by Claude-Servais- Mathias Pouillet, who

later employed this sensitive form of galvanometer to verify Ohm’s law. To use the galvanometer, it is

first set up on a level surface and the coil aligned with the magnetic north-south direction. This means

that the compass needle at the middle of the coil is parallel with the plane of the coil when it carries no

current. The current to be measured is now sent through the coil, and produces a magnetic field,

perpendicular to the plane of the coil and is directly proportional to the current.

The magnitude of the magnetic field produced by the coil is B; the magnitude of the horizontal

component the Earth’s magnetic field is B’. the compass needle aligns itself along the vector sum of B

and B’ after rotating through an angle Ø from its original orientation. The vector diagram shows that tan

Ø = B/B’. since the magnetic field of the Earth is constant, and B depends directly on the current, the

current is thus proportional to the tangent of the angle through which the needle has turned.

AIM OF THE PROJECT

The aim of the project is to find the ‘reduction factor’ of the given tangent galvanometer (K) and the

horizontal component of the Earth’s magnetic field (BH).

o To determine the reduction factor of the given tangent galvanometer (K).

o To find out the horizontal component of earth’s magnetic field (Bh).

TangentgalvanometermadebyJ.H. BunnellCo.around1890

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APPARATUS AND MATERIALS REQUIRED

o Tangent galvanometer (TG), o commutator (C), o rheostat (R), o battery (E), o ammeter (A), o key (k), etc o

Tangent Galvanometer Plug Key

Battery Eliminator a) Rotor view b) Ordinary view

Rheostat


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When a bar magnet is suspended in two Magnetic fields B and Bh, it comes to rest making an angle θ

with the direction ofBh.

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. When a current is passed through the circular coil, a magnetic field (B) is produced at the center of the coil in a direction perpendicular to the plane of the coil. The TG is

arranged in such a way that the horizontal component of earth’s magnetic field (Bh) is in the direction of

the plane of the coil. The magnetic needle is then under the action of two mutually perpendicular fields. If θ is the deflection of the needle, then according to tangent law,

Let I is the current passing through the coil of radius a with n turns, then the field generated by the

current carrying circular coil is,

Equating (1) and (2), we get,


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The left hand side of equation (4) is a constant and is called the reduction factor (K) of the given tangent galvanometer.

Now from equation (3) & (5), the horizontal intensity of earth’s magnetic field Bh is,

APPLICATIONS

o T.G can be used to measure the magnitude of the horizontal component of the geomagnetic field.

o The principle can be used to compare the galvanometer constants.

PROCEDURE

Connections are made as shown in the figure given below, 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. Taking the average of the resulting two readings for deflection averages out, any small error in positioning the

TG coil relative to the earth’s magnetic field Bh .


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PROCEDURE FOR PERFORMING EXPERIMENT

1. The plane of the coil is made vertical by adjusting the leveling screws.

2. The compass box alone is rotated so that the 90-90 line in the compass box is in the plane of

the coil.

3. The T.G as a whole is rotated till the Aluminium pointer reads 0-0.

4. Note down the number of turns in the coil.

5. A suitable current is allowed to pass through the coil.

6. Note down the currrent as well as the deflection in T.G.

7. Reverse the current and note the deflection again.

8. Repeat the procedure for different values of current.

9. Plot the graph.

10. Measure the radius of the coil from its perimeter by using a thread and rotating it around the

round circle.

11. Determine the reduction factor and horizontal intensity of earth's magnetic field.


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OBSERVATIONS AND GRAPH

Number of turns in the coil =....

Circumference of the coil, =......cm

Radius of the coil, a =....cm

TO DETERMINE THE HORIZONTAL COMPONENT OF EARTH’S MAGNETIC FIELD (BH)

The Horizontal component of earth's magnetic field (Bh) can be calculated using the formula,

TO DETERMINE THE REDUCTION FACTOR OF T.G


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FROM GRAPH

Reduction factor K of the tangent galvanometer

can be determined

From the graph drawn as,

RESULT

The reduction factor of the given tangent galvanometer, K =............A

Horizontal component of earth’s magnetic field, Bh =...........T

FACTS

The tangent galvanometer is an early measuring instrument for Current

The magnetic field produced by a circular coil carrying current I is Proportional to I

The S.I unit of magnetic field is Tesla

The magnitude of horizontal intensity of earth’s magnetic field is3.5x10⁻⁵ T

For better result while doing tangent galvanometer experiment, the deflection should be in

between 30-60

What is the value of µ₀ ? 4πx10⁻⁷ NA⁻²

APPLICATIONS

T.G. can be used to measure the magnitude of the horizontal component of the geomagnetic

field.

The principle can be used to compare the galvanometer constants.


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BIBLIOGRAPHY

Tangent Galvanometer (Procedure) : Electricity & Magnetism Virtual Lab : Physical Sciences :

Amrita Vishwa Vidyapeetham Virtual Lab

Tangent Galvanometer (Theory) : Electricity & Magnetism Virtual Lab : Physical Sciences :

Amrita Vishwa Vidyapeetham Virtual Lab

Tangent

Galvanometerhttp://physics.kenyon.edu/EarlyApparatus/Electrical_Measurements/Tangent_Gal

van ometer/Tangent_Galvanometer.html

Galvanometer - Wikipedia, the free encyclopedia en.wikipedia.org/wiki/Galvanometer

THE TANGENT GALVANOMETER


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Physics investigatory report - vanasthalischool.invanasthalischool.in/pdfs/physics-XII.pdf · The tangent galvanometer is an early measuring instrument for Current The magnetic field