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ACKNOWLEDGEMENT

I would like to thank our beloved principal, Shri L Neelakanta Pillai , forhis constant encouragement, support and guidance in the field of physics.

I am grateful to our physics teacher, Mrs. N Uma , for her enthusiasticguidance and encouragement throughout the academic year.

I would like to thank the school management for providing us withexcellent facilities such as well-stocked labaratory and good quality

equipment.

Lastly, I dedicate this to my family, and my friends who workedalongside me on this experiment

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Introduction

The magnetic field of earth is approximately like that of a giant bar ofmagnet embedded deep inside the earth.

Many theories by scientists like william gilbert, prof. Blackett, E.Bullardand W.M.Elaster all proved the existence of magnetic field of the earth.

Horizontal component of earth's magnetic field:

If B is the total magnetic field at a particular place, I is the angle ofinclination (or angle of dip) at that place, then

Horizontal component of Earth's magnetic field at that point (B H) is givenby

BH = B*cos(I)

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Aim of project

This project aims to determine the value of the horizontal component ofthe Earth's magnetic field (B H) using a tangent galvanometer.

Tangent Galvanometer

A tangent galvanometer is an early measuring instrument used tomeasure electric current. It consists of a coil of wire wound on a non-magbetic circular frame of brass or wood. The frame is fixed with itsplane perpendicular to a circular turn table provided with levelingscrews. At the centre of the circular turn table is a small uprightprojection of a compass box. The compass box consists of a small pivotedmagnet, to which a long pointer is fixed right angles and it over agraduated circular scale. The scale is graduated in 4 segments eachreading from 0 to 90 degrees. The compass box is supported in such amanner that the center of the pivoted magnet coincides exactly with thecentre of the coil of the wire. The coils of the wire is usually in 3 sections(2,5 and 50 turns each) and are connected to seperate terminals. The 50turns are of thinner wire.

Experiment

Aim

To determine the value of horizontal component of earth's magnetic field(BH) using a tangent galvanometer.

Apparatus required:

1. Tangent galvanometer2. Ammeter3. Commutator4. Battery 5. Plug key 6. Rheostat7. Connecting wires

Formula usedBH=( µ 0 *n*I)/(2a*tanx)

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where,BH is the horizontal component of earth's magnetic field