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PRAGATI VIGYA PEETH

PHYSICS INVESTIGATORY

PROJECT

TANGENT

GALVANOMETER

SUBMITTED BY: SIDDHARTH SINGH

KUSHWAH , XII

SUBMITTED TO: MRS. RANJANA

KHARE MA’AM

2019-

TABLE OF CONTENTS

S.No. Contents Page no.

1. ACKNOWLEDMENT 04

2. OBJECTIVES 05

3. INTRODUCTION 06-

4. ABOUT THE TOPIC 08-

EXPERIMENT 11-

OBSERVATION TABLE 13-

BIBLIOGRAPHY 15

 To determine the reduction factor of the given tangent galvanometer ( K ).  To find out the horizontal component of earth’s magnetic field (Bh). TANGENT GALVANOMETER DIAGRAM

INTRODUCTION Earth's magnetic field, also known as the geomagnetic field, is the magnetic field that extends from the Earth's interior to where it meets the solar wind, a stream of charged particles emanating from the Sun. Its magnitude at the Earth's surface ranges from 25 to 65 microtesla (0.25 to 0.65 gauss).Roughly speaking it is the field of a magnetic dipole currently tilted at an angle of about 10 degrees with respect to Earth's rotational axis, as if there were a bar magnet placed at that angle at the center of the Earth. Unlike a bar magnet, however, Earth's magnetic field changes over time because it is generated by a geodynamic (in Earth's case, the motion of molten iron alloys in its outer core).

Earth's magnetic field serves to deflect most of the solar wind, whose charged particles would otherwise strip away the ozone layer that protects the Earth from harmful ultraviolet radiation. One stripping mechanism is for gas to be caught in bubbles of magnetic field, which are ripped off by solar winds. ABOUT THE TOPIC Tangent Galvanometer: Electric current is often measured using an instrument called a tangent galvanometer. Able to measure the presence as well as the

direction and power of currents, the instrument was first used in the early 1800s. It typically has a vertical copper wire coil, wrapped around a circular frame, and a compass in the middle. The compass needle generally responds to the magnetic field of the electrical current, which is compared to the Earth’s magnetic field in the experiment. This scientific instrument has been built in many forms and more modern ones often use beams of light to determine measurements, while some versions are used to measure the magnetic field of the Earth The instrument works based on the tangent law of magnetism. This principle defines the tangent of the angle, traveled through by the compass needle, as being proportionate to a ratio of how strong two magnetic fields are. These fields are usually perpendicular to one another. Currents measured are typically proportional to the tangent of the same angle the needle goes through.

Circuit Diagram:

When a bar magnet is

suspended in two magnetic

Bh = μ 0 nK/2a (6) Applications

Tangent Galvanometer 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.

EXPERIMENT

Aim:

1. To determine the reduction factor of the given tangent galvanometer ( K ).
2. To find out the horizontal component of earth’s magnetic field (Bh).

Apparatus:

 Tangent galvanometer (TG), commutator (C), rheostat (R), battery (E), ammeter (A), key (k), connecting wires, meter scale etc.

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.

Principle & Formulae:

 The reduction factor of T.G is K=I/tanθ, where I is the current flowing through the T.G which produces the deflection θ.  The horizontal intensity of Earth’s magnetic field at a place. Bh = μ 0 nK/2r, where n is the number of turns of the coil, μ 0 = 4π×

• NA - is the

OBSERVATION TABLES

Table 1: For variation of θ with I.

SL.N o Ammete r Reading (A) Deflection in T.G Mean K =I/tan θ θ 1 θ 2 θ 3 θ 4 1 0.15 35 35 35 35 35 0. 2 2 0.20 49 47 60 64 53.6 0. 4 3 0.25 36 36 55 58 46.25 0. 9

4 0.30 50 50 65 68 58.2 0. 0 5 0.27 45 45 64 65 53.8 0. 6 Mean K = 0.  The reduction factor of TH = 0.  Number of turns of the coil = 50  Circumference of the coil (S) = 2π= 50.49 cm

TABLE 2: For radius of tangent galvanometer.

S.No. Inner diameter d 1 (cm) Outer diameter d 2 (cm) Mean diameter d Mean radius

1. (^) 16.0 × 10 − 16.40 × 10 −

16.20 ×

−

8.10 ×

−

2. (^) 16.16 × 10 −

16.08 ×

−

16.12 ×

−

8.06 × 10

−

3. 16.06 × 10 −

16.10 ×

−

16.08 ×

−

8.04 × 10

− Mean radius of coil R= 8.04x 10 − Horizontal Intensity at the place Bh = μ 0 nK/2r = 2πnK×10nK×

- /r = **7.6867×

T**

2. Horizontal Intensity at the place, Bh = 7.6867× - T

Conclusion:

Experiment in tangent galvanometer gives the reduction factor of galvanometer and horizontal intensity of Earth’s magnetic field. BIBLIOGRAPHY  Illustrative Oxford Book  http://en.wikipedia.org  Comprehensive Practical Physics  www.wisegeek.com  www.britannica.com  www.amrita.edu