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Experiment 9: Electromagnetic Induction

Laboratory Report

Department of Mathematics and PhysicsCollege of Science, University of Santo Tomas

Espaa, Manila, Philippines

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Abstract

The purpose of the experiment is to

determine how the production of current in

the presence of a magnetic field.

I. Introduction

In 1831, Michael Faraday, an

English physicist, performed a series of

experiments to determine whether currents

are produced in a magnetic field. He found

out that when a stationary magnet is placed

inside a coil of wire, it will not produce any

current. He later realized that a sudden push

or pull of pole of magnet inside the coil

produces current as evidenced by the

deflection of the needle of a galvanometer.

Faradays Law of Electromagnetic

Induction is perhaps considered to be the

most important concept in electromagnetism

as it bridges the gap between electricity and

magnetism. Absence of this law will also

lead to the absence of modern electronic

gadgets such as television, generators,

radios, telephones, and others to name a few.

Hence, the objectives of the experiment are

to determine how current is induced in a coil

of wire, to identify the factors affecting the

induced current, and to verift Lenzs Law.

II. Theory

A magnetic field is produced by

electrical currents which could be found in

wires or it could be associated with the

currents produced by an electron orbiting an

atom in accordance with the Lorentz Force

Law. In symbols,

Equation 2.0 Lorentz Force Law

Where F= ForceE= Electric field

q = electric charge

v= velocity of the charge

B= magnetic field

III. Methodology

In the experiment, two coils of wire

was used. In the first coil, there are 100

turns of wire. The magnet was then placed

inside the coil facing its north pole. The coilwas connected to galvanometer having a

scale of -10 to +10 and -5 to +5 between it.

The magnet was then quickly pulled against

the coil and the deflection of the needle of

the galvanometer was recorded. The same

was done with the south pole of the bar

magnet. The deflection of the needle of the

galvanometer was also recorded.

In the second coil, having 50 number

of turns, a bar magnet was placed in themiddle of the coil. Each pole was placed and

then quickly pulled against the coil. The

deflection of the galvanometer for each pole

was recorded.

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IV. Results and Discussions

Table 4.0 Deflection of galvanometer

Number of

turns of coil

50 100

North 5 towardsthe negative

10 towardsthe negative

South 5 towards

the positive

10 towards

the positive

Table 4.0 shows the amount of deflection of the

galvanometer corresponding to the number of

turns in a coil of wire.

A full-scale deflection of a

galvanometer is usually small, about 10A.

To determine the accurate amount ofcurrent, a shunt resistor must be connected

in parallel with the galvanometer.

From the table, in the 50 number of

turns of a coil of wire, same amount of

current was observed to both poles when it

was quickly pulled but in different

directions. In 100 number of turns of a coil,

both poles deflect the same amount of

current but in different directions. This

corresponds to the fact that when the

number of turns increases, magnetic field

becomes stronger which makes the current

also stronger.

V. Conclusions

From the experiment, it is highly

evident that the current is induced when

there is a sudden change of a magnetic field.

Repeating the same procedure with adifferent number of turns of wire, the

galvanometer still deflects its needle. This is

similar to what Faraday had discovered

which states that an electric will produce if a

magnetic field is in relative motion.

In Table 4.0, it is clearly manifested

that a change in the number of turns of wire

will correspond to the amount of current it

will produce. This factor stems from the fact

that the magnetic field strength is directly

proportional to the current that will beproduced.

V. References[1] Halliday, Resnick & Walker. (1997).

Fundamentals of physics.New York,

NY: Wiley.

[2] Knight, R. (2009). Physics for

scientists and engineers: Volume 4.New York, NY: Cengage Learning.

[3] Griffiths, D. (2012). Introduction toelectrodynamics. New York, NY:

Addison-Wesley.

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