Page 14 - 10-phy-15 Electromagnetism

15. Electromagnetism eLearn.Punjab

Activity 15.2: Take a rectangular loop of wire and connect its two ends with a galvanometer. Now

hold the wire stationary or move it parallel to the magnetic field of a strong U-shaped magnet.

Galvanometer shows no deflection and hence there is no current. Now move the wire downward

through the field, current is induced in one direction as shown by the deflection of the galvanometer

(Fig. 15.13-a). Now move the wire upward through the field, current is induced in the opposite

direction

(Fig. 15.13-b).

It implies that an electric

current is generated in a

wire only when the wire cuts

magnetic field lines. This

induced current is generated Fig 15.13: Demonstration of electromagnetic induction by the movement of a wire loop
by the induced e.m.f. in the in the magnet field
circuit. Faraday found that

to generate current, either

the conductor must move through a magnetic field or a magnetic field must change across the

conductor. Thus,
The process of generating an induced current in a circuit by changing

the number of magnetic lines of force passing through it is called

electromagnetic induction.

Activity 15.3: Fig.
15.14 shows one of Faraday’s experiments in which current is induced by moving a magnet into the
solenoid or out of the solenoid. When the magnet is stationary no current is induced.

Fig 15.14. Phenomenon of electromagnetic induction by the movement of a magnet through solenoid. (a) Magnet moves
towards the stationary solenoid. (b) Magnet moves away from the stationary solenoid

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