Lesson 3, Topic 2
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# Laws of Electromagnetic Induction

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The laws governing electromagnetic induction are Faradays laws and the Lenz’s law

This states that whenever there is a change in magnetic flux linking a circuit, an e.m.f is induced, the strength of which is directly proportional to the rate of change of the flux linking the circuit

Magnetic flux linking a coil depends on

1. The magnetic field strength
2. Number of turns of the coil
3. The area of each turn
4. Faraday’s law gives the magnitude of the of the induced e.m.f

Lenz’s law

Lenz’s law states that the induced e.m.f flows in such a way as to oppose the motion producing it.

Lenz’s law gives the direction of the induced e.m.f or current

When the north pole of a magnet is moved towards the coil, a current is induced in it, the induced current flows in an anticlockwise direction and the coil becomes a north pole. (N-pole). The two end poles repel (induced current opposes the motion of the approaching magnet). To move the magnet towards the coil work is done against the repelling force of the two N-poles.

If the N-pole of the magnet is moved away from the coil, the induced current flows in a clockwise direction. The end of the coil nearest to a receding N-pole becomes an S-pole attracting the receding N-pole. Work is done against the attracting force between the coil and the magnet in order to move the N-pole from the coil.

The mechanical workdone in moving the magnet towards or away from the coil is transformed into electrical energy (induced current in coil). Lenz law is an example of energy conservation.

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