Electromagnetic Induction

A voltage can be induced in a conductor when there is relative motion between the conductor and the magnetic field. The voltage can be induced in two ways:

• A conductor moves through a magnetic field OR
• The magnetic field changes through the conductor

• the speed of movement
• the magnetic field strength
• number of turns on the coil

Let's take a look at some questions on this topic from IGCSE Physics

The diagram shows a magnet held above a coil.The coil is connected to a voltmeter. The magnet is released and falls into the coil.

Example 1

Explain why the voltmeter shows a reading.

→ Voltage is induced because there is a change of magnetic field through the coil as the magnet moves through the coil.

Example 2

The magnet is released from a greater height. How does this affect the voltmeter?

→ When the magnet is released from a greater height, the magnet passes through the coil faster. This means that the rate of change of magnetic field through the coil will be larger. Therefore, the induced voltage is larger.

Example 3

Describe two ways that the direction of induced current can be changed.

1. Drop the magnet with the S pole facing downwards. OR
2. Instead of dropping the magnet, raise the magnet upwards.

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