Electromagnetic Induction

Definition

The production of an electric current in a conductor when the magnetic field around it changes, discovered by Michael Faraday in 1831.

Key points

• A current is induced whenever there is relative motion between a magnet and a coil, or any change in the magnetic field linking the coil (Faraday's law of induction).
• Lenz's law states that the induced current always opposes the change that produced it, which is a consequence of the conservation of energy.
• The electric generator (dynamo) uses this principle to convert mechanical energy into electrical energy by rotating a coil in a magnetic field; the bulk of the world's electricity is generated this way.
• The transformer uses mutual induction between two coils to step alternating voltage up or down; it works only with alternating current, not direct current.
• Induction is also used in electric motors (the reverse effect), induction cooktops, and electromagnetic braking.

Why it matters for CAPF

Faraday as the discoverer, the generator converting mechanical to electrical energy, the transformer stepping AC voltage up or down, and Lenz's law are core physics facts that appear regularly.

Common confusion

A generator converts mechanical energy into electrical energy, while a motor does the reverse; do not swap them. A transformer works only on alternating current because it needs a changing magnetic field; it cannot step direct-current voltage up or down.

Related concepts

concept electromagnetic spectrum, concept semiconductor devices, concept types of renewable energy

Parent note

physics everyday