What is Faraday's law of induction?

Faraday's law of induction: ℰ = −dΦ/dt. Change the magnetism passing through a coil of wire and a voltage appears in it, with no battery at all. The faster the change and the more turns of wire, the bigger the voltage, and the current it drives always pushes back against the change.

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Chapters in this interactive model

1. Change the flux, make a voltage: A magnet moving near a coil pushes current round it. Only change counts.
2. Transformers and wireless chargers: A changing current in one coil makes a voltage in another, with nothing joining them.
3. Motors are generators too: A fan’s rotor is pushed by currents it makes itself. An electric car brakes by making electricity.
4. Guitar pickups and induction hobs: A vibrating string makes a voltage. A fast-changing field heats a pan from the inside.
5. Where induction gets strange: Magnets that float down pipes, transformers that can’t make energy, and light itself.