A changing magnetic field near a coil of wire pushes on electric charges inside the metal. That push, called voltage, forces charges through the wire and into a connected bulb. When the magnets spin fast enough, charges speed up inside the bulb's narrow filament and produce the heat that makes it glow.

Spinning magnets inside a coil of wire can push charges through metal — and that push is voltage. In this experiment, you wind thin wire around a small cardboard box, then mount four ceramic magnets on a nail inside it. When you spin the nail fast with a hand-crank drill, the changing magnetic field forces charges through the wire and into a tiny bulb. The filament glows as charges speed up through its narrow wire and produce heat.