Linear alternator

A linear alternator is most commonly used to convert back-and-forth motion directly into electrical energy.

This eliminates the need for a crank or linkage to convert a reciprocating motion to a rotary motion in order to drive a rotary generator.

This is a torch (UK) or flashlight (USA) which contains a coil and a permanent magnet.

When the appliance is shaken back and forth, the magnet oscillates through the coil and induces an electric current.

The appliance can then produce light, typically from a light-emitting diode, until the capacitor is discharged.