Spark image

Light emitting diode - LED
This is a diode that emits light when a current is passed through it in one direction only.

This will make a noise when a current passes through it.

A small current passing through the coil will close a relay switch and so allow a much larger current to flow in another circuit.

Torch bulb
This is a small bulb that lights up when a current flows through it in either direction. The bigger the current the brighter the bulb.

© Keith Gibbs 2009