Wires in a three-pin plug         There are 3 different coloured wires and a fuse in a three-pin plug. The live wire has brown colour. The neutral wire has blue colour. The earth wire has a yellow - green colour. The earth wire protects the user and the appliance. Appliances with double insulation have plastic casing and do not require earth wire.         Example of an appliance with double insulation is the hairdryer.      Fuse A fuse is a thin wire in a small ceramic tube with two metal end caps.  The current rating of a fuse is the maximum current that can flow through it before it melts. The fuse provides protection for the user and the appliance.  . The fuse also provides protection for the circuit including the connecting wires.       Residual current circuit breaker (RCCB)  A circuit breaker is a safety device that does the job of a fuse by automatically breaking  the circuit when a change in electric current is detected. The circuit breaker can be reset.