The normal flow of electricity is not enough to heat up the connecting wires. If a large current flows more heat is produced. A fuse is a wire made of a metal which melts very easily when it gets hot. It is enclosed in a fire-proof container.

Fuses are fitted to plugs and all kinds of electrical equipment that use the mains. If there is a fault in the circuit a large current can be produced. This can produce a great deal of heat and then might cause a fire. As soon as a large current flows through a fuse wire the heat makes the wire melt. This stops the current flowing and prevents a fire breaking out in other parts of an electrical circuit.