Fuses and circuit breakers

Fuses and circuit breakers protect electrical circuits and appliances.

Fuses

The fuse breaks the circuit if a fault in an appliance causes too much current to flow. This protects the wiring and the appliance if something goes wrong. The fuse contains a piece of wire that melts easily. If the current going through the fuse is too great, the wire heats up until it melts and breaks the circuit.

Cross-section of a 13 amp fuse showing the low melting point wire inside.A 13A fuse contains a low melting point wire

Fuses in plugs are made in standard ratings. The most common are 3 A, 5 A and 13 A. The fuse should be rated at a slightly higher current than the device needs:

  • if the device works at 3 A, use a 5 A fuse
  • if the device works at 10 A, use a 13 A fuse

Circuit breakers

Circuit breakers act as resettable fuses.

Circuit breaker

These are automatically operated electrical switches that protect electrical circuits from overloading or short circuiting. They detect faults and then stop the flow of electricity. Small circuit breakers protect individual household appliances, whereas larger ones can protect high voltage circuits supplying electricity to entire cities.