Electrical safety — Explain

Explain how fuses and trip switches protect a circuit, and how you would choose an appropriate rating for each.

A fuse contains a thin wire that melts and breaks the circuit if the current exceeds its rated value, protecting the wiring and appliance from overheating or fire. A trip switch (circuit breaker) is an electromagnetic switch that automatically opens the circuit when the current becomes too large, and unlike a fuse it can simply be reset afterwards. The rating chosen for a fuse or trip switch should be the value just above the appliance's normal operating current (e.g. an appliance drawing 3 A should use the next standard rating above this, such as a 5 A fuse).