Electrical Safety: Fuses & Earthing Flashcards

All 6 cards in this deck

What is the function of the earth wire in an appliance with a metal case?

It protects a person from electric shock if a fault develops: it carries the current from the case safely to earth.

How does a fuse keep an appliance safe?

If the current is too large the fuse wire melts, which breaks the circuit and stops the current, preventing overheating or fire.

Why must switches and fuses be connected in the live wire of a domestic circuit?

So that when the switch is off or the fuse blows, the appliance is cut off from the 230 V live supply and cannot give a shock.

Why is a connection between the live wire and earth dangerous?

There is about 230 V across it, so a very large current flows, which can cause overheating and fire, or an electric shock to anyone touching it.

True or false? A circuit breaker must be replaced every time it switches off the current.

False. A circuit breaker can be reset and used again; it is a fuse that must be replaced.

How should the rating of a fuse compare with the normal working current of the appliance?

Slightly higher than the normal working current.

e.g. an appliance taking 2 A is given a 3 A fuse.