Why do you need fuses or circuit breakers?

Answer 1

If a fault occurs in a device, then it can cause high, dangerous currents. For instance, if the live of a household appliance comes into contact with the ground, then the resulting current could heat up wires and cause them to burn. Worse, if this connection to ground is made through the body then it can cause burns or even fibrillation.

If a high enough current must pass through a fuse, then the inside of the fuse melts and cuts off the current. The fuse must then be replaced. If a high enough current passes through a meter connected to a breaker, then the breaker is "tripped". This again cuts off the current, but the circuit can be re-made without replacing parts.

Answer 2

It would depend on the application, for instance fuses are typically used for the various electrical circuits in a vehicle. For household or industrial electricity services, fuses are commonly used nowadays for the electricity supply authority's main fuse where fluctuation in voltage is common, and for some electrical equipment, for example to protect motor circuits.

The use of fuses is standard in the electrical plugs used in the UK and other countries which use a 230 volt 50 Hz service to deliver power using Type G plugs and socket outlets.

Low-cost 1 amp, 3 amp, 5 amp and 13 amp fuses are commonly available and each appliance has to be fitted with the correct size fuse to protect it, according to the current it normally draws.

For more information see the answers to the Related Questions shown below.

Answer 3

Fuses or circuit breakers are added to circuits to limit the current. This allows the current to stay within the amperage rating of the conductors, that takes the supply voltage to the load.