Fuses and earthing

Earthing and fuses prevent electrical overloads.

The earth wire and fuse are included for safety.

If a fault develops and the live wire touches the metal case, because the case is earthed, the current will go into the case and out through the earth wire.

If too much current goes through an appliance (and is higher than the fuse capacity) , the fuse will melt to cut off the current.

Insulating materials make appliances double insulated.

All appliances with metal cases are usually earthed to reduce the danger of electric shock.

Earthing mean the case is attached to an earth wire.

If the appliance has a plastic casing, it is double insulated.

Anything with double insulation doesn't need an earth wire. 

Cables that only carry live and neutral wires are known as two-core cables.

Circuit breakers are an electrical saftey device used in some circuits.

Like fuses, they protect the circuit from damage if too much current flows.

When circuit breakers detect a surge in current in a circuit, they break the circuit by opening a switch. 

A ciruit breaker can easily be reset by flicking a switch on the device. 

This makes it more convenient than fuses as they have to be replaced once they are melted.

They are a lot more expensive than a fuse though.

One type of circuit breaker is the residual current circuit breaker (RCCB)