Alternating current from the is different to direct current from a . DC goes in one direction only while AC direction all the time. AC changes direction 50 times every second. We say its is 50 Hz.

The mains voltage in Europe is 230 volts. This is the effective voltage. The voltage is about 330 V.

The voltage at the neutral terminal is almost . Therefore the voltage of the wire goes from +330 V to 0 V to - 330 V.

In plugs a third wire called the wire is often used. This stops the metal case of an appliance getting if there is a fault. In the case of a fault, there is a short circuit so that the blows before the person gets a shock. Appliances with cases do not need an earth wire. They are -insulated.