What is the function of an earth wire? Why is it necessary to earth the metallic appliances?

To avoid electric shocks, the metal body of an electrical device is 'earthed'. A wire called 'earth wire' is used to connect the metal body of the electrical device to the earth, which is at zero potential. In household circuits, we have three wires, the live wire, the neutral wire and the earth wire. One end of the earth wire is connected to the device and the other end of the wire is connected to the earth. We now say that the device is "earthed" or "grounded". Usually the three wires are connected to a three-pin plug. The neutral wire or the earth connection carries the high current to the earth from the device and prevents an electric shock.