Question

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

Answer 1

The electrical wirings in any appliance or in the households require to follow a set of safety conditions to avoid any health hazards while operating. The necessity of using earth wires arise from this idea of using a useful resource with much less risk.

Complete answer:
We know that all the appliances in our house and the household wiring itself has earthing wire along with the phase and neutral connections. The earth wires act as the safety wear for the electrical users as the helmets do for riders. They protect the appliances and users from getting damaged or injured at times of danger or accidents.
The earthing wires are nothing but some thicker conducting wires which are connected from the metallic part of the appliances to the earth directly. The ‘thickness’ of the earth wire makes it a better conductor than the other wires used in the connection and even less resistive than the human body. We know that the resistance is indirectly proportional to the thickness of the wire used.
Consider a situation in which the phase wire of an appliance gets unwounded and happens to be in contact with the metallic surface of the appliance like an electric iron. We hold on to this surface for ironing. The instant we touch the surface, the current tends to flow through us giving a fatal electric shock as the human body is a very good conductor.
The earth wire, if attached to the metal body, acts as a better conductor than the human body, passes the current leakage to the earth, and therefore protects us from a shock. In this way, the earth wires are an integral safety condition in appliances.

Note: The earth wire is directly connected to the earth through the high conducting wire. This ensures that there is no further question about the leakage current as the earth acts as a body, which can accept a large amount of charge without any complications.