Question

what is the advantage of the third wire of earth connection in domestic electrical appliances?

Answer 1

An earth wire provide safety.

If there is any defect in the switchboard or by chance the live wire comes in contact to the metallic case of the appliance, a zero resistance path is created. So a HEAVY current flows through the live wire to the metallic appliance. Now if anyone touches the appliance, indirectly he will come in contact with the live wire due to which he will get a fatal shock.

Now if the appliance is earthed, when the live wire comes in contact with the appliance due to break of insulation, the heavy current flows through the earth wire to the earth. There is a huge potential difference as earth is at zero potential and the live wire is at high potential.
So a huge amount of current is drawn, due to which the fuse melts and saves the appliance from damage. So you also won't get a shock.

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