When an electrical appliance is working normally, the Earth wire does not serve any function. However, when there is an electrical fault that causes the metal casing of the appliance to be at a high potential, the Earth wire becomes very important as it provides a path for the charges to travel from the metal casing to the ground. This helps to prevent the user from suffering an electric shock if metal casing of appliances becomes live.

Hence an Earth wire should have negligible resistance, be connected between the metal casing of the appliance and the ground. When Earth wire becomes live, large surge of current through live wire above the rating of the fuse will cause the fuse to blow.

Faulty washing machine with no earth wire protection

Faulty washing machine with earth wire protection

 

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