The main function of the earth wire is to prevent live wire from overloading and absorbs the excess electrons & flows to beneath the ground . It is necessary because it prevents the electrical appliances from damage and absorbs the excess electricity from appliances.

1.It provides low resistance path to the leakage current. 2.It keeps the potential of metallic body of an electrical appliances equal to that of the ground.
Safety measure for leakage of current …low resistance and more currentgoes to earth…the user will get less shock