earthing The electric potential of the Earth remains always constant  because of its large dimension, and is taken  as zero. In an electronic circuit, a point to be held at constant reference potential   is   grounded.  In  household  electrical appliances, earthing  ensures  safety  to the user. The metallic body  of the appliance is connected to the ground using the earth terminal  of the  three pin socket. By convention in electrical appliances green/yellow  wire  is  used for earthing. The earth wire  of  the household  electrical  circuit  is generally thick copper wire, which is ultimately connected to a metal plate below earth.