Electric power to homes is supplied through the mains. It has two wires.
The potential difference between the two wires is 220V. The earth wire with green insulation is connected to a metal plate kept in the ground.
Two separate circuits are used.
1. One is of 15A for appliances with high power rating like gysers, air conditioners etc.
2. The other is of 5A for fans, bulbs etc.
The different appliances are connected in parallel so that every appliance gets equal voltage and even if one is switched off the others are not affected.
NOTE: The appliances having metallic body like electric iron, refrigerators etc., their metallic body is connected to the earth wire so that if there is leakage of current, it passes to the earth and prevents electric shock.