What is the main purpose of earthing an electrical appliance?

Usually three insulated wires of different colours are used in an electrical appliance. Name the three colours.

What is the usual colour of the insulation of:

(a) live wire,

(b) neutral wire, and

(c) earth wire?

Give two reasons why different electrical appliances in a domestic circuit are connected in parallel.

How should the electric lamps in a building be connected so that the switching on or off in a room has no effect on other lamps in the same building?