Question

Why is it necessary to have an
earth wire installed in a power
circuit, but not in a lighting circuit?

Answer 1

It is necessary to have an earth wire installed
in a power circuit, but not in a lightning
circuit because the power circuit carries high
currents (upto 15A) and costly devices while
the lightning circuit only carries low current
(upto 5A).
If there is a fault where the electric
appliances are exposed to the live wire it can
cause immense damage to the user in the
case of the power circuit, where the devices
utilize heavy currents.