Which instrument works on the principle of 'Electromagnetic induction'?

What is the frequency of $220 \ V$ $DC$ voltage? (In $Hz$)

$(a)$ What is the function of an earth wire in electrical instruments? Why is it necessary to earth the metallic electric appliances?
$(b)$ Explain what is short-circuiting and overloading in an electric supply.
$(c)$ What is the usual capacity of the fuse wire in the line to feed:
$(i)$ lights and fans?
$(ii)$ appliances of $2 \,kW$ or more power?

Describe an experiment to demonstrate the force acting on a current-carrying conductor placed in a magnetic field.

The material of the core of a strong electromagnet is:

Name the type of current:
$(a)$ used in household supply,
$(b)$ given by a cell.