CBSE Class 12-science Answered

Let us consider a conductor with a cavity, with no charges inside the cavity. Electric field inside the cavity is zero, whatever
be the size and shape of the cavity and whatever be the charge on the conductor and the external fields in which it might be placed.

Vanishing of electric field in the (charge-free) cavity of a conductor is a very general phenomenan.

Even if the conductor is charged or charges are induced on a neutral conductor by an external field, all charges reside
only on the outer surface of a conductor with cavity.

Whatever be the charge and field configuration outside, any cavity in a conductor
remains shielded from outside electric influence: the field inside the cavity is always zero.

This is known as electrostatic shielding. The effect can be made use of in protecting sensitive instruments from
outside electrical influence