Question

The figure shows a charge q placed inside a cavity in an uncharged conductor. Now if an external electric field is switched on then :

• A. Only induced charge on outer surface will redistribute.
• B. Only induced charge on inner surface will redistribute
• C. Both induced charge on outer and inner surface will redistribute.
• D. Force on charge q placed inside the cavity will change

Answer 1

Answer: (A)

Only induced charge on outer surface will redistribute.

Answer 2

The distribution of charge on the outer surface, depends only on the charges outside, and it distributes itself such that the net electric field inside the outer surface due to the charge on outer surface and all the outer charges is zero. Similarly the distribution of charge on the inner surface, depends only on the charges inside the inner surface, and it distributes itself such that the net, electric field outside the inner surface due to the charge on inner surface and all the inner charges is zero.

Also the force on charge inside the cavity is due to the charge on the inner surface. Hence answer is option (1).