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

The correct option is A Only induced charge on outer surface will redistribute.

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

(ii). 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 the inner surface and all the inner charges is zero.

(iii). External electric fields cannot penetrate a closed conductor because of electrostatic shielding. Hence, they cannot affect any charges in the interior.

(iv). Also, the force on charge inside the cavity is due to the charge on the inner surface.

<!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}--> Hence, $\left(A\right)$ is the correct answer.