A metal ball of charge +Q is lowered into an insulated, uncharged metal shell and allowed to rest on the bottom of the shell. When the charges reach equilibrium,

Question

Quizplus · Accepted Answer

When the metal ball is lowered into the uncharged metal shell, the electrons in the metal shell are repelled by the positively charged ball and move to the opposite side of the shell. This leaves a positive charge on the inside of the shell and a negative charge on the outside. However, since the shell is insulated, no charge can flow in or out of it. Therefore, the total charge of the system (ball + shell) must remain the same. Since the ball has a charge of +Q, the outside of the shell must also have a charge of +Q to balance the charge of the system. Therefore, the remaining charge must be distributed uniformly over the inner surface of the shell, resulting in a charge of zero on the ball. Thus, the outside of the shell has a charge of +Q and the ball has zero charge.

A Metal Ball of Charge +Q Is Lowered into an Insulated