Question

A solid spherical conductor of radius $R$ has a spherical cavity of radius $a(a<R)$ at its centre. A charge $+Q$ is kept at the centre. The charge at the inner surface, outer surface and at a position $r(a<r<R)$ are respectively

• A. + Q, - Q, 0
• B. - Q, + Q, 0
• C. 0, - Q, 0
• D. + Q, 0, 0

Answer 1

Answer: (B)

The solid conductor with a cavity is shown in figure.

The inner surface of cavity will be $-Q$ due to induction. At outer surface, the charge will be $+Q$ and at a point between $P$ at a position $r(a<r<R)$ will be zero.