Question

A small conducting sphere of radius $a$, carrying a charge $+Q$, is placed inside an equal and oppositely charged conducting shell of radius $b$ such that their centers coincide. Determine the potential at a point which is at a distance $c$ from center such that $a<c<b$.

• A. $k(Q/c+Q/b)$
• B. $k(Q/a+Q/b)$
• C. $k(Q/a-Q/b)$
• D. $k(Q/c-Q/b)$

Answer 1

The correct option is D $k(Q/c-Q/b)$

Potential outside the conducting sphere conducting sphere at distance $c=\frac{KQ}{c}$

Potential inside a conducting shell having charge $-Q$ and radius $b=-\frac{KQ}{b}$

Now net potential at point $c=\frac{KQ}{c}-\frac{KQ}{b}$