Question

A sphere of 4 cm radius is suspended within a hollow sphere of 6 cm radius. The inner sphere is charged to a potential 3 e.s.u. When the outer sphere is earthed. The charge on the inner sphere is

• A. 54 e.s.u.
• B. $\frac{1}{4}$e.s.u.
• C. 30 e.s.u.
• D. 36 e.s.u.

Answer 1

Answer: (D)

36 e.s.u.

Answer 2

Let charge on inner sphere be +Q. charge induced on the inner surface of outer sphere will be –Q.

So potential at the surface of inner sphere (in CGS)

$3 = \frac{Q}{4} - \frac{Q}{6}$

$\Rightarrow$ $Q = 36$ e.s.u.