Question

Two concentric spheres (hollow) are shown in diagram. What charge should be given to the smaller sphere so that potential at point P outside the sphere is zero ? (Inner sphere of radius = r, outer sphere of radius = R and charge on outer sphere = Q):

• A. –$\frac{Qr}{R}$
• B. –$\frac{QR}{r}$
• C. – Q
• D. –$\frac{2QR}{r}$

Answer 1

Answer: (C)

– Q

Answer 2

Let the charge on the inner sphere be 'q'

V_P = $\frac { \mathrm { kq } } { \mathrm { x } }$ + = 0

q = – Q