Question

A conducting sphere of radius R and a concentric thick spherical shell of inner radius 2R and outer radius 3R is shown in figure. A charge `+10Q` is given to the shell and inner sphere is earthed. Then charge on inner sphere is

A. `-4Q`
B. `-100Q`
C. zero
D. none of these

Answer 1

Correct Answer - A
a, Potential of sphere should be zero.
`V=(kq)/(R)-(kq)/(2R)+(k(10Q+q))/(3R)=0`
or `q=-4Q`