A solid spherical conducting shell has inner radius a and outer radius 2a. At the center of the shell is located a point charge `+Q`. What must the excess charge of the shell be in order for the charge density on the inner and outer surface of the shell to be exactly equal?

Options

A. `-5Q`
B. `+3Q`
C. `-4Q`
D. `+4Q`

Answer

A

Explanation

Inner charge density `=(-Q)/(4pi a^(2))`
Outer charge density`=((q+Q))/(4pi(2a)^(2))`
`(-Q)/(4pi a^(2))=((q+Q))/(4pi(2a)^(2)) rArr q=-50`