A thick conducting spherical shell of inner radius a and outer radius b is shown in figure. It is observed that the inner face of the shell carries a uniform charge density `-sigma`. The outer surface also carries a uniform surface charge density `+sigma`.
(a) Can you confidently say that there must be a charge inside the shell? Find the net charge present on the shell. (b) Find the potential of the shell.

Answer

(a). `Yes` `4pisigma(b^(2)-a^(2))`
(b) `(sigmab)/(in_(0))`