Browse Questions

A charge q is distributed uniformly on the surface of a sphere of radius R . It is covered by a concentric hollow conducting sphere of radius 2R . Find the charges on the outer surface of hollow sphere if it is earthed

$(a)\;q\qquad(b)\;-q\qquad(c)\;zero\qquad(d)\;None$

Explanation :
The charge on the inner surface should be $\;-q\;,$ because if we draw a closed gaussion surface through the material of the hollow sphere the total charge encloses by this gaussion surface should be zero . Let $\;q_{1}\;$ be the charge on the outer surface of sphere
Since outer sphere is earthed potential on it is zero . Therefore
$\large\frac{1}{4\;\pi\;\in_{0}}\;(\large\frac{q}{2R}-\large\frac{q}{2R}+\large\frac{q_{1}}{2R})=0$
$q^{|}=0\;.$