A solid conducting sphere of radius a has a net positive charge $2 Q$. A conducting spherical shell of inner…
A solid conducting sphere of radius a has a net positive charge $2 Q$. A conducting spherical shell of inner radius $\mathrm{b}$ and outer radius $\mathrm{c}$ is concentric with the solid sphere and has a net charge $-$ Q.The surface charge density on the inner and outer surfaces of the spherical shell will be
$-\frac{2 Q}{4 \pi b^{2}}, \frac{Q}{4 \pi c^{2}}$
$-\frac{Q}{4 \pi b^{2}}, \frac{Q}{4 \pi c^{2}}$
$0, \frac{Q}{4 \pi c^{2}}$
None of the above
Solution
Surface charge density $(\sigma)=\frac{\text { Charge }}{\text { Surface area }}$
So $\sigma_{\text {inner }}=\frac{-2 Q}{4 \pi b_{Q}^{2}}$
and $\sigma_{\text {Outer }}=\frac{Q}{4 \pi c^{2}}$
