Question

A solid sphere of radius $R$ has a charge $+2Q$. A hollow spherical shell of radius $3R$ placed concentric with the first sphere has net charge $-Q$. What would be the final distribution of charges, if a conducting wire joins the spheres?

Answer 1

All the charge on a metallic body resides on its outer surface. Therefore upon joining the spheres with a conducting wire, the net charge = $2Q-Q=Q$ resides on the outer surface of the outer hollow shell and zero charge resides on the inner sphere.