A thin spherical conducting shell of radius fi has a charge q. Another charge Q is place at the centre of the shell. The electrostatic potential at a point P a distance R/2 from the centre of the shell is

The electrostatic potential on the surface of spherical shell of fi having a charge g is given byV1=14πε0⋅qRThis potential is same at point P. When charge Q is placed at the can be, then potential at P V2=14πε0⋅Q(R/2)∴  Total potential at PV=V1+V2=14πε0qR+2QR                    =14πε0×1R×(q+2Q)