Question

A point charge q is placed at a distance 2r from the centre o of a conducting charged sphere of radius r. due to the induced charges on the sphere, find the electric potential at point p on the surface of sphere (in volt) (if kq/r = 18 volt).

Answer 1

the net potential at the center = potential due to surface charge + potential due to point charge

the net potential at the center = $\frac{Kq}{r}+\frac{Kq}{2r}$

but potential due to surface charge = 0

the net potential at the center = $0+\frac{18}{2}=9$v where [$\frac{Kq}{r}=18$]