1. The problem statement, all variables and given/known data A charge is distributed uniformly throughout a non-conducting spherical volume of radius R. Show, that the potential at distance r from center (r<R) is given by: V=q(3*R^2-r^2)/(8*PI*e0*R^3) 2. Relevant equations From Gauss low: E(r)=q*r/(4*PI*e0*R^3) E(r)=-grad(V(r)) 3. The attempt at a solution After integrating I got: V(r)=-q*R^2/(8*PI*e0*R^3) which is in fact stupid, as it yields V=0 at r=0. So probably I integrated with wrong limits. How to obtain correct formula?