Electrostatics and calculation is related to electric field and potential.
A static electric charge is distributed in a spherical shell of inner radius R_1 and outer radius R_2. The electric charge density is given by Rho=a+br, where, r is the distance from the center, and zero everywhere else.
(a) Find an expression for the electric field everywhere in terms of r.
b) Find expressions for the electric potential and energy density for r<R_1.
Take the potential to be zero at r->infinity.