A hollow dielectric sphere has R1 and R2 as its inner and outer radii. The total charge carried by the sphere is +Q which is uniformly distributed throughout the dielectric sphere between R1 and R2. The electric field for R1<r<R2 is given by :
If ρ be the volume charge density, charge Q=ρ.43π(R32−R31)....(1)
Let E be the electric field at r. Using Gauss's law,
E.4πr2=Qenϵ where ϵ is the permittivity of dielectric medium.
or E.4πr2=ρ.43π(r3−R31)ϵ
or E=Q(r3−R31)4πϵr2(R32−R31) using (1)