Electric field in a sphere
A nonconducting sphere of radius R has a cavity of radius a at its center. The rest of the sphere has a uniform charge density p C/m^3. What is the electric field in the following regions: (a) r > R; (b) a < r < R? (Hint: The charge within a shell of thickness dr is dq = p dV = p4(pi)r^2dr.)
I have no idea how to approach this problem. It's asking for the electric field, so I think it has something to do with E = kq^2/r^2 and the problem mentions 4(pi)r^2, which is the surface area of a circle. Please help!
