Question 5: A uniformly charged ball of radius a and charge -Q is at the centre of a hollow metal shell with inner radius b and outer radius c. The hollow sphere has net charge +2Q. a) Calculate the electric field E(r) for each of the four regions r c. b) Using your result from part (a), calculate the potential for the region r > c. Assume that the potential is zero at infinity, as we always do for spherical symmetry. 2