A thick-walled spherical shell of charge Q and uniform volume charge density p is bounded by radii r1 and r2 > r1. With V = 0 at infinity, find the electric potential V as a function of distance r from the center of the distribution, considering regions
(a) r > r2,
(b) r2 > r > r1, and
(c) r < r1.
(d) Do these solutions agree with each other at r = r2 and r = r1?