(2.16) A long coaxial cable carries a uniform volume charge density ρ on the inner cylinder (radius a) and a uniform surface charge density on the outer cylindrical shell (radius b). This surface charge is negative and just the right magnitude so that the cable as a whole is electrically neutral. Find the electric ﬁeld in each of the three regions: (i) inside the inner cylinder (s < a), (ii) between the cylinders (a < s < b), (iii) outside the cable (s > b). Plot |E| as a function of s. 2. Relevant equations Gauss' law 3. The attempt at a solution I am actually pretty confident at what to do except at one point. I can calculate the field inside the volume cylinder with Gauss' law. But by doing so I am not accounting for the field due to the surface of the outer cylinder. In my solutions manual it indeed seems that the field due to the outer cylinder is omitted - why is that? How can it be zero? I can certainly see it must be zero right in the center of the volume charge cylinder but why is it zero everywhere inside it?