The Coaxial Cable. A long coaxial cable consists of an inner cylindrical conductor with radius a and an outer coaxial cylinder with inner radius b and outer radius c. The outer cylinder is mounted on insulating supports and has no net charge. The inner cylinder has a uniform positive charge per unit length ?. Calculate the electric field at the following locations. (a) at any point between the cylinders, a distance r from the axis E = (b) at any point outside the outer cylinder E = (d) Find the charge per unit length on the inner surface and on the outer surface of the outer cylinder, in terms of ?. inner? outer?