A hollow metal cylinder has inner radius a, outer radius b, length L, and conductivity sigma. The current I is radially outward from the inner surface to the outer surface.
Find an expression for the electric field strength inside the metal as a function of the radius r from the cylinder's axis.
J = I/A
J = [itex]\sigma[/itex]E
The Attempt at a Solution
I tried setting the two equations for J equal to each other, so I/A = [itex]\sigma[/itex]E. Then to get E by itself, E=I/(A*[itex]\sigma[/itex]). I then substituted in the area of a cross section of the cylinder, where A=(pi)r^2. This gave me E=I/([itex]\sigma[/itex][itex]\pi[/itex]r^2). The problem is this equation doesn't include L.