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## Homework Statement

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.

## Homework Equations

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.