Chapter 27, Problem 57EAP

A hollow metal sphere has inner radius a, outer radius b, and conductivity $\sigma$ . The current I is radially outward from the inner surface to the outer surface.

a. Find an expression for the electric field strength inside the metal as a function of the radius r from the center.

b. Evaluate the electric field strength at the inner and outer surfaces of a copper sphere if $a=1.0\text{cm,}b\text{=}\text{2}\text{.5}\text{cm}$ , and $I=25\text{A}$ .