A hollow metal sphere has inner radius a, outer radius b, and conductivity . The current I

Question:

A hollow metal sphere has inner radius a, outer radius b, and conductivity σ. 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 cm, b = 2.5 cm, and I = 25 A.