Problem 3.169

A long round conductor of cross-sectional area $S$ is made of material whose resistivity depends only on a distance $r$ from the axis of the conductor as $\rho=\alpha / r^{2},$ where $\alpha$ is a constant. Find: (a) the resistance per unit length of such a conductor; (b) the electric field strength in the conductor due to which a current $I$ flows through it.