(Solved): Two concentric, cylindrical conductors of radii a and b are filled with a conducting material of ...

Two concentric, cylindrical conductors of radii $a$ and $b$ are filled with a conducting material of conductivity $?=\frac{?}{?}+?$, where $\underline{?}$ and $?$ are constants. Let ${\mathrm{V}}_{\mathrm{o}}$ is the potential difference between he two conductors, and $\mathrm{L}$ is the length of each conductor. a. What should be the unit of $?$ and $?$ ? b. Assume that the current $I$ flow from the outer conductor to the inner conductor, show that the current density is given by: $\overrightarrow{\mathbf{J}}=\frac{I}{2?sL}\hat{\mathbf{s}}$ c. What is the electric field between the conductors? d. Show that the resistance of the conducting material is given by: $R=\frac{1}{2??L}\ln \left(\frac{?+?b}{?+?a}\right)$