Find the temperature distribution in the space between two coaxial cylinders of radii `R_1` and `R_2` filled with a uniform heat conducting substance if the temperatures of the cylinders are constant and are equal to `T_1` and `T_2` respectively.

Explanation

In equilibrium `2 pi r k(dT)/(dr) = -A = constant`. So `T = B - (A)/(2 pi k) 1n r`
But `T = T_1` when `r = R_1` and `T = T_2` when `r = R_2`
From this we find `T = T_1 + (T_2 - T_1)/(1n (R_2)/(R_1)) 1n (r)/(r_1)`.