A long coaxial cable of radius a is carrying a non-uniform current density J = r z 2 (into the page). The outer shield is

A long coaxial cable of radius "a" is carrying a non-uniform current density J = r zˆ 2 (into the page). The outer shield is an un-grounded conductor and a dielectric r is filled between "a" and "b". (a) What are the magnetic fields inside the cable r < a? And in the dielectric a < r < b? (b) Use the formula s n H H J ˆ ( ? ) = 2 1 2 to derive the surface current density at r = a, and at r = b.