Current I flows along the positive z-direction in the inner conductor of a long coaxial cable and returns through the outer conductor. The inner conductor has radius a, and the inner and outer radii of the outer conductor are b and c, respectively.
(a) Determine the magnetic field in each of the following regions: 0 < r < a, a < r < b, b < r < c, and r > c.
(b) Plot the magnitude of H as a function of r over the range from r = 0 to r =10 cm, given that I =10 A, a = 2 cm, b = 4 cm, and c = 5 cm.