Hollow Cylindrical Conductor?

Question

The figure shows the cross-section of a hollow cylindrical conductor with radii a = 0.80 cm and b = 3.80 cm which carries a current 10.00 Amps uniformly spread over its cross-section. Find the magnitude of the magnetic field at a distance of 3.00 cm from the axis.

Answer 1

Determine the magnetic field B in a cylindrical cavity inside an infinitely long cylindrical conductor. The radii of the cavity and the conductor are respectively a and b and the distance between their parallel axes is d (b > a + d). Assume the current I is uniformly distributed across the cross section of the conductor.