Repeat Exercise 28.43 for the case in which the current in the central, solid conductor...

Repeat Exercise 28.43 for the case in which the current in the central, solid conductor is I₁, the current in the tube is I₂, and these currents are in the same direction rather than in opposite directions.

28.43 . Coaxial Cable. A solid conductor with radius a is supported by insulating disks on the axis of a conducting tube with inner radius b and outer radius c (Fig. E28.43). The central conductor and tube carry equal currents I in opposite directions. The currents are distributed uniformly over the cross sections of each conductor. Derive an expression for the magnitude of the magnetic field (a) at points outside the central, solid conductor but inside the tube (a < r < b) and (b) at points outside the tube (r > c).