Question: A long coaxial cable consists of two cylindrical shells. The inner cylinder with radius a carries a uniform line charge +λ (charge per unit length along the z direction), and the outer cylinder has a radius b and carries a line charge -λ. The charges move with velocity ¯v = vˆz along the surfaces of cylinders.
(a) Calculate the magnetic field: between the cylinders (a
(b) calculate the magnetic energy stored in the cable for a section of length /.