An infinitely long cylindrical tube, of radius a, moves at constant speed v along its axis. It carries a net charge per unit length λ, uniformly distributed over its surface. Surrounding it, at radius b, is another cylinder, moving with the same velocity but carrying the opposite charge (−λ). Find:
(a) The energy per unit length stored in the fields.
(b) The momentum per unit length in the fields.
(c) The energy per unit time transported by the fields across a plane perpendicular to the cylinders.