A long straight cable of length l is placed symmetrically along z-axis and has radius a(<<l). the cable consists of a thin wire and co-axial conducting tube. An alternating current I(t) = I0 sin (2πνt)flows down the central thin wire and returns along the co-axial conducting tube. The induced electric field at a distance s from the wire inside the cable is E(s, t) = μ0I0cos(2πνt) ln(sa)^k. The displacement current density inside the cable is