A long straight cable of length l is placed symmetrically along the z-axis and has radius a(<<l). The cable consists of a thin wire and a co-axial conducting tube. An alternating current It=Iosin2πνt 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)=μ0I0νcos(2πνt)lnsak^.

(i) Calculate the displacement current density inside the cable.
(ii) Integrate the displacement current density across the cross-section of the cable to find the total displacement current Id.
(iii) Compare the conduction current I0 with the displacement current I0d.