Field and Wave Electromagnetics 2nd Edition by David Cheng

Exercise 21

From the point of view of electromagnetics, the power transmitted by a lossless coaxial cable can be considered in terms of the Poynting vector inside the dielectric medium between the inner conductor and the outer sheath. Assuming that a d-c voltage V 0 applied between the inner conductor (of radius a ) and the outer sheath (of inner radius b ) causes a current I to flow to a load resistance, verify that the integration of the Poynting vector over the cross-sectional area of the dielectric medium equals the power V 0 I that is transmitted to the load.