http://en.wikipedia.org/wiki/Coaxial_cable http://en.wikipedia.org/wiki/Poynting_vector Could a coaxial cable be used for electric current instead of radio signals? 'For example, the Poynting vector within the dielectric insulator of a coaxial cable is nearly parallel to the wire axis (assuming no fields outside the cable and a wavelength longer than the diameter of the cable, including DC). Electrical energy is flowing entirely through the dielectric between the conductors. No energy flows in the conductors themselves, since the electric field strength is zero. No energy flows outside the cable, either, since there the magnetic fields of inner and outer conductors cancel to zero.' What causes resistance in a coaxial cable is it like normal conductors or does some resistance happen in the dielectric? Could you have a vacuum as the dielectric in a coaxial cable?