I understand that the speed of electricity varies with the conductor, but is supposedly 2/3 the speed of light. I had thought the speed would equal the speed of light. Why isn’t it? — AP
Although electricity involves the movement of electrically charged particles through conducting materials, it can also be viewed in terms of electromagnetic waves. For example, programs that reach your home through a cable TV line are actually being carried by electromagnetic waves that travel in the cylindrical space between coaxial cable’s central wire and the tubular metal shield around it. These waves would travel at the speed of light, except that whenever charged particles in the wires interact with the passing waves, they introduce delays. The charged particles in the wires don’t respond as quickly as empty space does to changes in electric or magnetic fields, so they delay these changes and therefore slow down the waves. The materials that insulate the wires also influence the speed of the electricity by responding slowly to the changing fields. The fastest wires are ones with carefully chosen shapes and almost empty space for insulation. In general, the less the charges in the wire respond to the passing electromagnetic waves, the faster those waves can move.