Hi I have a quesiton about current start signals in a simple circuit such as explained in http://amasci.com/elect/poynt/poynt.html. Turning on a switch somewhere in the circuit, sphere of influences, i.e. motions of electrons in wire and generation of Poynting vector around the wire, start from the location of switch and spread by exactly or slightly less than speed of light c. Could you teach me about the mechanism of this spreading, e.g. EM waves generation ? Best.