I want just the answer for how a potential difference across resistor causes electrons in it to move? Also, How the speed of electricity becomes equal to C(almost) means the electrons at a very long distance from terminals will start motion after a time the signal(at C speed) reaches it?
Let assume a situation for a resistor say R, A potential(maintained all the time even it losses some charges) of 1V,this 1V potential giving device is connected to R with a switch at one end say A of R and the other end say B is grounded(connected to earth) which offers OV(zero potential), the length of R is 100meter. When we close the switch, the electrons near B will start moving after a time which is approximately equal to the time taken by C speed to travel 100meter of lentgh. But don't forget the question is also and importantly about how potential difference provided actually causes motion to electrons with a brief and detailed explanation!