Consider a simple network of a bulb whose two terminals are connected to two wires with open ends A and B respectively
A o--------💡--------o B
Now if a DC current source is attached across A and B, say terminal B is at +5 potential and terminal A is at 0 potential, then exactly what happens is that "negative charge flows to terminal at higher potential, i.e. terminal B" and what that means, as I understand it, is that : -
Because of electromagnetic forces, all of the electrons in the wire are displaced towards A with a certain velocity causing a positive current towards B. This drift of electrons heats up the highly resistive filament wire in the bulb and makes it glow.
So something like the following is a good representation of the journey of a single electron
e in the wire for a DC circuit:
A o--------💡-----e--o B (+5) A o--------💡---e----o B A o--------💡-e------o B A o-------e💡--------o B A o-----e--💡--------o B A o---e----💡--------o B A o-e------💡--------o B
Assuming that my understanding of how a wire carries DC current is correct, I would like to understand how a wire carries alternating current.
I think that since AC current periodically changes direction, maybe the electrons move back and forth, (maybe oscillate along the length of the wire about their mean position?), which will also warm up the filament of the bulb and thus light it up. But I don't understand why they are able to move back and forth. Especially if the length of the wire was large, say 3 * 10^8 meters, then would the movement of electrons on one end of the wire be "in sync" with the movement of electrons on the other end?
Bonus question: how would the electron flow in DC circuits work if a bulb and a 5V voltage source kept 3*10^8 meters apart were connected by two straight 3*10^8 meter long wires? Assume that there's a switch halfway between one of the two wires and it has just been flicked to the "on" position.