We know that electrons move from the negative to positive terminal, and that holes flow in the conventional direction of current - from the positive to negative terminal.
I've always assumed that this means that electric signals travel in the conventional current direction and that it's the travel of holes that gets close to the speed of light. Upon further research I come across mentions of electric signals being the electromagnetic waves traveling through the medium by the excitation of the electrons.
This begs the question. If electric signals are the propagation of EM waves at close to c in which direction do these waves travel? In the conventional direction? In the direction of electron flow? In both directions?
I can easily imagine that the signal is directionless and propagates from the point of contact/source of signaling in all directions like light in a dark room. But I'm not sure.
Note: This merely presents an experiment to perhaps clarify the intent of the question above. I'd accept answers that don't address this part of the question. Note that you can treat this as a thought experiment but I think it's possible to physically set up this circuit. The only problem is we'd have to deal with resistance in the real world.
Consider a circuit that has 3km of conductors. We start with a DC source attached to 1km of conductor. For simplicity you can assume that the conductor has zero resistance. We attach an LED at the end of the conductor. Then we complete the circuit with 2km of conductor back to the DC source:
1km of wire ┌─────────────────────────────────[resistor]─(LED)───┐ │ │ ╱ switch │ │ │ [DC voltage source] │ └────────────────────────────────────────────────────┘ 2km of wire
Assume the wires are spooled so that physically the light bulb and the switch are next to each other.
If I close the switch would I expect the LED to turn on roughly 3.34 us later (the time it takes light to travel 1km) or 6.68 us later or somewhere in between?
Does it make a difference if the 1km line is attached to the positive or negative terminal?
Does it make a difference if the wires are not spooled but are physically laid out over the 1.5km distance? Does the physical geometry make a difference eg. a circle vs a straight line and back?