I've been doing some bedtime reading in Chabay & Sherwood's Matter & Interactions textbook (https://www.amazon.com/gp/product/0470503475/) and have come across some interesting tidbits. Here they are: I've always pictured electrons pushing each other through a wire, kind of like peas through a drinking straw. I thought this was a good way of explaining how, for example, a ceiling light comes on immediately even though the drift speed of electrons is relatively slow. Turns out Chabay and Sherwood say it isn't so: And so I think, okay, let's assume they're right. So what does the pushing? Chabay and Sherwood say it's electric fields that push the electrons through the wires, and that these fields are caused by particular, non-uniform arrangements of electrons on the surface of the wires -- electrons distinct from the "current carrying electrons" deeper inside: They even ask the student to draw a map showing the arrangement of surface charges in a simple circuit: And I think, Okay, that sounds reasonable. (Bear in mind that there's a lot of math between these excerpts where they make their case in a more quantitative fashion.) Then they explain why our ceiling light behaves as it does: And that's where, I think, they fumble the ball a little. Why? Because they say, "the rearrangement of the surface charges in the circuit takes place at about the speed of light," and that "the final steady state of the circuit is established in a few nanoseconds," just before they say, "Most lighting actually uses 'alternating current,' in which case the electron sea doesn't drift continuously but merely sloshes back and forth very short distances, everywhere in the circuit, 50 or 60 times per second." Which makes me think that the "final steady state" of my ceiling-light circuit isn't so steady. The surface charges on the wires must be re-arranging themselves continuously, 50 or 60 times a second. In other words, it appears that the movement of electrons in a wire carrying alternative current involves both constant "re-arrangement" and "flow" like so... ...where the blue dots represent the "surface electrons" that move toward and away from the surface of the wire, and the pink dots represent "current electrons" that move, longitudinally, through the wire. Now it seems to me we can picture the various arrangements of the blue "surface electrons" in such a circuit as a forming, over time, a kind of three-dimensional sine wave in the wire, pushing the pink "current electrons" back and forth. Like so: At time 0 we have the wire in equilibrium. The sine wave is at 0, start of a cycle. At time 1 the blue electrons on the left have made it all the way to the surface, while the blue electrons at the other end of the wire have hardly moved at all. This creates a potential difference that sucks the pink electrons leftward. The sine wave has reached it's positive peak. At time 2 all the blue electrons have reached the surface. There is no potential difference and the pink electrons have thus stopped moving. The sine wave is again at 0, in the middle of the cycle. At time 3 the blue electrons on the left have fallen inward while the ones on the right are still on the surface. This creates a potential difference that pushes the pink electrons to the right. The sine wave now reaches it's negative peak. At time 4 all the blue electrons have fallen back to the initial state, and the pink electrons have again ceased to move. The sine wave is again at 0, end of cycle. Ya think?