How fast do electrons move through power cables?

Electrons may not be the only movers and shakers among subatomic particles, but they do power the modern world. How much work do they actually do, and how fast are they? The answer is more complicated than it seems.

For one thing, electric current doesn't always flow. Sometimes it just . . . jiggles. (There will not be a gag photo to illustrate that. If that's what you're looking for, you might as well close the window.) Alternating current yanks electrons one way, and the pushes them back again. Since the movement is what matters, not the direction, alternating current is often more efficient than direct current.

How fast do electrons move through power cables?

Direct current, however, sends electrons jetting through wires. The question is, how fast?

Of course it depends. There are a number of different factors that affect the speed of the electron movement through the wire. For example, somewhat counter-intuitively, thinner wires and wires that have more resistance have higher electron velocities than thicker wires with less resistance, all other factors being the same. A good way to understand this is to picture a wave washing up on the shore. Any people who have spent time watching the tide come in, particularly on rocky shores, have seen waves slowly wash up a beach until they hit some narrow crag, at which point the water will jet forward down the narrow channel. The same amount of pressure, squished into a small passage, will have a bigger effect.

Water is a common metaphor used when describing electricity. People use the words ‘tide' and ‘current' and ‘flow' and ‘flood,' but to describe this phenomenon – the speed of electrons moving through a wire – scientists use the term ‘electron drift.' That alone should clue most people in to the fact that this movement is not the lightning speed which is usually imagined.

How fast do electrons move through power cables?

In fact, electrons drift, slowly and possibly bedecked with faded jean jackets and cowboy hats, through wires at around .1-.4 millimeters per second. This means they get beat by the average snail, which moves at around .3-1 centimeter per second.

No word yet on how fast an electrified snail's electrons would go. If any Io9er finds out, they should be sure to never, ever tell me.

Via School Science, Amasci and Animal World and enotes.

Top image via Itsray.