Is there any matter in an electric current?

03 October 2010

Question

What is an electric circuit? Is there any matter in an electric current? Does it move?

Answer

There is matter flowing. An electric current is a movement of electrons which are tiny particles. They're very, very light compared to nuclei of atoms, so they're about 2/1000ths of the mass. But they still do have mass. They are matter and they're moving around. What happens in electric current is, essentially, you've got a conductor where these electrons can move quite easily. You shove some electrons in, extra electrons in one end using a battery or a generator or something. Electrons repel one another so that extra density causes all the other electrons to move away a bit. And so, you get this sort of wave, essentially, you can think of it as a wave of movement, going all the way through to the other end of the conductor.

This wave of movement moves very close at the speed of light, maybe 0.8 of the speed of light, but the actual electrons themselves are only moving at millimetres a second. So, the actual movement of electrons is very, very slow, but there is a movement.

The actual signal moves very quickly because it's a bit like a Newton's cradle where you hit a ball on one end, and then all the other balls transfer that impact all the way along, until the one on the other end flies away far quicker than any of the balls themselves are moving.

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