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Comment by haberman | Hacker News Reader

If electricity doesn't travel through wires, why do resistors dissipate heat?

I'm having trouble understanding what is even being claimed. Electrons are moving, without the movement of the electrons there is no electricity travel, without the wires there is no flow of electrons, so what does it mean to say that electricity doesn't travel through wires?

Is the claim just that the electricity, by way of fields, travels at a rate much faster than the electrons themselves are traveling? That seems like a reasonable claim. But "electricity doesn't travel through wires" seems rather suspect.

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The video seems to make a point that is entirely wrong: that (all/most) energy in a circuit travels directly between the source and the power sinks.

Now, if you follow it carefully, it makes a different point, that is actually correct: it actually claims that some energy travels this way, since the electric field is not strictly bound to the wires, some part of it radiates out.

What the video is sorely missing is a discussion of the intensity of that field, which is going to be extremely low even 1m away from the wires, for typical batteries. These effects are absolutely important though in high power cases, where even a small fraction of the energy carried along the wire leaking to nearby wires still means you can actually light a lightbulb (or burn many other things).

Energy transfer can take place via electrons and fields. The latter has a common household example: the microwave oven.

This is the best demonstration of EM fields I've seen. It kinda demonstrates what Derek was going for, but with resonant antennas the power transfer is way more that his theoretical setup.

https://youtu.be/lslHtCUSfN4

"Friction". Mechanically, electrons in a metal conductor behave something like a glass bead in honey. Observe that the microscopic Ohm's law says that the velocity is _proportional_ to the force being applied, the electrons do not accelerate as they would in a uniform electric field in vacuum.

The electrical charge travels through the wires. This causes an electrical field and a magnetic field surrounding the circuit.

The point is that the energy goes through the field, not through the wires.

In your example, the Poynting vector would go towards the resistor, where the energy is turned into heat.

> so what does it mean to say that electricity doesn't travel through wires?

I think it’s specifically that the energy flux has a well-defined vector at every point in an electromagnetic field, and those vectors do not point along the wires.

> If electricity doesn't travel through wires, why do resistors dissipate heat?

Thanks, For me this is the best comment in this thread.

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