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Q & A: is electricity in wires?

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Most recent answer: 06/10/2011
Q:
Why does electricity stay on the wires? Your reply would interest all your readers for the "explanations" given are so bogus! Such as "vacuum" and air are insulators. (But electrons travel well in vacuum and in air they diffuse along just like they do in copper!) Schrodinger says think of electrons as waves (of "probability") and I will tell you where they are both INSIDE AND OUTSIDE of the copper. Maxwell says think of the copper as a continuum (even at its surface!) and I will tell you where and how the electrons move both INSIDE AND OUTSIDE of the copper. So they agree! The eleccricity does not stay in the wires!
- John (age 70)
Surrey, UK
A:
There are several issues here. One is where the actual current flows. It really does flow in the wires. The mobility of charge carriers may well be high in the air or vacuum but since there are virtually no charge carriers there, it doesn't matter. That's true whether you calculate their concentration via classical means or via quantum mechanical means. I'm puzzled about what point you're trying to make.

Perhaps what you're referring to is the other side of electromagnetism- the fields, not the charges. It's true that if you ask where the energy is flowing in a current-carrying wire, it's largely in the fields outside the wire. Furthermore, in steady-state the Poynting vector describing the energy flux points mainly into the wire, near the wire. Energy is flowing from the field into the wire, which explains why it heats up.

Mike W.

(published on 06/10/2011)

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