I know that it's the accelerating electrons in an AC current that are the cause of far field effects. But, what about the reactive near field close to a wire that has a 60Hz AC current? What is the cause of the time-varying electric and magnetic fields around that wire? Is the cause of the (AC) magnetic near-field due to the flow of electrons within the wire? And is the (AC) electric near-field due to the charges of the electrons flowing within the wire? If it's the charges of electrons flowing in the wire that cause the time-varying electric near-field, then how is that possible since the wire would actually be considered electrically neutral (filled with uncharged charge), leading to a 0 field?

  • $\begingroup$ The wire is electrically neutral. Saying uncharged may be the source of your problem. There are charges, and they are accelerating. $\endgroup$ – garyp Jun 5 '15 at 16:42
  • $\begingroup$ garyp -- please see the edit to my last sentence. $\endgroup$ – adam3033 Jun 5 '15 at 16:50
  • $\begingroup$ Why do you assume that a wire on a non-zero potential is neutral? Of course it isn't. The total number of electrons in a wire only changes by very little because most of them are neutralized by the positive charge of the atoms in the bulk of the metal, but there is a non-zero net charge on every wire that is not on the same potential as "ground". $\endgroup$ – CuriousOne Jun 5 '15 at 17:09
  • $\begingroup$ CuriousOne -- You say that most of the electrons are neutralized by the positive charge of the atoms. That part I understand. But where is the non-zero net charge coming from in an AC wire if you have the same amount of electons and protons? $\endgroup$ – adam3033 Jun 5 '15 at 17:19
  • $\begingroup$ A time-varying current and a time-independent current do not require a finite charge density to exist. A current is just a net relative drift between oppositely charged particle species (e.g., electrons and protons). If you take the time derivative of Ampere's law and use Faraday's law, you will see from where the electromagnetic fields arise. $\endgroup$ – honeste_vivere Jun 11 '15 at 11:39

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