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A traveling magnetic field is created by means of applying out-of-phase currents to a number of coils. Is it identical to that created by a moving magnet, including relativistic effects?

  • Depends on what you mean by "identical". A local observer can't tell the difference for a suitable choice of coil excitations, but an assembly of coils can potentially produce magnetic fields that can not be produced by moving a single magnet (or even any number of magnets). – CuriousOne Dec 21 '15 at 16:38
  • You planning a new type of rail gun? :-) – Carl Witthoft Dec 21 '15 at 16:40
  • @CuriousOne Potentially the coil generated field could move faster than light. I am interested in what the practical differences might be, and how sub-luminally they can be identified. –  Dec 21 '15 at 16:46
  • Isn't a "travelling magnetic field" produced by a long series of coils analogous to this? – RedGrittyBrick Dec 21 '15 at 16:58
  • @RedGrittyBrick Partly, but the question is really about how to tell the difference between the two possible origins of the field –  Dec 21 '15 at 17:08
  • I had a hunch that you would be asking about the superluminal phase velocity case. :-) That's why I said that coil assemblies can produce fields that can't be produced with a single moving magnet. Can we detect the differences? Of course, just not locally. The physical vacuum is a linear medium, so to detect the phase and amplitude of n transmitters unambiguously, we need, at least, n receivers. – CuriousOne Dec 21 '15 at 17:12

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Yes, they are the same, at least at the scales of size, distance, and field variability at which the different generating methods cannot be discerned.

Terry Bollinger
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