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At the place where I work there are lots of motors and generators. Could I explain to an apprentice how a motor and/or a generator works with arguments based solely on special relativity?

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  • $\begingroup$ When you say based solely on special relativity, do you mean based solely on a Lorentz-symmetric model? $\endgroup$ Jun 13, 2021 at 2:08
  • $\begingroup$ Solely on special relativity? I would hazard that the answer is no. Wouldn't you need something else? $\endgroup$ Jun 13, 2021 at 2:09
  • $\begingroup$ Electric motors have been invented before SR, so SR is not even strictly needed to explain them (unless you have a very fast rotator) en.wikipedia.org/wiki/Timeline_of_the_electric_motor $\endgroup$
    – Quillo
    Feb 21, 2023 at 13:05

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Could I explain to an apprentice how a motor and/or a generator works with arguments based solely on special relativity?

No. You would also need electromagnetism. Maxwell’s equations are fully relativistic, but they are not usually considered to be part of special relativity.

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See the paper, "Magnetism, Radiation, and Relativity: Supplementary notes for a calculus-based introductory physics course" by Daniel V. Schroeder, Weber State University http://physics.weber.edu/schroeder/ [email protected] for a clever and pleasing explanation of how special relativity can be used to explain the origin of forces between current-carrying wires, etc. upon which motors are based.

The essential point (very briefly) is that electrical charges in motion (as in a wire) get relativistically contracted, and nearby charges that are not in motion feel extra forces because of that. Those extra forces are conveniently designated as "magnetic" in nature, although they all arise from electrostatic forces in moving frames of reference.

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  • $\begingroup$ @VincentThacker, thanks for that, will edit. BTW the paper really is worth reading. $\endgroup$ Jun 14, 2021 at 16:37

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