The questions I ask are based on the peculiarities of quantum physics that I except but don't necessarily understand.

Thought experiment: If you are able to place a single static electron in a vacuum (ignoring the possible effects of virtual particles) with the understanding that there are virtual photons surrounding it (do not know if these are only present when the electron is in motion) how fast would the electron have to be accelerated to produce an electromagnetic field? Would an electromagnetic field be produced instantly at any velocity above 0? Second: When shown a typical stationary bar magnet with "particles" spread around it to help vizualize the magnetic field, once placed" do those "particles" remain influenced by the magnetic field?

  • $\begingroup$ Can you rephrase the second part of the question? $\endgroup$ May 25, 2020 at 17:32
  • $\begingroup$ A perfectly static electron has no uncertainty in its position and no uncertainty in its momentum. The Heisenberg Uncertainty Principle forbids that. So if you insist that its momentum is very small (and hence the uncertainty in its momentum is also very small), you have to accept large uncertainty in its position. $\endgroup$
    – PM 2Ring
    May 26, 2020 at 10:33
  • $\begingroup$ If you would like to resubmit an answer please re-read the question. I didn't ask about the Heisenberg uncertainty principle and I didn't ask about momentum. $\endgroup$
    – Cooper
    May 26, 2020 at 19:08
  • $\begingroup$ To S's Cat. You often see a horseshoe magnet or a bar magnet with Magnetic particle sprinkled around 2 show magnetic fiel $\endgroup$
    – Cooper
    May 26, 2020 at 19:10
  • $\begingroup$ To S's Cat. You often see a horseshoe magnet or bar magnet with Magnetic particles sprinkled around to visually depict magnetic lines. One Source magnetic particles are placed are those particles still under the influence of the magnetic field? Meaning, I guess I can answer my own question, is a magnetic field always "on"? It's a question trying to figure out if the magnetic field is fluctuating even though the magnetic particles in the field or stationary? $\endgroup$
    – Cooper
    May 26, 2020 at 19:13

1 Answer 1


Would an electromagnetic field be produced instantly at any velocity above 0?

Even a static electron produces an electric field. And an electron moving with a constant velocity also produces an electric field, along with a time-dependent magnetic field. Only when an electron attains a non-zero acceleration (however that may be), it starts radiating electromagnetic radiation and can produce a time-dependent magnetic field as well. In total, what we get is an electromagnetic field.

  • $\begingroup$ I'm sorry, are you saying that stationary electrons do not produce magnetic fields? $\endgroup$ May 25, 2020 at 18:29
  • $\begingroup$ @GiorgioComitini Yes. You need steady currents to produce a magnetic field. $\endgroup$ May 25, 2020 at 21:11
  • $\begingroup$ A single electron with non-zero constant velocity does produce a magnetic field (stationary electrons do produce magnetic fields). Before you modified your answer you said it doesn't. It's alright now. $\endgroup$ May 26, 2020 at 7:26
  • $\begingroup$ However, note that the magnetic field produced by the stationary electron (as well as its electric field) is time-dependent: the time dependence is due to the change in the electron's position. It's not oscillatory, but still time-dependent. $\endgroup$ May 26, 2020 at 7:34
  • $\begingroup$ @GiorgioComitini A single electron moving with a constant velocity constitutes a current. But a stationary charge does not. So a stationary charge \textbf{does not} produce a magnetic field. $\endgroup$ May 26, 2020 at 7:41

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