EM wave generation using a single charge in a vaccum?

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Discussion Overview

The discussion revolves around the possibility of generating a propagating electromagnetic (EM) wave by oscillating a single charge in a vacuum. Participants explore the theoretical implications and distinctions between single charges and dipole antennas in the context of EM wave generation.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether a single oscillating charge can generate a propagating EM wave, noting the differences from a dipole antenna where opposite charges oscillate.
  • Another participant asserts that an oscillating charge does generate an electromagnetic wave, suggesting that the definition of an electromagnetic wave involves oscillating charges.
  • A different participant references the Lienard-Wiechert potentials to support the idea that a single oscillating charge can indeed generate a propagating EM wave.
  • One participant critiques the initial understanding of the electric fields involved, stating that the depicted electrostatic fields do not represent radiated fields and do not propagate as traveling waves.

Areas of Agreement / Disagreement

There is no consensus on the nature of the EM wave generation by a single charge. Some participants support the idea that it is possible, while others express confusion or challenge the initial assumptions about the fields involved.

Contextual Notes

Participants express uncertainty regarding the interpretation of fields around a single oscillating charge and the distinction between electrostatic fields and radiated fields. There are unresolved questions about the conditions under which an EM wave can be said to propagate from a single charge.

DoobleD
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I wonder if it is possible to generate a propagating EM wave by making a single charge oscillate in vacuum ?

In practice, when we create EM waves, we (always ?) have opposite charges oscillating, like with a dipole antenna :

67.jpg

felder_um_dipol-jpg.jpg


In the dipole antenna case, I can see how the fields detach from the antenna when opposite charge oscillate. But if we only have a single charge oscillating in vaccum, is it still possible for the fields to "detach" from the charge ?

23.jpg


When the single charge oscillates, I can picture in my head the E field progressively updating, like waves on ropes (the rope being the E field here). That sounds kind of like an EM wave. But it seems a totally different situation than with a dipole antenna. Here it doesn't seem like the field can "detach" from the charge. Also, I'm not sure the magnitude of the field really varies in space and time here, it seems more like only its direction changes.

I didn't try to calculate anything, not sure where to start for this question. So I'm just trying to picture things in my head, and I realized I don't know how to interpret the field around a single charge oscillating in vaccum. Is it a an wave, is it not really ?
 

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To my knowledge, this charge will generate an electromagnetic wave. The very definition of an electromagnet is a wave generated by a oscillating charge.

I think you are also confusing many terms. Your question seems very jumbled up and I am finding it difficult to interpret the question.
 
DoobleD said:
I wonder if it is possible to generate a propagating EM wave by making a single charge oscillate in vacuum ?
Certainly. This is described by the Lienard Wiechert potentials.
 
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DoobleD said:
I wonder if it is possible to generate a propagating EM wave by making a single charge oscillate in vacuum ?
I think your dipole drawings (a) to (d) depict the electric field (electrostatic field) from the charges and not from the radiated field. The latter comes from the acceleration of charges in the conductors and is greatest near the centre. The electrostatic fields are just energy stores and do not propagate away as traveling waves as you depict.
 
Last edited by a moderator:
Thank you for the answers. I'll have a look at Lienard Wiechert potentials.
 

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