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B EM wave generation using a single charge in a vaccum?

  1. Nov 28, 2017 #1
    I wonder if it is possible to generate a propagating EM wave by making a single charge oscillate in vaccum ?

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


    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 ?


    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 ?
  2. jcsd
  3. Nov 28, 2017 #2


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    Gold Member

    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.
  4. Nov 28, 2017 #3


    Staff: Mentor

    Certainly. This is described by the Lienard Wiechert potentials.
  5. Nov 28, 2017 #4


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    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 travelling waves as you depict.
    Last edited by a moderator: Nov 28, 2017
  6. Nov 30, 2017 #5
    Thank you for the answers. I'll have a look at Lienard Wiechert potentials.
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