Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

EM waves from standing charge

  1. Jul 1, 2004 #1
    Text books talk about EM waves from moving charges, but don't mention EM waves radiating from a standing ie. not moving charge?

    I would think that for one standing charge to exert a force on a second standing charge, there must be a carrier particle/wave. Is this not an EM wave?


  2. jcsd
  3. Jul 1, 2004 #2
    The action at a distance that effects the non-moving charge is known as an electric field, and the force arises from the fact that the Force, F, equals the Electric field, E, divided by the test charge q (F=E/q).

    An EM wave is caused by a changing electric field, which in turns causes a changing magnetic field, and vice-versa. All this is a consequence of Maxwell's equations.

    But what you may be confused about is that the carrier, at it may be called, does not exist. An EM wave can travel through vacuum. It requires no carrier.

    Hope this helped.
  4. Jul 1, 2004 #3
    By "carrier particle" I didn't mean the medium in which the wave travels (air, water, vacuum etc.) but the way one charged particle learns that there is another charged particle nearby, and then acts according to the electric field equation.

    Something must travel from the first particle to the second. No?
  5. Jul 2, 2004 #4
    I haven't had any lectures on quantum ED yet, but as I understand it the particles that cause the force in the non-moving case are only virtual Photons, they "transport" momentum between the two electrons but do not affect any other particle, therefore cannot be detected. So they do not form a wave. If the electron is accelerated, there also appear "real" Photons who can be detected.
  6. Jul 4, 2004 #5
    That seems reasonable. . . at least reasonable enough that I can stop thinking about it for a while. Thanks for your help brentd49 and kuengb.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook