How EM wave travels

Discussion in 'General Electronics Chat' started by darshanmehta2k, Aug 22, 2004.

  1. darshanmehta2k

    Thread Starter New Member

    Aug 22, 2004
    5
    0
    Hi All,

    I have one very basic question about Electro Magnetic wave. Could anybody explain me, how EM wave travels in air. In wire, EM wave travels because Electron moves from ome place to other. As electron is associated with EM energy and as electron is travelling, EM wave will also travel. But in case of air, how EM wave travel. I am basically talking about Antena.

    Thanks!!

    Best Regards,
    Darshan Mehta
    http://www.geocities.com/darshanmehta2k/main.htm
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Hi,

    Electrons are chage carriers in conductors, of course. But we start speaking of electric fields in space. Dr. Maxwell said it much more elegantly, but the basis of EM propagation stems from the fact that a moving electric field gernerates a moving magnetic field, whic in turn generates a moving electric field, and so on. The effect propagates at teh speed of light, but its intensity decreases as the square of the distance due to the attenuation of the growing field surface.

    The electrons in wires are secondary phenomena. We find them useful, but they are not actors in EM field propagation.
     
  3. darshanmehta2k

    Thread Starter New Member

    Aug 22, 2004
    5
    0
    Hi Beenthere,

    Thanks a lot for the reply. So basically you are telling that EM wave is nothing but only field is travelling and not Electron. So to generate Electric field, we should have something like Dipole arrangement with Q+ and Q- charge on oppposite side. Now I think the charge should be very high to increase the intensity of Electric field. Could you please tell me the direction of Electric field. Becuase in case of conductor, the direction of Electric field is parpendicular to direction of current. I am little bit confuse about direction so could you please explain me about that. Once again thanks a lot.

    Best Regards,
    Darshan
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Hi,

    The electric field determines the potential in the dipole that drives the current (in effect, the electrons). The current, the electric field at the diople, and the corresponding magnetic field all exist along axes at right angles to each other. That is, there is a Z axis as well as the conventional X & Y. The Q- and Q+ charge distribution of charge comes about as a result of the electron folw under the influence of the driving electric field.

    This is a paraphrase. Dr. James Clerk Maxwell said this with a great deal more precision about 1886.
     
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