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Electromagnetic waves

  1. Sep 28, 2004 #1
    I have a project but problems in formulating...
    the project is about the conductivity of a charged metallic body which is spinnig on a fixed axis. I am trying to find out whether there is a relationship between the characteristics of the electromagnetic waves emitted by the body and the conductivity of it. can you suggest a textbook? or any idea? thanks for all help...
  2. jcsd
  3. Sep 28, 2004 #2
    I am also interested in this, if anyone has directions. I believe Lorentz (in 1920-something) did a similar calculation, in order to prove to students that the spin of an electron does not work that way.
  4. Sep 28, 2004 #3


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    The conductivity is a major player in determining the current. in a pure conductor, the current is at the surface. With finite conductivity, the current will penetrate into the volume. TheE&M fields will vary with the current. And, eddy currents are probably at play also. Older E&M book authors, Smyth and also Stratton, love these kinds of difficult problems. Check out one or both of the Ss.
    Reilly Atkinson
  5. Sep 28, 2004 #4
    gonzolo what do you mean that the spin of the electrons does not work that way? by spinning i mean that the body has a constant or or accelerated angular velocity. but i understand your point. I would be pleased to find the works of lorentz, i am sure he made amazing studies to discover the nature of elec. mag. waves.
    reilly thanks for reminding the eddy current problem, i almost forgot about that :)) is that julius adams stratton? i examined his book, it was really great. i think the books were better in the past.

    i would like to ask both of you about the details soon.
  6. Sep 29, 2004 #5
    When the notion of spin was introduced for particles (Pauli exclusion principle etc.) in the 20's, some people did wonder whether the electron could be modeled as a solid spinning charged sphere, since this would also cause a magnetic field and an angular momentum in the required direction. However, calculations taking into account the mass and charge of the electron showed inconsistencies (not the same order of magnitude that is observed in particular, and perhaps an enormous electron radius).

    I read an annecdote about students asking the question to Lorentz. He replied with calculations which clearly showed they were wrong, but that they barely inderstood. I am not sure how much work is such a calculation, what it is exactly that was contained the annecdote calculation, or where one could find it. Whether any proof that electron spin wasn't actual mechanical spin has ever been published, I am not sure either. Perhaps it is too elementary for publishing, and more of a textbook problem.
  7. Sep 30, 2004 #6
    i think to source of the problem is my english. i am not so fluent... i konw that the spin of the electrons shouldnt be understood as a solid spinning. think of a metal disk which is has an amount of charge on. by spin i meant the rotation of this disk on a fixed axis. now if you read carefully my posts you may see the point. sorry for any misunderstanding
  8. Sep 30, 2004 #7
    I understand. The thing is that we are interested in the same calculations, but for entirely different reason. I am interested because of the Lorentz annecdote, while you are interested for your project. Although I believe it, I am interested to see the proof that electron spin is not like actual solid spin. If someone answers your question, it might also answer mine. Sorry to intrude.
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