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Energy in Magnetic Field

  1. Jun 26, 2004 #1
    I am curious about is there any energy can be found / get in the magnetic field?
     
  2. jcsd
  3. Jun 27, 2004 #2
    Yes: in classical electrodynamics, a magnetic field in vacuum has an energy density of u0B2. This energy can be extracted. For example, a conductor moving at an angle through a magnetic field develops a potential difference between its endpoints. This can be used to run a current, thus performing work. The energy for that could only have come from the field, and indeed the resulting assembly produces a magnetic field that partially cancels the original field, maintaining energy conservation.
     
  4. Jun 27, 2004 #3
    Then where is the energy come from?
     
  5. Jun 27, 2004 #4
  6. Dec 10, 2004 #5
    Uh...you of course meant to say energy density is B2/2u0, right zefram?

    Creator :wink:
     
  7. Dec 10, 2004 #6
    Indeed that's what I meant. Can't everyone take a nap in class every now and then?
     
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