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Flux in magnetic core according to special relativity

  1. Feb 10, 2016 #1
    So say you have a magnetic flux in a closed magnetic path circuit (like a TX core). Well I mean we draw arrows and stuff to indicate how the magnetic flux travels, but after watching this:

    I'm having trouble understanding why there is any flux moving through at all.
    Can someone please help me to rectify these two non-mutually exclusive concepts?
  2. jcsd
  3. Feb 10, 2016 #2


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  4. Feb 10, 2016 #3
    I have seen that video before some time ago...
    I 'always' knew pernanent magnets were due to electron spin (magnetic moments and grain alignment of domains), but: Oooh, so, and this is really irritating, but you're saying that it's really just current in a wire that is described by Special Relativity, (this model is of very limited use). But electro-magnts with a core or permanent magnets must be treated quantum mechanically.
    And special relativity and quantum mechanics don't seem to mix, which is where the frustration comes in.

    in other words is is not very helpful to think of Special Releativity when dealing with magnetism?

    Thanks for the reply.
  5. Feb 10, 2016 #4


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    You don't need SR or QM to describe current flow in a wire nor the generation of an electric and magnetic fields
    Classical physics and Maxwell's equations describe things adequately

  6. Feb 10, 2016 #5


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    It's not that you can't think of SR when dealing with magnetism, SR provides us with a very good explanation of why moving charges produce magnetic fields. My understanding is that that fundamental particles like the electron simply have an intrinsic magnetic field. Unfortunately I don't know enough to explain any more.
  7. Feb 11, 2016 #6
    I am a huge fan of Maxwell, but I'm not really thinking about practical application, more curiosity about the universe (I'm just getting interested in The Standard Model)

    Yeah that's fine, I just don't like how it seems like there are two different things that don't mix, explaining the same phenomenon: moving charges -> magnets
    quantum magnetic spin -> magnets
    Like it seems hard for me to accept from the video that 'this is how magnets work, but there are other ways to do it as well, that have nothing to do with this'. There must be some connection.
    I'll only accept it if I have to, if this is the current limit of our knowledge.

  8. Feb 11, 2016 #7


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    I think you can model the magnetic field from an electron as being generated from a small loop of current, but I really don't know any details about it.
  9. Feb 12, 2016 #8
    I appreciate this isn't your specific expertise.
    I was wondering if you were directly above the centre of a tiny tiny internal current loop, even at a fair distance in the material, if the circumferene/path would look contracted enough to explain the effect....just a thought
  10. Feb 13, 2016 #9
    Also, I suppose what the issue I have with the aforementioned video is, is that it kind of implies that the a magnetic field is just an electric field, in which case the 'electromagnetic field' which permeates the universe would really just be a 'charge field' (positive and negative, like an electric field rather than electromagentic)....
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