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Rise of electromagnetism

  1. Jan 7, 2009 #1
    Dunno whether this is the right place for this question! but As it is related to subatomic particles, I think it is!!


    We know that magnetism arises due to rotation of an electron around its own axis in metals, but after all what happens due the moving electric current?
    Will the same thing happen on the movement of a proton here to there?

    Is the spin quantum number of electron somehow related with the magnetism?
    If yes, Why it has values like +1/2 & -1/2?
     
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  3. Jan 7, 2009 #2

    malawi_glenn

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  4. Jan 7, 2009 #3

    ZapperZ

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    The spin angular momentum for particles such as electron, proton, neutron, etc. has nothing to do with "rotation of an electron around its own axis". Yet, these can provide a net magnetic dipole moment. This already falsifies your starting point.

    Zz.
     
  5. Jan 8, 2009 #4
    May be it is not the 'rotation of the electron about its own axis', but surely it IS the 'movement' of electron causing the magnetism. My question is that whether any moving charge (positive or negative) causes magnetism or does the electron have some additional property causing the magnetism due to which only moving 'ELECTRON' causes magnetism.
     
  6. Jan 8, 2009 #5

    malawi_glenn

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    If you put a voltage over a conductor, you'll obtain an overall "motion" of electrons (electric current) which will induce a magnetic field.
     
  7. Jan 8, 2009 #6

    ZapperZ

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    We don't know that, and nothing in the physics says so. So if you are insisting that it is such a movement, you have to show evidence and the physics. If not, you're speculating.

    Note that for the spin 1/2, the rotational symmetry is such a way that you have to rotate TWICE (i.e. over 4pi) to get back to the same condition. This is definitely DIFFERENT what we are familiar with, i.e you turn around by 2pi, and you get to where you started. This already tells you that it isn't your ordinary "rotation".

    Zz.
     
  8. Jan 20, 2009 #7
    YOU mean If we rotate over 4pi we get to the same condition for an electron. But that seems impossible. Plz can you explain it?
     
  9. Jan 21, 2009 #8

    malawi_glenn

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    the spin 1/2 of an electron can not been seen as a rotation, rotation transformation of 2pi does not give the original state back, as required for rotations. For spin 1/2 particles - You must rotate 4pi to get the original state back - contradictorous to ordinary rotational systems.
     
  10. Jan 21, 2009 #9
    So our ordinary objects are with spin 1? But what makes the differce between 'ordinary' objects And electrons?
     
  11. Jan 21, 2009 #10

    f95toli

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    No, it is not really useful to talk about "spin" when dealing with ordinary objects.
    Spin is similar to e.g. charge in that it is just another intrinsic "property" of elementary particles; the name is bit unfortunate since it conjures up images of something rotating but that is -as has already been pointed out above- NOT what it is about.
    Electrons carry charge -e and spin 1/2, and that determines most of their behaviour.

    We are getting better and better at manipulating spin; e.g. spin valves for controlling spin currents (which carrys currents of spin as opposed to ordinary current that carries charge) are currently under development in many labs around the world.

    Note also that e.g. a graviton is assumed to have spin 2 so spin 1 and 1/2 are not the only possibilities; although the graviton particle has of course never been detected.
     
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