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Simple diamagnetic question

  1. Sep 12, 2011 #1
    suppose that i have a piece of magnet close to a piece of diamagnetic material
    the piece of diamagnetic material is held still

    will the magnet be repulsed isotropically , or will there be a torque exerted on the magnet so that its poles face perpendicularly towards the piece of diamagnetic material?
     
  2. jcsd
  3. Sep 13, 2011 #2
    The permanent magnet and the diamagnetic material will repel each other no matter how they are oriented to each other. If the north pole of the permanent magnet is facing the material, it will induce a north pole in the near side of the object, and "likes repel". If the south pole of the permanent magnet is facing the material, it will induce a south pole in the near side of the material, and again "likes repel". It think your problem is that you are trying to rely on intuition to make a sense of it. But intuition (aka, everyday experience) will not help you out here because diamagnetism is such a weak effect it does not show up in everyday life. You have to go looking for it using lab equipment. Think of diamagnetism as the opposite of paramagnetism/ferromagnetism. Just as your steel refrigerator door attracts magnets no matter their orientation and exerts no torque, diamagnetic material always repels.
     
  4. Sep 13, 2011 #3
    you are very right about intuition indeed

    Based on my experiences of handling magnets so far, they tend to want to orient themselves so that their poles will contact a piece of ferromagnetic material

    as in, if there is a thin disc shaped magnet, almost like a coin, where the faces are the poles, when near a piece of iron, it will want to go 'face first' into the iron; the attraction is harder if the magnet was face-on to the piece of iron

    now if there was a piece of bismuth , which is diamagnetic, instead... the magnet would want to go away from the bismuth ... following from the effect of inducing a like pole within the piece of bismuth, can i say that the repulsion will be harder if it was face-on , than it would be if it was side-on? and, by extension, if the magnet was facing at an angle from the piece of bismuth, will it tend to reorient itself so that it faces the bismuth piece side-on?
     
    Last edited: Sep 13, 2011
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