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Three-poled bar magnet?

  1. Dec 9, 2014 #1
    Hello everyone!

    I am a high school physics teacher, and I am witnessing something with a piece of classroom equipment I can't quite explain: I have a bar magnet with three poles. There's a North pole on the top AND bottom, and a south pole in the middle. This would make sense if two magnets had been fused together, but that is not the case.

    The bar magnet was stored in the same place as all the other bar magnets, which are still functioning as simple N/S polar magnets, but this one somehow has a south pole in the center. The only difference is that the other magnets have partner magnets in their storage units, and this one did not, though I don't see how that could cause this.

    Would anyone care to offer any potential explanations?
  2. jcsd
  3. Dec 9, 2014 #2


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    Science Advisor
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    welcome to PF :)

    can you draw a pic showing where you think the poles are ... just to make it clear to us

    what experiment(s) did you do to determine the pole positions ?

  4. Dec 9, 2014 #3


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    Staff: Mentor

    And in addition to the sketch, if you could put a piece of paper on top of it and sprinkle on some iron filings, that would be helpful.... :-)
  5. Dec 10, 2014 #4
    So, I feel as if the iron filings speak for themselves as opposed to a drawn picture. We discovered this anomaly when I assigned my students to use compasses to determine the magnetic field around a bar magnet, and they drew this. I told them it was wrong, and went to correct me, and they insisted it was right. I took a look at their compass map around it, and to my surprise, it was the way it looks in the picture. Two similar poles on each end of the bar magnet, and then one different pole in the center.
    I gave them another bar magnet, and they saw the way it is usually configured.
    See for yourself.
    (PS: sorry about the learning goal and scale in the background of the picture.) photo.JPG

    Attached Files:

  6. Dec 10, 2014 #5
    Looks like NSN to me. Must have had a stronger magnet SN packed on top on the right side.
  7. Dec 11, 2014 #6


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    Staff: Mentor

    That's an interesting anomaly! Thanks for sharing. :oldsmile:
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