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Question about opposing magnets

  1. Sep 5, 2015 #1
    My fundamental question is, do opposing magnetic fields eventually degrade each other over time? If they do, is there a way to mitigate or eliminate their ability to degrade one another?

    If I had one permanent magnet facing up and another permanent magnet facing down hovering over it (with the desired effect to keep it hovering, including the effect of gravity), would their fields eventually cancel each other out over time - or is there a way to keep it hovering, indefinitely, until the end of time, without introducing external energy inputs?
     
  2. jcsd
  3. Sep 5, 2015 #2

    Hesch

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    Gold Member

    You are speaking of permanent magnets.

    It depends on the steel used in the magnets. As for a steady state of the magnets, the answer is no. But if the magnets e.g. vibrate, the point in their magnetizing curve will be displaced some. This displacement will follow hysterisis-curves, and if these curves are not exactly closed, the magnets could be demagnetized. You could say that if the area within a hysterisis-curve is large, the magnet will be more rigid to demagnetizesation ( hope this is the right word ).

    Manufacturers will, after having magnetized the magnets, "shake" them a bit magnetically, so that they are not extremely magnetized by delivery, but say you have some PM-motor and the specified max-current is excessed, the magnets will be demagnitized, and the performance of the motor will be decreased permanently.

    200px-Hysteresis_loops.PNG
     
    Last edited: Sep 5, 2015
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