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Dropping magnet through vertical aluminum tube

  1. Jan 30, 2012 #1
    A well known physics experiment is dropping a magnet through a vertical aluminum tube.
    The magnet slows noticably before passing completely through the tube. Electrical current is created in the aluminum tube thereby creating a magnet thereby creating an opposing magnetic flux to slow down the falling magnet.

    My question is whether, theoretically, current is also induced in the magnet and/or forces are exerted on the magnet about its axis ?

    Another question is whether the Right Hand Motor Rule or the Left Hand Generator Rule can be applied to this experiment ?

    Thoughtfully, Doug Ettinger
  2. jcsd
  3. Jan 30, 2012 #2
    The basic rule is Lenz's law.
    The falling magnet causes a changing magnetic flux linkage in the Aluminium tube which causes an emf and a resulting induced current.
    The induced current opposes the change causing it.... the falling magnet.... currents circulate around the aluminium tube to effectively try to 'repel' the falling magnet.
  4. Feb 2, 2012 #3
    A problem similar to the subject experiment is posed. How is the de-acceleration calculated for a magnetized object of mass, m, and velocity, v, moving through a conductive material (assume an aluminum tube)? No other force fields including gravity are involved.

    The magnetized body has a magnetic field intensity of H = B/u where B = magnetic induction and u = permeability of the medium.

    Need help, Doug Ettinger
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