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Electromagnets Repelling Metal

  1. Jun 18, 2011 #1
    I have a small physics book that states that if you run electricity throught a magnet it will repel metal. I just want to know if this is true.
  2. jcsd
  3. Jun 18, 2011 #2
    I'm pretty sure that is false.
  4. Jun 18, 2011 #3


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    Gold Member

    Electromagnets can be used to launch non-ferrous metal rings. See here.

    Last edited by a moderator: Sep 25, 2014
  5. Jun 18, 2011 #4
    If the word "magnet", in the OPs question, is changed to "wire" or "conductor", then the statement would be true. It's an effect described by Lenz's Law.

    Last edited by a moderator: Sep 25, 2014
  6. Jun 18, 2011 #5
    Now say I did change the word magnet to "wire" or "conductor". Could you explain how that would work?
  7. Jun 19, 2011 #6
    Did you look at the links? In the case of the video link, when a changing current flows through the wire, it sets up a changing magnetic field around the wire. This changing magnetic field induces a current in the nearby metal plate, which in turn creates another magnetic field that opposes the magnetic field created by the current in the wire. Because the two fields oppose, there is a repusion force between the wire and the metal plate.

    Here's another cool demonstration of Lenz's law:


    Notice how the magnet appears to momentarily float before it touches the copper base. In this case, the magnet has a steady magnetic field around it. However, because the magnet is moving as it approaches the copper base, the magnetic field of the magnet cuts across the copper plate inducing a current in it, which in turn creates another magnetic field that apposes the magnetic field of the magnet.
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