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Lenz's Law and a bar magnet

  1. Jan 16, 2007 #1
    I'm stuck with Lenz's law, and questions involcing magnet/electromagnet theory

    such as:
    The diagram shows a bar magnet falling through an aluminum pipe. Electric currents are induced in the pipe immediately above and below the falling magnet. In which direction do these currents flow?

    http://www.quizmebc.ca/images/exams/4000130.gif

    Any help/explainations would be greatly appreciated.

    Thanks
     
  2. jcsd
  3. Jan 17, 2007 #2
    Lenz's law states that the emf induced opposes the cause of its production. So when the north pole of the magnet approaches a cross-section of the pipe, the opposite pole, ie the magnetic south pole is formed when viewed from the north pole of the magnet, hence the current flows in the clockwise direction.

    When the magnet passes that same point, the south pole is moving away from it, since electric flux is decreasing due to the south pole, the emf will try to maintain the flux in the same direction and hence when viewed from the southpole of the magnet, the magnetic south is formed in that cross section of the pipe, and hence, the current flows in the anti clock wise direction when viewed from the frame of the magnet

    Sorry if I couldnt make it clearer, but tell me what part irks you and ill help you if I can.
     
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