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Help with understanding electromagnetic induction

  1. Jul 17, 2010 #1
    When a charge is in motion, it produces a magnetic field. If the charge is in an external magnetic field, a magnetic force is induced on the charge. This I understand.

    When a conductor is moving relative to a magnetic field, there is an induced current in the conductor. This I don't get. If the conductor is stationary, and the magnet is moved around it, then how is there a magnetic force exerted on the electrons in the conductor to induce a current? Wouldn't the conductor need its own magnetic field for a magnetic force to be exerted on it, and for it to have a magnetic field wouldn't it have to be in motion?

    Thanks in advance.
  2. jcsd
  3. Jul 17, 2010 #2
    It doesn't have to be magnetic force to induce current. If the magnet is moved, the field it creates is no longer a static magnetic field; it's electromagnetic field instead. The E-component of the field exerts forces on the electrons of the conductor.
  4. Jul 17, 2010 #3
    I don't get it.
  5. Jul 17, 2010 #4
    Where do you not get it?
  6. Jul 17, 2010 #5
    The entirety of what you said.
  7. Jul 17, 2010 #6
  8. Jul 18, 2010 #7
    Take a look at the illustration of an aviation ignition magneto on page 3 of this article by Will Fox:

    http://eaa691.org/files/Tech Note #2 Magnetos.pdf

    The rotating 4-pole magnet induces an alternating magnetic field in the iron core, which generates a voltage and current in the coil (primary = 180 turns). This is a battery-less ignition system, where the power is generated by the rotating permanent magnet. This works on the Faraday law of induction.

    Bob S
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