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Whats reverse electromagnetic force?

  1. Jun 12, 2007 #1

    can you please tell me what is reverse electromagnetic force?

  2. jcsd
  3. Jun 12, 2007 #2


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    Staff: Mentor

    I believe that you are referring to "back EMF" that is generated in a coil or transformer.


    When you put an AC voltage across the primary of a transformer, that generates an AC (lagging) current in the primary. That AC current generates an AC magnetic flux, which couples to the secondary coil. That changing flux induces a current in the secondary coil, which generates its own flux in the core, and that secondary flux opposes the primary flux. So any current flowing in the secondary causes a reduction of input impedance in the primary (the so-called Back EMF, or reverse voltage due to the reflected load impedance).

    Does that help?
  4. Jun 13, 2007 #3
    ya that helps!!
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