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Drag in a Dynamo

  1. Sep 2, 2010 #1
    I was wondering;

    Imagine two situations:

    1) I rotate an axle with a strong magnet attached within a conductive coil (a dynamo).
    2) I rotate an axle with a strong magnet attached without a conductive coil.

    Does the presence of a coil (and therefore the generation of current in the coil) add any drag to the rotary mechanism, or is the dynamo simply harnessing a form of energy potential that would have been lost otherwise?
  2. jcsd
  3. Sep 2, 2010 #2
    Traditionally, it's called "back EMF"
    Conceptually, one can consider the well established fact that the generation of electricity(actually, movement) with a mechanical generator REQUIRES resistance to that generation.
    That is, in ALL cases of mechanical electrical generators, there will be an opposing force.
    If it were not the case... Free Energy!!
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