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Flux rule for motional emf

  1. Aug 31, 2012 #1
    The flux rule for motional emf can be stated as:

    d[itex]\phi[/itex]/dt = -[itex]\epsilon[/itex]

    I have some questions regarding this. 1) Should I find this rule intuitive?
    And secondly a proof of this rule is given in my book, which I have attached. I don't really understand the idea of the proof - is the idea to proof the above rule or to just proof that if it works, it will do so for loops, which "do not even maintain a fixed shape". Because the words seem to suggest the later but on the other hand that would mean that the above rule is generally unproved in my book.

    Attached Files:

  2. jcsd
  3. Aug 31, 2012 #2
    Just answering 1: You may find it intuitive by means of Lenz's law, which is a qualitative version of the above. It has similarity to Newton's third law, in the sense of action is reaction.
  4. Aug 31, 2012 #3
    okay but Lenz' law is just a more qualitative statement of the flux rule - but perhaps there isn't more to it.
    What about 2)? That one was more of a puzzle to me.
  5. Sep 3, 2012 #4
    It seems to prove the flux rule from their definition of flux plus the Lorentz force law. Both should appear earlier in the text.
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