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Thread: Why the induced emf is always negative?

  1. #1 Why the induced emf is always negative? 
    Forum Bachelors Degree
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    Hi! I read this article about Faraday's law, which states, that the emf will be always negative, by the formula, is this correct?


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  3. #2  
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    This is to do with Lenz's law which you should look up.

    It basically states that when you produce the EMF, the current prduced creates a magneti field
    the magnetic field that is induced will always act to keep the magnetic flux constant and thus the negative value.

    If you think about simple harmonic motion, the formula contains a negative sign indicating the direction towards the equilibrium point.

    It is similair in this situation, the magnetic field always tries to get the magnetic flux of the system constant.
    Not a great explanation but hopefully it helps


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  4. #3  
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    That explanation coincides perfectly with what I just read in my physics book. If the current flowed opposite of how you stated, then the flux would be in the same direction as the magnetic field. This would create a even greater flux and so a even greater emf and so on. It would basically spiral toward infinity. We all know that energy is neither gained nor lost in a system so thats just a statement of one of newtons laws really.

    so thats why emf= -N (Delta Flux/delta t)

    I guess its just a vector.
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  5. #4  
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    Yeh the negative sign just shows direction
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