CourseNotes.42 - Recall the definition of potential V f V i...

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Unformatted text preview: Recall the definition of potential V f- V i =- Z f i ~ E · d~s From the last chapter (Kirchoff’s loop rule) we know that the potential is a single valued quantity and therefore if we walk around a closed circuit and come back to the original point we should get zero change in potential. To get at the concept of emf, lets go back to the definition. E = dW dq So, emf is the amount of work done per unit charge around a closed loop in the circuit. Recall from physics 2048 the definition of work W = Z ~ F · d~s = q Z ~ E · d~s Hence, taking the work to be done around a closed loop and differentiating with respect to charge we find E = I ~ E · d~s (37) We can see that this looks very similar to the definition of potential. We know however that if we integrate the electric field around a closed loop we must get zero potential difference. The moral of the story is: potential only has meaning for electric fields produced by static charges and must be abandoned when talking about electric fields produced by induction...
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