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Faradays law and EMI confusion

Physics Asked on September 2, 2021

According to EMI definition, it is the changing magnetic field acting ON the conductor that induces an emf. However when using Faraday’s law, instead of finding the changing magnetic field acting on the conductor we find the changing magnetic field in the space enclosed by the conductor. Why?

2 Answers

Strictly speaking, a changing magnetic field acting on the conductor does not induce an emf. Emf is a an integral concept (it is defined as the work per unit charge along a finite path).

What can be said is that a changing magnetic field at one point (independently if there is or not a conductor) induces a non zero curl of the electric field at the same point. The existence of a local relation involving derivatives, as well as a reasonable assumption of smoothness of the fields, ensures the possibility of recasting the same information in the form of a global (integral) relation between the change of the magnetic flux due to the time variation of the ${bf B}$ field, and emf. At this level, it is possible to combine this result with the expression for motional emf to obtain the Faraday law.

Answered by GiorgioP on September 2, 2021

found the SIMPLE answer I was looking for while thinking about it myself. gosh it was hidden in plain sight lol. textbooks really dont want our lives to be easy as they never reveal how or why just what (regarding faradays law).

Answered by mad112 on September 2, 2021

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