Faraday's Law integral

  • #1

Main Question or Discussion Point

My textbook said Faradays law EMF = integral of E.dl is only valid if the integration path is stationary.

Could someone explain what this means? Does it mean if the conductor changes shape Faraday law is not valid?

In motional EMF a conductor moves through a magnetic field and a EMF is generated, this can also be explained using Faraday's law
 

Answers and Replies

  • #2
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Faraday's Law in integral form is written

∫E·dl = -(d/dt)∫B·dA

where the line integral on the left side is exactly around the perimeter of the area being integrated on the right side. This can be seen by applying Stokes' Theorem (see Eq 7 in)

http://mathworld.wolfram.com/StokesTheorem.html

from which the differential form of Faradays Law is easily derived. So as long as the line represented on the left side is the perimeter of the area on the right side, even if the area is changing (moving), the integral form of Faraday's Law is valid.

Bob S
 
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