Physics 201- Introduction to Electricity & Magnetism
November 25- Induced electric fields






  Faraday's Law


We must calculate the magnetic flux, just as we did the electric flux, by integrating the field over some surface.   Unlike the electric flux in Gauss' Law, here we are concerned with an open, rather than closed surface.

The unit of magnetic flux is a weber: 1 Wb= 1 Tm2

Find the magnetic flux through a solenoid that is 40cm long, has a radius of 2.5cm, has 600 turns, and carries a current of 7.5A.

Notice that in Faraday's Law, what is important is the change in the flux, not simply the flux.

Given some change in magnetic flux, there will be an induced electric field and emf.  (If that electric field lies within a conductive wire, there will also be an induced current.)


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Jeff Phillips
Loyola Marymount University
Fall 2002