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Homework Help: Induced emf and magnetic flux

  1. Feb 22, 2010 #1
    1. The problem statement, all variables and given/known data
    The setup is a pair of two circular wires, a small one of radius b and a large one with radius 2b, both sharing the same center and located on the same plane. There is a magnetic field of strength B within the smaller circle that comes out of the paper towards the observer. The field covers a circular area with radius A such that A<b. The magnetic field is changing at a constant rate and creates an induced emf of e in the smaller wire. What is the induced emf in the larger wire?

    2. Relevant equations
    magnetic flux=B*A*cos theta
    theta=0 degrees

    3. The attempt at a solution
    As far as I can tell, the induced emf should be the same for both wires because the area of the field is contained within the circumference of both wires, so each has the same change in magnetic flux over time. The only other way I would think possible is if the distance away from the wire has an affect in the induced emf, but I can't think of any equations that deal with the distance between the magnetic field and the wire. You're input is most appreciated!
  2. jcsd
  3. Feb 22, 2010 #2
    Biot-Savart is your equation of choice here, try find the field as a function of radius and work on the answer from there...
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