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Homework Help: Motional EMF

  1. Feb 24, 2009 #1
    1. The problem statement, all variables and given/known data

    I have the following problem for physics homework:


    We are supposed to take t=0 as the instant when the corner of the square is just about to leave the magnetic field.

    2. Relevant equations


    3. The attempt at a solution

    Since the magnetic flux will decrease as the square leaves the field, the induced magnetic field because of the induced EMF in the square will also point downward. This tells us that the current will flow clockwise.

    That's all I've got so far, and I don't even know if it's right. What is producing the forces here that would oppose our push on the square?

    Edit: OK, I think that before tv=L/sqrt(2), power is 2IBtv^2. After tv = L/sqrt(2), power is 2IBv(sqrt(2)L - tv). Is it true that the current in the wire will change as the square gets pushed? If so, what do I do to figure out what current is in terms of the other variables?
    Last edited: Feb 25, 2009
  2. jcsd
  3. Feb 25, 2009 #2


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    How much power is needed to move the loop outside the B-field?
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