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Metal Detector Coils

  1. Nov 22, 2006 #1
    Can i get some help with this problem?
    This problem deals with the basic loop configuration you will use in the laboratory to construct a metal detector. Two concentric circular coils of wire lie in a plane. The larger coil has 49 turns and a radius of a = 7.90 cm. The smaller coil also has 49 turns but has a radius of b = 0.85 cm. The current in the larger coil has a time dependence given by = Io sin(ωt) where ω = 14,000 rad/s and Io = 0.50 A. What is the magnitude of the EMF induced in the small coil at t = 2.00 s if you make the approximation that the magnetic field inside the small coil is spatially uniform?
    Thanks in advance.
     
  2. jcsd
  3. Nov 22, 2006 #2

    OlderDan

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    Show us some attempt to solve the problem. What do you know that you think is relevant to the solution?
     
  4. Nov 23, 2006 #3
    Are there any hints on this one...I am using Faraday's Law
    where EMF = N*(change in flux over change in time). The
    magnetic flux is equal to BA, which is the B for the center
    of a loop (with radius of the outer circle) times A for the
    inner circle...my final equation is coming out something
    like this...[(N^2)*Pi*Rb^2*mu*I(nought)*w*cos(w*t)]/(2*Ra)

    This is long, but it seems right to me...Any suggestions?
     
  5. Nov 23, 2006 #4
    the velocity induces an emf, the emf gives a current, and
    the current gives a backward force F=ILB, so you can set up
    and equation mdv/dt=F=-Cv, for some const C you will get.
    am i right? im still not getting the right answer
     
  6. Nov 24, 2006 #5

    OlderDan

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    This looks OK, although the answer might be looking for a minus because the emf is the negative of the flux derivative.
     
  7. Nov 24, 2006 #6

    OlderDan

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    I assume this was supposed to go with your other problem. It is right if you get C right. So as it asks in the other thread, what function for v will give you a derivative proportional to v?
     
  8. Nov 24, 2008 #7
    I have tried to solved it and got answer in minus more then one time so its might possible. I think you are right...
     
  9. Dec 1, 2008 #8
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