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Homework Help: Question about changing magnetic flux

  1. Apr 28, 2012 #1
    1. The problem statement, all variables and given/known data

    A 200-loop coil of cross sectional area 8.5 cm2 lies in the plane of the page. An external magnetic field of 0.060 T is directed out of the plane of the page. The external field decreases to 0.020 T in 12 milliseconds.
    What is the magnitude of the change in the external magnetic flux enclosed by the coil?

    2. Relevant equations

    [itex]\Phi[/itex]m = A * B

    3. The attempt at a solution
    Ive tried solving for both values of magnetic flux at each time and finding their difference. However, I still seem to get it wrong. I dont know If I am missing something, any help or tips would be greatly appreciated.
  2. jcsd
  3. Apr 28, 2012 #2
    i believe it would just be the initial flux - the final flux...

    the full equation you want is [itex]\Phi[/itex]= N*B*A*cos([itex]\phi[/itex])
    (N = the number of turns of the coil)

    however the direction of the area and the magnetic field are the same so cos(phi) = 1
    just convert 8.5 cm2 to m2 which is 8.5 * 10-4

    so.... N(.06T)(A) - N(.02T)(A), just plug in your numbers...i believe this is right anyway, someone should check my work
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