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Homework Help: Faraday's Laws

  1. Jul 16, 2008 #1
    1. The problem statement, all variables and given/known data
    A 21.8 cm diameter coil consists of 18 turns of circular copper wire 1.70 mm in diameter. A uniform magnetic field, perpendicular to the plane of the coil, changes at a rate of 8.15E-3 T/s. Determine the current in the loop.


    2. Relevant equations
    V=IR
    V=B/T * A * N
    permitivity of copper= 1.72e-8
    R=p * L / A'

    3. The attempt at a solution
    V = 8.15e-3 * (.218/2)^2 * pi * 18 turns = 0.005475 V

    L = N * pi * coil diameter = 18 * pi * .218 = 12.32 m
    A'= pi * (.0017/2)^2 = 2.269e-6 m^2
    R = 1.72e-8 * (12.32 m/2.269e-6 m^2) = 0.0934 ohms

    I = V/R = 0.005475 V / 0.0934 ohms = 0.0586 A

    But thats wrong... where'd I go wrong?
     
  2. jcsd
  3. Jul 16, 2008 #2
    It's been a long time since I've done any questions like this, but the equation "V=B/T * A * N" you use but you do not use the 'T' anywhere. You have "V = 8.15e-3 * (.218/2)^2 * pi * 18 turns" but unless I'm missing something, I don't see 'T' in there or a value of 'T' given in the question.
     
  4. Jul 16, 2008 #3
    Isn't B/T = 8.15e-3 Tesla per second?

    If not, what do I do in that case.
     
  5. Jul 16, 2008 #4
    Ya, I ignored that for a second when doing the calculation and got the same 0.005...V that you did, units cancelled. I'll wait for somebody else's reply because I am a bit confused now too haha. Do you have a correct answer for that?
     
  6. Jul 16, 2008 #5
    Unfortunately no. I looked at other similar problems, but they all had the process I'm doing, but I couldn't compare answers.
     
  7. Jul 17, 2008 #6
    Anyone?
     
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