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Homework Help: Rotational coil induction

  1. Feb 22, 2009 #1
    1. The problem statement, all variables and given/known data

    1.A circular coil, with radius of 10 cm, and 25 turns, rotates in a constant magnetic field of
    strength 2.4 T, with the axis of rotation perpendicular to the direction of the magnetic

    A. If the coil rotates at a frequency of 50 Hz, what is the induced peak voltage?
    B. Sketch the time-dependence of the induced voltage.
    C. If the magnetic field that the coil is in points down the page, which direction does the coil rotate? Answer for both cases: (1) q traveling from left to right and (2) q traveling from right to left in the coil.

    2. Relevant equations

    V = -N * [ dΦ / dT ]
    Φ = B * A * cosθ

    V = -N * B * A * ω*sinθ
    ω = 2π*f

    3. The attempt at a solution

    A. A = π*.1^2
    .031416 m^2

    ω = 2π*50
    314.159 rad/s

    peak voltage would occur when the coil is perpendicular to the magnetic field correct? So would I put π/2 in for sin(x) and get the following?
    V = 25 * 2.4 * .031416 * 314.159*sin(π/2)
    1.88496 * 314.159
    592.177 V
    B. If A is correct, then would the time-dependence of induced emf look like a sin wave?
    C. I take it I'm supposed to use the right-hand-rule and Lenz's Law for this question, but I'm slightly confused as to how to go about doing so
    Last edited: Feb 22, 2009
  2. jcsd
  3. Feb 23, 2009 #2
    bump, I believe A and B are correct from what I understand, but I'm still having trouble with C.
  4. Apr 1, 2009 #3
    I need help with this question too.
  5. Apr 14, 2009 #4
    Yeah, I don't understand how to use the 50Hz to determine the peak voltage. I really hate this class! None of this was taught in the lesson or explained at any point. An explanation of the equations would be helpful. Please, anyone?
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