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Homework Help: LC circuit and fixed inductance problem

  1. Apr 24, 2006 #1
    A fixed inductance 0.66 [tex] \mu H [/tex] is used in series with a variable capacitor in the tuning section of a radio. What capacitance tunes the circuit into the signal from a station broadcasting at 8.11 MHz? Answer in units of pF.

    I used the equation [tex] \omega = 1/ \sqrt LC [/tex]
    Solving for C gave me [tex] (1/ \omega)^2 /L [/tex]
    Then I converted all my numbers.
    0.66[tex] \mu H [/tex] = 6.6e-7 H
    8.11 MHz= 8110000 Hz
    So plugging in, (1/8110000)^2 / 6.6e-7
    gave me 2.30e-8 F
    then converting to pF, gave me 23000, which isn't right.. can someone tell me what I'm doing wrong?
  2. jcsd
  3. Apr 24, 2006 #2
    Might be easier to use

    F = 1/(2PI * Sqrt (LC))

    then solve for C.

    omega = 2 PI * F.
    Last edited: Apr 24, 2006
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