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Homework Help: A radio inductor.

  1. Apr 18, 2004 #1
    A radio inductor. Please help!

    Hello.
    I am seeking immediate help with a problem I have. Here is the problem:

    A Radio Inductor. You want the current amplitude through a inductor with an inductance of 4.60 mH (part of the circuitry for a radio receiver) to be 2.20 mA when a sinusoidal voltage with an amplitude of 12.0 V is applied across the inductor.
    What frequency is required?

    What I tried to do was use this equation:
    w = 1/(square root of(LC)) and combining it with w = I/Q which is also w0 = I/(CV), and then I would have C which I could use to find w. But that's gotta be the wrong way. I've tried some other ways which I think would make more sense, but it just doesn't seem to come out right. Is there any chance you can help me with this?
    Thank you,
    Cernie.
     
    Last edited: Apr 18, 2004
  2. jcsd
  3. Apr 19, 2004 #2

    HallsofIvy

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    I don't see how we can do this without knowing the frequency of the applied 12 volt current.
     
  4. Apr 19, 2004 #3

    chroot

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    The (real) impedance of an inductor of inductance L at frequency [itex]\omega[/itex] is [itex]Z = \omega L[/itex]. Ohm's law is V = IZ.

    Substituting and rearranging,

    [tex]\frac{V}{L I} = \omega[/tex]

    Solving for [itex]\omega[/itex], I get ~188 kHz.

    - Warren
     
    Last edited: Apr 19, 2004
  5. Apr 19, 2004 #4
    How?

    How do you get that answer?
    I've already tried this method and I always get the same answer, w = 1185771 Hz = 1.19MHz.
     
  6. Apr 19, 2004 #5

    chroot

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