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Homework Help: Capacitor in an AC circuit

  1. Apr 7, 2016 #1
    1. The problem statement, all variables and given/known data
    A capacitor has a peak current of 240 μA when the peak voltage at 250 kHz is 2.7 V .
    Part A
    What is the capacitance?

    Part B
    If the peak voltage is held constant, what is the peak current at 500 kHz

    2. Relevant equations

    3. The attempt at a solution
    I rearranged equation 2 to solve for Xc = 2.7V/0.000240A = 11250
    I then rearranged equation to to solve for C =1/wXc = 3.56x10-4

    This is not correct. Why is this not correct and what is the proper way to go about solving it?
    Thank you.

    Correction: I re-did the second calculation and got 3.56x10-10F by properly converting kHz to Hz but it's still wrong.
    Last edited: Apr 7, 2016
  2. jcsd
  3. Apr 7, 2016 #2


    User Avatar

    Staff: Mentor

    Hi ReidMerrill. aerobanner.gif

    Did you convert kHz to radians/sec?
  4. Apr 7, 2016 #3
    Oh you know what I did not. I wasn't aware I needed to. My professor did not explain this well at all.
    I would just divide the frequency by 2pi, correct?

    EDIT: That worked. Thank you!
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