1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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
    Xc=1/wC
    Vc=IcXc

    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

    NascentOxygen

    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!
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted