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Looking for capacitive reactance but missing "C"

  1. Jul 22, 2014 #1
    1. Current and voltage graphs are shown for a capacitor circuit with ƒ=1000Hz.
    What is the capacitive reactance Xc?

    2. I know the equation is Xc= 1/2∏ƒC to solve for capacitive reactance but where do I find C? All of our in class examples had C and ƒ given.

    3. The attempt at a solution

    Attached Files:

  2. jcsd
  3. Jul 22, 2014 #2


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    Staff: Mentor

    That formula is not correct. You need a pair of brackets to set it right or you'll never get the right answer!

    What would be the equation for current if you connect that capacitance C to an AC voltage source V volts?
  4. Jul 22, 2014 #3


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    Staff Emeritus
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    Gold Member

    Get the reactance from the graph.

    What are peak voltage & peak current?
  5. Jul 22, 2014 #4
    The only other thing I can think to do is rearrange ΔVc= I*Xc

    Xc= ΔVc/I
    Xc= 10V/10x10^-2 A which gives me 100Ω
  6. Jul 23, 2014 #5


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    Staff: Mentor

    10V looks right for the voltage. But that's not the right way to write 10mA.
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