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RC Circuit Problem

  1. Oct 3, 2004 #1

    I am stuck on a question to work out the value of a capacitor,

    The Question is:
    A capacitor and a 2Kohm resistor pass the same current when each is separately connected across a 100Hz power line.
    What is the value of the capacitor?
  2. jcsd
  3. Oct 3, 2004 #2


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    Staff Emeritus
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    Gold Member

    The impedance of a capacitor is

    [tex]\frac{1}{j \omega C}[/tex].

    The resistance of the capacitor at 100 Hz is just the real part of that impedance (this is the hard part). Use Ohm's law (V = ZI) to solve for the capacitance.

    - Warren

    - Warren
  4. Oct 3, 2004 #3
    ohms law shows us that e = i times r, when considering capacitance and frequencies, we substitute r with Xc (capacitive reactance). when a frequency is applied to a capacitor it allows current flow at a rate of ;
    Xc=1/[2 * pie(3.14) * f (freq.) *c(farrads)]
    ***this is the formula for the impedence of a capacitor.
    Xc= 2000, f= 100:
    therfore C= ???? you do the math
    Last edited: Oct 3, 2004
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