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Homework Help: Rlc circuit with ac current source

  1. Apr 18, 2012 #1
    1. The problem statement, all variables and given/known data
    An AC current source, 1 ∠0° A, with angular frequency 1 rad/s is to be applied to the input
    terminals of the circuit. Circuit is RLC, the current source is in parallel with a 1F capacitor which is in parallel with a 1H inductor which is in series with a 1Ω resistor. I need to find the Voltage across the capacitor.

    2. Relevant equations

    Xc = 1/ωC

    Vc = Xc * I

    3. The attempt at a solution

    I know that the voltage into the circuit is the same as the voltage across the capacitor since they are in parallel. This is a current divider problem so I need to find the current across the capacitor to solve for the Vc. I know I need to use the impedences to solve for voltage using Vc = Xc * Ic, but I cannot recall how to do this for a series/parallel RLC circuit.
  2. jcsd
  3. Apr 18, 2012 #2
    Is it that impedences act the same as resistors? In that case I just add the series elements and then use the current divider rule to find the current across the capacitor, but I don't know if that is right.
  4. Apr 18, 2012 #3
    First find the net impedence of the circuit.
  5. Apr 18, 2012 #4

    rude man

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    Homework Helper
    Gold Member

    Have you been introduced to the concept of complex imedance?
  6. Apr 19, 2012 #5


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    Staff: Mentor

    Step 1. The impedance of the capacitor = 1/(wC) ∠-90°

    Step 2. Impedance of the inductor + impedance of resistor = [PLAIN][PLAIN]https://www.physicsforums.com/images/icons/icon5.gif [Broken] [Broken] [Broken] ∠[PLAIN][PLAIN]https://www.physicsforums.com/images/icons/icon5.gif [Broken] [Broken] [Broken] + [PLAIN][PLAIN]https://www.physicsforums.com/images/icons/icon5.gif [Broken] [Broken] [Broken] ∠[PLAIN][PLAIN]https://www.physicsforums.com/images/icons/icon5.gif [Broken] [Broken] [Broken]
    Last edited by a moderator: May 5, 2017
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