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Homework Help: Series R and LC circuit question

  1. Jul 25, 2010 #1
    1. The problem statement, all variables and given/known data

    Since I dont have a pic.. I will explain my problem. I have a circuit with 3 terminals x , y and z.
    Between x - z I have a resistance , say R,
    Between z - y I have an inductor L and then a capacitor C in series.
    I apply a square wave input between x and y.

    2. Relevant equations

    How will the voltage at output look like? and why does it look like it? output terminals being z-y.
    3. The attempt at a solution

    I already know the answer except I cant understand it. Answer being, Vzy would be discontinuous. So far, I have , at the rising edge of the square wave, an impulse current would be across L, now I dont understand how the capacitor will react. can someone explain it? so how would Vzy be discontinuous?
    Last edited: Jul 25, 2010
  2. jcsd
  3. Jul 25, 2010 #2


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    The current through an inductor is always continuous, and the voltage across a capacitor is always continuous. Does that help?
  4. Jul 31, 2010 #3


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    Since the three elements are in series, the current is the same in all three. Write the equations of voltage as a function of the current for the three elements. The sum of the voltages is the input square wave, or a series of positive and negative steps.
    Solve the resulting integral-differential equation, to obtain the current in the circuit.
    Having the current, you have the voltages in the inductor and capacitor.
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