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Homework Help: Thevenin Equiv with just Capacitors

  1. Feb 25, 2016 #1
    1. The problem statement, all variables and given/known data


    imgur link: http://i.imgur.com/TWB5rRu.png

    2. Relevant equations

    3. The attempt at a solution

    I can find the equivalent capacitance, 10F, but I'm not really sure how to find the equiv. Thev. voltage. I figured that with the voltage source present, half the voltage will be lost across that first capacitor (since the next two parallel caps have an equivalence of 5F as well), so therefore at the very least in the Thev equiv circuit we should be seeing 22.5 V across the terminals. But the answer in the back gives Vth as 15V, less than 22.5.

    How does one find the Vth?
  2. jcsd
  3. Feb 25, 2016 #2


    User Avatar

    Staff: Mentor

    Hmm. I wonder if at some point the problem was changed slightly without the answer key being updated. If the voltage source was 30 V rather than 45 V, then the given answer would make sense. I can't see the open circuit voltage being anything other than 22.5 V.
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