Finding Q2 4sec after switch closes

Discussion in 'Homework Help' started by metelskiy, Nov 24, 2010.

  1. metelskiy

    Thread Starter Member

    Oct 22, 2010
    Here i have a circuit where I need to find Q2 4μ seconds after switch closes:
    Practice #3.png
    Here is my work where i got so far and now i'm stuck what do next. First, did i take appropriate steps to get to Thevenin circuit and reattaching the load?
    P1070208 [1280x768].JPG
  2. mik3

    Senior Member

    Feb 4, 2008
    I assume your Vth and Rth are correct (haven't checked the calculations).

    Then find the RC time constant of the equivalent circuit and find the voltage (Vctotal) across the total capacitance of the circuit at 4us.

    Then use this to find the voltage across C2 and C3:


    Then the charge Q2=Vc23*C2.
    Last edited: Nov 24, 2010