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Homework Help: Finding the Time Constant in a circuit

  1. Mar 14, 2013 #1
    1. The problem statement, all variables and given/known data
    Find the time constant in the following circuit when switch K1 is open.
    R1 = 100 Ohms
    R2 = 200 Ohms
    C1 = 6 micro Farads
    E1 = 9V

    2. Relevant equations

    T = RC

    3. The attempt at a solution
    When the resistors are in series or parallel, I am clear on how to do this, however when the capacitor is discharging, I don't think the resistors are in series or parallel, so I don't know how to find the equivalent resistance.
  2. jcsd
  3. Mar 14, 2013 #2


    User Avatar

    Staff: Mentor

    Is the diagram correct? What is that wire that runs from where the switch and R1 meet down to the bottom node? Doesn't it prevent the switch and voltage source from affecting the rest of the circuit?
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