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Homework Help: Circuit with a switch

  1. Feb 24, 2016 #1
    For the circuit shown in the figure, the switch S is suddenly closed with the capacitor uncharged. After one time constant, the charge on the capacitor is closest to:
    a) 2.0 mC
    b) 0.74 mC
    c) 1.0 mC
    d) 1.3 mC
    e) 0.00 mC

    Relevant Formulas
    q = Q⋅(1-e-τ/R⋅C)
    τ = RC

    My Attempt
    q = Q(1-e-τ/T)
    q = (10⋅10-6)(1-e-1)
    q = (10⋅10-6)(1-.36788)
    q = (10⋅10-6)(0.632)
    q = 6.32⋅10-6 C = 0.00632 mC

    I am not sure how else I would approach this problem. Any suggestions?
  2. jcsd
  3. Feb 24, 2016 #2


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    Q is not ##10^{-5}## C.
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