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Homework Help: RC circuit and kirchoff's loop rule

  1. Sep 19, 2010 #1
  2. jcsd
  3. Sep 19, 2010 #2
    Let's see here, it can't be a because the cap isn't in parallel with the battery. A capacitor has infinite impedance at DC, so after an infinite time it can be modeled as an open circuit.

    So loop 1)
    Vb-Vc-IR=0
    Loop 2)
    Vb-2IR=0

    combine to get
    Vb-Vc-Vb/2=0

    so
    Vc=Vb/2

    Vc=Q/C

    so Vb/2=Q/C

    Q=C*Vb/2

    Voila.
     
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