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Homework Help: RC Charging

  1. Oct 15, 2012 #1
    Hello Everyone,
    I need to solve this problem:
    How many seconds does it take to charge a 7.7 x 10-7 farad capacitor to 70V if it is initially uncharged, then connected to a 190V battery through a 11000 ohm resistor.

    What I have so far:
    q = CV
    q = (7.7 x 10-7f)(70V)
    q = 5.39 x 10-5C

    q = q0e-t/RC
    5.39 x 10-5 = q0e-t/(11000)(7.7 x 10-7)

    What is q0 here?
  2. jcsd
  3. Oct 15, 2012 #2
    just multiply the capacitance by 190V.
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