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Homework Help: RC circuit help?

  1. Jul 16, 2007 #1
    1. A 6V battery is connected to a 1F capacitor and 3 resistors (R1=1, R2=4, R3=2) R1 is is series with the battery. A junction then appears after R1, which creates 3 different paths, 2 for each remaining resistor, and another for the capacitor. After a long time, what is the magnitude of the current that runs through the battery? (i hope my description is ok, I have no picture)

    2. V=IR

    3. I keep reading that after a long time, when the capacitor has been fully charged, there is no current in the circuit. But I don't think this can apply when it is in parallel with 2 other resistors? Will the current stop in the path that leads to the capacitor, but will it continue to flow through the other resistors? I am confused on this aspect of the problem. I previously was trying to solve by saying that there are 2 charge sources when fully charged, so that the total V = 12V, and then I would calculate the current based off of total resistance. Can it be done this way? Any advice is greatly appreciated!! Thanks!
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Jul 16, 2007 #2


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    You are correct. After a period of time no current will flow through the capacitor. That line will be an open circuit.
  4. Jul 16, 2007 #3


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    After a very long time, there will be no current in the branch of teh circuit which contains the capacitor but current will still flow through the resistors which are in parallel with the capacitor. So basically, for the purpose of this question, simply ignore the branch that contains the capacitor. Then you simply have the three resistors.
  5. Jul 16, 2007 #4
    ooook! thank you!! makes much more sense now. you guys rock :smile:
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