Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Another one of them circuit questions

  1. Mar 22, 2005 #1
    The circuit in the drawing shows two resistors, a capacitor and a battery. When the capacitor is fully charged, what is the magnitude of q of the charge on one of its plates?

    Here's what I got so far:

    So 12= 2I + 4I

    Since q=CV and I have C=9.0uF, all I need is the voltage. And since the voltage drop between parallel circuits is the same then all I have to find is the voltage at the node going into 4 ohm resistor? Sounds like a good method but I can't seem to get the voltage drop.

    Any ideas? :uhh:
     

    Attached Files:

  2. jcsd
  3. Mar 22, 2005 #2
    okay for those who can't see the attachment because it's waiting approval:

    Code (Text):


    |-R=2.0ohm-|--------|
    |                |           |
    V=12V        R=4ohm  C=9.0uF
    |                |           |
    |__________|_______|          

     
    Ok where I placed the letters is where you'll get a resistor or capacitor or voltage etc.
    ugh, the code thing doesn't work so well, but the R=4ohm is in the middle branch and the C=9.0uF is at the end branch.
     
  4. Mar 22, 2005 #3
    Ack, I got it nvm.

    Easy really, almost had it too

    12=2I+4I, I=2

    V=IR at the 4
    V=2*4
    V=8 Volts

    q=CV
    =9.0x10^-6Fx8Volts
    =7.2x10^-5 C.

    Thanks notaphysicsman :)
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook