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Homework Help: DC Circuit trouble

  1. Feb 26, 2004 #1
    I'm having trouble solving this problem:

    Three resistors(parallel) across a DC voltage source...If the total current through the circuit is I = 2.0A, what is the currect through the 12ohm resistor?

    The circuit runs into a junction which splits 3 ways. Along each path there's are resistors 2ohm, 6ohm, and 12ohm, respectively, and all meet again andthen flows back to the battery.

    It's parallel so I breaks up into I1, I2,I3
    I found two equations:

    8/3V = I1(2ohm) + I2(6ohm) + I3(12ohm)
    I = I1 + I2 + I3

    I found the voltage by first find the equivalent resistor for R1, R2, and R3, (R = 4/3 ohm) So V = IR => V = 2(4/3) => V = 8/3V.

    I need to find the current through R3, and I could if I had one more equation, but I'm stuck. I can't see any other equations by loop rule or Kirchoff's law. So, any help will be appreciated, thanks.
    Last edited by a moderator: Feb 26, 2004
  2. jcsd
  3. Feb 26, 2004 #2

    Tom Mattson

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    Staff Emeritus
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    Gold Member

    Good start!

    Two words: Ohm's Law

    You know the voltage across the 12Ω resistor (it's the same as the voltage of the battery). You also know the resistance, so just use V=IR and you're home free.

    edit: typo
  4. Feb 26, 2004 #3
    I knew I was forgetting something. Thanks.
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