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Homework Help: Loop Rule - Batteries and Resistors

  1. Mar 22, 2010 #1
    1. The problem statement, all variables and given/known data

    Two batteries and three resistors are connected as shown in the figure .
    http://session.masteringphysics.com/problemAsset/1122583/1/Walker.21.52.jpg

    A) How much current flows through 6.0 V battery when the switch is closed?
    B) How much current flows through 9.0 V battery when the switch is closed?
    C) How much current flows through 6.0 V battery when the switch is open?
    D) How much current flows through 9.0 V battery when the switch is open?


    2. Relevant equations

    Kirchoff's Rule

    3. The attempt at a solution

    I broke it down into two different loops, the one on the left and the one on the right. I labeled the 6V battery as E1 and the 9V one as E2. I called the current flowing upward from 6V I1 and the current flowing upward from 9V I2. I labeled the resistor under the 6V battery R1 and the resistor under the 9V battery R2.

    From this, here are my equations:

    For Loop 1:
    E1-E2-I1R1+I2R2=0

    For Loop 2:
    E2-I3R3-I2R2=0

    Both of these due to Loop Rule.

    I'm not sure where to go from here, or even if these are totally correct.

    Help would be great :)
     
  2. jcsd
  3. Mar 22, 2010 #2

    tiny-tim

    User Avatar
    Science Advisor
    Homework Helper

    Hi ihearyourecho! :smile:

    (try using the X2 tag just above the Reply box :wink:)

    An equation relating I1 I2 and I3 would be pretty cool. :rolleyes:
     
  4. Mar 22, 2010 #3
    After sitting down with my teacher and getting some help from him, I was able to crank through the problem. Thanks for the tip about super and subscripts though!
     
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