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[Solved] Batteries, resistors, find the currents

  1. Sep 8, 2011 #1
    1. The problem statement, all variables and given/known data
    Two batteries and three resistors are connected as shown in the figure

    Ez4ca.png
    Determine the magnitude of the current that flows through 6V battery when the switch is closed.

    2. Relevant equations

    V = IR, Kirchhoff's rules (junction, loop).

    3. The attempt at a solution
    Currents:
    9v going up = I1
    9v's top junction to 6v to 9v's bottom junction = I2
    9v's top junction to the 5 ohm resistor to 9v's bottom junction = I3
    I1 = I2 + I3

    Loop with 9v, 6v, 2 ohms, 4 ohms
    9 - 6 - 2I2 - 4(I2 + I3) = 0
    Loop with 9v, 5 ohms, 4 ohms
    9 - 5I3 - 4(I2 + I3) = 0
    Have I set up these two simultaneous equations correctly?

    I1 -> 0.868421 A, I2 -> -0.236842 A, I3 -> 1.10526 A

    Edit: Yes I did. :)
     
    Last edited: Sep 8, 2011
  2. jcsd
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