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Homework Help: Circuit with two voltage sources (Kirchoff Rules)

  1. Oct 23, 2012 #1
    1. The problem statement, all variables and given/known data
    The circuit shown in the figure below is connected for 3.10 min. (Assume R1 = 7.90 Ω, R2 = 2.60 Ω, and V = 16.0 V.)
    28-p-021-alt.gif
    The circuit shown in the figure below is connected for 3.10 min. (Assume R1 = 7.90 Ω, R2 = 2.60 Ω, and V = 16.0 V.)


    2. Relevant equations
    Kirchoff's Rules
    V = IR


    3. The attempt at a solution
    So naming the current in the left segment I1 downwards, the current in the middle section I2 downwards, and the current in the right most section I3 upwards, I find from the junction rule that I1 + I2 = I3. Then using the current rule, I find that -16 +7.9 * I1 + 2.6 * I3 = 0. Substituting in I3 as I1 + I2, and then solving for I1 I find that I1 = (16 - 2.6I2) / 10.5 . Using the current rule again, I find that -4 + 7.9 * I1 - 6.0 * I2 = 0 and so I substitute for I1 and then solve for I2 to find that I2 = 1.0103. Then use that value back in other equations to find that I1 = 1.2736 Amperes downward, I2 = 1.0103 Amperes downward, and I3 = 2.2839 Amperes Upward.

    Web Assign keeps saying these values are wrong and I have reworked these problems several times and keep getting the same answers.
     
  2. jcsd
  3. Oct 23, 2012 #2

    ehild

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    Homework Helper

    R2 is connected to a 3 ohm resistor in series.

    ehild
     
  4. Oct 23, 2012 #3
    I cannot believe I missed that. Thank you!
     
  5. Oct 23, 2012 #4

    ehild

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    You are welcome.:smile:

    ehild
     
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