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Homework Help: Help finding error in my Circuit Analysis

  1. Oct 31, 2017 #1
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution

    My values for i1,i2,and i3 were: -.005179,-.002857 and .004857. When I ran the same circuit through LT Spice the values they gave me were .00059081,.000809628, and .00119037. Where did I make my error?
    * as a side not I notices I only have 1000 instead of 10,000 in my matrix for the first line. The values I got were using 10,000 instead of 1000 in the first line.
  2. jcsd
  3. Oct 31, 2017 #2


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    Homework Helper
    Gold Member

    Since you know the answer from your simulation result, I'd post the values I am getting.
    I am getting VAB= 7.221V and IR3= 1.4mA.

    For I1, I2 and I3 (labelled differently in my working) I am getting the same values as your LTspice result (just 10 times more, since you used 10000 instead of 1000).
  4. Oct 31, 2017 #3

    The Electrician

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    Gold Member

    I see a couple of mistakes. In your equation for loop 1 you left out the 5k resistor.

    In your equation for the super mesh, you have a term 4k(I1 - I2). This should be 4k(I2 - I1).
  5. Nov 2, 2017 #4
    After making these changes I got my numbers to match the LT Spice number! Thanks!!
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