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Homework Help: Circuit analysis is this correct?

  1. May 15, 2013 #1
    1. The problem statement, all variables and given/known data

    We have the the circuit in the figure. gCUraSq.jpg

    2. Relevant equations
    I have to find I2.

    3. The attempt at a solution
    I apply KVL in the "left " part of the circuit and I have -42 V+ 2I1 +8I2=0 .(I 1 is the current through 2 Ohm).I apply KCL in the nod between R1 R3 and R2 and I have (Current through R3)=I1-I2. I apply KVL in the right part of the circuit and I have -8I2+4(I1-I2) +2I2=0. I form a system with -42 V+ 2I1 +8I2=0 and -8I2+4(I1-I2) +2I2=0 and here I find that I1=(10/4)*I2.I replace this in 2I1+8I2=42 and I have I2=3.2 A.Is this correct?
  2. jcsd
  3. May 15, 2013 #2


    User Avatar

    Staff: Mentor

    No, J = 2I2 is a current source. So your KVL expression for the second loop is not correct; you cannot say offhand what the potential drop across that current source will be.

    Note that this current source tells you something about the current flowing through R3...
  4. May 15, 2013 #3
    Oh,that current is 2I.So now I have I1-I2=2I2. Then I1=3I2.I replace this in 2I1+8I2=42. Now I have 14I2=42.Now I2=3 A.Thanks :)
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