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Homework Help: Super-node question, one equation or two?

  1. Sep 8, 2014 #1
    1. The problem statement, all variables and given/known data
    Use the mesh current method to solve for the power dissipated

    2. Relevant equations

    3. The attempt at a solution
    I was trying to solve the question using two equations,
    eq1) 20=4*i1+i1
    eq2) -90=9*i2+6*i2

    So I obviously made a mistake since the 6A is doing nothing in my equations, and both equations 1 and 2 have no unknowns. Am I suppose to just use one equation, and use the super node as my second? How can I tell when I need to use only one equation?

    Attached Files:

  2. jcsd
  3. Sep 8, 2014 #2


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    Gold Member

    In both eq1 and eq2 you are missing the voltage drop Vo
  4. Sep 8, 2014 #3


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    Staff: Mentor

    You are asked to use mesh equations, so rather than a supernode, you want a supermesh. You should write one equation for the supermesh and one constraint equation tying the two "normal" mesh currents to the 6 A source.
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