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Need help with supernode equation

  1. Oct 25, 2009 #1
    I am trying to resolve this super node but i am having trouble with the equation, more specifically node c, this is where i got so far


    5 = Va/20 +(Va - Vd)/10 + (Vb - Vc)/12.5
    -10 = (Vd - Va)/10 + Vd/25
    -Va + Vb = 100

    please explain the c node equation
     

    Attached Files:

  2. jcsd
  3. Oct 26, 2009 #2

    The Electrician

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    Assuming the positive end of the 150 volt battery is connected to node C, then the equation is simply: Vc = 150
     
  4. Oct 26, 2009 #3
    but dont we have to include the 12.5 resistor from node b to node c?
     
  5. Oct 26, 2009 #4

    The Electrician

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    That resistor is taken care of by your first equation.

    When you have a voltage source connected from ground to some node, you need a (constraint) equation that simply says that the voltage at (in this case) node C is 150 volts.

    It's similar to your third equation.
     
  6. Oct 28, 2009 #5
    i am getting an error on node d can anyone tell me what i am doing wrong, its the 3rd equation on the last process
     

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  7. Oct 29, 2009 #6

    The Electrician

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    I think that equation should be:

    -5Va + 7Vd = -500

    For final answers, I get:

    Va = 11.712
    Vb = 111.712
    Vc = 150
    Vd = -63.063
     
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