Quick Nodal Anaylsis Question

Discussion in 'Homework Help' started by Digit0001, Jun 6, 2011.

  1. Digit0001

    Thread Starter Member

    Mar 28, 2010
    89
    0
    Hi
    DSC00069.JPG
    i have another quick question, i am finding the voltage nodes in this circuit and wondering are my equations correct?

    KCL SuperNode
    V1/2+V2/4+V3/3=0

    KVL(V1-V2)
    10+V2=V1

    KVL(V2-V3)
    V3+5i=V2

    KVL(V1-V3)
    V1+6+V3=0

    P.S
     
  2. jegues

    Well-Known Member

    Sep 13, 2010
    735
    43
    I'm not 100% certain, but I think you should do this in 2 super nodes rather than 1 big one encompassing the 2 sources. (If that's not at all what you've done then I can't follow your work)

    Also, in your KCL for the supernode equation there is no mention of any current through the 6Ω resistor.

    I've managed to write a set of equations for two seperate supernodes around each source.

    Here's the supernode equation I've come up with around the independent source.

    \frac{V_{1} - V_{3}}{6} + \frac{V_{1} - 0}{2} + \frac{V_{2} - 0}{4} = 0

    Give the rest a shot.
     
    Last edited: Jun 6, 2011
  3. Digit0001

    Thread Starter Member

    Mar 28, 2010
    89
    0
    yes i was trying to use one big supernode. This is what i got for the other three equations

    SuperNode between V2 and V3
    V2/4+V3/3=V1-V3/6

    KVL between V1 and V2
    10+V2=V1

    KVL between V2 and V3
    V2+5i=V3
     
  4. jegues

    Well-Known Member

    Sep 13, 2010
    735
    43
    Why are you writing KVL's?

    From each of the two supernode equations you wrote, you should be able to obtain another equation.

    For example, using the independent source, one can note that,

    V_{1} - V_{2} = 10

    Now do the same for the dependent source, and express i in terms of your node voltages.

    Your 2 supernodes give you a total of 4 equations, more than enough to solve for the 3 unknown node voltages.
     
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