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Nodal Analysis 1 equation 2 Unknowns Problem

  1. May 25, 2013 #1
    http://imgur.com/W9sWTv7


    V=IR, that is all I think



    3. I have put my ground at the bottom branch. I have tried to write a KCL for the top branch but end up with 0=0 when I substitute in equivalencies. My KCL: (V1+5Ix-0)/20+2+Ix=0. (V1+5Ix)/20=-2-Ix. So 0=0. I am not sure if I am writing my KCL correct also I know I am missing something.

    Can I make the voltages sources and the top node for a supernode?
     
    Last edited: May 25, 2013
  2. jcsd
  3. May 25, 2013 #2

    SteamKing

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    I think you are being hasty in concluding that you first equation develops into 0 = 0. The algebra doesn't support this conclusion.
     
  4. May 25, 2013 #3

    rude man

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    Your first expression isn't even an equation - where's the = sign?

    It says to use nodal analysis. Are you summing currents to zero at each independent node?

    (I myself don't ever use KCL. I sum currents at each node to zero - is that KVL? I don't know. Never heard of a supernode either).
     
  5. May 25, 2013 #4
    Is it correct that (V1+5Ix)/20=-2-Ix ? If so that is where 0=0 comes from
     
  6. May 25, 2013 #5

    SteamKing

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    If (V1 + 5Ix)/20 = -2 - Ix,
    then
    (V1 + 5Ix) = 20*(-2 - Ix)
    (V1 + 5Ix) = -40 - 20Ix
    V1 + 25Ix = -40

    which is not 0 = 0
     
  7. May 26, 2013 #6
    This is wrong. It should be:

    (V1-5Ix-0)/20+2+Ix=0
     
  8. May 26, 2013 #7

    NascentOxygen

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    With the Electrician's correction, you have one equation. Your second equation comes from the branch on the right side, giving its own equation relating V1 and IX.
     
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