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Nodal analysis question

  1. Feb 6, 2014 #1
    ssvjv.png

    I understand their method. However, if you use the node to the left of the 2 ohm resistor (the node where the voltage = 75 V) then you get:

    (75-Vx)/2 -10 = 0

    so 75-Vx = 20
    so Vx - 75 = -20
    Vx = 55 V

    But this is not 25 V as it should be?

    When doing nodal analysis, do you have to consider each node?
     
  2. jcsd
  3. Feb 6, 2014 #2

    donpacino

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    Gold Member

    You did not include the current through the 75 v voltage source. your first equation should have been
    (75-Vx)/2 -10 -(i3+0.4*Vx)= 0

    that being said when you do nodal analysis you should only do kcl's at nodes with unknown voltages. you know that the 75v node is 75 v above ground. So try a KCL at nodes Vx and V1

    does that make sense?
     
  4. Feb 8, 2014 #3
    Ah yes! Thanks a lot mate.
     
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