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Circuit Theory Question KCL and Dependent Sources?

  1. Mar 15, 2015 #1
    1. The problem statement, all variables and given/known data
    I need to find the voltages (if any) and currents of these circuit, but particularly Io
    I do know that I have to use KCL bot I dont know how, can somebody help me with a node or somethinghttps://www.physicsforums.com/attachments/c2-jpg.80412/ [Broken]

    I do not have any other info apart from this image

    2. Relevant equations

    C2.jpg
    KCL

    3. The attempt at a solution

    I don't know how to tackle this problem
    I think by KCL

    -Io = -I(Vx)+5A-3Vx

    but not sure

    and how do I find Vx? is
    Vx=I(5 amp)*R(4 ohm)=5*4=20 volts ??????

    then the dependent current is 3*20=60 volts? but is current it should be on ampere not volt

    or should I solve the resistors and get Req
    1/ (1/(8+4)+1/6) = 4 ohm = Req

    C2.jpg

    there is one node on the top and another one on the bottom, but that one is ground, so shoul I transform the current source and the Io resistor into a voltage source?
     
    Last edited by a moderator: May 7, 2017
  2. jcsd
  3. Mar 15, 2015 #2

    Orodruin

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    Why don't you try applying KCL yourself and show us what you get. Note that providing an attempt is mandatory according to forum rules, we need to see where/if you go wrong to help you properly with your understanding.
     
  4. Mar 17, 2015 #3

    donpacino

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    Gold Member

    you are on the right track

    -Io = -I(Vx)+5A-3Vx There is an error in this equation.

    Remember that in most cases you must have one equation for every unknown.
    This implies that you might have to apply Kirchhoff's laws one more time (seeing as there are two unknowns).
     
    Last edited by a moderator: May 7, 2017
  5. Mar 18, 2015 #4
    so my node is 5 (the current source) = Io (the one I need to find) + 3Vx (the one with the dependent source) + I1 (the one with the 8 and 4 resistances)

    5=Io+3Vx+I1

    I1=Vt/12
    Vt=V(in 4)+V(in 8)
    Vt=Vx+2Vx
    Vt = 3 Vx

    I1 = Vx/4

    my unknowns are Io and Vx,

    5=Io+3Vx+Vx/4

    I really have no clue where is the other equation
     
  6. Mar 18, 2015 #5

    donpacino

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    I see 3 voltage nodes. If you reference one as ground, the other two are unknown.
     
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