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Power generated by dependent source

  1. Jan 24, 2012 #1
    1. The problem statement, all variables and given/known data
    Determine the power generated by the dependent source in the circuit shown below:

    blah-5.jpg

    2. Relevant equations
    Ix=V/R
    Pgen=V*I

    3. The attempt at a solution
    I made an equivalent circuit, but it may not be correct (resistors in parallel?):

    blah2-1.jpg

    Ix=-(12V/(12/7)Ω)=-7A
    2Ix=2(-7a)=-14A

    Passive sign convention is satisfied for the dependent source, so Pgen = -Pabs:
    Pgen=-(12V)(-14A)=-168W

    I am not sure I did this correctly, as this is my first time in a class like this. If I am going about this wrong, could someone point me in the right direction? I understand most of the homework in this class, but this one kind of confused me.

    Thanks
     
  2. jcsd
  3. Jan 25, 2012 #2

    NascentOxygen

    User Avatar

    Staff: Mentor

    I think you are straying way off course. The independent voltage source produces a current in that 3 ohm resistor. You can determine its value.

    ix has a direction opposite to what the voltage source produces, so you need to attach a negative sign to the magnitude of the current and call it ix

    continue ....
     
  4. Jan 25, 2012 #3
    Yeah, my professor showed us how to do it in class today and it makes a lot more sense now. I had just learned the material and the book we have isn't very good at giving examples/explanations.
     
  5. Jan 28, 2012 #4
    Yeah it can get tricky for a newbie but stick to basics...

    First of all realise that the wire connecting the two parts of the circuit cannot provide for both forward and return path for current. So current in the middle wire has to be zero. Now analyse both the parts of the circuit individually following what nascent oxygen told in the previous post...

    As far as a book is concerned you can refer to :
    Engineering Circuit Analysis by Hayt
    Best of luck
     
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