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Thevenin's Theorem with Source Transforms

  1. Dec 12, 2014 #1

    Zondrina

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    1. The problem statement, all variables and given/known data

    I was able to find the Thevenin equivalent between ##A## and ##B## using loop analysis and then Ohm's law:

    Screen Shot 2014-12-12 at 3.38.19 PM.png

    The Thevenin equivalent was ##V_{th} = -4.0 V## in series with ##R_{th} = 0.8 k##.

    Now I had a question about solving the problem using a different approach. I realized now source transforms are a sort of "corollary" to Thevenin and Norton's theorems. So I was wondering if it was possible to use those in solving this problem.

    2. Relevant equations


    3. The attempt at a solution

    From what I can understand, first I should use ##V = IR \Rightarrow I = \frac{5}{2} mA##. Then I could have a current source in parallel with the ##2k## on the left.

    Now ##R_{eq} = (\frac{1}{2k} + \frac{1}{4k})^{-1} = \frac{4k}{3}##.

    So I have that ##\frac{5}{2} mA## in parallel with ##\frac{4k}{3}##.

    From this point I have not been able to continue using source transforms to simplify to the correct answer. Is it just not possible? Or is it a combination I'm not seeing?

    I see that superposition would be useful from this point as well, but I want to know if it's possible with source transforms.
     
    Last edited: Dec 12, 2014
  2. jcsd
  3. Dec 12, 2014 #2
    Convert ##\frac{5}{2} mA## in parallel with ##\frac{4k}{3}## back into a voltage source of 10/3 volts in series with a resistance of 4000/3 ohms. Now you have 2 voltage sources in series with two resistors. Slide the 4000/3 ohm resistor to the right so it's just above the 2k output resistor. Those two resistors form a voltage divider driven by the difference in the two voltage sources.

    I get Vth = -4V
     
  4. Dec 12, 2014 #3

    Zondrina

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    I tried this earlier, but I messed the numbers up and it didn't spit the right answer out.

    Reading your post and going back to it, I face-palmed and realized my mistake. I now get the same answer in 10 different ways so I should be good.

    Thank you.
     
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