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Determine sources being charged

  1. Feb 4, 2006 #1
    i keep getting stuck in this problem, i dont see what im doing wrong.
    the problem says to determine which sources absorb positive power, then show that algebraic sum of the five absorbed power values is zero.
    i have attached a picture of the circuit, and here is what i have done:
    Starting from left to right,
    p=-4W
    p=-16W
    p=40W
    p=-50W
    p=-30W
    Im not getting the sum to equal 0.
    From what i understand, when current is going from + to - in a independent voltage source it is charging and when it is going from - to + it is releasing power, and that is the guidelines i have used to get the bove answers. Im just not sure if im supposed to follow the same guidelines for independent current sources. Is there a website that discusses these topics, kuz my book has not done a good job to demonstrate these ideas very clearly.
     

    Attached Files:

  2. jcsd
  3. Feb 6, 2006 #2

    berkeman

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    Staff: Mentor

    Yeah, something is nonsensical there. First of all, there is a really weird mixed notation for the sources. Some of them are drawn as current sources (with the arrow inside), but are labelled with a voltge. That's incorrect.

    And if you correct the notation so that all sources labelled with a voltage are drawn as voltage sources, then you basically get three 10V voltage sources in parallel, with a single current source also connected in parallel. But the currents don't add up correctly in that case either, since you end up with different currents in different legs, even though they have the same voltage source in each.

    Are you sure you have correctly drawn the circuit?
     
  4. Feb 6, 2006 #3
    ya, im positive that the circuit is drawn correctly, i just copied it straight out of the book...
     
  5. Feb 6, 2006 #4

    berkeman

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    Staff: Mentor

    But a current source with a voltage notation across it is not standard. Sorry that I'm not of more help.
     
  6. Feb 6, 2006 #5
    its ok, im just gonna wait until the professor goes over the answer in class today. i mean thats the circuit the book has given us, so thats what ive been trying to work on. thanks for your help tho
     
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