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Understanding how to re-draw circuits

  1. Dec 14, 2014 #1
    1. The problem statement, all variables and given/known data

    I need to find I1,I2,I3,Va,Vb but i dont even know to read the circuit. i know how to to do series circuits and parallel circuits but not this. How do i read this circuit and know which ones are in parallel or in series. is there a way to re-draw it? I have the solution and answer. Therefore i dont need the step by step solution since i already have it,is just that it doesnt explain why they did it that why.
    These are the I1=4A ,I2=1.33, I3=.67, I4=2.67,va=8.0,and vb i dont know.
    Please help understanding what is going on in this circuit.
    Last edited: Dec 14, 2014
  2. jcsd
  3. Dec 14, 2014 #2

    Stephen Tashi

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    Science Advisor

    If you need a loop, put in a 20 V battery with the positive plate connected to E. Connect the negative plate of the battery to the 3 grounds at the bottom of the diagram.
  4. Dec 14, 2014 #3


    Staff: Mentor

    I would work my way up from the bottom, simplifying bits and pieces as I go. R5 and R3 are in parallel, right? So you could combine those two resistors into a single resistance. Keep chipping away at it until you have a single loop.
  5. Dec 15, 2014 #4


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    Gold Member

    If you combine circuit elements you will lose that components individual voltage and/or current.

    I reccoend doing a KCL at Va and Va. Then solve for Va and Vb, and the currents will be easy to find.
  6. Dec 15, 2014 #5
    thanks for the tip
  7. Dec 15, 2014 #6
    if i do ((R5||R3)+R2)||R4 and this would be in series with R1 right? now to get Vb i think i would do Vb=R5(I2-I3) but what if that R5 was not there then how would i solve for vb
  8. Dec 15, 2014 #7


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    Gold Member

    If R5 was not there then I2 and I3 would change. you cannot solve for an unknown value with unknown values
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