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Find the two figures and the get value of the resistor and current

  1. Feb 14, 2017 #1
    resistor.jpg 1. The problem statement, all variables and given/known data
    finding the resistor and current which is following through the circuit



    2. Relevant equations
    kirchhoff law

    3. The attempt at a solution
    almost as fig 1 ( 9v=3.458 mA and 12v=11.122 mA)
    fig 2 (9v=1.472 mA and 12v=12.882 mA) i3=2.48 mA
     
  2. jcsd
  3. Feb 14, 2017 #2

    gneill

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    Staff: Mentor

    Hi Hamood97,

    Welcome to Physics Forums!

    I presume that you are required to find the resistance R3? (It's hard to tell because the writing on the image is very small). What current are you meant to find?
    Is that meant to specify the currents produced by the voltage sources? It doesn't make sense to equate voltages and currents in an equation so that is my guess. The diagram doesn't indicate where i3 is.
     
  4. Feb 15, 2017 #3
    thanks for your reply. i should have told you before about value of R3 which is 560 ohm. i want to find all the currents in figure 1 and figure 2.
     
  5. Feb 15, 2017 #4

    gneill

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    Staff: Mentor

    Okay, perhaps to avoid confusion you should annotate your drawing to show currents and their directions.

    What circuit analysis technique(s) have you applied? Can you show your work?
     
  6. Feb 15, 2017 #5
    Untitled.jpg IMG_0985.JPG
    R3 =560
     
  7. Feb 15, 2017 #6

    gneill

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    Staff: Mentor

    It really would be better if you could type in your equations. It's hard to make out others' handwriting when it's sideways.

    You didn't identify your loop currents on the diagram, but after looking at your equations I determined that this was where you started and that you chose to use mesh current analysis:

    upload_2017-2-15_10-55-10.png
    It would better if you stated these things so that others don't have to puzzle it out before thy can help you. Typing in your equations would also be a big help. That way helpers can easily quote them for commentary.

    Your mathematical results for the three mesh currents look okay to me.

    Your experimental results for figure 2 look a bit off if the math is to be believed. Perhaps not all the resistor values are precise (cheap resistors can be +/- 20% in value)? Did you measure the voltage source values while the circuit was in operation (to make sure they didn't change value under load)?
     
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