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Thevenin Equivalent Circuit

  1. Feb 20, 2015 #1
    1. The problem statement, all variables and given/known data
    The question is in the photo attached.

    2. Relevant equations


    3. The attempt at a solution
    I have found the Thevenin voltage as the 10 and 20 ohm resistors are in series (30 ohms) and the 50 and 40 ohm resistor are in series (90ohms). The 30 and 90 ohm resistors are in parallel so

    30||90 = (30×90)/(30+90) =22.5 ohms

    I am having struggles with determine the Thevenin voltage as the solution says the 8 A current gets divided equally among the 10 and 20 ohm resistor but I don't understand why.
     

    Attached Files:

  2. jcsd
  3. Feb 20, 2015 #2

    gneill

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    Staff: Mentor

    What is the total resistance of each branch (ignore the terminals A and B for the moment)?
     
  4. Feb 20, 2015 #3
    60 ohms but how can we ignore terminals a and b?
     
  5. Feb 20, 2015 #4

    gneill

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    Staff: Mentor

    I said ignore them for the moment. You can do this because they are open: not connected to anything so they do not pass any current.

    So both of these branches have the same resistance, correct? The branches are in parallel, correct? How will current divide between equal resistances in parallel?
     
  6. Feb 20, 2015 #5
    So since current doesnt pass through terminal a and b, they just flow down to the next resistor?
     
  7. Feb 20, 2015 #6

    gneill

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    Staff: Mentor

    Yes. They are the only available paths.
     
  8. Feb 20, 2015 #7
    Okay, that makes sense then, thank you!
     
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