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Homework Help: Application of Circuit laws (KCL and KVL)

  1. Jan 16, 2013 #1
    1. The problem statement, all variables and given/known data
    Calculate the resistance of this combination of resistors

    2. Relevant equations


    3. The attempt at a solution

    By using KVL :

    V= 3[itex]I_{5}[/itex] = [itex]I_{2}[/itex] = 2[itex]I_{4}[/itex]
    I = [itex]I_{1}[/itex] + [itex]I_{2}[/itex]
    [itex]I_{3}[/itex] = [itex]I_{2}[/itex] + [itex]I_{4}[/itex]
    [itex]I_{1}[/itex] = [itex]I_{5}[/itex] + [itex]I_{4}[/itex]
    I = [itex]I_{3}[/itex] + [itex]I_{5}[/itex]

    Now the final result could be obtained by the simple equation : R =V/I (this is where my progress stagnates)

    Attached Files:

  2. jcsd
  3. Jan 16, 2013 #2


    User Avatar

    Staff: Mentor

    Your first equation relates currents I2, I4, and I5 to the potential across the circuit. Now, if you take your last equation and make substitutions so that you express I in terms of those same currents in the first expression, I think you'll get somewhere.
  4. Jan 16, 2013 #3
    You mean like this :

    I = [itex]I_{5}[/itex] + [itex]I_{2}[/itex] + [itex]I_{4}[/itex]

    Thus R = V/I

    that does not solve the problem ...
  5. Jan 16, 2013 #4


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    Staff: Mentor

    But you can substitute your expressions for those currents from your first equation...
  6. Jan 16, 2013 #5
    Oh yes, I overlooked this .
    Thanks you
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