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Simple Circuit with Two Sources

  1. Apr 3, 2015 #1
    1. The problem statement, all variables and given/known data
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    2. Relevant equations
    KCL and KVL

    3. The attempt at a solution
    The sum of the currents at the top node equals the current out through the middle
    (Call ##I_1## the current from the left and ##I_2## the right)

    ##I_3 = I_1+I_2##

    And the sum of the voltages around the loops equals 0.

    ##-I_3(4k)-I_1(6k) + 10V = 0##

    ##-I_3(4k) + 4V = 0##

    The system of equations yields solutions
    ##I_3 = 1mA##
    ##I_1 = 1mA##
    ##I_2 = 0##

    Now, it appears that either I made a mistake, or there is zero current going through the source on the right. Is it logical to conclude that the source on the right is irrelevant to the circuit?
     

    Attached Files:

  2. jcsd
  3. Apr 3, 2015 #2

    phinds

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    No mistake. Well, irrelevant to the circuit as drawn, yes; if other components were added it would likely come into play.
     
  4. Apr 3, 2015 #3
    Could I have predicted this from the start, and crossed off the right side source, and solved for just a single source with series resistors?
     
  5. Apr 3, 2015 #4

    SammyS

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    That's difficult to say.

    You might have noticed that removing the right side source & leaving that branch open would give a simple series circuit with the voltage across the 4kΩ resistor being 4 Volts.

    That's not something one would normally look for.

    Hindsight is wonderful.
     
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