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Homework Help: Help with two electrical circuits please

  1. Oct 13, 2016 #1
    • OP warned about not having an attempt at a solution
    Hey, im having problems with this. I need help with these 2 circuits im basically lost and not sure how to start. I need to find voltage, current and potency on each resistance

    help would be much appreciated, thank you


  2. jcsd
  3. Oct 13, 2016 #2


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    Staff: Mentor

    What have you tried?
  4. Oct 13, 2016 #3
    i know that i have to use the KCL in each node, then use KVL to find the 4 equations so i can get the currents and voltages, the thing is that i dont know if the currents are going in or out of the nodes
  5. Oct 13, 2016 #4


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    Staff: Mentor

    It doesn't matter what you choose for the current directions, the math will "self correct" any bad choices so long as you stick to your choices while you write the equations. If a current direction was chosen incorrectly the result will be a negative value for that current, telling you that it flows in the direction opposite of your guess.
  6. Oct 13, 2016 #5


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    Science Advisor
    Homework Helper
    Gold Member


    Choose/define an arbitrary direction for +ve current in each loop and mark on the diagram.
    Work out what that current means for the polarity of voltage drops across resistors and mark those on the diagram.
    Write KVL equations based on those voltages.
    Write KVC equations for the nodes (perhaps assume current going into a node is +ve).
    Solve the simultaneous equations
    If a current turns out to have a -ve value then it's going the opposite way to the arrow on your diagram.
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