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Circuit with 2 loops, find the current in one of the loops

  1. May 24, 2009 #1
    1. The problem statement, all variables and given/known data
    A circuit composed of one battery and four resistors is arranged as shown in the attached pic.

    E = 19 V

    R1 = 12 W
    R2 = 2 W
    R3 = 15 W
    R4 = 2 W


    Calculate the current I1 through R1?




    2. Relevant equations
    V=IR (obviously)



    3. The attempt at a solution

    first i got the net current in this circuit by doing the following..
    i summed resistors in series to get 14ohm on first loop and 17ohm on second loop.
    then i applied resistance in parallel rule :
    Req = (1/R1) + (1/R2)
    = 7.69ohm = Rtotal
    then I = V/R = 2.47A = total current in the circuit.

    Then to get the current on the 14 ohm loopm i multiplied 2.47 by (14/17) . ( i think this is where I am erring, but cant see why this doesnt work??)

    = 2.03A (wrong)
    thanks for any help!
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     

    Attached Files:

  2. jcsd
  3. May 24, 2009 #2
  4. May 24, 2009 #3
    you're making this too complicated.

    the voltage between the two nodes must be the battery voltage.

    so if you know the voltage accross a resistor (or an Eq Res) you can find the current through it.


    use I = V/R, where R is the equivalent resistance of the branch and V is the voltage accross the branch.
     
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