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Homework Help: Current in 2 parallel wires

  1. Apr 20, 2009 #1
    1. The problem statement, all variables and given/known data

    Two straight parallel wires carry currents in opposite directions. The wire on the right carries a current of I2 = 11.5 A. Point A is the midpoint between the wires. The total distance between the wires is d = 10.7 cm. Point C is 5.88 cm to the right of the right wire carrying current I2. Wire on the left carries current I1 and is adjusted so that the magnetic field at C is zero. Calculate the value of the current I1.

    2. Relevant equations

    I2/R2 =I1/R1
    Know I2< I1

    3. The attempt at a solution

    I know you have to use the 1st equation as a ratio but I do not know how to find R1.
    R2 I believe in just 5.88cm (.0588m)
  2. jcsd
  3. Apr 20, 2009 #2


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    Homework Helper
    Gold Member

    R1 is the distance from the left wire to point C. You know the distance from the left wire to the right wire, and you know the distance from the right wire to C, so how far is the left wire from C? Draw a picture.
  4. Apr 20, 2009 #3
    The distance would be 16.58 cm = 0.166 m

    So plugging that into the proportion equation:


    11.5A/.0588m = I1/0.166m
    I1= 32.5A

    Ok I think I forgot to change the cm to meter the first time!

    But thank you for your help!
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