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Homework Help: Magnetic forces between parallel wires

  1. Dec 4, 2007 #1
    1. The problem statement, all variables and given/known data

    What is the force magnitude on the first, second, and third wires in the figure?


    2. Relevant equations

    0L I1 I2)/(2πd)

    μ0 = 1.2566*10-6

    3. The attempt at a solution

    Substituting 0.5 as L, 0.02 as d and 10 as I1 and I2 I get 5*10-4,
    which comes up as incorrect...what am I doing wrong?

  2. jcsd
  3. Dec 4, 2007 #2


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    Homework Helper

    well if you did some more about current carrying conductors.
    you may come across the formula

    [tex]F=\frac{\mu I_1 I_2 l}{2 \pi d}[/tex]

    but are you sure you converted cm to m?
  4. Dec 4, 2007 #3
    yea that us the formula i used...and i converted everything....the numbers i put in post 1 are the numbers i used for d and L respectivly
  5. Dec 4, 2007 #4


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    What is the correct answer? well....you would have to find the resultant force on wires 1 and 3...
  6. Dec 4, 2007 #5
    idk the correct answer....

    and since the wires are the same, wouldnt some cancel eachother out? (due to the direction of the current)
  7. Dec 4, 2007 #6
    well the force in the second wire zero
  8. Dec 4, 2007 #7


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    yes the force in the 2nd wire is zero, so you should have to only find the force of attraction of wires 1 and 3...

    EDIT: thing to remember...like currents attract, opposite repel
    Last edited: Dec 4, 2007
  9. Mar 28, 2010 #8
    So the just say that the first wire was going in the opposite direction to the other 2 wires... How would u calculate the force acting on wire 1 due to wire 2 (and wire 2 was going the opposite direction) and 3 ?

    2 --->
    3 --->
    Last edited: Mar 29, 2010
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