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Homework Help: Force on 2 wires near each other with current

  1. Mar 31, 2015 #1
    1. The problem statement, all variables and given/known data
    Two wires are placed parallel near each other in free space at a distance of d=0.08m. They have a length of L=0.4m and each carry a current of i=3.7A (in the same direction.) Find the force exerted on each other. Consider attraction as positive force and repulsion as a negative force.

    2. Relevant equations
    F = B*I*L
    B= = u*Hs = (u*I/(2*PI*R))*I*L

    3. The attempt at a solution
    4*PI*10^-7*3.7/(2*PI*.04)*3.7*.4 = 27.38uN
    The correct answer is apparently 13.69N. Anyone see where I am going wrong? Is my B equation incorrect? Thanks!
  2. jcsd
  3. Mar 31, 2015 #2


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    2017 Award

    Staff: Mentor

    I don't understand what you calculated here.
    And I wonder how you got units of tesla out of that calculation (a good check to see if everything went right).

    A different issue: the approximation of very long cables (compared to R) you used might not be a good one.
  4. Apr 1, 2015 #3
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