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Two very long parallel wires 1.0m apart lie on the ground

  1. Dec 15, 2014 #1
    1. The problem statement, all variables and given/known data
    Two very long parallel wires 1.0m apart lie on the ground carrying currents 4.0A and 6.0A in the same direction.
    How far from the 4. wire are the magnetic field completely cancelled? 1.0m on the other side of the 4.0A wire, what is the magnitude of the magnetic field?

    2. Relevant equations
    B= UoI/2pir; B = (UoI/4pix)(cos alpha + cos betta) ; F/L = UoI1I2/2pid

    3. The attempt at a solution
    I have attempted to use the magnetic field equations in that they are both moving in same direction; the wires will attract each other meaning that they will be opposite signs, but still cant find the solution. I also tried using the Force per length but am not sure how to truly approach the problem.
  2. jcsd
  3. Dec 15, 2014 #2

    Simon Bridge

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    Science Advisor
    Homework Helper

    The magnetic force is not in the same direction everywhere.
    Start by drawing a picture and working out which direcetion a compass needle points on each side of the wires.
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