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Balancing magnetic forces on rods

  1. Dec 29, 2015 #1
    1. The problem statement, all variables and given/known data
    If two parallel rods are placed 1mm apart, with one directly above the other, each carrying a current I in opposite directions, of length L what is the mass of the upper rod as to balance the force

    2. Relevant equations

    3. The attempt at a solution
    I have little idea of how to go about attempting this solution, thankyou!
  2. jcsd
  3. Dec 29, 2015 #2

    Mister T

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    You need to assume the lower wire is held in a fixed position. It exerts a magnetic force ##IL\times B## on the upper wire.
  4. Dec 29, 2015 #3
    Thankyou, but how do you work the magnetic field strength?
  5. Dec 29, 2015 #4


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    Homework Helper

    Biot-Savart's law or Ampere's law will be useful here.
  6. Dec 29, 2015 #5

    Mister T

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    I suggest you look in a textbook. There should be a section on force between long parallel current-carrying wires.
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