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Homework Help: Magnetic Fields and Forces

  1. Jun 7, 2012 #1
    1. The problem statement, all variables and given/known data
    Two straight wire are suspended from the ceiling by strings length of 0.75m.
    each wire has a mass of 45g and a length of 1m
    When identical current flows in opposite directions, the angle between the string is 12°.


    2. Relevant equations
    Fg=mg
    B=μI/2πR
    F=LIBsin(theta)


    3. The attempt at a solution
    From the looks of it, I assumed that this was an equilibrium question meaning that the force of (BIL) is the same on both wires, working in opposite directions to create an angle of 12°.
    I also assumed that the force of gravity (.441) is equal to the Y component of the string, so then i used trig to solve for the force of the X component which i found to be .0464.

    The force of the X component is the same force as the (BIL) and in order for the forces to be the same, the magnetic field and current has to be the same.

    so then i combined B=μI/2πR with F=LIBsin(theta) in order to cancel out the magnetic Field since it did not matter.

    I got F= LμI2/2πR

    I figured out the current to be 131.9

    I would attach a picture of my work but i don't have 10 post..
    imageshack.us/photo/my-images/265/photo20120607121104pm.jpg/
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
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