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Magnetic Fields Produced by Currents

  1. Feb 25, 2007 #1
    A circular loop of wire and a long, straight wire carry currents of I1 and I2 (see the drawing), where I2 = 5.2I1. The loop and the straight wire lie in the same plane. The net magnetic field at the center of the loop is zero. Find the distance H, expressing your answer in terms of R, the radius of the loop.


    2. Relevant equations
    Magnetic field produced by a long straight wire:
    B = (u*I)/2 pi r

    Magnetic field at center of a loop:
    B = N * [(u*I)/(2R)]

    3. The attempt at a solution
    honestly i dont know where to begin. im not getting how the equations i listed will help me to solve for H in terms of R. obviously, i know i have to solve for R in order to find H. i'm confused as to which equation to use. id also assume some type of triangle will come into play here since i am given a right angle. If someone could please help me get going in the right direction on this one i would greatly appreciate it..
  2. jcsd
  3. Feb 25, 2007 #2
    The r in this equation is equal to H. You also know that the wire's field has to cancel out the loop's field. Proceed from there.
  4. Feb 27, 2007 #3
    i was just about to post this big long reply...but i finally got it! thanks

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