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Homework Help: What is the magnitude of the force the first exerts on the second?

  1. Jul 4, 2009 #1
    1. The problem statement, all variables and given/known data

    A circular loop of wire of radius R = 3.67 m
    lies in the xy-plane, centered about the origin.
    The loop is carrying a current of I = 6.2 A
    flowing in counterclockwise direction.

    Consider two l = 1.63 mm segments of the
    loop: one centered about the positive x-axis,
    the other centered about the positive y-axis.
    Hint: Use Biot-Savart law.
    The permeability of free space is
    1.25664 × 10−6 Tm/A

    What is the magnitude of the force the first
    exerts on the second? Answer in units of N.

    2. Relevant equations

    dB = Uo*i*ds×r/(4*pi*r^2)

    3. The attempt at a solution

    i didnt understand the problem well, as a result i couldnt figure out how to solve it

    i am seeking for your help
    thanx in advance
  2. jcsd
  3. Jul 5, 2009 #2


    User Avatar
    Homework Helper

    Field at the point on the y-axis due to the current element on the x-axis is
    dB = μο/4π*i*ds*sinθ/r^2. Here θ is 45 degrees. Direction of the field is perpendicular to the current element on the y-axis. Hence the force on the current element is
    df = dB*i*ds.
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