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Homework Help: Magnetic force on coil problem

  1. Apr 12, 2005 #1
    I'm stuck on the following problem:

    A long thin coil of length l, cross-sectional area S, and n turns per unit length carries a current I. It is placed along the axis of a large circular ring of radius a, which is carrying a current I'. If d is the displacement of the center of the coil from the center of the ring along the coil axis, find the force on the coil as a function of d.

    I'm not sure what formulas to use, and what I have to integrate to get the following result:
    [tex] F = -\frac{\mu_0 II'nSa^2}{2} ((a^2 + (\frac{l}{2} - d)^2)^\frac{-3}{2} - (a^2 + (\frac{l}{2} + d)^2)^\frac{-3}{2})[/tex]

  2. jcsd
  3. Nov 1, 2011 #2
    Hello,first post ever, you could try to use the force from the formula

    [itex]F=\int I(dl\times B)[/itex]

    Where B is the field from the ring
    Last edited: Nov 1, 2011
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