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Homework Help: Magnetic Effects of Currents

  1. Mar 18, 2005 #1
    1] Two long straight parallel conductors each carrying a current of 24 amps flowing in the same direction are fixed at a distance of 40mm from each other. A third parallel conductor is placed equidistant from the other two and carries a current of 30 amps.

    Show that the force on the third conductor is a maximum when its distance from the other conductors is 28.2mm and calculate the force per metre at this distance.


    I know that F=BIL, is this sufficient for solving this problem? just need a little guidence.
  2. jcsd
  3. Mar 18, 2005 #2


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    Looking along the conductors, so that each is represented by a point, the two conductors (24 A) form a line segment or base of a triangle. The third conductor forms the apex of an equilateral triangle. The magnetic forces from each of the two conductors are add as vectors.

    One is to solve for the 'maximum' force, so one must write the formula for the magnitude of magnetic force, differentiate, and solve for the maximum.
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