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Homework Help: Find the force on each wire

  1. Apr 12, 2016 #1
    1. The problem statement, all variables and given/known data
    Two wires AD and DC are put in the magnetic field with induction B=0.01T so that they form the angle pi/3 radian and the extremities A and C are in the same force line (what does it mean???). In the wires passes the current I=2A (intensity). Find the forces with which the field acts on each wire. (SOLUTION: 8.5*10^-4 N)

    2. Relevant equations
    F=B*l(intensity)*l(length)*sin alpha
    3. The attempt at a solution
    What does be in the same force line mean and how does it affect the problem and the equations?. I don't know how to find the length and how to use the fact that the angle is pi/3 radian
  2. jcsd
  3. Apr 12, 2016 #2


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    Science Advisor
    Homework Helper
    Gold Member

    The force lines are the lines showing the direction in which the magnetic field flows. Imagine that in the number plane the mag field (which we assume is uniform, although the question does not state that) flows in the positive y direction (ie up). Then the statement 'extremities A and C are in the same force line' means that A and C have the same y coordinate.

    The trouble is that the problem is not fully specified, because we do not know the relative lengths of AD and DC. If they are the same then the triangle ADC will be equilateral and the forces on the two wires will be of equal magnitude but opposite direction. If the lengths are not the same then the triangle will not be equilateral, the angles the wires make with the force lines will be different, and the magnitude of the forces will be different.
  4. Apr 12, 2016 #3


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    Staff: Mentor

    It seems they share a common answer…so first try equal lengths. Might also have to look at determining force per unit length?
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