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Homework Help: The Magnetic Field

  1. Mar 5, 2008 #1
    1. What are the magnetic field strength and direction at points 1 to 3 in the figure?
    Okay, sorry, once again i dont know how to get the picture up here so ill describe it!
    There are 2 long wires 4 cm apart, the one on top with a current of 10 A in the positive x direction and the one on the bottom with a current of 10 A in the negative x direction.
    Point 1 is 2cm above the top wire.
    Point 2 in directly in between the two wires.
    Point 3 is 2cm underneath the bottom wire.

    2. Relevant equations
    Okay so here im thinking something along the lines of that B = (u0/4pi)(Is 'r-hat'/r^2)
    or maybe i found this equation in my notes that could be helpful and my gut says its the better bet
    B = (u0I)/(2pid)

    3. The attempt at a solution
    Point 1 : (u0*10A)/(2pi*0.02m)
    Point 2 : since it is inbetween two wires with opposite currents, so opposite fields (???) my guess is that it is equal to 0???
    Point 3 : the opposite of point 1

    Im also curious as to whether we assign a negative or positive value to the current??
    And also would the bottom wire have an effect on the magnetic field at point 1??
  2. jcsd
  3. Mar 6, 2008 #2


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    Homework Helper

    You have to decide the direction of the field by right hand clasp rule. Accordingly the field at point 1 due to top wire is coming out of the paper at a distance 2 cm from the wire and field due to bottom wire is going into the paper at a distance 6 cm from this wire. Apply the same rule to the other points.
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