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Homework Help: Total magnetic field from two long parallel wires

  1. Nov 3, 2008 #1
    1. The problem statement, all variables and given/known data

    Two long, straight, parallel wires, 10.0 cm apart carry equal 4.00-A currents in the same direction, as shown in the figure. ( in the figure the current carrying wires are at the end of a straight 10cm line and they are each in the direction coming out of the page).
    point p is at the center of the 10cm line.
    find the magnetic field at point p2 which is 20cm directly above p
    2. Relevant equations

    3. The attempt at a solution

    I have no idea how to do this, for the last problem before this it wanted to know the field 25cm to the right of p, so I used the equation B=[tex]\mu_{0}[/tex]I/(2*pi*r) for each wire and used the right hand rule to determine they were both facing up so I added them. I'm confused on what to do now though.
  2. jcsd
  3. Nov 3, 2008 #2
    I figured out to the the right answer you need to do 4*pi*10^-7 * 4 / ( 2*pi *.206) take this answer and multiply by the cos of 14 and multiply that by 2 but I don't get why you would do the cos of 14 and not the sin of 14 can someone explain it to me please
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