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Homework Help: Ampere's law problem help please

  1. Mar 10, 2007 #1
    1. The problem statement, all variables and given/known data
    So a long straight wire lies on a horizontal table and carries a current of 1.2x10^-6A. In a vacuum, a proton moves parallel to the wire(opposite the current) with a constant speed of 2.3x10^4 m/s at a distance d above the wire. Determine the value of d. You may ignore the magnetic field due to the Earth.

    2. Relevant equations
    ampere's law
    F(magnetic field)=q(vxB)
    Biot savart law?

    3. The attempt at a solution
    So what I did is have the magnetic field formula for a wire, I then substitute this into the magnetic force equation. But now I don't really know where to go from there. Please help. Thanks very much.
     
  2. jcsd
  3. Mar 10, 2007 #2

    Doc Al

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    Staff: Mentor

    Hint: Since the proton moves with constant velocity, what must the net force be on it?
     
  4. Mar 11, 2007 #3
    well net force should be zero but then would it mean F(magnetic)= mg or I am not sure what it would be equal to?
     
  5. Mar 11, 2007 #4

    Doc Al

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    Staff: Mentor

    You got it.
     
  6. Mar 11, 2007 #5
    oh thanks very much
     
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