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Homework Help: Magnetic Fields

  1. Apr 2, 2007 #1
    A long straight wire lies on a horizontal table and carries a current of 2.00 µA. In a vacuum, a proton moves parallel to the wire (opposite the current) with a constant speed of 1.90E4 m/s at a distance d above the wire. Determine the value of d. You may ignore the magnetic field due to the Earth.

    ok so we have
    0.000002 A
    19000 m/s proton with mass and charge

    the only problem i have is trying to understand what is going on in the problem and what needs to be balanced... once i understand what needs to be equated the physics behind it becomes more apparent.... can anyone give me a brief explanation of what needs to be understood to solve this?
  2. jcsd
  3. Apr 3, 2007 #2


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    Homework Helper

    The current in the wire creates a magnetic field around the wire as predicted by Ampère's law. There are two forces acting on the proton: Lorentz force (a charged particle in an electromagnetic field) and gravity.
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