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Homework Help: Two very long straight conducting wires problem

  1. Jul 27, 2009 #1
    1. The problem statement, all variables and given/known data

    My picture won't upload but there is an x-y plane with point P at (5,4) and a vector shooting off from P in the SW direction. There are two wires pointing into the page (in the z plane) at (5,2) and (10,2).

    Here is the actual problem:

    Two very long straight conducting wires are perpendicular to the x-y plane. At point 'p', the magnetic field, shown on the figure below, is due to the currents in wires '1' and '2', with |B| = 4.782×10-4 T. Its components Bx= -4.470×10-4 T and By= -1.700×10-4 T.

    I. Indicate the direction of the currents in the wires, +z (out of the page) or -z (into the page).

    II. Calculate the magnitude of the current in wire2.
    2. Relevant equations

    III. Calculate the magnitude of the current in wire1.

    3. The attempt at a solution

    The current in wire 1 is in the -z direction and wire 2 is +z?
    For the second part Bwire = (miu*I)/ (2*pi*R)
    I'm especially unsure of what R would be... please help!
  2. jcsd
  3. Jul 27, 2009 #2


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    Homework Helper

    Welcome to PF!

    Hi cate25! Welcome to PF! :smile:

    Isn't R just the distance from P to each wire (so you'll need two equations, one for the field from each wire, and with different R's)?
  4. Jul 27, 2009 #3
    Re: Welcome to PF!

    Thanks, tiny tim!
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