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Electromagnetics - Two long wires carry equal, but opposite currents

  1. May 29, 2006 #1
    Another Electromagnetics question....

    Two long wires carry equal, but oppositely directed, 25 A currents. What is the magnitude of magnetic field due to these currents at point P? The wires are 0.1 m apart and point P is 0.05m in between the wires.

    Would the following be the correct way to solve it?

    B = (4pi * 10^-7)(25) / (2)(pi)(0.05)

    (Phys. 12)
  2. jcsd
  3. May 29, 2006 #2
    1. Do you know the expression for magnetic field set up by a long straight wire (of course you do).

    2. At point P can you determine the directions of the two fields (due to the two wires)?

    3. Determine the fields and add them vectorially :smile:
  4. May 30, 2006 #3


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    HINT: The question is easier than it first seems and can be answered by inspection; no calculations are nesscary, but they could be used to obtain the same answer. Think bout what determines the magnitude of the magnetic field. Think about what determines the direction of the magnetic field.

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