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Homework Help: Magnetism between two electrical wires

  1. Nov 27, 2008 #1
    1. The problem statement, all variables and given/known data
    Point P is midway between two long parallel straight wires that run north-south in a horizontal plane. The distance between the wires is 1 cm. Each wire carries a current of 1 A toward the north.

    a) find the magnitidue and direction of the magnetic field at point P.
    b)repeat a but assume the current in the wire on the east side runs towards the south instead.

    3. The attempt at a solution

    Okay, so for a), this is what I did.

    I drew a diagram and concluded at point P there would be two magnetic fields due to the two electrical wires, that are equal and opposite in direction.

    So the answer is 0.

    b) drew another diagram and concluded the same thing. The answer is 0.

    Is that the proper way to approach a question like this?
  2. jcsd
  3. Nov 27, 2008 #2
    One of your diagrams is wrong, try redrawing them.

    This is the proper way to approach the problem, if the fields are indeed of equal magnitudes and opposite directions. If this turns out not to be the case, you will have to calculate the fields.
  4. Nov 27, 2008 #3
    Got it, when the currents are in opposite directions, the magnetic fields interfere with each other in such a way that I simply superimpose them by addition. Correct?
  5. Nov 27, 2008 #4
    Yup, that's right.

    (In general, the fields are vectors, and the result is the vector sum of the fields. If they are equal and opposite, the vector sum is zero)
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