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Homework Help: Direction of Magnetic Fields

  1. Mar 16, 2017 #1
    1. The problem statement, all variables and given/known data
    How do I find the direction of the magnetic field at the points?

    2. Relevant equations

    Ampere's B = (UI) / (2*pi*r)

    3. The attempt at a solution

    I know how the Right hand rule, where your thumb is the direction of the current and your hand wraps the direction of the field, but I'm not sure how it plays in when both the current are opposite.
  2. jcsd
  3. Mar 16, 2017 #2
    Try applying the right-hand rule to each of the currents separately and combining the results. Remember that fields add as vectors. and that the diagram is symmetric except for the directions of the currents.
  4. Mar 16, 2017 #3
    Yes , but aren't they equal and opposite? Wouldn't they just cancel each other?
  5. Mar 16, 2017 #4
    Have you tried it? Start with point (b). For the upper current your thumb points towards you and your fingers are under your hand. For the lower current your thumb points away from you and your fingers are above your hand . . .
  6. Mar 16, 2017 #5

    Oh I see~ I was taking into consideration of of the whole rotation of my hand, so the back of my hand should face wherever the point is? So they're all in the positive x direction?
  7. Mar 16, 2017 #6
    looks that way to me.
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