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Homework Help: What is the magnetic field at point P?

  1. Nov 19, 2016 #1
    1. The problem statement, all variables and given/known data
    A closed loop carries a current of 8.0 A in the counterclockwise direction. The radius of the outer arc is 0.6m and that of the inner arc is 0.40m. What is the magnetic field at P?

    2. Relevant equations
    F = ILxB
    F = qV x B

    R = outer radius
    r = inner radius

    3. The attempt at a solution
    ILxB = mV2/R

    I don't even know how to APPROACH this problem. Please help me. These equations above have too many unknowns to give me an answer and so I need more. I can find L but I can not find m and V in terms on knowns, and even still I think this is a horrible way of solving the problem. I would like to do a sum of forces but ∑F = ILxB + qvxB = ma doesn't exactly help because if I replace a with mv2/R I still have as many unknowns as before but this time I need q and v.

    Attached Files:

  2. jcsd
  3. Nov 19, 2016 #2
    There is a concept I'm not getting. The majority of the problems on this homework set are like this - so if I can understand how to approach one of these I can approach many. For example a lot of these require me to relate the B field and time, acceleration, etc. but only in terms of B and I.
  4. Nov 19, 2016 #3


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    Homework Helper
    Gold Member
    2017 Award

    This problem does not involve force. So, your "relevant" equations are not applicable.

    You need to find the magnetic field at point P. The field is due to the current in the wire. You should have covered some methods for finding the field produced by a current.
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