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Homework Help: Magnetic field at the center of the loop

  1. Mar 13, 2005 #1

    Here's the question:
    "What is the magnetic field at the center of the loop in the figure?"

    OK, the question is really simple and it looks easy. However, when I put in the answer, it's wrong. I tried different methods/formulas but still got the wrong answers. Anyone cares to enlighten me?

    First, I used the formula B = I(mju_0)N/2R:
    - I is 5A
    - mju_0 is 4pi * 10^-7
    - N is 1
    - R is 0.01 m
    The wrong answer was 3.14×10-4 T.

    I then tried modified B = (2*10^-7)I/R (I multiplied this equation w/ some whole numbers to account for the multi directions of the field - which I then realized that it was the wrong way) I still got the wrong answers.

    I then think, hell, the field might cancel out to zero, which was still wrong. (Obviously, the field was in one direction.)

    PLEASE HELP. I'm desperate. :cry:

    Attached Files:

  2. jcsd
  3. Mar 13, 2005 #2
    Anyone? What I don't get is I cannot treat it as a single loop solenoid? If not then what method should I use?

    Please help.
  4. Mar 13, 2005 #3

    Doc Al

    User Avatar

    Staff: Mentor

    It's not just a single loop. Don't neglect the field from the long straight wire.
  5. Mar 13, 2005 #4
    people on this board do not seem to know a lot about electromagnetic. I posted two questions and so far no replies yet.
  6. Mar 13, 2005 #5


    User Avatar
    Staff Emeritus
    Science Advisor

    Doc Al provided an answer. We expect students to do their homework.

    The key is superposition of two magnetic fields due to the long straight wire and the loop.

    Meanwhile, we'll take a look at the other questions.
    Last edited: Mar 13, 2005
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