# Magnetic field at the center of the loop

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.)

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Anyone? What I don't get is I cannot treat it as a single loop solenoid? If not then what method should I use?

Doc Al
Mentor
It's not just a single loop. Don't neglect the field from the long straight wire.

people on this board do not seem to know a lot about electromagnetic. I posted two questions and so far no replies yet.

Astronuc
Staff Emeritus