# Magnetic field of a circular loop

Discussion in 'Homework Help' started by mo2015mo, Jul 5, 2013.

1. ### mo2015mo Thread Starter Member

May 9, 2013
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1
HI guys ,

i can solve it as attached picture ,, BUT i don't Know How dl x R = dl,,

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2. ### WBahn Moderator

Mar 31, 2012
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What is the magnitude of AxB if A and B are perpendicular?

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3. ### mo2015mo Thread Starter Member

May 9, 2013
157
1
the magnitude of AxB = AB sin (theta)
(theta) = 90° so , = AB

4. ### WBahn Moderator

Mar 31, 2012
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So.... what do you get when you apply that to the problem at hand?

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5. ### mo2015mo Thread Starter Member

May 9, 2013
157
1
|dl x R |= dl,,
Why used the magnitude of dl x R in my problem,, Although the Biot-Savart NOT include the magnitude of dl x R?? ...as attached fig2

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6. ### WBahn Moderator

Mar 31, 2012
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Did you not read the next paragraph? It explicitly deals with this.

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May 9, 2013
157
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8. ### mo2015mo Thread Starter Member

May 9, 2013
157
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Please Explain to me in simple,,,

9. ### WBahn Moderator

Mar 31, 2012
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From a given element of current you have a magnetic field that is at an angle to the axis of the loop. But the element on the other side of the loop generates a magnetic field that is at the same angle but in the opposite direction. The components in the direction of the axis add while the components perpendicular to the axis cancel. So you figure component in the direction of the axis using the magnitude and the angle and then integrate it around the loop.

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10. ### mo2015mo Thread Starter Member

May 9, 2013
157
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thankkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkks u vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv muchhhhhhhhhh
Dr. WBahn

11. ### WBahn Moderator

Mar 31, 2012
20,225
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You're welcome. Glad you got it. Now take a moment to read that that paragraph again and be sure that you understand why it is telling you the same thing that I did, only requiring that you fill in a couple small blanks. Those blanks are things that you should be very comfortable with by this point in your education. This is a trend that will continue -- the size of the blanks will get bigger and deeper and require you to draw upon more and more of your background. So you need to work on being able to do that now, while the blanks are relatively small and shallow.

12. ### mo2015mo Thread Starter Member

May 9, 2013
157
1
I have read that paragraph again and have understood well, thanx