A simple example of the Biot-Savart law is given with a current carrying loop for a quater of a circle as shown in Figure 1.
Figure: Figure 1: Quarter Current Loop
![\includegraphics[scale=.8]{QuarterCurrentLoop.eps} \includegraphics[scale=.8]{QuarterCurrentLoop.eps}](http://images.physicslibrary.org/cache/objects/104/l2h/img1.png) |
The differential line element dl is perpendicular to
, so the Biot-Savart law simplifies from the definition of the cross product
Note that the direction is into the web browser, so we have a
. For the differential dl of a circular arc
plugging this in and setting up the integral gives
which simply yields
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