(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

A square coil of wire of side length 2a lies in the yz plane. A current I flows through the loop. The x axis is defined such that it passes through the centre of the loop, with the loop boundaries being at z±a and y=±a respectively. Given that I flows in a direction anticlockwise with respect to the x axis use the Biot Savart law to show that the B field at a point P along the positive x axis due to the side of the loot at z=a is given by

B=[itex]\frac{I*u_{0}}{4* pi}[/itex]∫(x[itex]\hat{k}[/itex] + a[itex]\hat{i}[/itex])dy/(y[itex]^{2}[/itex] + a[itex]^{2}[/itex] + x[itex]^{2}[/itex])[itex]^{3/2}[/itex] . This integral goes from negative to positive a.

2. Relevant equations

Biot Savart law, written in the solution. Note that dl has direction, same as current.

3. The attempt at a solution

Shown in the image

Issues:

My issue is that I get a negative sign in my solution, thus I believe that the negative sign was forgotten in the given answer of the problem.

http://img263.imageshack.us/img263/8818/solutiondj.jpg [Broken]

1. The problem statement, all variables and given/known data

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# Biot-Savart law My proof includes a negative sign

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