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http://img71.imageshack.us/my.php?image=pic1ik.gif

The figure above shows a rod of length L caused to move at a constant speed v along horizontal conducting rails. The magnetic field B (the magnitude and direction of which are qualitatively shown by the figure) is not constant, but is supplied by a long wire parallel to the conducting rails. This wire is a distance a from the rail and has a current i.

L=3.13 cm, v=3.11 m/s, a=15.6 mm, and i=11 A.

What is the induced emf (e) in the rod?

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B = (u_0 I)/(2pi y), and it is not uniform, so I integrated over y=a...L

I got (u_0 I)/(2pi)*ln(L/a).

emf = vBL = v * (u_0 I)/(2pi)*ln(L/a) * L = 3.11 * 1.544597242E-6 * 0.0313 = 1.503557293E-7 V

That is not the right answer, however.

I double-checked that my calculations are correct. So I'm guessing that my steps are incorrect. Can anyone point me to where I'm going wrong?

Thanks.