How do I calculate the magnetic field genereated by a very long metal plate with width(adsbygoogle = window.adsbygoogle || []).push({}); wand currentiflowing along the direction of the largest dimension? If I calculate the intesity of the magnetic field in a point with distancebfrom the border of the metal plate, I get:

[tex]B = \frac {\mu_0 i} {2 \pi w} \ln \left(1 + \frac w b \right)[/tex]

(using Biot Savart Law to a long wire integrated over the area)

But I saw another solution for this problem with a different answer. This time, Ampere's Law was used along a square path where current flows, getting the following answer:

[tex]B = \frac {\mu_0 i} {2w}[/tex]

My questions are:

1. Why are the answers different?

2. What does the second answer mean, i.e., in which point of space is that field intensity valid? I don't understand how he could not have used a point to calculate the field.

Thanks for the help

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# Homework Help: Magnetic field generated by a metal plate

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