- #1

zimo

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- 0

## Homework Statement

In a plastic film factory, a wide belt of

thin plastic material is traveling between two successive

rollers with the speed v. In the manufacturing process, the

film has accumulated a uniform surface electric charge

density σ. What is B near the surface of the belt in the

middle of a large flat span?

## Homework Equations

B(x) = [itex] \frac{\mu I}{4\pi}\int \frac{dx' \times (x-x')}{|x-x'|^{3}}[/itex]

## The Attempt at a Solution

I tried to calculate the integral, starting with assuming that the sheet can be represented via cylindrical coordinates - to better use the r and sin(theta) - a result from the cross product.

But then I've got in the integrand [itex]\frac{sin(\theta)}{r} and then solved the dr part with log(r)|{inf to 0} and couldn't progress from there, so I suppose I made an error somewhere but can't find it.