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## Homework Statement

A hollow cylinder with thin walls has radius R and current I, which is uniformly distributed over the curved walls of the cylinder. Determine the magnetic field just inside the wall and just outside, and the pressure on the wall.

## Homework Equations

F = IL×B

## The Attempt at a Solution

The field just inside is zero by ampere's law, and μ

_{0}I/2πr just outside. I can't find the pressure though! If I can find an expression for dI, then I can find an expression for dF, and dF/dA would be the pressure.

dI = dr/2πr * I where I is total current, which would make dF=(dr/2πr)L(μI/2πr)sinθ,

the angle between them is 90° so sinθ=1

dF = μ I dr / (2πr)

^{2}

I'm pretty sure this is wrong though! And I don't know how to express dA.

Thanks for any help :)