Calculating magnetic field of an infinite strip.

[Berrius]

Homework Statement

Given an infinite long (in the z-direction), with width 2b in the y-direction and no thickness in the x-direction. There is a current with density J in the z-direction.
Calculate the magnetic field on the y-axis if |y| > b.

Homework Equations

Amperes law: ∫B*dS = μ0*I

The Attempt at a Solution

My first thought was that the strip is build out of infinite wires, so according to the right hand rule the magnetic field would be in the negative x-direction for y > b and the positive x-direction for y < -b. But I see no possibility to choose a suiting ampere path.

 

[tiny-tim]

Hi Berrius!

Amperes law: ∫B*dS = μ0*I

(use ds for length, not dS, or the examiner may think you mean area)

… I see no possibility to choose a suiting ampere path.

so integrate!