# Does a uniform magnetic field without fringing exist?

1. Mar 3, 2010

### Jimmy25

1. The problem statement, all variables and given/known data

Show that a iform magnetic field that has no fringing field is impossible because it violates ampere's law. Do this calculation by applying Ampere's Law to a rectangle that contains the edge of the field with two sides running parallel to the field.

2. Relevant equations

3. The attempt at a solution

SOLUTION: The contour integral consists of four portions, two horizontal portions for which the integral equals 0 and two vertical portions. The portion within the magnetic field gives a non-vanishing contribution to the contour integral Hence the contour integral has a finite value. However, it encloses no current; thus, it appears that Amperes law is violated. What this demonstrates is that there must be a fringing field so that the contour integral does disappear.

First off, what is fringing? - I can't find a definition. I'm assuming it is the field lines that run outside the contained field.

If my above assumption is correct how would this fringe field make the contour integral disappear?