- #1

Agent 47

- 10

- 0

## Homework Statement

Experiments show that a steady current I in a long wire produces a magnetic field B that is tangent to any circle in the plane perpendicular to the wire and whose center is the axis of the wire. Ampere's Law relates the electric current to its magnetic effects and states that

##\int B \cdot dr = \mu I##

where ##I## is the net current that passes through any surface bounded by a closed curve ##C## and ##\mu## is a constant called the permeability of free space. By taking ##C## to be a circle with radius ##r##, show that the magnitude ##B = |B|## of the magnetic field at a distance ##r## from the center of the wire is

##B= \frac {\mu I} {2 \pi r}##

Could someone explain this to me? I've already googled the question and found two "answers"

Here: http://answers.yahoo.com/question/index?qid=20130501142004AAfJ8Nn

and

Here: http://sites.fas.harvard.edu/~math21a/handouts/hw28.pdf

but they weren't in depth enough.