- #1
quantumlolz
- 8
- 0
Homework Statement
A long bar magnet is bent into the form of a closed ring. If the intensity of magnetisation is M, and ignoring any end effects due to the join, find the magnetic field H and the induction B:
(a) Inside the material of the magnet
(b) just outside
Homework Equations
Ampere's law: [tex]\oint\vec{H}.d\vec{l}=\mu_{0}I[/tex]
[tex]\vec{B}=\mu_{0}(\vec{H}+\vec{M})[/tex]
The Attempt at a Solution
I've done problems like this far too many times but after a while I always go rusty. So there's no current flowing, so I=0. And we integrate around a closed loop (would this be in the plane of the magnet or perpendicular to it?) of radius r. Usually for this sort of thing we end up with something like H.(2.pi.r) = 0, so H would be zero.
I don't know how to modify it for just outside the magnet.
As I say, I've done problems like this before but I think I've probably just always gone through the motions rather than really understanding what I'm doing. Any help would be greatly appreciated!