# Help with investigation

1. Jul 15, 2005

### gorillawarfare

Hi, I'm doin an investigation in physics - magnetism, to be specific - and basically I'm takin 1 or 2 bar magnets, and a hall probe, and placing the magnets at different distances from the probe, and different angles to see the variation in magnetic field strength. However, I need to extend it a lot more than this, and I'm not really sure how. I should do more research but I haven't had much time.

I was wonderin if anyone could gimme some pointers on what I could do next, or gimme a site with some information on this topic. Thanks a lot.

2. Jul 16, 2005

### Meir Achuz

At large distance from a bar magnet, the field is due to a magnetic diipole.
It is given by
${\bf B}=\frac{[3{\bf (\mu\cdot{\hat r}){\hat r}-\mu}]} {r^3}.$, with $\mu=MAL$, all in Gaussian units.
At small distances (r~L or r^2~A), it is more complicated.