Re: novice user: on track or not?

["David Meeker" <dmeeker@xxxxxxxx>]

This sounds a little odd--it's hard to say what's going on without
seeing your model. Anyhow, I've uploaded a model of the sort of
geometry that you'd described that seems to behave in a reasonable
way. It's in the mailing list's Files section at:
http://groups.yahoo.com/group/femm/files/2magnets.zip

Dave.

--- In femm@xxxxxxxxxxxxxxx, "r_dingo" <rd@xxxx> wrote:
> Hi all
> 
> I'm a novice to using FEMM. I'm finding that solutions often look a 
> little unexpected. Probably this just means that I don't know much 
> about magnetic fields. However, it would be good to know whether I 
> have set up the program correctly.
> 
> For example: imagine a pair of cylindrical magnets, with their long 
> axes collinear, and unlike poles facing each other across a moderate 
> airgap (width similar to the diameter of the magnets). The solution 
> shows that there is a circular locus of zero field strength 
> surrounding the gap between the poles (ie, lying in the plane which 
> bisects the air gap and is normal to the axis of symmetry). 
> Furthermore, this ring of zero field strength is fairly close in - 
> it's definitely part of the near field, not the far field. Without 
> the benefit of any training in EM theory, I had expected the high 
> local field strength between the poles would decrease monotonically 
> out into the far field pattern, without any near-field minima.
> 
> Is the solution correct, or have I set up the model incorrectly?
> 
> Thanks, Ross