Humbuckers... well, duuuh...

[David Schwab]

A number of people explore magnetic fields using the shareware program FEMM http://femm.neil.williamsleesmill.me.uk/.

I've not used this program myself, but from what I've seen it seems too show the field extending way too far above the pickup. Since the field drops off with the square of the distance (it's early but you know what I mean), I doubt the field extends that far above a pickup. Not in a usable way.

[Joe Gwinn]

I've not used this program myself, but from what I've seen it seems too show the field extending way too far above the pickup. Since the field drops off with the square of the distance (it's early but you know what I mean), I doubt the field extends that far above a pickup. Not in a usable way.

Actually, the fields go to infinity. But they become auditorially insignificant pretty fast, which isn't obvious from a field plot.

By the way, the inverse square law is for isolated poles. If one has N and S poles near one another (such as in a humbucker), the effect falls off with the inverse cube of distance. This is another reason that strings must be close.

But, there is another twist. The inverse square and cube laws above are for 3D space. Think little spherical poles. If one has an extended structure of constant cross-section, like a pickup (which is much longer than it is wide or tall), near the center the fields are confined to be ~2D, and the laws become inverse and inverse square respectively. But near the ends it looks more like isolated poles. And so on.

In FEMM, one specifies a cross-section, and must specify if one is solving a 2D or a 3D problem. This is why.

[David Schwab]

Actually, the fields go to infinity.

Same as gravity... Good thing Jupiter is so damn far away.

Then of course everything is a magnet due to electron spin, but the domains aren't lined up and cancel out...