> On Apr 18, 2019, at 11:18 PM, dwight via cctalk <cctalk@classiccmp.org> wrote:
>
> Although, after written, there is little magnetism lost out side of the ring,
> while being magnetized, there is quite a bit of stray magnetism. By placing
> the the rings at 90 degrees, it minimizes the magnetism induced in the
> adjacent ring. The fields follow the inverse square law so the effect drops
> off quite quickly. Also the ring tend to pull the magnetic field into the
> ring, at least until saturated. At that time the field can leak into a
> neighbor and flip its state. Not being aligned with the direction of the ring
> also minimizes this stray field.
> Dwight
… inverse cube (?) … depending on the geometry you are talking about?
Real physicists please set me right if I have this wrong, but I think
only radiating and static point fields (like electric or gravitational) from a
finite source fall off as inverse square. That’s easy to see, it’s the same
effect crossing the total area of a sphere centered at the source. Area on the
sphere goes up like square of radius, so intensity has to go down like the
square.
Magnetic field (from a finite source) I think goes down like the cube
of the distance - north and south poles of the source tend to cancel better as
the apparent angle between them gets smaller, in addition to the above effect.
(That is a mnemonic, not a real explanation.)
On the other hand, if you were talking about field around a wire with
current in it (a non-finite source, at least locally), then it *is* inverse
square for the magnetic field, where inverse square refers to distance from the
axis of the wire.
- Mark
