> 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

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