19 Apr
2019
19 Apr
'19
7:19 a.m.
On Apr 18, 2019, at 11:18 PM, dwight via cctalk
<cctalk at 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