Paul wrote:
Stephen A. Lawrence wrote:
[snip]
> > They attract until they are perfectly aligned NS
NS.
>
> When they're aligned
>
> N
> |
> |
> |
> |
> S
> N
> |
> |
> |
> |
> S
>
> they can flip (rotate) so that they're aligned
>
> NS
> ||
> ||
> ||
> ||
> SN
Sure if you ***add*** energy Stephen. That takes
energy. I have written far too many
simulations to know. I have seen physical grids of
permanent magnets on swivels and you
are completely wrong on this. Magnet dipole moments
prefer NS....NS.
Really?? Sigh....
That's what I get for relying on intuition. I certainly had not done
any calculations to show which way they should end up -- the potential
energy and force calculations by themselves don't say. And we don't
have any sufficiently whizzy bar magnets here to let me test it
macroscopically. (But see below in this note -- uh, oh, it sure looks
like you're right...)
> BTW, your drawings of
dipoles are way out of proportion. You
are drawing cigarettes. An electron is not in the
shape of a cigarette, lol.
Well, yeah, they're kind of stubby, aren't they. Not quite like a bar
magnet, not at all...
> It increases versus a single magnet, that's true.
But compared with
> two distant magnets? I'm not so sure; we need to
ask:
No, the net magnetic field increases from two nearby
fully aligned magnets as compared to
if they were far apart.
> Does the field increase or decrease as they're
drawn apart along a
> line?
More of the fields overlap as they approach each other
in fully alignment.
So it appears. And certainly the result is far larger field energy than
the half-aligned case, however it may compare with the case where
they're far apart.
> [ snip ]
>
> > Two aligned electromagnets do not repel. They
> > *attract*.
>
> Arrgh. We're both right. If they're end-to-end
they attract when
> they're aligned. If they're side by side they
attract when they're
> misaligned.
Correct, but what you seem to miss is the front
magnetic density is twice as compared to
the sides,
Ummm hmmmm so it is, the field strength ratio at the end versus the side
is something like 2:1, and, if the dipole is allowed to align with the
field, the net force it feels is always in the direction of increasing
field strength.
Hmmm hmmm hmmm...... this seems to imply pretty strongly that you're
right about how two permanent magnets should like to line up, too.
I hate it when I'm wrong.
which is why the PM's have less entropy in
full alignment as compared to half
alignment.
Sorry, my thermo is very weak -- second semester freshman year
introductory physical chemistry course level, at best. So this
statement goes over my head.
> > That's backwards. :) As they attract and move
closer
> > there's back EMF, which consumes
> > energy from the battery.
>
> Yes, no matter the alignment, we "pay" for the work
done as they pull
> themselves together, by pumping in electrical
energy.
Yes, but again that is not the point. We are trying
to figure out where the energy comes
from such a gain in both kinetic and magnetic energy.
When you pull the magnets apart you
are adding energy, but to what? This is still a
mystery, one day to be solved when
humanity learns exactly what sustains the electrons
existence. Who know, may the energy
comes from God. :-)
