Paul wrote:
[snip]
Stephen A. Lawrence wrote:
>
>
> Paul wrote:
>> >> So you need to ask yourself where that energy
>> >> comes from.
>> >
>> > I'm well aware of that.
>>
>>
>> Good, then you do acknowledge there is *real work*
>> being done while two magnetic dipole moments
rotate toward alignment.
>
> Absolutely! The "magnetic fields do no work"
mantra fails. It is false.
I wonder why so many physicists still cling to such a
false idea that the B-field does no
work.
I don't know but they sure do. I think part of the answer may be that
physics is a very big field, and every "real physicist" must specialize;
if you ask a physicist a question outside his/her specialty you may get
a completely bogus answer. Not many of them pay much attention to this
little corner of E&M.
>> > But you might just as well say, where does the
>> > energy "come from" when something falls off a
>> table?
>>
>> There is a big difference? In the magnet example
>> there's a way of replicating the magnetic dipole
moment by using an
>> air coil. IOW, we
>> have technology that generates magnetic fields.
We know it requires
>> energy to create
>> a magnetic field. We know it requires energy when
two coils accelerate
>> toward each
>> other due to their own attraction-- essentially
two magnetic fields
>> overlapping to some
>> degree.
>
> It appears that in terms of accounting for the
energy, one must treat
> permanent magnetic fields and fields from currents
differently.
It's interesting electron spin is in units of Ampere
Meters^2. And what's a current
carrying wire loop? It's current flowing in a wire,
and the diameter of wire has area.
An "ideal dipole" can be modeled as the field produced by a current
loop, where the magnitude of the dipole is the area of the loop times
the current. The field takes the form of an "ideal dipole" only in the
limit, though, as the area of the loop shrinks to zero and the current
goes to infinity. The natural units for such a dipole are amperes*meters^2.
But you can also model an "ideal dipole" as two charges, a + and a -.
The magnitude of the dipole in this case is the separation between the
charges, time the magnitude of one charge. Again, the field only takes
the form of an "ideal dipole field" as the separation between the
charges shrinks to zero while the charge magnitude goes to infinity.
The natural units for a dipole modeled this way would be meters*charge.
The dimensions used for the two forms of a dipole look different but the
field is the same. Nature doesn't care what units humans use, and
doesn't care what model we use to explain the field of an electron to
ourselves.
> The permanent ones are just a "given" -- they may
or may not contain energy
> but if they do, we can't get it out. The ones
associated with currents
> are a different story; we pump energy in when
they're formed and we get
> it back out when they collapse.
Who knows, perhaps one day we'll learn to get the
energy in both cases. Perhaps that's
what Steorn accomplished. To within experimental
error evidence indicates the charge
radius of the electron is found to be zero. IOW,
measure twice as close to that so-called
point charge and the E-field doubles. According to QM
the E-field goes to infinity, as
the electron is claimed to have no physical extend
beyond the Poynting vector. That's a
whole lot of energy (infinite) stored in that tiny
little particle, LOL. How odd is that.
When I was in college this was one of the Big Unsolved Problems (or so I
was told). There were people who thought the key might lie in hyperreal
analysis, but as far as I know nobody was sure.
Since then this has been "solved" at least to the satisfaction of many
working physicists. I understand that the solution has to do with
"renormalization" but I have no idea how it actually works. :-(
>> As far as something falling from a table ... I'm
not aware of gravity
>> field
>> generating device to measure the consumed energy.
If there was such
>> an electro-gravity device
>> then we could measure the consumed power from the
source while some
>> mass (object) is
>> accelerating toward the device. :-) Perhaps it
would or would not
>> consume energy from the
>> source.
>>
>>
>>
>> > In the case of a permanent dipole in a
permanent B
>> field, the energy was
>> > apparently there all along, in the form of the
>> -mu*B potential energy
>> > function.
>>
>> Again that's not the point! Energy may be in
>> different forms, but energy is energy regardless
if it is potential or
>> kinetic energy. Point being that energy is
*indeed* being added to
>> kinetic and field energy, but we cannot
>> point to any source and say, "Yeah, that's where
it is definitely
>> coming from." We can
>> assume it comes from within the electron or
whatever is attached to
>> the electron. For
>> all we know there could be some unknown higher
dimensional aspect to
>> reality-- a sea
>> of unknown energy that sustains elementary
particles, perhaps akin to
>> how the ocean
>> may sustain a hurricane. I want to know from where
that energy comes
>> from. Where is that
>> source?
>
> :-) I have no idea.
>
> I don't know what causes the field of a permanent
dipole, either.
>
> I can write a potential function for its behavior
in the field of a
> permanent magnet, and that convinces me that a
permanent magnet motor
> can't be OU. But I can't tell you where the energy
is before the magnet
> starts to move.
>
> I also can't answer this one: If two permanent
magnets accelerate
> toward each other, does the gravitational field of
the system increase
> as a result? (Hmmm, maybe I'll post that to
sci.physics.relativity --
> should be good for a few confused responses,
anyway...)
You mean sci.physics.relativity.pub? I'd like to know
where physicists such as Ed Witten
hang out online. :-)
The news group "sci.physics.relativity". It's crawling with total
loonytunes with just a few real physicists. Ed Witton doesn't sound
familiar; I don't think he hangs out there (probably has more sense).
>> > If you want to ask more than that, then you're
>> asking why the
>> > electron's B field is quantized,
>>
>> I wouldn't go so far as to say that, but
>> understandably that's a QM thing. I very much
question many QM
>> concepts such as the so-called
>> photon. On one of my lists is a relatively simple
radio frequency
>> experiment to see if
>> the sub-photon exists.
>>
>>
>>
>> > and why its spin can't "slow down",
>>
>> Ahh, now we talking. I've asked many QM
physicists if
>> spin may slow down. Some don't know how to answer
such a question.
>> Most say "No." The
>> more honest ones say they don't know and encourage
a test to verify.
>
> As far as I know, according to current theory it
can't slow down. It
> can't speed up, either. It has just one speed. In
fact it seems kind
> of inaccurate to call it "spin" at all, but that's
just my opinion and I
> already admitted I don't understand quantum
mechanics.
>
>
>
>>
>> Another option I've tossed around is perhaps ZPE
or
>> some unknown sea of energy.
>>
>> Another option is perhaps there's a decrease in
>> electron velocity. The electron must always be in
motion, correct?
>> Therefore, there's
>> always room for the electron to slow down.
>
> I don't think so. The linear motion of the
electron is not at issue;
> its dipole, which is providing the energy here, is
due entirely to its
> "spin".
Yes, understandably, but I'm just trying to come up
with ideas to meet the demands of
conservation of energy. I'm sure there must be some
genius QM physicists out there that
have an answer. So far haven't met any with an
answer, but I would expect some silly
answer such as, "Oh yeah, the energy comes at the cost
of information. The probability of
knowing the electrons location decreases." ;-)
Actually as I think about this it seems like the overall field strength
and, hence, field energy must decrease as two dipoles approach (due to
the fields of the two dipoles "mostly canceling"). I don't know if the
reduction in field energy matches the gain in mechanical energy but it
might.
That, on the other hand, leads to problems in the case with two
electromagnets, where the same reduction in total field strength must
occur, _but_ where we've already paid the energy bill by overcoming the
back EMF in the coil as it moves through the field....
Regards,
Paul Lowrance
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