Grimer wrote:
At 05:10 pm 15/06/2006 -0400, you wrote:
Of course permanent magnets are conservative! In the macroscopic world
in which we live and in which perpetual motion machines are built, they
follow Maxwell's equations; the A field, which describes the combined E
and B fields, is conservative.
What's more, a magnetic field _does_ _no_ _work_, _ever_. It's
typically hard to see exactly what's really happening with a permanent
magnet, but this law is always followed: the force exerted by a
magnetic field on a charged particle is always perpendicular to its
motion, and hence cannot impart energy to it.
As to a citation, check any E&M text. The "standard" reference on this
is probably Jackson, titled something like "Electrodynamics".
Griffiths' text on the same subject, "Intro to Electrodynamics", is
generally considered more accessible, however.
Dearie me. You disappoint me Dr.Lawrence.
I have never claimed to have a PhD.
8-(
Vortex is no place for people who believe
without doubting what they've been taught.
And you are making the common mistake of assuming I was told it, so I
blindly believe it.
I've spent years digging through the math. I have a reasonably firm
grasp of the basic theory, and I can see how it applies to predict the
results we get with magnets. I have a pretty clear mental model of
macroscopic magnets, and enough hands-on EE experience and general
knowledge of the state of the art to take with a very very large grain
of salt any claim that all mainstream scientists have just _overlooked_
some grossly obvious property of permanent magnets, or that there's some
conspiracy to hide some property of magnets.
And need I point out that the request was made for a citation? In
referring to two common textbooks I was answering the question which was
asked.
The theological virtue of Faith (belief
without doubting) may be appropriate for
religion, but it has no place in science.
So? That has nothing to do with the current discussion.
And the way you defend it so vehemently
"_does_ _no_ _work_, _ever_" makes me
wonder just how secure you really feel
in your religion.
My religion is Lutheran and Luther said nothing about magnets.
The statement that magnetic fields do no work follows directly from the
Lorentz force law
F = q(E + v x B)
and if you know of an exception to that law, by all means please post
it. Like all physical laws it's only
"valid" until a counter example is found. AFAIK no such counterexample
is yet known (a magnetic monopole would, of course, provide such a
counterexample).
I emphasized the statement not in order to "defend it vehemently" but
because it is, on the face of it, such a bizarre statement; it flies in
the face of our everyday intuition, and is hence worth calling out as a
remarkable and unexpected assertion which none the less appears to be
correct.
More generally, in the absence of magnetic monopoles the B field can be
modeled as nothing more than the Lorentz transform of the E fields of
all involved particles; the E fields are, of course, conservative.
This is, of course, a _macroscopic_ view of the fields; at the quantum
level things may be different. But the question at issue involved
macroscopic behavior of large aggregates of particles so the model applies.
Frank
Frank
