[SI-LIST] Re: Circle bus topology; Circular Firing Squad?
- From: "David Banas" <david.banas@xxxxxxxxxx>
- Date: Thu, 2 Aug 2007 14:43:48 -0700
Sorry to fuel this, but there're a few corrections that need to be made
here...
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]
> On Behalf Of olaney@xxxxxxxx
> Sent: Wednesday, August 01, 2007 2:16 PM
> To: Arpad_Muranyi@xxxxxxxxxx
> Cc: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: Circle bus topology; Circular Firing Squad?
>=20
> I've added an additional note to forestall a dead end line of
reasoning.
> You are headed in the right direction. The electrons only drift
slowly
> with the current. Meanwhile, they wander all over the place under
> thermal influence. Note that being electrons, they mutually repel and
> never actually collide.
[David Banas] This statement conveys the notion that there is an exact
boundary between particle locations, which must be crossed, in order for
a "collision" to have occurred. This is not a physically correct
interpretation. After all, we know that particles can be accurately
described by wave functions that have exponentially decaying amplitudes,
which never go completely to zero. That is, there is a small but finite
probability for every particle to "be" anywhere. Therefore, one could
argue that all particles are "colliding" all the time.
>To do that, electrons require energies typical
> of a particle accelerator. The temperature would have to be so high
that
> the metal would have long since vaporized.
>=20
> For solid metals at room temperature (and considerably higher), the
sea
> of electrons in the metal acts like a 3D mesh of tiny masses suspended
by
> electrostatic "springs". The wave is transmitted at close to the
speed
> of light by the electrostatic forces in the mesh (action at a
distance).
[David Banas] No, E&M waves require no medium in which to propagate.
They are perfectly happy propagating through free space. In fact, just
the opposite of what you posit is true; it is very difficult for an E&M
wave to propagate very far into a conductor.
> The response of the mesh to disturbances is linear and superposition
> applies.
[David Banas] Actually, atomically bound electrons also exhibit some
non-linear characteristics in their response to electromagnetic field
perturbances. They are very small compared to the linear component of
the response, but they are NOT zero.
Waves can pass in all directions simultaneously and
> independently.
>=20
> Note: The electric wave propagation is so fast compared to the
electron
> drift, that though the electrons will wiggle slightly in response,
their
> nominal positions are as if they are frozen in a snapshot. Drift
> movement is of no consequence to the wave propagation.
[David Banas] You need to be careful here. If by "drift movement" you
mean the d.c. component of the current in the conductor induced by the
incident electromagnetic field, then I agree with you. However, that
induced current also has a.c. components (which I think might be what
you're referring to when you say "wiggling"), and those a.c. components
very much affect the electromagnetic field, both near to and far from
the conductor. (After all, if they didn't, there'd be no difference
between a conductor's and an insulator's effect on E&M fields, right?)
The thermal
> portion averages to zero, and the slow drift with current is a
response,
> not a cause.
[David Banas] It's actually both. For instance, there will definitely be
a magnetic field generated around the conductor by this current, which
would not be generated if the E&M field were incident upon an insulator.
>=20
> Orin
>=20
>=20
>=20
> On Wed, 1 Aug 2007 12:03:15 -0700 "Muranyi, Arpad"
> <Arpad_Muranyi@xxxxxxxxxx> writes:
> > Now that I think of it, the electrons in the copper lattice
> > are moving in all different directions, not just in the
> > direction of the wave, so they not only hit the electrons
> > of the other wave where the waves meet, but they also hit the
> > electrons of their own wave... So the bouncing will basically
> > follow a random pattern allowing some to go through, some
> > go sideways, others to turn around, etc...
> > =3D20
> > Arpad
> >
> > -----Original Message-----
> > From: Muranyi, Arpad=3D20
> > Sent: Wednesday, August 01, 2007 11:13 AM
> > To: si-list@xxxxxxxxxxxxx
> > Subject: RE: [SI-LIST] Re: Circle bus topology; Circular Firing
> > Squad?
> >
> > This is why we need to use coloring dye... :-)
> >
> > Seriously, I wonder about the particle and
> > wave duality of electrons. Remember, the
> > drift velocity of electrons is not the same
> > as the propagation velocity of the EM waves.
> >
> > So what happens at the "collision" point (i.e.
> > the electrical midpoint of the loop)? Do=3D20
> > the electrons hit each other and bounce back
> > like balls with the drift velocity speeds,
> > while at the same time the waves go through
> > each other (at speeds close to c) without
> > changing directions?
> >
> > Another analogy comes to my mind, when two laser
> > beams on different path cross each other. After
> > the cross point we are still going to see their
> > original colors without any mixing. However,
> > if you did the same with two water streams,
> > the cross point will result in a splash in all
> > different directions...
> >
> > Is there someone out there with a good physics=3D20
> > background who could shed some light on this?
> >
> > Thanks,
> >
> > Arpad
>=20
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