Ahh, we're back on this thread! It's an interesting discussion. Dick's
comments, below, are mostly correct about electrons traveling from a heated
cathode to the anode. However, electrons don't move anywhere near the speed
of light. They start off with thermal kinetic energy from the hot cathode,
probably a few hundred meters per second, and then pick up speed as they're
sucked toward the anode by the plate-cathode potential voltage. Typically
they crash into the plate (depending on the plate voltage) with a speed of
about a million meters per second, which is roughly one percent the speed of
light, which is still pretty fast, and certainly much faster than the
so-called "drift velocity" of the electrons in a copper wire. That's about 1
cm per second, so you can think of the electrons in a metal moving like warm
sludge, just oozing along the length of the wire. That fact alone suggests
that the relationship between electric current and moving charges is more
complicated than one might imagine. For example if you measure a fast pulse,
say 1 nsec duration, on a coax cable, then obviously there's more going on
than slowly moving charges migrating like sludge down the cable.
Now, at the risk of muddying the water further, the picture of electrons as
tiny little particles carrying an electric charge dates from early twentieth
century thinking. In fact, the model of electric current and electrons
moving in, say, a vacuum tube or copper wire, was proposed around 1900 by a
German physicist named Paul Drude (pronounced Drood-eh). (You can google
"Drude Model" to read about it.) Mr. Drude's theory is clever, and sometimes
useful, but it is a result of "classical physics," and, alas, doesn't hold
up to close scrutiny. Electrons are not tiny, hard little balls of charge,
any more than atoms are balls of neutrons and protons with electrons
whirling around them like tiny planets. Unfortunately, that classical
picture, however wrong and inaccurate, is still taught in elementary schools
and high schools, because the real picture is too abstract for young minds
to comprehend.
The description of the electrons in a metal, or anywhere else, is quantum
mechanical. An electron in a block of copper, for instance, is described by
something called a Bloch wave, or Bloch wavefunction (Google it, but be
forewarned: it ain't easy to understand.), and the amazing thing about the
electron is that it isn't localized in the copper block at all. It's
everywhere at once in the copper, and you can't point to a specific position
in the copper and say that the electron is there. This is not just
mathematical abstraction. The electron really is everywhere in the copper at
once. Quantum mechanics isn't just a model theory. It's the way the universe
is assembled. There's probably no theory that has been so extensively tested
and verified, thousands upon thousands of times. Unfortunately, our tiny
brains can't visualize quantum mechanical wavefunctions very well, so we
fall back on classical pictures to guide us, such as the idea that atoms are
like tiny solar systems, or that electrons in a vacuum tube are ejected from
the cathode like BBs and fly through the vacuum until they crash into the
anode. Sorry, but that picture is misleading and wrong, even though we can
easily imagine it.
73,
Jim W8ZR
> -----Original Message-----
> From: Amps [mailto:amps-bounces@contesting.com] On Behalf Of K9FFK
>
> Electrons travel from a heated cathode or filament to the anode. Charge is
a characteristic
> associated with the electron (much like the color blue being associated
with sky).
>
> Electron speed in a vacuum tube is approximately equal to the speed of
light. This speed
> defines the transit time and thus upper useable frequency of the tube.
>
> Nothing travels from anode to cathode. (No protons, no positrons.)
Residual gas molecules
> may be ionized and end up at the cathode or the anode.
>
> "Holes" are a convenience tool to explain certain characteristics and
operation of solid state
> devices. Allowing "holes" to be equal a negative thing does not change
tube theory. Results
> are same, same.
>
> OK...flame suit on...
>
> Dick K9FFK
>
>
> On 12/2/2016 10:52 AM, Mike Waters wrote:
> > Thank you for your comments, Al. But in an amplifier's vacuum tubes
> > (as Jim, myself, and others discussed earlier in this thread), are
> > charges moving from anode to cathode opposite the flow of electrons?
> >
> > 73, Mike
> > www.w0btu.com
> >
> > On Dec 2, 2016 10:19 AM, "Al Kozakiewicz" <akozak@hourglass.com> wrote:
> >> Current is the flow of charges, not particles. Charges are carried
> >> by
> > particles such as electrons (negative) or ions (positive), but the
> > particle itself is not the charge. Charges aren't a physical object
> > that has mass or occupies space. Just like gravity - it can be
> > measured and its effects observed and felt, but you can't point to a
gravity object.
> >> In the case of electrons it is most definitely NOT like a river. ...
> > Actual electrons drift about the conducting medium at rate of
> > something like 1 meter per hour. On the other hand the charge is
> > propagated at near the speed of light. Negative charges flow one way;
positive the other.
> >> It adds nothing to the understanding and application of electric
> >> circuits
> > to change the convention for current flow.
> >> Al
> >> AB2ZY
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> >
>
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