There's utterly nothing that suggested what you write. It is assumed
that everyone knows current flow is in the opposite direction from
electron transfer. That's one of the first things taught in
electricity, but there's a lot of history there and confusion until a
student arrives at this fundamental convention. The water valve
example was a simple teaching device because 1000 words should not be
needed to genuinely help someone understand one single concept.
Everything I wrote was true if you accept basic physics. If you want
to obfuscate with a lot of E.E. professor mumbo jumbo about linearity
go ahead but are you really helping or befuddling someone?
73
Rob
K5UJ
On Fri, Nov 1, 2019 at 12:52 PM MU 4CX250B <4cx250b@miamioh.edu> wrote:
>
> Rob,
> I think analogies to a water pipe to describe vacuum tube conduction
> can be helpful in conveying very simple ideas about current and
> voltage, but the parallel shouldn’t be pushed too far. Vacuum tube
> conduction is inherently non-linear, which means that the plate
> current is not linearly proportional to the plate voltage. In fact,
> for tetrodes especially and triodes to a lesser degree, plate current
> is roughly independent of plate voltage over a wide range of
> conduction. The degree of independence can be seen by inspecting the
> constant-current graphs of plate current vs plate voltage for any
> given tube type. (For semiconductors, especially MOSFETS, the drain
> current curves are nearly flat, meaning that drain current is pretty
> much unaffected by drain-source voltage.)
>
> I also respectfully suggest that it is best to avoid trying to explain
> conduction dynamics in terms of electrons “boiling” off the cathode
> and being drawn to the plate. It’s not that this view is wrong, but it
> can muddy the waters because it suggests that current flow in a vacuum
> tube is from cathode to plate, whereas in truth plate current always
> flows from plate to cathode. The Brits have the right idea when they
> call tubes “valves” and it’s too bad us Yanks didn’t follow their
> lead.
> 73,
> Jim W8ZR
> Sent from my iPad
>
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