Plate Resistance
On May 30, 12:46*pm, Richard Clark wrote:
I have shifted the following post to this thread where it fits the
context perfectly:
On Sun, 30 May 2010 06:59:58 -0700 (PDT), K1TTT
wrote:
does it really matter what the mechanism of generating the heat is?
the fact that there is heat generated in the plate means there is
energy lost from the electrons, be it due to impinging on the plate
mechanically or due to the metal resistance it is still a loss of
energy. *And since there is more heat when there is more plate current
we can model it as a real resistance. *The only question is then, is
it linear or not. *that should be a 'relatively' simple measurement,
and one that has likely been done by a researcher somewhere along the
line.
Yes.
This post is sufficiently informing for many. *Others may take its
lead and derive EXACTLY how much resistance, heat, power from the data
provided by Walt and confirm the bench experience of real resistance
within the source.
This response quoted above also corrects my mis-observation of my
having the only perception of this universally experienced phenomenon.
By count, we are up to two who acknowledge what is obvious.
73's
Richard Clark, KB7QHC
Hi Richard,
On reviewing the paper you sent me I’ve given a lot of thought
concerning the source of the induced current flowing in the external
resistance, R, the load of the plate of the tube. You say the source
of the I^2R power dissipated in R is plate resistance, Rp. However, as
I read Par 7.2 on Pages 140 and 141, the reality of Rp is described in
there, but only indirectly, thus requiring a deep inquiring mind to
ferret it out. For me, it takes a leap and a stretch to understand
that Rp is the source of the I^2R power delivered to R.
In Par 7.2 the author says this power is supplied by the kinetic
energy of the electrons in the beam. It takes no great amount of
mental concentration to understand that that statement is true. But
where I see a tangential approach to describing Rp is in the statement
that “Since each electron in the beam faces a decelerating electric
field due to I^2R, it loses an amount of energy eIR during its flight
from the grid to electrode P.” This energy is lost, of course, because
the plate voltage is decreasing due to the increase in voltage drop IR
across R, caused by resistance Rp. We know, of course, that although
Rp is real, it is non-dissipative because it is not a physical
resistor, but is only the result of the ratio deltaE/deltaI.
Again quoting from Par 7.2, “It is evident that IR must be smaller
than the voltage to which the electrons have been accelerated in order
that they reach P.” I understand this to be caused by Rp. However,
this still doesn’t make clear that Rp is the source of the I^2R power.
Only until we see the quote “…the total power lost by the electrons in
the interelectrode region is (equation 7.12), which is equal to the
heat power dissipated in the resistance (R) by the induced current.”
does the reduced power seem to have any relevance to Rp.
Now continuing the quote from Par 7.2, “The remaining part of the
electron’s kinetic energy is transformed into heat energy when they
strike electrode P.” It’s my understanding that this is the energy
that’s dissipated in the plate, causing it to heat.
However, the relationship between energy lost in the interelectrode
region and the energy dissipated in R seems to say that Rp is the
source of the energy dissipated in R, but it is difficult for me to
accept that relationship. I find it difficult to accept that a loss in
energy due to decelerating field in the interelectrode region could be
the source of the energy dissipated in R.
Richard, can you help me out here in understanding this concept, if
it’s really true? It seems to me that the loss of energy due to Rp is
simply energy that was never developed in the first place due to the
deceleration of the electric field in the interelectrode region.
Walt
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