The Rest of the Story
On Apr 11, 3:30*pm, Cecil Moore wrote:
Roger Sparks wrote:
You write "The only other device in the entire system capable
of dissipation is the source resistor." which is a correct statement.
Therefore, all power dissipated in the circuit must be dissipated
in the load resistor and the source resistor because there is
nowhere else for it to go.
Please do not forget the source. It can absorb energy.
Since the reflected power is not
dissipated in the load, by definition, it has to be dissipated
in the source resistor but not at the exact time of its arrival.
There is nothing wrong with delaying power dissipation for 90
degrees of the cycle.
If you can't identify where the energy is stored for those 90
degrees you do not have a complete story. Or you are violating
conservation of energy and therefore have no story what-so-ever.
In Parts 2 and 3 of my articles, I will show
how the source decreases it power output to compensate for destructive
interference and increases it power output to compensate for
constructive interference.
Unfortunately, the circuit is intended to illustrate the absence of
[AVERAGE] interference under special circumstances but an instant analysis shows
that all the power can not be accounted for. *
Not surprising since there is no conservation of power principle.
Conservation of energy means that energy flows must be conserved.
Therefore, conservation of power.
We can only conclude that
[instantaneous] interference is present. Not good because the circuit was intended to
illustrate a case of NO [AVERAGE] interference.
I took the liberty of adding adjectives in brackets[*] to your
above statements. It doesn't matter about the instantaneous values
of power since not only do they not have to be conserved, but they
are also "of limited usefulness", according to Eugene Hecht, since
the actual energy content of instantaneous power is undefined even
when the instantaneous power is defined.
Are you sure that is why Hecht wrote what he did? He would, in all
likelihood, have an apoplexy if he knew how his words were being used.
The circuit is very useful to investigate interference more carefully because on the AVERAGE,
the interference IS zero. *Using spreadsheets, we can see how the
interference both adds and
subtracts from the instantaneous applied voltage, resulting in cycling
variations in the power
applied to the resistor and other circuit elements. *A very instructive
exercise.
Instructive as long as we remember that a conservation of power
principle doesn't exist and therefore, equations based on instantaneous
powers do not have to balance. The joules, not the watts, are what must
balance.
Since the total energies in your equations do not balance either,
there is still a problem with your hypothesis.
It would be helpful, however, if you could actually demonstrate a
system where the energies balance, but the flows do not. This would
settle the matter once and for all. (You won't find one, since
balanced flows are a consequence of conservation of energy).
...Keith
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