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On Mar 4, 3:36*pm, Cecil Moore wrote:
After discovering the error on Roy's web page at: http://eznec.com/misc/Food_for_thought.pdf I have begun a series of articles that convey "The Rest of the Story" (Apologies to Paul Harvey). Part 1 of these articles can be found at: http://www.w5dxp.com/nointfr.htm Looks good. And well presented. There is only one small problem with the analysis. When the instantaneous energy flows are examined it can be seen that Prs is not equal to 50 W plus Pref. Taking just the second example (12.5 ohm load) for illustrative purposes... The power dissipated in Rs before the reflection arrives is Prs.before = 50 + 50cos(2wt) watts The reflected power at the source is Pref.s = 18 + 18cos(2wt) watts But the power dissipated in Rs after the reflection arrives is Prs.after = 68 + 68cos(2wt-61.9degrees) watts Prs.after is not Prs.before + Pref, though the averages do sum. And since the energy flows must be accounted for on a moment by moment basis (or we violate conservation of energy), it is the instantaneous energy flows that provide the most detail and allow us to conclude with certainty that Prs.after is not Prs.before + Pref. The same inequality holds for all the examples except those with Pref equal to 0. Thus these examples do not demonstrate that the reflected power is dissipated in the source resistor. ...Keith |
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