On Fri, 11 Apr 2008 13:25:40 GMT
Cecil Moore wrote:

Keith Dysart wrote:
The computation using energy instead of power has
also been done (and published here) and found also
to demonstrate that the reflected is not dissipated
in the source resistor.

Well, that certainly violates the conservation of
energy principle. We know the reflected energy is
not dissipated in the load resistor, by definition.

The only other device in the entire system capable
of dissipation is the source resistor. Since the reflected
energy is not dissipated in the load resistor and you say
it is not dissipated in the source resistor, it would
necessarily have to magically escape the system or build
up to infinity (but it doesn't). You keep digging your
hole deeper and deeper.


You write "The only other device in the entire system capable
of dissipation is the source resistor." which is a correct statement. Unfortunately, the circuit is intended to illustrate the absence of interference under special circumstances but an instant analysis shows that all the power can not be accounted for. We can only conclude that interference is present. Not good because the circuit was intended to illustrate a case of NO interference.

Our choice of a voltage source is incomplete because we did not assign it a mechanism to provide a reactive voltage, allowing the source to only apply a sinsoidal voltage without specifying the current or current timing. As a result, reflected power will return to the source resulting in an apparent loss of power to the system and resistor Rs. It is not a magical loss of power, only the result of interference acting within the cycle.

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.

--
73, Roger, W7WKB