On Jun 8, 4:20*pm, lu6etj wrote:
I believe I undestand your reasoning: P=V*I, = not V, not P!, it is
OK. But power not represent the internal system energy, power
implicate "energy developed = work/time", you need energy (applied
during certain time, then "power") to accelerate a charge, ...

One comment here. "Power" is defined differently in pure physics vs
engineering. In physics, power requires work to be done. In
engineering, one definition of power is energy passing a point in a
unit of time, i.e. the energy doesn't have to be used up to be defined
as power. One might think of it as potential power waiting to be used.
These two quite different definitions of "power" are at the root of a
lot of disagreements.

For RF engineers we should probably honor "The IEEE Dictionary"
definition: "power - the rate of generating, transferring, or using
energy". Since energy cannot be destroyed, all energy that has been
generated and is so far unused, is in the process of being
transferred. Thus any reflected energy in a transmission line that is
in the process of being transferred will be used (lost to heat or
radiated) during the transient state following key-up.
--
73, Cecil, w5dxp.com