Richard Harrison wrote:
Roy Lewallen, W7EL wrote:
"The average power is therefore relatively small, much smaller than the
product of RMS volts times RMS amps."

RMS is short for root-mean-square. RMS is synonymous with the "effective
value" of a sinusoidal waveform.

Therefore, the average power for the time period of one complete cycle
or any number of complete cycles is the product of the effective volts
times the effective amperes.

No, I'm sorry, that isn't true. The average power isn't the product of
the product of the RMS voltage times the RMS current, except in the
single circumstance of their being in phase.

See page 19 of "Alternating Current Fundamentals" for derivations of the
proof.

I don't have this book, but I know that in the past you've quoted from
books without having fully understood the context of the quote. I'm sure
that's the case here. Any electrician or technician should know that for
sinusoidal waveforms, Pavg = Vrms * Irms * cos(theta) where theta is the
phase angle between V and I. And hopefully you can see with a few
moments and a calculator that if theta = 90 degrees, Pavg = zero
regardless of V and I.

Average power is exactly the product of rms volts times rms amps in
usual circumstances.

Perhaps your "usual circumstances" are that the load is purely
resistive. But that's not "usual circumstances" for a host of applications.

Roy Lewallen, W7EL