[Amps] rms Volts, Amps and Watts

[Paul Christensen]

> rms voltage x rms current does not give rms power. It gives mean or 
> average power. rms power can be calculated but has no useful value.

An insightful perspective on "RMS Power" can be found here:

http://www.eznec.com/Amateur/RMS_Power.pdf

As Steve notes, it's a meaningless term that through the years, became an 
abused adjunct for the multiplication of RMS voltage and RMS current.  In 
1974, the U.S. Federal Trade Commission required manufacturers of stereo 
audio amplifiers to state power in terms of  "continuous watts."  Even so, 
only a few did after the new regulation went into effect.

Most of us probably remember some of the absurd power claims made mostly by 
importers of Asian stereo equipment.  Back in the early '70s, our own 
household had a "200-watt" stereo system that if measured today probably 
could not produce 5 clean watts of power per channel.

Between 1974 and now, a lot has changed with the advent of multi-channel 
sound systems designed for home entertainment.  For those interested, the 
most recent regulatory update occurred back in 2010 and can be found in the 
link below.

http://www.ftc.gov/os/2010/01/P974222amplifierrule.pdf

Paul, W9AC