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Red-faced Dr. Rich.(RAMBLINGS)(power rating calculations)
In my review of the NHT active speaker, the power rating of the power amplifiers was given in units of RMS (i.e., root mean square). I cannot tell you how many times I have taught my students in EE101 that power is not measured as an RMS quantity. Just to make sure they do not forget, I repeat a small derivation in almost every course I teach.
The output power of an amplifier is an average measurement. When a resistive load is driven by a sinusoidal voltage waveform or a sinusoidal current waveform, the average power dissipated by the load is calculated from an RMS voltage measurement. Typically, a voltmeter will express an AC voltage as an RMS quantity.
I will briefly explain what this RMS thing is about. If a DC voltage is applied across a resistor, the power thrown off by the resistor as heat can be measured. If the DC voltage is replaced with an AC sinusoidal voltage, and the AC sinusoid has a peak voltage equal to the DC voltage, then the resistor only throws off half as much heat because the instantaneous power across the load is not constant when a sign wave is applied. When the sine wave crosses zero, no power is supplied to the load; only when the ...
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Source: HighBeam Research, Red-faced Dr. Rich.(RAMBLINGS)(power rating calculations)