Randall R Schulz wrote:
On Friday 15 February 2008 22:29, Aaron Kulkis wrote:
...
Ummm... He was talking about RMS, which implies voltage or current. There's no such thing as RMS power. RMS is short for Root-mean-squared i.e. _______ / _ 2 V X
RMS can apply to any function vs. time (voltage, current, power, etc.)
Of course you can blindly apply that formula to any time-varying function (if the function is constant rather than time-varying, the result is just the constant value of the "waveform")
However, the point is that by squaring the primitive (and time-varying) quantity first (voltage or current, but not power which depends on both current and voltage)) then taking the average over a cycle and then taking the square root of that value, you'll get the average power. That's because the power varies with the square of the current or the voltage.
So the RMS voltage and the resistance allow you to compute the average power over a full cycle. (Note that power is voltage squared divided by resistance and that this is the real reason that RMS is the way to compute the average power dissipation in a resistive circuit.)
But if you have an instantaneous power function and apply the RMS calculation to that, you'll get a value with no physical meaning.
The units of RMS voltage is the volt, not volt^2. -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org For additional commands, e-mail: opensuse+help@opensuse.org