RMS vs. absolute value

[gsingh2011]

I never really understood why using the Root Mean Square of negative data is the preferred method of finding the average of the data as opposed to taking the absolute value of the data and taking the average (arithmetic mean) of that. The example that recently made me wonder about this is alternating current. The RMS current is the maximum current divided by root two. But why isn't the average current simply the average value after taking the absolute value of the current?

[ych22]

I never really understood why using the Root Mean Square of negative data is the preferred method of finding the average of the data as opposed to taking the absolute value of the data and taking the average (arithmetic mean) of that. The example that recently made me wonder about this is alternating current. The RMS current is the maximum current divided by root two. But why isn't the average current simply the average value after taking the absolute value of the current?


THe RMS current is not the average current, it is the root of the average squared current. You do not use RMS current/average current interchangeably, I believe (but hey I'm not a physicist/EE)

[bpet]

The RMS current is useful because it's directly related to the power consumption.

[vk6kro]

I never really understood why using the Root Mean Square of negative data is the preferred method of finding the average of the data as opposed to taking the absolute value of the data and taking the average (arithmetic mean) of that. The example that recently made me wonder about this is alternating current. The RMS current is the maximum current divided by root two. But why isn't the average current simply the average value after taking the absolute value of the current?

The difference is that power depends on the square of the voltage, not just the voltage.
The RMS voltage of a waveform is the DC voltage that would have the same heating effect as the this waveform.

So, the parts of the waveform that are twice as big as others have 4 times as much heating ability.

The average voltage of a sinewave (allowing for absolute values) is 0.637 times the peak value, but the RMS value is 0.707 times the peak value.
The difference between these values is due to the heating effect of the parts of the sinewave near the peak value.