What is RMS Voltage? specifically, what is it A MEASURE OF?

Question

What is RMS Voltage? specifically, what is it A MEASURE OF?

Answer 1

For a wave shape that has a lot of variation, even a sine wave or a wave with a lot of noise on it, it is a standardized way of measuring its amplitude. If you picked any one point you might get a high or low number. If you just averaged the part above zero and the part below you would likely get zero. There is a formula that squares all of the readings of voltage (because that makes plus and  minus go away) and then takes the square root of their total. That would give you something that is more independent of wave shape. That is why it is popular in specifications.

Answer 2

It is the equivalent heating power to a DC voltage of the same value.

In other words, 120 VAC RMS has the same heating effect applied to a resistor that 120 volts DC would.

RMS means Root-Mean-Square which is how it is theoretically calculated, by squaring the waveform, computing the mean, then taking the square root.

In practice, the magic number is 0.707, 1/√2.

A sine wave of peak amplitude of 100 volts has an RMS voltage of 70.7 volts.

When an AC voltage is listed, it is assumed to be the RMS value. For example, house voltage of 120 volts is an RMS value.

RMS is very useful in irregularly shaped waveforms, or sine waves with a lot of distortion. You can buy voltmeters that read directly in RMS values and will work with non-sine wave inputs.

However, note that common AC voltmeters are *calibrated* in RMS, but do not read true RMS voltages. That means the meter will read correctly for a pure sine wave. Any thing else and there are errors.

Answer 3

RMS = Root Mean Square

when you are trying to find a RMS voltage simply times voltage by 0.7071

Example

The RMS of 24 v

= 24x0.7071

=16.97 v RMS

Answer 4

RMS voltage is 70% of the peak voltage of the sinosoidal waveform or RMS value is  the square root of 1/2 (approximately 0.707).

Answer 5

The answer you are looking for is that RMS voltage is a measure of work. 1VRMS will do the same amount of work as 1VDC.

That is, if you put 1VDC into a resistor and got 1W of work out of it, then it would take 1VRMS to get the 1W of work out if you put AC through the resistor.

As others have pointed out, RMS calculations depend on the waveform.

Answer 6

"Root Mean Square" - Think of it as the area

under the curve, the average voltage of the

waveforms half cycle.