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RMS stands for Root Mean Square. It is a method of averaging where you take the squares of a bunch of samples, average them with an ordinary mean, and then take the square root. This gives greater weight to larger values. In the case of an ordinary sine wave, the RMS value is 0.707 times the peak value, 0.707 being 1/2 the square root of 2, and the peak value being one half the peak-to-peak value. For example, in the US, a "standard" 117VAC line voltage is actually an RMS voltage that corresponds to a peak voltage of 166VAC.

RMS is a necessary unit because, often, the waveform is not sinusoidal, it is sawtooth, such as in a power supply. Using an ordinary VOM, calibrated for a sinusoidal AC scale in such a case, will give an inaccurate reading of ripple voltage. Most modern DMM's have a true-RMS mode which will work correctly by using sampling and analysis technology.

RMS is also a necessary unit because RMS is a better indication of how much power a signal can impart to a load.

Another answer

RMS stands for Root Mean Square value.

In electrical technology, where alternating current (AC) is used, RMS Voltage and RMS Current (Amps) must be used to calculate the average power supplied or consumed. See the link below on how to find the RMS.

In fluid flow technology related to gases, velocity is calculated as an RMS value because it can be used to find the average velocity of an ideal gas.

Yet Another Answer

Because a AC current is continuously varying in both magnitude and direction, it's necessary to measure it in a meaningful way. The rms-value of an AC current is equivalent to the value of DC current necessary to do exactly the same amount of work. For example, a sinusoidal AC current which peaks at 100 A has an rms-value of 70.7 A, and does exactly the same amount of work as a DC current of 70.7 A.

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Related Questions

Which has a higher RMS value given a sine wave a square wave and a sawtooth wave?

A square wave has the highest RMS value. RMS value is simply root-mean-square, and since the square wave spends all of its time at one or the other peak value, then the RMS value is simply the peak value. If you want to quantify the RMS value of other waveforms, then you need to take the RMS of a series of equally spaced samples. You can use calculus to do this, or, for certain waveforms, you can use Cartwright, Kenneth V. 2007. In summary, the RMS value of a square wave of peak value a is a; the RMS value of a sine wave of peak value a is a divided by square root of 2; and the RMS value of a sawtooth wave of peak value a is a divided by cube root of 3; so, in order of decreasing RMS value, you have the square wave, the sine wave, and the sawtooth wave. For more information, please see the Related Link below.


Is 240v rms value or peak value for AC source?

rms. dat means Vp-p will be 325V.


Household supply of 230volts is rms value or maximum value of voltage?

When you say holdhold supply of 230volts, you are referring to the RMS value, not the peak value.


How do you measure rms value of complex waveform?

rms value is measured using voltmeter with the use of heat sensing elements.


Does a volt meter read rms?

Yes, if it is set to measure AC, it is usually calibrated to RMS.


How to derive the RMS of a full wave rectifier?

AC RMS Value x 1.414


Is utility voltage ie 110 VAC given as a RMS value or as a Peak value?

All AC voltages and currents are expressed as rms values, unless otherwise specified. So 120 V AC is an rms value.


What is the value of US AGM 1941?

Please post a new question with a denomination, and please explain what AGM is.


Why do we need exactly one cycle data for computing the RMS value?

You don't need exactly one cycle data for computing the RMS value. It is just a convenient normalization. 1 cycle = 1Hz. RMS values can also be specified in 1 Mcycle, 1kcycle, even 2.39384kcycles. Again, 1 cycle is simply convenient. In other words, if the RMS value were specified in MHz, the RMS value will be 20*log(MHz/Hz) higher.


Find rms and average value of 15a current?

RMS is just 15/sqr2 average is 15 * 0.637


Which wave is highest RMS value peakvalue being the same?

The wave with the maximum RMS value, in comparision with the peak value, is the square wave.


Peak voltage 100volts what is rms value?

70.7