AEMC® - What is RMS?

This video introduces the concept of “root mean square,” commonly called RMS. This is a mathematical method for determining the average of a constantly varying value. In electronics, RMS is used to calculate effective AC power in a way that allows it to be compared to the equivalent heating value of a DC system. This video begins by defining RMS and explaining why it is needed and how it is used. We then introduce the concept of “averaging” RMS, a technique that is useful when the sinusoidal AC wave is relatively symmetrical and undistorted. We conclude with a discussion of “true” RMS, a more complex mathematical method for calculating effective voltage and current when the AC waveform is non-sinusoidal and/or significantly distorted by factors such as harmonics.

[@navidmohammadzadeh2141]

Finally, I find out what RMS means. Thank you so much.

[@aadisingh5086]

Wow , i found very unique chennal Your video finally cleard my doubts realated THD and this topic thanks

[@mayasinha884]

This video is uncomparable...totally incredible.....this actually cleared all my doubts.....aemc rocks....lots of love😀😁

[@asully3006]

As an EE instructor, very nice intro indeed!

[@curtpiazza1688]

Great explanation!

[@AEMCInstruments]

Glad it was helpful!

[@HakonSkjold]

Good explanation, but squaring a graph - say sin(x) - will not make the graph look the same with pure positive values, like the graph that appears around 3:32. Put sin^2(x) and |sin(x)| into a grapher and notice dy/dx differ by as much as 45 degrees near y=0. What you say, however, is precisely correct:)

[@yashdave4752]

C'mon Man.....Its 1.41...Use Calculator

[@deepakbhoi6995]

Håkon Andreas Skjold p what is your real nick name

[@AmitPatel-ce3rj]

its really good way to exp;ain rms value

[@Gallardo6669]

And again: super great video, thank you for your effort!!

[@EfeBaris21]

Incredible video. Thanks a lot.

[@AEMCInstruments]

Glad you liked it!

[@RobBob555]

great explanation thanks

[@reyyanuysal908]

what a clear explanation, thank you so much!

[@AEMCInstruments]

You're very welcome!

[@kabandajamir9844]

So nice

[@aadisingh5086]

6:40 then what is 2nd harmonic?

[@HamidrezaAsadi-o3k]

hi .Thanks for the detailed explanation

[@AEMCInstruments]

You are welcome!

[@5mania5]

wow this was really helpful

[@omaraaziz6706]

Thank you. Much appreciated.

[@AEMCInstruments]

You're welcome!

[@dineshmehta3688]

Excellent

[@AEMCInstruments]

Thanks

[@sridharchitta7321]

Current in a resistor is a start-stop motion of conduction band electrons due to their collision with the rocking lattice ions, and this causes a resistor with a sinusoidal voltage applied, to produce heat. The polarity reversals of an applied sinusoidal voltage (with the direction reversals of the applied electric field) do not affect electron collisions with the lattice ions. Electrons colliding with lattice ions from either direction will continue to produce heat and there is no cancellation of the heat developed! Mathematically, the average value of a sinusoid is zero, and so, the average value of the current will also be zero. The average values cannot therefore represent the heat developed in a resistor with a sinusoidal current. A resistor cannot develop heat due to a current in one half-cycle and then cool itself by a like amount of heat during the next half-cycle! It develops heat either way whether the current is positive or negative. The lattice ions vibrate from collisions irrespective of the directions in which the electrons collide with them. Therefore, since the average value is zero, it necessitates the use of the root-mean-square values of the voltage and current to compute the power, which is a statistical measure of the magnitude of a varying quantity and is the square root of the arithmetic mean of the square of the sinusoidal function. Electrostatics and circuits belong to one science not two. To learn the operation of circuits it is instructive to understand Current, the conduction process, resistors and Voltage at the fundamental level as in the following two videos: i. kzbin.info/www/bejne/iHbWiJeabJukrsU and ii. kzbin.info/www/bejne/bnO0fpKurJeFnNE It is not possible in this post to discuss in more detail average and rms values. The last frame References in video #1 lists textbook 4 which discusses in detail using a unified approach sinusoidal voltage, current, their average and root mean square values.

[@bc82870]

Great video

[@Alex-rv8gw]

vp is not the effective voltage while vrms is right ???? so we need to find out rms value ???

[@AEMCInstruments]

Correct. RMS is needed to calculate the effective voltage, not the peak.

[@gerardvoughnfaust4167]

If taking the average RMS is peak mutiply by 0.707, what nmber will i multiply to get the true RMS from peak?

[@harizirfananwarulhalim3146]

The 0.707 multiplication value or division to the sqrt of 2 is only applicable to perfect sine wave form which gives a quick calculation or approximation to the RMS value. In the real world, wave forms has some distortion and you need to calculate based on the true RMS formula as per described in the video

[@Alex-rv8gw]

True RMS method is suitable for distorted waves???

[@AEMCInstruments]

Yes, it is.

[@surgingcircuits6955]

Excellent. Thx!

[@ahmedsyed4335]

Thank you

[@gerardvoughnfaust4167]

Can this method can be use also in determining the RMS power of an amplifier?

[@researchcapt]

Yes, for AC outputs.

[@deepkumar6380]

what is the need of Rms value? still it is not cleared to me. please.

[@AEMCInstruments]

AC is alternating current. It performs work when the voltage is positive *and* negative. This means that the standard mathematical average is an invalid measure of voltage or current. Instead, RMS is used. With RMS the quantity is first squared, to "flip" the negative to positive. It is then integrated, and finally, the square root is taken to remove the error caused by squaring.

[@amrnandoo2974]

@@AEMCInstruments why cant we use max voltage or current . Why R.M.S ??? How did they come to that conclusion Thankx for the help:)

[@dxking1empire887]

☺️tiny#1💝

[@hussainqaizar4440]

what is the need of Rms value? still it is not cleared to me.

[@AEMCInstruments]

AC is alternating current. It performs work when the voltage is positive *and* negative. This means that the standard mathematical average is an invalid measure of voltage or current. Instead, RMS is used. With RMS the quantity is first squared, to "flip" the negative to positive. It is then integrated, and finally, the square root is taken to remove the error caused by squaring.

[@smittyflufferson1299]

@@AEMCInstruments but it isn't, an RMS is different from a numerically intigrated absolute value. I think he's wondering why this different value is mathematically valid

[@smittyflufferson1299]

@@AEMCInstruments if the error was removed then the sum of the squares would be divided by the square of the period over which you've intigrated but that's not how an RMS is taken

[@khosravisg]

Perfect

[@josephstratti52]

Looks like he quared half the value using either half,but said we square the value.AC is a directional power by convention from negative to positive.AC has power coming and going it will turn a motor both ways.As students we need a different way of understanding electricity than convention teaches.It may be fine for the mathematics to say we have a negative voltage but the power is not negative and this leads to confusion.PS I am probably wrong as I am not versed in electronic or physics but this whole convention thing sucks confusion like a vacuum.

[@kabandajamir9844]

So nice

[@AEMCInstruments]

Thanks

[@negraliblade5135]

Excellent. Thx!