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.

[navidmohammadzadeh]

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

[aadisingh]

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

[mayasinha]

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

[Gallardo]

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

[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:)

[asully]

As an EE instructor, very nice intro indeed!

[reyyanuysal]

what a clear explanation, thank you so much!

[AmitPatel-cerj]

its really good way to exp;ain rms value

[sridharchitta]

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:

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.

[HamidrezaAsadi-ok]

hi .Thanks for the detailed explanation

[gerardvoughnfaust]

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

[Alex-rvgw]

True RMS method is suitable for distorted waves???

[Alex-rvgw]

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

[deepkumar]

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

[gerardvoughnfaust]

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

[hussainqaizar]

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

[josephstratti]

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.