RMS (Effective) Voltage and Current
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- เผยแพร่เมื่อ 22 ม.ค. 2012
- Shows how RMS (Root Mean Square) voltages and currents are defined and used in average power computations. More instructional engineering videos can be found at www.engineeringvideos.org.
This video is licensed under the Creative Commons BY-SA license creativecommons.org/licenses/b....
I wanna thank you for this and the DC circuit analysis series ... They've helped me alot during my circuits course
You have great energy ; you put your heart & soul into your lessons ..with great effect ! Well done !
AWESOME!
too good.
I would be preparing for my Fundamentals of electronics exam from your lessons! :)
Thanks a million
Very helpful & beautifully explained!!
it comes from inside the integral, it's the sum of the values (V) divided the number of values (T), as in an average, but it's an integral, and as 1/T is an scalar you can put it outside the integral to make things easier
Very well explained.
Perfect - thanks!
For such complex and difficult to understand (for some) equations in maths, scribbling is bad news. On a 32 inch screen, I can barely make out what you've scribbled, which makes following your voice even more challenging.
I am trying to do is analyse a triangular wave that superimpose on the 120Vrms AC power line. The triangular wave amplitude (ramp) is not constant along the 60Hz cycle but would rise (@ 0volt AC or 0 degree sine) and increase its ramp as the AC voltage rise to its peak (@ 120volt AC or 90 degree sine), and vice-versa when the AC line fall back to 0volt (@ 180 degree sine). I am basically describing a Continuous Conduction Mode Power Factor Correction of the AC Line...continue
Actually, that was very informative. Thanks :)
The 1/T comes from the fact that we are computing the mean (average) value of the squared waveform; we integrate over one period (of length T) and then divide by that length.
I really appreciate your work, thank you very much for this video, and thank you for clarity.
@xxZeroK00Lxx I am not sure from your description exactly what waveforms you are asking about. With more detail, I might be able to put together a video with these waveforms as examples.
Excellent 👍👍👍
very helpful it was sir
The RMS voltage (or effective voltage) is 120V. Since the voltage is sinusoidal, the peak voltage is sqrt(2)*120V which is very close to 170V.
Thanks for great informative video.. it was really helpful. Can you please suggest some good tutorial or book on AC three phase and single phase .
This was very helpful :)
Nice video
Thank you
sir i want to know why we square the value of voltage or current curve? ...what i knew we square it to get rid of the -ve part of the curve but in the 2nd example where you have taken the square wave as an example there the voltage wave form is not going into -ve quadrant don't you feel that v^2 is not necessary there to find the RMS value ?
It would also be great if you could also show a trapezoidal (triangle sitting on top of at rectangle) wave that peak along the AC line with a ramp described in my previous post [
The trianglular wave ramp (peak and valley) would be in the path between A*sin(w*t) and B*sin(wt)., A is greater than B]
I am not sure if what I am asking for can be done mathematically, maybe it can be done through a combination of intregration and Fourier, not sure.
thnx
How do you know, that the average value is the area under the plot ?
Is it possible for you to show how to calculate the Average and RMS of a:
1) 20 KHz triagular wave with with an envelope of 120Vrms sine (60 Hz) and a valley of 100Vrms sine (60 Hz)?
2) 20 KHz trapezoid wave with with a peak envelope of 120Vrms sine (60 Hz) and a delta ramp voltage of 20Vrms?
thnx
what software do you use to create this video.
where did the 1/T outside the integral come from??
At the next minute 10:23 you did not prove where you got = 1/2 * v ^ 2. You had to integrate the square sine for a while. V (t) = Vp * sin (t). Then you had to integrate sin ^ 2 (omega * t)
I'm confused. Veff(squared) is a non-zero value, hence Veff will also be a non-zero value. But isn't the waveform of V alternating about the zero point, which means Veff = 0V?
And the whole waveform of V(squared) is more than or equal to the zero point, which means Veff(squared) should be a value somewhere above [Vp(squared)] / 2. But at the same time, the waveform of V(squared) is alternating about [Vp(squared)] / 2 , making that it's effective value.
Can someone explain this to me? Thanks.
How do you get in the very last formulas in the example from I_eff = .833A to i(t) = 1.18A*cos(377t)
+Patrick Mullan i(t)=Ip cos 377t its basic current equation so we have to find Ip from Irms=Ip/square root of 2. here Irms value is 0.833, Ip=Irms*square root of 2.
This really helped me in my work towards a bachelor! Thanks!
But I dont keep up with you in the last example: where does the 377t come from?
Anyone anywhere on this epic planet who could help a broh out here?
That comes from the formula for the angular frequency which is 2*Pi*f, where f is the standard frequency of 60Hz in the US.
Hi, thank you very much for the video i was wondering if you could help me with this:
I would like to calculate the RMS value of an experiment i did for physics, i connected a primary coil (420 turns) to an AC with a frequency of 100 Hz, and connected a secondary coil (1200 turns) to an Oscilloscope to measure the voltage induced in it. I recorded the Vpp (voltage peak to peak) and i changed the distance between the coils. example: 6cm, Vpp=620, Vmax=260, Vmin=-320. i will appreciate your help
it 's easy think you
why use v=Vmcos377t rather than v=Vmsin377t?
nice video but how 120v become 170v?
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. th-cam.com/video/REsWdd76qxc/w-d-xo.html and
ii. th-cam.com/video/8BQM_xw2Rfo/w-d-xo.html
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.
377 came form the fact that the frequency of AC current in The Us is 60hz so w = 2*pi*60*t
what is the integral of v(t)^2 ?
(Vpeak.sin(wt))^2) generic function...
how would I find the ems value of the voltage with the amplitude being 320v and the time period being 0.015 seconds ? please help my exam is tommorow
sorry Vpp=580
Thank you