# Find Vavg and Vrms

#### Sajan Gurung

Joined Dec 20, 2018
33
Find average value and effective value of V and form factor.

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#### ericgibbs

Joined Jan 29, 2010
15,708
hi Sajan,
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#### MrAl

Joined Jun 17, 2014
9,161
Hello there,

If the image was a little darker it would be easier for everyone to read.
Here is the same image enhanced by darkening a little and improving contrast. Much easier to read.
The handwriting is very neat though that's a plus

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#### WBahn

Joined Mar 31, 2012
26,451
Find average value and effective value of V and form factor.

What is the definition of form factor?

#### Sajan Gurung

Joined Dec 20, 2018
33
Form factor is the ratio of effective value to the average value.
I am confused while putting the value of T.

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#### WBahn

Joined Mar 31, 2012
26,451
Form factor is the ratio of effective value to the average value.
I am confused while putting the value of T.
In calculating Vavg, why are you only integrating the first part from 0 to pi/2?

#### MrAl

Joined Jun 17, 2014
9,161
Form factor is the ratio of effective value to the average value.
I am confused while putting the value of T.
Hi,

Quick note...

You know what RMS stands for right?
It stands for "the Root of the Mean of the Square". The proper math follows from that and i am not sure you are doing that yet.

#### WBahn

Joined Mar 31, 2012
26,451
Hi,

Quick note...

You know what RMS stands for right?
It stands for "the Root of the Mean of the Square". The proper math follows from that and i am not sure you are doing that yet.
Depending on where he is in the material, they may not have gotten there yet. The rms is not the definition of effective voltage, it followed from the definition of effective voltage.

#### MrAl

Joined Jun 17, 2014
9,161
Depending on where he is in the material, they may not have gotten there yet. The rms is not the definition of effective voltage, it followed from the definition of effective voltage.
Hi,

I thought i saw in one of his papers that he was trying to calculate the RMS value but it did not look like the right calculation exactly. The writing was a little small though.

#### WBahn

Joined Mar 31, 2012
26,451
Hi,

I thought i saw in one of his papers that he was trying to calculate the RMS value but it did not look like the right calculation exactly. The writing was a little small though.
He might have. But was he calculating RMS, or what we calculating effective voltage based on the definition? Both will end up with the same setup result, so the only way to tell is from how the setup was done -- was it does by regurgitating an RMS formula or from setting up the problem to find the average power into a resistive load over one cycle?

I only looked at the first paper because once I find an error I generally figure there's not much point going any further until that issue is resolved. If I could get the TS to grasp that notion, he could save everyone, himself most especially, a lot of time pursuing work that is past repair.

#### MrAl

Joined Jun 17, 2014
9,161
He might have. But was he calculating RMS, or what we calculating effective voltage based on the definition? Both will end up with the same setup result, so the only way to tell is from how the setup was done -- was it does by regurgitating an RMS formula or from setting up the problem to find the average power into a resistive load over one cycle?

I only looked at the first paper because once I find an error I generally figure there's not much point going any further until that issue is resolved. If I could get the TS to grasp that notion, he could save everyone, himself most especially, a lot of time pursuing work that is past repair.
Hi,

Well i seem to recall seeing Vrms written down with a formula to the right that is not the whole calculation for an RMS value

#### WBahn

Joined Mar 31, 2012
26,451
Hi,

Well i seem to recall seeing Vrms written down with a formula to the right that is not the whole calculation for an RMS value
I will absolutely take your word for it. Again, I didn't look at the work beyond the first major mistake as I would rather the TS learn to check their work incrementally instead of just blindly bashing through to an answer that was doomed to not be a solution from literally the second line of their work and for which just a bit of asking, "Does it make sense thus far," could have saved all that effort.

While certainly far from alone, this TS has a particularly troublesome habit of not realizing that the first step to get out of a hole you are digging is to stop digging.

#### Sajan Gurung

Joined Dec 20, 2018
33
In calculating Vavg, why are you only integrating the first part from 0 to pi/2?
First part is symmetrical function and average value is zero so for complete cycle in symmetrical so i only took half the time which is equal to pi/2, but i think since i only took half should i multiply it by 2 to get averwge for complete cycle? Did you mean that in second part aswell i should integrate from 0 to pi?

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#### ericgibbs

Joined Jan 29, 2010
15,708
hi Sajan,
Forget the maths for a minute.
Just look at the graph in your first post, consider what the Vavg would be for a complete cycle, if the 2nd half of a full cycle is zero.
How can it be 'times 2' .????

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#### Sajan Gurung

Joined Dec 20, 2018
33
Hi,

Quick note...

You know what RMS stands for right?
It stands for "the Root of the Mean of the Square". The proper math follows from that and i am not sure you are doing that yet.
What i know is it stands for root mean square.

#### ericgibbs

Joined Jan 29, 2010
15,708
hi,
Look at this image.
What is the Vavg over 2pi.?
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#### ericgibbs

Joined Jan 29, 2010
15,708
That would be 1?
How can that be correct.?
Consider this alternative.
Say you drive your car at 60mph for 30 minutes then stop for a further 30 minutes, what is your average speed over the hour.???

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#### Sajan Gurung

Joined Dec 20, 2018
33
How can that be correct.?
Consider this alternative.
Say you drive your car at 60mph for 30 minutes then stop for a further 30 minutes, what is your average speed over the hour.???

E
30 mph, oh and in first fig avg would be .5, it was silly me to say 1.

#### ericgibbs

Joined Jan 29, 2010
15,708
hi,
OK.
So, your earlier post when you said 'it would be Vavg times 2' is incorrect.
What should you have posted.??
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