# Is RMS value same as Average Value?

Discussion in 'Homework Help' started by JDR04, May 31, 2012.

1. ### JDR04 Thread Starter Active Member

May 5, 2011
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4
Can someone help me out here please.

I want to know if a RMS value is the same as an AVERAGE Value? Is a RMS value derived by the adding of all positive instantaneous values in an AC CYCLE and then divided by the number of instantaneous values you took?

Am I making any sense or does it sound like gibberish?

Thanks guys - JDR04

Apr 5, 2008
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3. ### MrChips Moderator

Oct 2, 2009
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3,454
RMS and average value are not the same.

Average value is taking the sum of all instantaneous values and dividing by n the number of values.

RMS is taking the sum of the square of all instantaneous values, dividing by n and then taking the square root.

The RMS value is the value of a DC voltage or current that will give the same heating effect as the random waveform.

4. ### JDR04 Thread Starter Active Member

May 5, 2011
339
4
Thanks MrChips, you've made it a lot clearer now. Much appreciated. JDR04

5. ### WBahn Moderator

Mar 31, 2012
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Just remember that the name says it all:

RMS: Root of the Mean of the Square.

So you take the square root of the mean (average and mean are the same) of the squared waveform.