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:confused:
     
  2. bertus

    Administrator

    Apr 5, 2008
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    JDR04 likes this.
  3. MrChips

    Moderator

    Oct 2, 2009
    12,414
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    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
    17,715
    4,788
    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.
     
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