The value of the voltage or current in an AC sinewave is continually changing, but we use a single number to describe it. That number is the “RMS” value or the root-mean-square. When we specify a voltage or current, we don’t usually include the term “RMS,” but it’s implied.
RMS is a formula that calculates the equivalent DC value of an AC voltage or current sinewave. To calculate it, the instantaneous voltage or current is first squared, then those squares are averaged over a single cycle, and finally the square root of that number is taken.
By way of illustration, let’s take a sample of a few values of a sinewave and find its RMS value. In this case, we’ll use 12 sample points at regular intervals, and ...
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