RMS Voltage


AC voltage rises positive and falls negative 60 times per second, so how do you state its value? Industry practice is to quote the RMS voltage. RMS is a value 70.7% of the peak positive voltage. An RMS voltage will produce exactly the same heating rate in a resistive load as a DC voltage of the same value. RMS is the acronym for the mathematical steps used in its derivation. Square the voltage at all moments in an AC cycle, take the mean of these, and then take the square root of the mean. For reasons lost in obscurity, the steps are stated in reverse sequence, Root Mean Square.

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