Root mean square current

The power formula ...

... gives the average heat produced per second in a resistor if current I is the average value of the current squared. The required value is the square root of the mean of the square. With the rms value of current, the power relationship is the same for both AC and DC currents.

For a sine wave the average current squared is easily calculated, since a sine wave squared, is another sine wave with a mean value equal to half the original amplitude squared.

For a sine wave current the rms value is given by the peak current divided by root 2.

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