Alternating currents or AC currents regularly change their direction of flow. The current and voltage obey equations that involve the sine function and that are derived through the use of calculus:
The term refers to the maximum amplitude of the sine wave.
Since sine waves are symmetrical, calculating the average current or voltage over one complete cycle yields an answer of 0. Since this quantity is meaningless, when considering the current of an AC circuit, a quantity known the root-mean-square (rms) current is used. This quantity is calculated to be
