Alternating current (AC / alternating current) is the electric current in which the magnitude and direction varying flow back and forth. Unlike direct current, where the current flows do not change with time. Wave form of alternating current electricity is usually sinusoidal wave-shaped, as this allows the most efficient energy conduction. But in specific applications, other, other waveforms can also be used, for example triangular waveform (triangular wave) or a rectangular waveform (square wave).