With direct current covered and understood it is now time to delve into the world of alternating current. Alternating current is when current flows in one direction for a set time, then changes direction, then changes back, and so on in a repeating cycle. The alternating motion is most commonly in the form of a sinusoidal wave, but it can also be square or triangular.
AC is produced by generators in power stations and can be found in homes, radio equipment, car alternators, and even synthesizers. AC voltage has several advantages over DC voltage (generation and transmission, transformer voltage increase / decrease, electromagnetic emissions, etc.), but the analysis can be more complex, involving imaginary numbers, phasor diagrams, Laplace transforms, and even second-order differentiation equations (oscillators).