Little bits of a cycle

Engineers break the alternating current cycle down into small parts for the process analysis and reference. One cycle can be likened to a single revolution around the circle.

Degrees

One method of specifying phase of an alternating current cycle is to divide it into 360 equal parts, known as degrees or degrees of phase. The value 0 degree can be assigned to the point in cycle where the magnitude is 0 and positive-going. The same point on next cycle can be given the value 360 degrees. Then the halfway through cycle is 180 degrees; a quarter cycle is 90 degrees, and it carries on. This is shown in the figure given below.

Figure--   A cycle is divided into 360 degrees.

Radians

Another method of specifying phase is to divide cycle into 6.28 equal parts. This can be approximately the number of radii of a circle which can be laid end-to-end around the circumference. The radian of phase is equal to around 57.3 degrees. This unit of phase is something you would not often be required to use, because it is more common among physicists than among the engineers.

At times, the frequency of an alternating current wave is measured in radians per second, rather than in hertz. Because there are around 6.28 radians in a complete cycle of 360 degrees, angular frequency of a wave, in radians per second, is equal to around 6.28 times the frequency in hertz.