How can a cycle be defined in electrical terms?

In electrical terms, a cycle is defined as two alternations. This means that one complete cycle consists of the waveform returning to its original state after completing the positive and negative phases of its oscillation. In alternating current (AC) systems, the voltage and current change direction continuously; the positive alternation is the portion of the cycle where the flow of electricity is in one direction, followed by a negative alternation where the flow changes direction. Hence, two alternations represent a complete cycle of AC, which is critical for understanding waveforms in power systems.

Other options, while related to electrical concepts, do not accurately define a cycle. For instance, one complete revolution of the power source may relate to rotational machinery but does not specifically describe the electrical signaling context of a cycle. Three phases refer to a configuration in electrical systems where three alternating currents are used, while four transitions are not a standard term used in defining cycles in AC systems. These concepts contribute important context but do not capture the essence of what constitutes a cycle in electrical terms.