Definition
In electronics, one half-cycle of alternating current. A complete AC cycle consists of two alternations: one positive (current flowing in one direction) and one negative (current flowing in the opposite direction).
Plain English
Half of one back-and-forth swing of alternating current. The current rises from zero, peaks, and returns to zero — that single swing is one alternation.
Context Anchor
Seen in aircraft electrical-system study when alternating current, alternators, and electrical output are explained.
Derivation
From the Latin alternare, meaning 'to do by turns.' AC current takes turns flowing one way, then the other — each turn is an alternation.
Why Pilots Care
Aircraft AC systems (such as those powering certain instruments and avionics) operate on cycles built from alternations. Understanding the term helps when reading electrical schematics or troubleshooting AC equipment.
Analogy
An alternation is like one swing of a pendulum from the middle out to one side and back to the middle. The next alternation is the swing to the other side and back.
Intuition Check
Alternation does not just mean any change from one thing to another. In this context, it means one half of an alternating electrical cycle, in one direction only.
Example Sentence 1
Two alternations make up one full cycle of 400-Hz aircraft AC power.
Example Sentence 2
Each alternation in the waveform shows the current moving in one direction before reversing.