Definition
A smooth, repeating waveform that rises from zero to a positive peak, falls back through zero to a negative peak, and returns to zero, completing one full cycle. It is the natural shape produced by a rotating coil in a magnetic field and is the standard waveform of alternating current (AC) electricity used in aircraft electrical systems.
Plain English
A wavy line that goes up and down in a smooth, even pattern, repeating over and over. It is the shape of standard AC electrical power.
Context Anchor
Seen in aircraft electrical system training, especially when discussing alternating-current electrical power, generators, inverters, and test equipment displays.
Derivation
From the mathematical sine function in trigonometry, which describes the position of a point as it moves around a circle. Because a generator's coil rotates in a circle through a magnetic field, the voltage it produces traces out exactly this sine pattern.
Why Pilots Care
Aircraft AC systems run on sine wave power. Equipment is designed to expect this clean waveform; distorted or irregular waveforms can damage avionics or cause systems to malfunction.
Analogy
Picture the smooth up-and-down motion of a child on a swing, viewed from the side. The position over time traces a sine wave -- steady, even, and repeating.
Grounding Statement
On a graph, picture voltage rising smoothly above zero, crossing back through zero, falling smoothly below zero, and then repeating the same pattern.
Intuition Check
Do not think of a sine wave as any wavy line. In this context, it means a specific smooth, repeating curve with a regular shape.
Example Sentence 1
The aircraft's AC generator produces a 400-hertz sine wave to power the avionics and lighting systems.
Example Sentence 2
Technicians inspect the sine wave pattern on test equipment to verify proper generator output before flight.