Which system type would use AC based on an ignition system?

The AC ignition system operates using alternating current, which is generated as the engine runs. This type of ignition system is essential in certain vehicle applications, particularly in smaller engines found in motorcycles, scooters, and some lawn equipment. An AC ignition system generates high voltage required to create a spark for the combustion process directly from the engine's generated power, eliminating the need for a battery.

In contrast, a battery-powered ignition relies on a constant supply of voltage from a battery, serving functions such as powering the spark plugs and the ignition coil. A mechanical ignition typically refers to systems that use a series of levers and weights to create a spark but do not employ AC or have the same operational needs as AC systems. Magneto ignition systems, while somewhat similar to AC ignition systems in that they are self-contained, traditionally use magnets to generate electricity and do not strictly align with the definition of an AC-based ignition linked directly to the engine's performance. Thus, the AC ignition system is characterized by its reliance on current generated by the engine, making it the correct answer.