An ignition coil is a transformer that converts the roughly 13.5 volts available from the vehicle's electrical system and converts it into a very high voltage (about 20,000 to 60,000 volts) that is capable of jumping the spark plug gap. Coils can be designed individually, or as a coil pack.
Ignition coils have a pair of windings inside of them, a primary winding for the primary circuit, and a secondary winding for the secondary circuit. The primary side is supplied voltage from the car (either about 12.6 volts from the car battery during start-up, or about 14 volts from the alternator once it starts working) and is made up of a wire winding wrapped around an iron core.
The secondary windings are also wound around the iron core, but the number of windings from the primary compared to the secondary creates a conversion, based on the number of windings. For example, if the primary side has 100 windings and the secondary side has 500,000 windings, it will convert 12 volts on the primary side into 60,000 volts on the secondary side.
Inside an Ignition Coil by SpeedKar99
- This assumes an ideal transformer, which allows for easier math and a less complicated understanding of the math.