Ignition Coil

What is an ignition coil?

An ignition coil, also known as a spark coil, transmits electrical current from an automobile’s battery to the spark plugs in an internal combustion engine. The role of an ignition coil is to convert a battery's low voltage (typically 12 volts) into a much higher voltage (typically between 20,000 to 100,000 volts). The ignition coil is responsible for providing the spark (electrical arc) necessary to ignite the air–fuel mixture within a combustion chamber. Ignition coils are found only on spark-ignition engines (petrol/gasoline and gas engines), not compression-ignition engines (diesel engines).


Ignition Coil Parts

The main parts of an ignition coil include two separate windings or coils known as the primary winding and secondary winding, a high voltage cable connecting the ignition coil to the other ignition system parts, an insulator which serves as a barrier between both windings and an iron core which concentrates the magnetic field created by the electrical current passing through the coils.


How does an ignition coil work?

When electrical current passes through the primary winding it creates an electromagnetic field around it, inducing current into the neighboring secondary winding; this process is known as mutual induction. The voltage induced in the secondary winding is far higher than the voltage in the primary winding because it has a larger number of windings. The high voltage is passed to spark plugs to create an electrical arc, which is used to ignite the air-fuel mixture within the combustion space.

Note - ignition coils are essentially electrical transformers with one end connected to a battery and the other to spark plugs via a contact breaker. To understand how electrical transformers work, see our electrical transformer theory article.

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