VIDEO: ASE G1 Test Prep - Ignition Coil Operation
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VIDEO: ASE G1 Test Prep – Ignition Coil Operation

This ASE G1 Test Prep question explains how ignition coils operated. This video is sponsored by Autolite.


Technician A says that in an ignition system, the voltage supplied to the coil during starting is battery voltage. Technician B says the coil uses electromagnetic induction to create high voltage. Who is right?

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Both techs are correct and here’s why.

Technician A is correct because the electrical system in your vehicle works on 12 volts, so every component must be based on 12 volts, as well. There is a wire connected to the ignition coil that carries the 12 volts into the coil itself. The power is initially created in the battery and alternator setup. A vehicle’s battery provides the voltage and amperage to get the engine started, and the alternator takes over from there, providing constant voltage and amperage to all the vehicle’s components, as well as keeping a good charge on the battery.


Technician B is correct also. For combustion to take place, a spark is needed to ignite the air-fuel mixture in the engine. This is the job of the ignition coil. It is atype of electrical transformer, it converts the battery’s voltage of 12 volts –to the thousands needed to jump the spark plug gap, ignite the fuel, and ultimately start the engine.

Some systems will need one only coil to do this, however, most late-model vehicles use an individual coil for each cylinder. Ignition coils consist of three parts; a primary circuit made up of several hundred turns of primary winding, a secondary circuit with many thousand more turns, and an iron core. As current flows through the primary circuit, a large magnetic field builds around the core, charging up the coil. However, when the power flow is stopped, the magnetic field collapses and it induces a surge of current in the secondary coil, multiplying the voltage until there is enough to create an ignition spark.


This ASE G1 Test Prep Video is presented by Autolite.

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