How an Ignition Coil Works

by Derek Odom

Electicity Goes In

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 (known as a "hot wire") 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 of the vehicle's components, as well as keeping a good charge on the battery so the vehicle will start the next time.

The Coil Windings

Inside the coil are thousands of tiny copper windings. In other words, there is an extremely thin series of copper wires wrapped around each other, which amplifies the 12 volts coming into the coil. Once the electricity begins passing through the coil windings, a magnetic field is created that exponentially increases the voltage. The creation of power causes heat, so try not to touch the coil for a while after it has been working.

Electricity Goes Out

The average vehicle ignition coil puts out 20,000 to 30,000 volts, and coils used in racing applications are capable of 50,000 or more volts at a constant rate. This new voltage is then routed to the distributor via the coil wire, which is just like the spark plug wires, only normally much shorter. This high voltage output is exactly why the plug wires in your vehicle should be kept in good shape, because when they begin to arc and fail, the car not only loses horsepower but the electrical system can be affected, as well. Some vehicles use one coil per cylinder. That means that each spark plug in the engine has its own coil. The theory is the same, however, in those setups.

The Distributor

The distributor takes the voltage produced from the coil and sends it to the individual spark plugs in the order that they need to fire. This is done via a spinning component inside the distributor known as the rotor. As it spins, it contacts the spark plug connections inside the distributor cap and sends voltage through them, which then travels to the plugs, causing them to spark and ignite the fuel inside the engine.

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