How Ignition Coils Work

How Ignition Coils Work


Conventional automobiles burn gasoline in an internal combustion engine and convert that energy into motion but first a spark is needed to ignite the fuel mixture.
This demonstration shows how twelve volt battery generates the high voltage required to create such a discharge.
The heart of the car’s ignition system is its ignition coil.
This coil is a kind of transformer a device that transfers voltage from one circuit to another either as a lower voltage or in the case of the ignition coil as a higher voltage.
It does this by creating a changing magnetic field that induces a current in a conductor exposed to that field.
A principle known as electromagnetic induction.
Like other transformers an ignition coil consists in part of two coils of wire both wrapped around the same iron core.
The inner or secondary coil has far more turns of wires in the primary or outer coil
Making this a “step up” transformer that will convert the batteries 12 volts into some 40,000 volts of electricity.
First we will close the knife switch to create a circuit that includes the battery and the induction coil.
Although electrons move from negative to positive the convention is to think of electrical current as moving from positive to negative so that’s how we’ll show it here.
As current flows to the primary coil the magnetic field gradually builds up around it as well as around the secondary coil housed inside.
If we open the knife switch to stop the current.
The magnetic field suddenly collapses.
Due to the principle of electromagnetic induction this rapid change induces a surge of current in the secondary coil
Which streams out and jumps the spark gap in the circuit.
There is something else happening with the knife switch is opened – let’s watch again.
This time keep your eyes on the capacitor.
A simple coil of wire that can store electricity.
When the knife switch opens and the field around the coil collapses
That collapsing field around the primary coil induces a surge of current called back EMF in the primary coil.
This unwanted surge of electricity travels back toward the switch.
The job of the capacitor, called the condenser in auto ignition systems,
Is to safely absorb the back EMF and prevent the surge from reaching the switch and creating a damaging spark across those points.

Leave a Reply

Your email address will not be published. Required fields are marked *