How Ignition Coils Work

Conventional Automobiles burn gasoline an in internal combustion engine and convert that energy into motion. The heart of a car's ignition system is the ignition coil. This coil is a kind of transformer, which transforms voltage from one circuit to another, creating a changing magnetic field by inducing a current, called electromagnetic induction. 

The coil has 2 coils, with secondary the inner coil that has far more turns than the primary or outer coil. 

We will first close the switch. We'll try to do current as from positive to negative. Then we build a magnetic field. 

If we end the magnetic field due to electromagnetic induction, this rapid change induces a surge of current in secondary coil which jumps spark gap in the circuit. When the switch opens then the collapsing field in primary coil induces back emf and capacitor (condensor) safely absorb the back emf and prevent a surge and a damaging spark.