Lesson3/Learning Event 1
Spark plugs provide an air gap in each cylinder for the highvoltage surges to arc across, which is the
reason we need such high voltage in the secondary circuit. It takes a lot of voltage to force the
current to jump across the air gap between the electrodes of a spark plug. The current, arcing
across the air gap, is what actually ignites the fuel-air mixture.
The primary circuit consists of the components between the battery and the breaker points,
including the breaker points.
The secondary circuit consists of the secondary winding in the coil, the distributor cap and rotor,
the distributor, spark plug wires, and spark plug.