What happens when the primary field collapses in an ignition system?

When the primary field collapses in an ignition system, high voltage is induced in the secondary windings. This process occurs because the ignition coil operates on the principle of electromagnetic induction. When current flows through the primary winding, it creates a magnetic field. When the current is abruptly interrupted, this magnetic field collapses, leading to a rapid change in magnetic flux. According to Faraday's law of electromagnetic induction, this change in flux induces a high voltage in the secondary winding. This high voltage is what enables the ignition system to create a spark at the spark plug, igniting the air-fuel mixture in the engine cylinders.

The other options do not accurately describe the outcome of the primary field collapse. For example, the battery does not recharge as a result of this process; instead, the ignition system relies on the battery's charge to power the coil initially. Current flowing to the starter motor is unrelated to the events occurring in the ignition coil, as the starter motor operates within a different circuit altogether. The idea that the spark plug cools down is also incorrect; in fact, the induced high voltage causes the spark plug to fire, leading to a rapid increase in temperature due to the combustion process.