Ontwerpvoorbeeld: auto-ontstekingssysteem

An automobile's ignition system includes an essential component, the spark plug, with two electrodes separated by an air gap. When high voltage is applied between these electrodes, a spark forms across the air gap, igniting the fuel.

Designing a spark plug operating with a small car battery involves the use of inductor properties.

When the ignition switch is closed, the spark coil's current rises steadily until it stabilizes. At constant current, the voltage becomes zero.

However, when the switch abruptly opens, the rapidly collapsing magnetic field inside and around the inductor generates a high voltage, triggering a spark.

For design purposes, consider a spark coil with known inductance and resistance. If a 12-volt battery supplies power, the goal is to estimate the final current through the coil when the switch is off and the voltage across the air gap, assuming a 2-microsecond switch opening time.

The ratio of the battery's voltage to the coil's resistance gives the current.

While the voltage is determined by substituting the known values in the inductor's voltage relationship.