What is the working principle of a gasoline engine spark plug?

[EvelynFitz]

The working principle of a gasoline engine spark plug: The spark plug's ground electrode is connected to the metal shell, which is threaded into the engine block via the cylinder head. The insulator primarily serves to isolate the metal shell from the center electrode. The terminal nut is the part of the spark plug that contacts the high-voltage coil. When current passes through the terminal nut and the center electrode, it ionizes the medium between the center electrode and the ground electrode, generating a spark to ignite the air-fuel mixture in the cylinder. Spark plugs are installed on the side or top of the engine. Early spark plugs were connected to the distributor via ignition wires, but in the past decade, most car engines have switched to direct connection between the ignition coil and the spark plug. If a spark plug is damaged, it can directly cause issues such as ignition system leakage, increased fuel consumption, and reduced power. The most significant problem is difficulty in ignition, affecting the vehicle's normal operation. Severe spark plug erosion, including scarring at the top, damage, or melted and eroded electrodes, indicates that the spark plug is damaged and should be replaced.