What is the tube above the spark plug?

[JasperRose]

The long component above the spark plug is called the ignition wire, also known as the spark plug wire, distributor wire, or high-voltage ignition wire. The spark plug mainly consists of a terminal nut, insulator, terminal stud, center electrode, side electrode, and shell. The main types of spark plugs include: standard spark plugs, extended insulator spark plugs, electrode-type spark plugs, seat-type spark plugs, surface-gap spark plugs, and surface-discharge spark plugs. Spark plugs are installed on the side or top of the engine. In early designs, spark plugs were connected to the distributor via ignition wires. Over the past decade, most car engines have switched to direct connection between the ignition coil and the spark plug. Spark plug working principle: 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 isolates the metal shell from the center electrode. The terminal nut is the part of the spark plug that contacts the high-voltage coil. Current passes through the terminal nut and center electrode, then ionizes the medium between the center electrode and ground electrode to generate a spark, thereby igniting the air-fuel mixture in the cylinder.