How Spark Plug works

Under the action of high voltage, the air between the center electrode and the side electrode of the spark plug will rapidly ionize, forming positively charged ions and negatively charged free electrons. When the voltage between the electrodes reaches a certain value, the number of ions and electrons in the gas increases like an avalanche, so that the air loses its insulation, and the gap forms a discharge channel, causing a "breakdown" phenomenon. At this time, the gas forms a luminous body, that is, a "spark". As it heats up and expands, there is also a "pop" sound. The temperature of this electric spark can be as high as 2000～3000℃, which is enough to ignite the mixed gas in the combustion chamber of the cylinder.