Working principle of spark plugs

Under the action of high voltage, the air between the center electrode and the side electrode of the spark plug will rapidly undergo ionization, 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, causing the air to lose its insulation, and the gap forms a discharge channel, causing a "breakdown" phenomenon. At this point, the gas forms a luminescent body, known as a "spark". Along with its thermal expansion, there is also a "popping" sound. The temperature of this type of electric spark can reach as high as 2000-3000 ℃, which is enough to ignite the mixture in the combustion chamber of the cylinder .