
Spark plug is an electrical device threaded into cylinder of spark ignition engine, which produces spark at the required time to ignite the combustible air-fuel mixture in the cylinder bore. The device comprises shell, resistance, electrodes, and insulator. During the engine operation, when high tension current flows through the center electrodes, it ionizes the gas present between the electrode gap, producing spark. The modern spark plug is designed to deliver a powerful ignition spark around 500-3,500 times per minute. Temperature at the tip of the spark plug is normally between 500°C and 800°C. Passenger cars and commercial vehicles such as heavy-duty trucks and buses integrate more than four spark plugs, depending on the number of cylinders, whereas two-wheelers, small boats petrol generator, mowers, and saws are generally integrated with single spark plug.