How spark is produced in spark plug

The spark plug is a small device in which there are two metal electrodes separated by a small distance of about one millimetre and one electrode is connected to a high voltage circuit while the other is grounded. The spark plug is fitted in such a way that it becomes sealed from the outside environment and is exposed to the chamber where combustion is required for starting the fuel-burning for realising power to the motor and getting the desired work done. There is an electrical ignition system in the vehicle from which we send a high voltage to this spark plug for a small time and as the gap is very small there is a breakdown of electrical insulation of this gap in presence of that high voltage and a spark is produced in the gap which is sufficient to ignite and start the combustion process. With repeated use of the spark plug, some amount of black carbon smoke is also deposited in and around this gap and that is why the plug requires a periodic cleaning so that its efficiency remains intact. Sometimes the gap is widened and the mechanic has to adjust it. If the electrodes are worn out then generally replacing the spark plug with a new one would be advised by the mechanic.

A spark plug is an electrical device used in internal combustion engines for igniting fuels using an electric spark. They allow fuel to burn and release energy which will cause the moment of the vehicle. These components are having two functions. In addition to igniting the fuels, they will remove the heat also.
The various parts that are present in a plug are
1. Insulator
2. Terminal
3. Ring, Parking Washer
4. Gasket
5. Center Shaft
6. Glass Seal
7. Electrode with Copper
8. Housing
9. Center Electrode
10. Ground Electrode
Copper spark plugs, Iridium spark plugs and single platinum spark plugs are the types of spark plugs that are available.
These devices will have an insulated centre electrode. In addition to this, one or more ground electrodes are available on the bottom end. There will be a gap between these two electrodes which is known as the spark gap. Once the voltage is supplied from the ignition coil to the spark plug,the electrical energy will jump the gap and produces a spark.

The voltage should be high enough to produce the spark. As the voltage rises, the structure of the fuel between the electrodes begins to change. Once the voltage is more than the dielectric strength of the fuels, it becomes ionized. This ionized gas allows electrons to flow across the gap between the electrodes. The voltage that is normally required is more than 2000 volts. At this voltage, the electrons in the gap will increase causing the temperature of the spark channel to increase. Then the ionised gas expands and will cause a small explosion in the chamber.

There is an old Tamil cine song,'paravaiyaik kandaan, vimaanam padaiththan......' which means an aero plane was invented. Similar to that it is heard that in olden days fire was made out of clicking two stones. I believe observing this idea the spark plug might have been invented and the fire (spark) came in a spark plug by friction.