What Is Spark Plug?

A spark plug is a critical component of an internal combustion engine that ignites the air-fuel mixture within the engine's cylinders, enabling the engine to generate power. It is a small device with a metal threaded shell, a central electrode, and an insulator, designed to withstand high temperatures and pressures inside the engine. The spark plug receives high-voltage electrical current from the ignition system, creating a spark across a gap between its electrodes.

This spark ignites the compressed air-fuel mixture, causing an explosion that drives the engine's pistons, producing the power needed to propel the vehicle. Spark plugs play an essential role in engine performance, fuel efficiency, and emissions, and their condition can directly affect how smoothly an engine runs. Regular maintenance and replacement of spark plugs are necessary to ensure optimal engine operation.

Working Principle of Spark Plug:

The working principle of a spark plug involves generating a high-voltage spark that ignites the air-fuel mixture in an internal combustion engine. Here’s how it operates:

1. Ignition Coil Activation: When the ignition key is turned, the ignition system activates the ignition coil, which transforms the battery’s low voltage into a high-voltage charge (typically between 12,000 to 45,000 volts).


2. Electrical Transmission: This high-voltage charge travels through the spark plug wire to the terminal of the spark plug, reaching the central electrode.
3. Spark Generation: As the voltage builds up, it creates a potential difference between the central electrode and the ground electrode (side electrode). When the voltage is sufficiently high to overcome the resistance of the air gap (the spark plug gap), an electric spark jumps across the gap..
4. Ignition of Air-Fuel Mixture: The spark ignites the compressed air-fuel mixture in the engine cylinder. This ignition creates a rapid expansion of gases, resulting in a mini-explosion that pushes the piston down, generating power for the engine.
5. Cycle Continuation: This process repeats in rapid succession as the engine cycles through its intake, compression, power, and exhaust strokes, with each spark plug firing at the appropriate moment in the engine’s cycle to maintain smooth operation.