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How does a spark plug produce current ?

A spark plug is a crucial component in an internal combustion engine, playing a key role in igniting the air-fuel mixture within the engine’s cylinders. The process by which a spark plug produces a spark involves the generation of high-voltage current and the creation of an electric spark. Here’s a detailed explanation of how a spark plug produces current:

  1. Basic Structure:
    • A spark plug consists of a metal shell, an insulator, a central electrode, and a ground electrode. The central electrode extends into the combustion chamber, while the ground electrode is mounted on the plug’s outer shell.
  2. Voltage Source:
    • The high-voltage current needed for spark generation is supplied by the ignition system of the engine. In modern vehicles, an ignition coil generates a high voltage, typically in the range of tens of thousands of volts.
  3. Ignition Coil:
    • The ignition coil is a type of transformer that steps up the low-voltage electrical power from the vehicle’s battery to the high voltage required for spark generation. It consists of two sets of windings – a primary winding and a secondary winding.
  4. Primary Winding:
    • The primary winding is connected to the battery, and when an electric current flows through it, it creates a magnetic field around the winding.
  5. Breaker Points or Electronic Switch:
    • In older ignition systems, breaker points served as the switch that interrupted the primary current flow, causing the magnetic field to collapse. In modern systems, an electronic switch, such as a transistor, is used for the same purpose.
  6. Induced Voltage in the Secondary Winding:
    • The collapsing magnetic field in the primary winding induces a high-voltage current in the secondary winding due to electromagnetic induction. The secondary winding typically has many more turns than the primary winding, leading to a significant voltage increase.
  7. High-Tension Cable:
    • The high-voltage current generated in the secondary winding is transmitted to the spark plug via a high-tension cable.
  8. Spark Plug’s Role:
    • The spark plug acts as a bridge between the high-voltage cable and the air-fuel mixture in the combustion chamber. It creates a gap between the central electrode and the ground electrode.
  9. Air-Fuel Mixture Ignition:
    • When the high-voltage current reaches the spark plug, it ionizes the air-fuel mixture between the electrodes. Ionization causes the air-fuel mixture to become conductive, allowing current to flow across the gap.
  10. Electric Spark:
    • The flow of current across the gap produces an electric spark. This spark serves as the ignition source for the air-fuel mixture, initiating combustion in the engine cylinder.
  11. Repeated Operation:
    • The spark plug undergoes this process repeatedly in each engine cylinder, synchronized with the engine’s firing order.

In summary, a spark plug produces a spark by serving as the endpoint for the high-voltage current generated by the ignition coil. The electric spark across the gap between the electrodes ignites the air-fuel mixture in the combustion chamber, initiating the power stroke in the engine’s internal combustion cycle.

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