What is an Ignition Coil: Main Parts, Diagram and Working?

An ignition Coil is (also called a spark coil) an induction coil which is used to increase the low voltage of the battery (12 Volt) to a very high voltage ( about 50,000 Volt) to produce a spark within the engine cylinder for the combustion of fuel. It is used in automobile ignition systems. We can also say that it is a short step-up transformer.

Working Principle of Ignition Coil

The ignition coil mainly consists of a primary winding, a secondary winding, and an iron core. When the current through the primary winding makes and breaks repeatedly by contact breaker, it induces a very high voltage in the secondary winding (about 50000 V). This high voltage from the secondary winding is transferred to the spark plug through ignition distributor to produce spark within the cylinder.

Ignition Coil Diagram

Ignition Coil Main parts, Working Principle and Application

Main Parts of Ignition Coil

The various main parts of the ignition coil are
1. Primary Winding
2. Secondary Winding
3. Iron core

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1. Primary Winding

It is made up of thick copper wire having 200 to 300 turns insulated from each other

2. Secondary Winding

It is made up of thin copper wire having a large number of turns about 21000 turns. The wires in the secondary winding are insulated from each other by enamel on the wire.

3. Iron Core

It consists of a laminated iron core. It is used to store energy in the form of a magnetic field.

Construction of Ignition Coil

In an ignition coil, the iron core is present at the center, and the primary and secondary windings surround it. The primary winding consists of thick wire of copper having 200 to 300 turn insulated from each other. On the other hand secondary winding is made up of thin copper wire having 2100 turns and insulated form each other by enamel on the wires and layers of oiled paper insulation.

Working of Ignition Coil


  1. When the ignition switch is ON, the current through the primary winding starts to flow, this creates magnetic field in the iron core and around it.
  2. As contact breaks in the contact breaker, the primary current collapses. This also collapses the magnetic field in the core. This sudden breaking of the magnetic field induces a very high voltage across the secondary winding. The magnitude of the voltage induced is about 50000 Volt.
  3. This high voltage then is transferred to the spark plug through the ignition distributor to produce spark for the ignition.

For a Better Understanding of ignition coil Watch the video:

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  • It is mostly used in the automobile ignition system and in those vehicles which are run by petrol engines such as scooters, motorcycles, cars, etc.
  • It is not used in vehicles running on diesel engines.

How to Identify Failure of Ignition Coil?

The various symptoms of its failure are

  • Backfiring
  • Starting problems
  • Less fuel economy
  • Engine misfiring
  • Vehicle stalling
  • Engine shaking
This is all about the ignition coil, If you find this piece of information valuable and useful then don’t forget to like and share it.

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