Spark Plugs

Claimed By Christopher Skretkowicz

This page chronicles the inner workings and hidden mechanisms involved with spark plug applications in the real world.

The Main Idea

Spark plugs are essentially what their namesake says they are: plugs that screw into the cylinders of an engine and produce sparks that ignite fuel in combustion engines. Spark plugs take advantage of Faraday's Law and induction to create large spikes of voltage that would otherwise be impossible to achieve with a regular 12 volt car battery.

A Mathematical Model

The primary physics equation used when analyzing spark plugs is Faraday's Law, which states [math]\displaystyle{ \mathcal{E} = -{{d\Phi_B} \over dt} \ }[/math], where [math]\displaystyle{ \mathcal{E} }[/math] is the emf produced from the time-varying magnetic flux Φ_B. The flux is given by [math]\displaystyle{ \int_{\Sigma} \mathbf{B} \cdot d\mathbf{A}. }[/math]

The spark plug essentially consists of 2 coils, a primary coil and a much larger secondary coil. As current from the car battery runs through the primary coil, it is interrupted by cam action, which varies the electric current running through the circuit. Because the primary coil is is wrapped around the secondary coil, a varying magnetic field induces an electric current to be run through the secondary coil, which is much larger, which in turn produces a much larger EMF due to the number of loops in the coil.

A Computational Model

Spark Plug Modeled in Car

Examples

Anatomy of a Typical Spark Plug

Firing Spark Plug

Connectedness

Spark Plugs are literally the spark behind all combustion engines that power motorized vehicles such as cars, trucks and motorcycles. I have always had an interest in cars when I was growing up, but never really knew (and still don't completely know) how they work. Spark plugs may be a small part of a cars engine, but they are vital to creating the power that drives engines. It is very intriguing to see how exactly these spark plugs are able to created large voltage spikes to produce sparks within engines by using Faraday's law, a concept covered in an intro Physics class. Spark plugs do not necessarily link directly to my Civil Engineering major, but I have gained an appreciation for the electromagnetic ins and outs that drive mechanical systems in the real world.

History

The first known spark plug was invented by Étienne Lenoir as a part of the first internal combustion engine in 1860. Lenior and his French buddies dominated the spark plug market in the early 1900s, supplying gasoline engine manufacturers with only a limited line of plug configurations. They were also known to be quite costly and had substandard quality. It wasn't until in 1903 when Oliver Lodge created his spark plug and manufactured it throughout the United States.

See also

Magnetic Field of a Solenoid

Curly Electric Fields

Faraday's Law

Inductance

Transformers

External links

History of Spark Plugs

Spark Plug Anatomy

References

http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/ignition.html

http://auto.howstuffworks.com/spark-plugs.htm

https://www.youtube.com/watch?v=b2udCm7DMzU