Induction - Magneto / Flywheel

Get quicktime 3.0 or higher The magneto is a device used to create a large potential difference capable of creating a spark to "fire" the combustion of gasoline in an engine with no battery.  These are typically found on lawnmowers, weed eaters, chainsaws, mopeds and other small engine devices.  A magnet is embedded in the flywheel on the engine.  A coil is placed near the edge of the flywheel so that as the flywheel goes around the magnet passes by the coil.  This creates a rapidly changing magnetic field which induces a current in the coil.  The potential difference across this coil is not usually enough create a spark in the spark plug.  To make a bigger potential difference, the first coil is used as a primary coil and a secondary coil is used with many more windings than the primary.  This results in a step-up transformer which produces enough potential to cause electrons to jump the gap on the spark plug. 

This view is slightly simplified, as a few devices have been left out of the explanation.  A few devices (points, choke) are used to control the timing of the spark.  They however are not directly related to how the spark gets created.  

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