Hey Jon,
I'm no electronic wizard, but I have been taught the following :
One of the laws governing electrical flow is that when a conductor
intersects a magnetic field, current is produced in the conductor. In
the case of the DC generator, AC current is produced by rotating a
several conductors (the armature) through a magnetic field (opposing
field coils) the commutator and brushes convert the AC to DC. In the
alternator a rotating field coil is rotated inside a set of three sets
of windings producing AC current and the diodes convert the AC to DC
giving full wave rectification (all the current produced is usable.
Early alternators used rectifiers to syphon off half the AC current
produced.
The ignition coil also works under the same laws. Point ignition - DC
current flows from positive through the primary winding of the coil to
negative (ground) when the points close. During this time of flow a
magnetic field is building in the primary circuit. When the points open
(the condenser allows current to continue flowing until it is fully
charged and the points are adequately opened so that current cannot
cross the gap) the magnetic field collapses producing an AC current in
the secondary windings. The voltage has been magnified (stepped up)
because of the relationship between the number of turns in the primary
and the secondary windings. An iron core is used in the coil to
strengthen and concentrate the magnetic field. In many coils the
secondary and primary windings are connected at one point. The primary
continuing on to ground and the secondary continuing to the coil tower.
The condenser acts as both a shock absorber (the current bounces back
and forth in the circuit until it dissipates) and as a kick start for
the next magnetic field build up, by releasing its stored energy when
the points close.
Most electronic ignition systems work in the same manner. The points
have been replaced by solid state circuitry which is used to control the
coil's action.
I hope that this is a adequate explanation for you.
Tom, Redding CA - #216 D/GCC
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