Notes
From autorepair.about.com:
"The basic ignition system consists of the ignition coil, points, condenser, distributor and spark plugs. A ballast resistor may also be included in this system. When all of these parts are connected and working properly, we will get the spark the engine needs to run. Now, what are these parts and what so they do?
"Ignition Coil: This is the part that makes high voltage, up to 40,000 volts, for the spark plugs from the low voltage that is supplied to it by the battery. The reason an ignition coil works lies in the physical properties of electrical current. When a current flows through a conductor it generates a magnetic field around the conductor. Conversely, when a conductor is moved through a magnetic field, a voltage will be induced in the conductor. The coil takes advantage of these principles of inductance by winding one coil over the top of another around an iron core. The changing voltage in the primary winding serves as the 'movement' needed to induce a voltage in the secondary winding. The voltage in either winding is proportional to the number of coils in the inductor; if there are more turns in the secondary, its induced voltage will be higher than the voltage in the primary.
"When the points close, current through the coil primary increases from zero to maximum in an exponential manner, rapidly at first, then slowing as the current reaches it's maximum value. At low engine speeds, the points are closed long enough to allow the current to reach a higher current level. At higher speeds, the points open before the current has time to reach this maximum level. In fact, at very high speeds, the current may not reach a level high enough to provide sufficient spark, and the engine will begin to miss. This current through the coil builds a magnetic field around the coil. When the points open, the current through the coil is disrupted, and the field collapses. The collapsing field tries to maintain the current through the coil. Without the Condenser, the voltage will rise to a very high value at the points, and arcing will occur.
"Points: Ignition points are a set of electrical contacts that switch the coil on and off at the proper time. The points are opened and closed by the mechanical action of the distributor shaft lobes pushing on them. The points have a tough job, switching up to eight amps of current many times per second at highway speed. Indeed, as engine speed increases the efficiency of your ignition system decreases, thanks to heating problems and fundamental electrical laws. This declining efficiency has a serious effect on your spark voltage and results in poor high-speed performance, incomplete combustion and other drivability problems."