Short answer? Current control. Longer response? Points and condenser are matched to control arcing. This is a function of Voltage and materials. If the condenser is too small it will pull material from one contact and deposit it on the other contact. If it is too big it will pull that material the other way. Either condition is bad and shortens the life of the points. So the engineers ran tests and calculations to make that combination work as long and as well as they could. At 6 Volts. Why do all that work over again when a "ballast" resister will do it for you? And.. they are cheap. Those points open and close 3 times every time that engine goes 1 revolution. And that engine goes around thousands of times every minute it is working. That is a lot of open and close for each mile. And they last for thousands of miles. So congratulations to the original engineers for getting it right all those years ago. So? Use that "ballast" resister and celebrate the work that went on before us. Now was that helpful?
