Condenser is a device which transfers the heat. It is used to condense the gas to its liquid by cooling it.
The ignition points is a minimum temperature at which the substance will start burning but without any additional application of heat.
The function of the condenser in a coil ignition circuit is to reduce the spark. It is use to keep the points from sticking together during ignition. Otherwise it may lead to burn the point.
Therefore, the function of the condenser in a breaker points ignition system is to prevent electricity from arching across the points.
It depends on the size of the cube, but you could use a ruler for almost any size, or if it is small enough, you could use a caliper to get a very precise measurement.
