The secondary winding, with about 100 times as many turns as the primary winding, can have an induced voltage about 100 times greater than the primary induced voltage. However, the actual firing voltage depends on many factors.
A ballast resistor coil is designed to operate at approximately 7.5 volts and still provide the step-up transformer action needed, for secondary circuit operation.
The dwell angle in contact breaker systems determines the time allowed for current to flow through the primary winding and establish the necessary magnetic field. In electronic ignition systems the equivalent process is referred to as the primary circuit 'charging time'.
The ignition timing point can be advanced by a centrifugal type mechanism according to engine speed and by a vacuum operated mechanism, according to load.
