The current runs from the positive terminal of the battery (or generator) through the gap in the spark plug, to the negative terminal of the battery. The loss of electrons in the circuit is compensated by the discharge of the battery (or generator). The outside air is not needed as part of the circuit.
V= dO/dt = (dO/di)(di/dt)= L(di/dt). Two perimeters are important in generating, break down voltage are circuit lnductance and rate of change of current in circui, making zero by opening circuit by switching...