/diy/ - Do It Yourself

>>1197156
>(much stronger) spark when the current is interrupted
I'd say it only sparks when the current is interrupted.

Ignition in a nutshell:

Contact closes, current ramps up, coil collects energy. Then the contact opens and the stored energy is released but has nowhere to go. Tension rises until a spark forms and creates a conductive path (ionized air) that the energy can follow and dissipate. Next cycle.

The effect is greatly magnified by the number-of-turns ratio of the secondary winding to that of the (switched) primary coil (as in any transformer). The function of the Tesla coil is based on this: a few primary turns and many, many secondary turns - sparks all around.