@Jonny @BowsacNoodle @Shadowman311 Right; I’ve seen a guy building a Tesla Coil using a disk mounted on an angle grinder, with points around the circumference as a rapidly switching spark-gap. Worked pretty great, though it was very noisy. I suspect that‘s capitalizing on the flyback effect, at least somewhat - with the magnetic field rapidly collapsing as the spark breaks, cutting the current off.