Good morning,
I think the neon current is V batt divided by R coil. The resistor makes the "on time" of the neon shorter. If you want to limit the current of the neon, a resistor (470 Ohms for example) should be placed in series with the battery. This makes the lightning more independent in the size of the transformer.
But in real live I use my VARIAC and an amperemeter to test transformers
.
Kind regards,
Darius
Lenz told something like: " A coil tries to keep the last current flow alive untill the stored magnetic energie is empty."