I've been wanting to show/understand the difference between positive and negative back emf.

First I made a small spark from a 900V negative back emf. It looked different, white and gasous, and was very loud.

https://youtu.be/zQNKQWFCFCs

Then I realized the voltage was simply to low. I needed to step it up.
I ordered a step up transformer from china, but realized, I havr a xar bobine/ignition coil.

I hooked it up to my 12V battery and a lowside igbt switch (creating "regular" positive back emf).

I put a 0.1uF plus 10k parallel over the primary, to restrict the back emf (I first used a diode but then there is no spark as all energy is shorted via the diode).

tuned in a 400Hz square wave and turned it on.

Spark works. blue lightning as expected.

but also a loud noise out of my speakers, and led lights turning off
lol :P

the emp is rather intense :emperor:

but it works...
need to tune the snubber cap/resistor so a 500V back emf on the primary is possible.

after filming it, I want to use a high side switch, and show the negative spark. and the difference between them.

I hope the neighbors will not get mad with all the emf noise this will produce, and, I need to make sure I dont nuke my electronics with those EMPs...

 talking about longitudinal pressure... EMP is such a bad name...
its should be MDP
Magneto Dielectric Pulse.

did the same test, with the high side switch, spark looked the same, also purple, not gaseous (slightly but not like before).
I wonder if it is due to a not proper grounded primary (need to test this)
Or if it is due to the secondary of the ignition coil, It could be I have connected it the wrong way round.
I feel it has to do with the counter rotation of the coil (and the Aether) when the magnetic field collapses.

also I'm not happy with my snubber cap resistor. I want to reverse it, place the cap on the back emf (switcheded) side, so the cap gets charged, and slowly discharges through the resistor.

pulsing at 400Hz works best