How does a high voltage generate plasma I know extremely high temperatures can generate plasma, but I've heard that high voltages can too, does anyone know how a high voltage ionises gas?
 A: the ionization process of gas by high voltage takes several steps, as follows. we assume the case where we have an air gap between two electrodes with the high voltage between them.
when the voltage first comes on, it "looks" for any randomly-occurring ionization event within the gap, as would happen if for example an ultraviolet photon happened to hit the surface of one of the electrodes at that time, or if that photon hit a gas molecule just right and temporarily dislodged one of its electrons within the air space in the gap.
The voltage then accelerates the loose electron towards the (+) electrode and any positive ion towards the (-) electrode before they have the opportunity to recombine. They pick up energy from the field and speed up enough that if they happen to collide with another gas molecule on the way, it too gets ionized and the charged particles join in and get accelerated too.
Soon you have an avalanche of ions approaching the electrodes and the air between them is rapidly becoming electrically conducting as it gets populated with ions.
Then, when one of the positive ions smacks into the negative electrode, it busts loose a whole bunch of electrons which zoom off toward the positive electrode  and very quickly the air gap's resistance falls to almost nothing and if there is no external resistance to limit the current, a huge current develops between the electrodes- and since the current is huge and the air gap is still a (small) resistor, ohmic heating then raises the temperature of the ionized gas to incandescence and you have a power arc consisting of an extremely hot plasma.
A: An electric field pulls positively-charged protons in the direction of the field and negatively-charged electrons in the opposite direction. Make the field strong enough and it will pull them apart and ionize the atom.
