In spark discharge- there is that "surrounding ambient" interaction, that is why we end up with much much more electrons, that we start with.
I agree.
Electron Avalanche is a real effect but the kinetic energy gained by the accelerated electrons is taken from the source of the HV electric potential connected across the cathode and anode of the spark-gap (e.g. HV capacitor).
@yfree, @Grizli, @MileHigh, @TinselKoala, @Pirate...
What if the accelerated electrons in a spark-gap are deflected by a localized magnetic field near the
anode and thus are prevented from ever reaching the anode? Will the work done by the source of the HV electric potential be reduced ?
We do liberate relativistic electrons during that event.
I disagree.
For example: In air, any electrons above 14.5eV are capable of ionizing
nitrogen and oxygen (the major constituents of air) and causing secondary electron emissions able to sustain the
Electron Avalanche.
However 14.5eV electrons are not fast electrons. They move at 0.7532% of the speed of light. Hardly a "relativistic" speed.
All electrons that have kinetic energy below 13eV and collide with
nitrogren or oxygen in a spark-gap are absorbed by these atoms and do not cause the release of secondary electrons. Only photons at most.
Any electric potential higher than 15V (measured between the interatomic collision distance) will create faster electrons but will also create an intense Electron Avalanche resulting in an arc discharge that will short out the HV power supply, limiting the potential appearing at the electrodes of the spark gap.
In order to accelerate the electrons to 50% of the speed of light the HV power supply would need to maintain a potential difference of over 79kV between the atoms (over 10 MegaVolts between electrodes of realistic spark gaps!).
So give it a rest.
Practical atmospheric spark gaps do not produce "relativistic" electrons.
But most importantly, the combined energy of secondary electron emissions
is not larger than the energy of the impacting primary electrons ionizing the atoms in the first place (assuming that the atoms were not preionized a priori, as in a thundercloud).
For any energy gain, the energy of the secondary emissions would have to be greater than the energy of the primary incoming electron.
The only way this can happen is if the atom releases some of its internal energy (ionic or nuclear) in response to the incoming primary electron that triggers this release.
Releasing a priori ionization atomic energy can and does happen all the time, but ionizing atoms a priori costs energy, so it is not free.
Releasing nuclear energy by incoming electrons requires very high energy electrons in the MeV range. These electrons are "relativistic" this time. Such electrons cannot be produced by kitchen table spark-gaps - only by
beta decay of some isotopes or by particle accelerators.
Initiation of nuclear reactions by energetic electrons is possible and is illustrated by the
Betatron (an electron accelerator) used as an initiator for some nuclear weapons.
