Re: Minimum arc voltage of air was: Definitions of High Voltage

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "boris petkovic by way of Terry Fritz <twftesla-at-qwest-dot-net>" <petkovic7-at-yahoo-dot-com>


> Tesla list wrote:
> 
> >
> > Interesting is the fact that bellow 300-400 V in a
> > very narrow gap there is still no gas discharge
> before
> > metal to metal touch (standard atm. conditions).
> 
> Yes, it is interesting. North states that 340 is the
> "absolute minimum"
> (in air), therefore, anything below this value
> should not arc a gap
> regardless of eletrode size, shape, gap distance, or
> barometric
> pressure. He goes on to say that breakdown voltage
> decreases as pressure
> decreases until the 340V minimum is reached, due to
> the fact that as the
> melocular density of air is reduced, there is
> greater likelihood that a
> free ion can traverse the space between electrodes
> without running into
> something. But (here's the thing), as pressure is
> further reduced, the
> required voltage for breakdown increases once again
> because a more
> limited number of air molecules make ionization more
> difficult. So, we
> have a dip and it's value is 340V. Thus, it's the
> physical makeup of air
> and pressure that give us this minimum voltage.
> 
---
Hi Bart,
Yes,I copy you.That's why I mentioned standard
atmosphere (air) in my post.Some other gases ,given
lower pressures,have much lower minimum firing
voltages.
The applications are known.
 
regards,
Boris