Re: Paschen's law

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

Original poster: Jim Lux <jimlux-at-earthlink-dot-net> 

At 01:10 PM 3/8/2004 -0700, you wrote:
>Original poster: "Antonio Carlos M. de Queiroz" <acmq-at-compuland-dot-com.br>
>Hi:
>
>Some update about the final form of the translation of Paschen's
>article? And about the pictures? (usually in the last pages of
>the Annalen).

I'll have to ask the library to get me the pages..



>I am thinking about how to apply the law to determine the breakdown
>voltage of gaps that would break down at low voltages, or because
>the distance is small, or because the radius of curvature of the
>surfaces is small, always at normal pressure.
>
>For example, assuming a maximum electric field of 30 kV for each
>cm of radius for a ball, a 0.2 mm ball would have breakout at 300 V,
>and a 2 um ball at just 3 V. In this case there is no distance to
>consider, so how to apply the law?
>
>For a gap between two flat plates, the law says that the breakdown
>voltage is a function of the product of pressure and distance, with
>a minimum of about 340 V for p*d=0.2 cm.mmHg. With 760 mmHg, the
>minimum corresponds to d=0.00026 cm, or 2.6 um. Below this distance
>the law says that the breakdown voltage increases. Very strange.

Very strange, but true... It may not breakdown, but the leakage current may 
go up (because the electron hits the other side before an avalanche occurs)


>And about gaps between points with small radius of curvature and
>small distances? The strange effects appear to occur at um distances,
>what is not so small.


At some point, you get field emission, too...



>I think that there is something missing in this law. Specially a
>reason for it being as stated.
>
>Antonio Carlos M. de Queiroz