Re: volume polarization vs. surface charge

[Bob Sciamanda <trebor@VELOCITY.NET>]

Sure, I include this as one mechanism whereby an E field ionizes air - by
accelerating chance free electrons until they ram into an air molecule.
Ionization of gases is a very involved phenomenon; many factors and
mechanisms involved; much literature on the subject.  I am ignorant of
details in this field, but I do demonstrate the photoelectric effect as an
enhancement to ionization :

Connect an NE2 neon lamp (with a current limiting series resistor) to a
Variac.  You can then demonstrate that a higher firing voltage is required
in darkness than when a flashlight illuminates the NE2 - a UV lamp gives a
still lower firing voltage.

Bob Sciamanda
Physics, Edinboro Univ of PA (ret)
trebor@velocity.net
http://www.velocity.net/~trebor

-----Original Message-----
From: Brian McInnes <bmcinnes@PNC.COM.AU>
To: PHYS-L@LISTS.NAU.EDU <PHYS-L@LISTS.NAU.EDU>
Date: Sunday, March 07, 1999 6:32 AM
Subject: Re: volume polarization vs. surface charge


> ----------
> > From: Bob Sciamanda <trebor@VELOCITY.NET>
> > To: PHYS-L@LISTS.NAU.EDU
> > Subject: Re: volume polarization vs. surface charge
> > Date: Sun, 7 Mar 1999 1:51 PM
>
> > > The surface charge due to polarization of a dielectric is,
> whether
> > you
> > > consider it "real" or "virtual", not capable of constituting the
> > charge
> > > which makes the spark when the capacitor discharges. It isn't
> > > macroscopically mobile.
> >
> >
> > But the field of such "bound" charges can drive currents in nearby
> > conductors, ionize air,
>
> Does it ionise the air?  The field would have to be very
> large for that.  I think what goes on there (and leads to
> sparks) is a mechanism such as that describe by Chabey and
> Sherwood (Electric and Magnetic Interactions, page 79:
> cosmic rays produce the odd (transient) free electrons in
> the air; the electric field accelerates these; ionization
> occurs when accelerated electrons collide with neutral air
> molecules; etc, etc
>
> Brian McInnes