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Re: fluorescent tube question



Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>


----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Friday, March 22, 2002 5:11 PM
Subject: Re: fluorescent tube question


> Original poster: "davep by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<davep-at-quik-dot-com>
>
> Tesla list wrote:
>
> > Original poster: "Michael Rothberg by way of Terry Fritz
> ><twftesla-at-qwest-dot-net>" <fishboymichael-at-telocity-dot-com>
>
> > How does the output of a tesla coil light a fluorescent tube from a
> > distance without direct contact?
>
> The tube lights, largely, from current flows thru the tube.

The  E field doesn't have to be lengthwise...  You can set up a parallel
transmission line (at higher frequencies) that has standing waves, and lay a
tube in the middle and see the voltage peaks. In this case the field is
transverse to the tube.


> This happens when the voltage across the ends goes higher
> than the strike voltage.  (say a few hundred volts, varying
> with tube length.)  The Tesla secondary pushes the local
> voltage  to '1000's' of volts/meter, which drives
> the current flow.  The tube can be thought of as part of
> a series circuit, formed by air dielectric capacitors.
>
> (Experiment:  try larger foil electrodes on the contacts
> of tube.  (hmmmmm useful demo trick anyway....)  This makes
> the 'air capacitor' have a larger value, more current...
> (I believe Tesla used this illustration in his writings.)
> (Fluorescent tubes will ALSO light (same mechanism) under
> HVAC power lines...)
>
> (Question:
> Is there any lighting due to 'direct' excitation of the
> phosphors?  Tricky experiment to do....   Hmmmmm.  Use
> loose CRT instead of a fluorescent tube?  Caution with the
> loose CRT....)

Most CRT phosphors can't be excited just by an efield... not enough
energy...
You need either photons of UV (in the fluorescent lamp case) or electrons
(or other particles) zooming along.