Re: fluorescent tube question

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

Original poster: "davep by way of Terry Fritz <twftesla-at-qwest-dot-net>" <davep-at-quik-dot-com>

Tesla list wrote:

> Original poster: "David Thomson by way of Terry Fritz
<twftesla-at-qwest-dot-net>" ><dave-at-volantis-dot-org>
 
> Hi Ed,
 
> I don't see any posts suggesting there is no current flowing.  The only
> posts I have seen are those that said there is a lot of current flowing and
> those that say there is very little current flowing.  Air is not a good
> conductor, therefore energy must be increased in potential and decreased in
> current in order for power to flow across it.

	Or thru the capacitance presented by the two electrodes
	and the air
 
> Considering that we're usually using 60mA or less at 15KV or less and
> stepping the voltage up to around 100,000V or so, the radiated current would
> therefore be around 4mA.

	4 mA 'average' (i use that term advisedly).  The typical
	gap based Tesla system provides very high peak currents.
	Further, the deionization time of the mercury vapor, the
	decay time (persistence) of the phosphors and the
	persistence of the human eye ALL act to smooth the peak.
 
> Then there is the inverse square law that applies between the coil and
> the free fluorescent tube.

	Inverse square applies outside the near field.  cf any antenna
	text.

> It doesn't take much to realize

	I suggest measuring it as useful aid to realizing what
	goes on.  Useful exercise to figure how.  (hint: rf ammeter,
	hot wire or rectified....)

> at this point that the current is very low in a fluorescent tube
> that is not in contact with the secondary; a lot less than 1mA,
> in fact.

	Measured?

> Fluorescent tubes do not have voltage step down transformers in them,

	The associated FIXTURE has a BALLAST.  The ballast drops
	the line voltage.

> so we can correctly state that the nature of electrical energy in the
> fluorescent tube is high voltage, low current.

	'nature' is nice.  I suggest measuring.  Measurement will
	show a lowish voltage (say 40-60vac, rms) across the tube,
	in normal operation.  (varies, a bit, with tube length
	(power) Current in proportion.  I suggest that measurement is
	'correct', if done right.

	(In a bit more detail:
	I am describing the normal operation of the tube,
	once lit.  The mode when lit by a Tesla coil is more like the
	striking mode, with a few hundred volts across the tube (and,
	as apropos, filaments lit).  The 'few hundred volts' comes
	either from the 'kick' from opening the starter, or from
	subtle resonances in more recent ballasts, and even more
	subtle control in the solid state ballasts used for new work.

> Dave
 
> -----Original Message-----
> From: Tesla list [mailto:tesla-at-pupman-dot-com]
> Sent: Sunday, March 24, 2002 3:19 PM
> To: tesla-at-pupman-dot-com
> Subject: Re: fluorescent tube question
 
> Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> <evp-at-pacbell-dot-net>

> Some of the posts here seem to overlook the fact that current must flow
> through the tube to ionize the mercury vapor/gas fill and excite it into
> generating UV light.  Since there is a voltage drop across the tube that
> means power must flow.
 
> Ed