Re: Lighting incandescent lamps with TC

["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>

>>>I was wondering how many of you have tried the
>>>experiment where you cause an incandescent lamp to
>>>glow from current coupled by induction, by connecting
>>>a wire loop across the contacts of the bulb.  I tried
>>>this using a flashlight bulb, wire loop and approached
>>>(as close as I dared without being tagged by
>>>streamers) my running 6" coil.  Nothing.  Not even the
>>>slightest glow from the filiment (spelling?).

>>        Lighting a filament (a demo Tesla used to do) I've
>>        not tried.  The physics are simple:
>>                need to get enough current into the filament.
>>        (Tesla used to use Very heavy copper, i've heard
>>        tales of bus bars....) to demonstrate that The Freqs
>>        are Different and the behaviour is different.)
>>        Random thoughts:
>>                Pick a LOW CURRENT lamp (measure them)
>>                Flashlight lamps are high current FOR THE
>>                EQUIVALENT WATTAGE.
>>                Try a multiturn coil.
>>                Fat Wire (current operated device).
>>                Build a series resonant circuit AT THE COIL
>>                freq?

>>>Does anyone have any ideas as to what the problem is?

>>        Not enough current.
>>
>>        (Filaments are very nonlinear.  Might be Just
>>        Under incandescence and Not Quite There.)
 
> I can't understand the problem, as it should be easy to burn out a
> filament - after all you have at least several hundred watts to play
> with!

	Depending on coil size  8)>>
	Also, the cold power is going in all directions:
	some small fraction couples to any given 'receiver'.
	My impression was that the attempt was made with
	no tuning.

> I have an absorption wavemeter (series tuned circuit comprised of
> inductor, variable capacitor, and bulb filament) here which I built for
> measuring appropximate TC operating frequencies.

	Exactly.  Series tuned.
	(One might wonder if Tesla's receive coils were carefully
	crafted for resonance.  I Assume they were.)

> The indicator is a 60 ma, 2 volt pilot lamp shunted with a small

> inductor.  I can burn out the bulb if I get too close to the

> primary of a 30 watt miniature coil I built a while back, and with

>a bigger coil I need a separation of feet. 

	'the power of resonance'.

> Interestingly enough, because of the high peak power/low duty factor
> nature of the spark signal, I can get sparking [voltage breakdown]
> between the plates of the 0.001 mfd variable capacitor (old Cardwell ca
> 1922) long before the filament goes.
	...and the cap looks like an open circuit (OK, more so at

	DC than at coil freq) so IT 'sees' voltage.

	AND any incandescent has a lower R cold than hot
	(the nonlinearity i mentioned).  This means a sort of
	threshold must be passed to get enough power into the
	filament (as opposed to lost elsewhere) to light it up.
	Numerics:
		A room temp filament is roughly 10% of the
		resistance of the same at normal brightness.

	Thus, if a constant current, well below that required
	for full brilliance is applied ( 0.06A, in the case just
	above), the thing may not light off at all:  Normal
	power systems (battery, mains wiring, etc) cheerfully
	supplies, briefly, the excess current.

-- 
	best
	dwp

...the net of a million lies...
	Vernor Vinge
There are Many Web Sites which Say Many Things.
	-me