Unusual request - hope you can help. There is a TV program being made on the subject of lightning, and the producers want to know urgently if there is a lab in the UK which can generate impressive looking sparks for the cameras, either in the open air or in glass gas-filled tubes to demonstrate an electrical discharge, from a Van der Graaf generator, or whatever. Email me at physics.org if you have any ideas. Thanks.
-- Brian.Blandford
5 Kingsway Mansions Red Lion Square London WC1R 4SE Tel: 020 7405 9984 Mobile: 079 7405 9984
A more impressive spark can be had from a good Van de Graf generator, or perhaps an excellent Wimshurst wheel. Tesla coils are great for continuous arcs, but the others can do some impressive lightning simulations (static electricity and all).
One characteristic of lightning is the discharge of an enormous amount of energy in a very brief time interval. While Tesla Coils and static electric generators are capably of producing impressive sparks, they lack the concentration of stored energy to produce anything resembly a artificial lightning bolt.
To the best of my knowledge, artificial lightning is alway produced using a large bank of energy storage capacitors that are generally connected in parallel while being charged, but switched to a series configuration to produce the actual lightning bolt itself. (Apparatus like this is commercially manufactured by a number of firms who supply the EMP testing field.)
You may want to contact The Franklin Institute in Philadelpha, PA. They have (or at least had) one of the best artificial lightning demos, accessible to the public, that I have ever seen. IIRC they discharged a 2-foot bolt into a spike driven into the center of a roughly 12" diameter log, splitering the log into many pieces just as is seen in nature. I won't even begin to describe the sound it made, but it suffices to say that you could hear it even outside the building housing the museum!
The greatest source of artificial lightning I know is my wife's eyes when she gets pissed off at some one.
Bolts of lightning literally spring from her eys and stike the offender dead. . . I DO NOT FOLLOW MANY OF THESE NEWS GROUPS To answere me address mail to snipped-for-privacy@aol.com
Do you think DM could do it with no intelligence? . . I DO NOT FOLLOW MANY OF THESE NEWS GROUPS To answere me address mail to snipped-for-privacy@aol.com
I have 3 center-tapped transformers typically used to cause neon-filled bulbs to light up. with 110V AC at 60Hz (I'm in the U.S.) the voltage difference between the secondaries and the (assumed grounded) case is up to
7,500 volts and are 180 degrees out of phase with one another, yielding up to 15,000 volts.
The nameplate of the largest of these transformers claims 30mA max current, which is quite painful, but far from deadly.
15,000 volts can overcome a fairly significant amount of resistance, though. goes right through skin, will draw glowing arcs through almost 2 inches of cedar and will go right through the insulation of most hookup wire.
In dry air at approximately sea level, a spark will jump between electrodes connected to the secondary leads at any distance less than about 3/4 of an inch (assuming the absence of a more conductive path than air, to either ground or the opposite lead).
Once arc is drawn, the leads can then be moved apart to a fairly impressive distance (under extreme conditions i've gotten as much as 5 or 6 inches of arc) without interrupting the current flowing along a path of relatively conductive ionized (and hot) air.
If the electrodes are bent so as to be close enough for an arc to strike between them, and to draw slowly away from each other and upward until exceeding the maximum distance that arc will be maintained even through plasma, the result is a construction known as a Jacob's Ladder, in which an arc starts at the bottom and travels upward getting longer and more impressive as it does until it evaporates and immediately strikes again at the bottom.
rinse, repeat.
construction is simple... one neon light transformer + 2 coat-hangers
components are heavy, but the overall effect is impressive.
It WILL ignite any flammable anything, so if anyone tries this at home (i recommend it...) please, be aware of that, and have fire extinguishers at hand. also, it WILL shock you through some pretty startling conditions... definitely, do NOT LICK IT!!!
air movement will significantly affect the performance of the device. If you really want it to do a jacob's ladder kind of thing with the regular zzzot, zzzzot, zzzzzot of the mad scientist's laboratory instrument, it is best to enclose it in something nonconductive and transparent.
the UV generated by this device can be harmful to eyes, skin, etc. if looked at directly and too closely and ozone and nitrous oxide is produced, both of which are noxious, caustic, increases the flammability (is that a word?) of materials the gasses come into contact with, are (relatively) highly conductive and bad for the ozone layer.
it is also NOT a good example of electro-static discharge - like lightning - as there is a complete circuit (several) through which current properly flows, more-or-less continuously, as long as the device is functioning.
A tesla coil or a van de graff generator is more like what you are looking for. these guys
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build and conduct experiments with these sorts of devices, and do a fairly wide ranging show tour of some pretty amazing stuff (to paying audiences) to help fund their incredibly expensive private experiments.
They also sell a few little devices like what you are describing, if you want something over the counter-like, that are pretty impressive at the prices charged, if you ask me.
hope this helps.
DJ Bartlett Overlord Evil Genius Consulting, L.L.C. Oakland, California, USA
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