Plasma lamp
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Plasma lamps (also variously plasma globes, balls, domes, spheres, or orbs) are novelty items which were most popular in the 1980s. The plasma lamp was invented by Nikola Tesla after his experimentation with high frequency currents in an evacuated glass tube for the purpose of studying high voltage phenomena. Tesla called this invention an inert gas discharge tube.
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[edit] Description
Most commonly, Plasma lamps are available in spheres and cylinders. Although there are many variations, a plasma lamp is usually a clear glass orb, filled with a mixture of various gases at low pressure, and driven by high frequency alternating current at high voltage (approx. 35 kHz, 2–5 kV), generated by a high voltage transformer. A much smaller orb in its center serves as an electrode. Plasma filaments extend from the inner electrode to the outer glass insulator, giving the appearance of multiple constant beams of colored light (see corona discharge and electric glow discharge). The beams initially follow the electric field lines of the dipole, but move upwards due to convection.[citation needed]
Placing a hand near the glass alters the high-frequency electric field[citation needed], causing a single beam to migrate from the inner ball to the point of contact. An electric current is produced within any conductive object near the orb, as the glass does not block the electromagnetic field created by the electric current flowing through the plasma (though the insulator does block the current itself).[citation needed] The glass acts as a dielectric in a capacitor formed between the ionized gas and the hand.
[edit] Potential hazards
One should be careful when placing electronic devices (such as computer mice) near or upon the plasma lamp: not only may the glass become hot, but the high voltage may place a substantial static charge on the device, even through a protective plastic casing. The radio frequency field produced by plasma lamps can interfere with the operation of touch pads used on laptop computers, digital audio players, and other similar devices. Some types can radiate sufficient RFI to interfere with telephones several feet away. If the phone uses tone dialing, then the RFI can add digits to the number being dialed, effectively preventing dialing.[citation needed] Additionally, when a metal object (such as a coin) or Play-Doh is placed on the surface of a plasma lamp's glass, a danger of shock and burning exists; it is very easy for electricity to be emitted from the lamp if the metal comes in contact or proximity with certain other materials, including human tissue. If a medium-sized lamp is wrapped in grounded metal foil, capacitive coupling can transfer tens of milliamperes to ground through the foil: enough to light a small lamp or give a small arc burn. This is possible because the glass acts as a capacitor dielectric; the inside of the lamp acts as one plate, and any conductive object on the outside acts as the other capacitor plate.
In addition, it is possible (although difficult) to cause a minor burn to the finger by hovering the fingertip just above the surface of the glass. This causes a small arc to form and generate heat by simultaneously "optimising" both the voltage across the gap and the current through it.
Ozone, which is harmful to humans, may also accumulate far outside of the surface of the glass orb after a few minutes of constant operation. It accumulates at an accelerated rate if a hand or metal object is placed on the glass.
[edit] History
In U.S. Patent 0,514,170 ("Incandescent Electric Light" , 1894 February 6), Nikola Tesla describes a plasma lamp. This patent is for one of the first high intensity discharge lamps. Tesla took an incandescent type lamp globe with the suspended conductive element and excited the element with high voltage currents from a Tesla coil, thus creating the brush discharge emanation. He gains patent protection on the particular forms of the lamp in which a light giving small body or button of refractory material is supported by a conductor entering a very highly exhausted globe or receiver. Tesla later called this invention an "Inert Gas Discharge Tube".
The popular product sold throughout the world today was invented by Bill Parker, while an undergraduate student at MIT in 1970.
The technology needed to formulate gas mixtures used in today's plasma spheres, primarily combinations of high purity rare gases, was not available to Tesla. These gas mixtures, glass shapes and integrated circuit driven electronics used to create the vivid colors, range of motions and complex patterns seen in today's plasma spheres were all developed and patented by Bill Parker in the 1980s and 1990s. The lamps typically contain xenon, krypton and/or neon, though a number of other gases can be used as well.
[edit] Applications
Plasma lamps are mainly used as curiosities or toys for their unique lighting effects and the 'tricks' that can be performed on them by moving the hands around them. They might also form part of a schools laboratory equipment for demonstration purposes. They are not usually employed for general lighting. However as of recent years the novelty store Spencer's Gifts began selling a night light plasma lamp that can fit into any standard light socket.
[edit] Uses in popular culture
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Plasma balls and their variations have been employed as props and sources for special effects for science fiction television shows.
Among the first appearances was the pilot for the Greatest American Hero (March 1981), where two plasma balls appeared in the sky as a prelude to the arrival of an alien spaceship, the plasma balls reappeared in subsequent episodes featuring contact with the craft.
A ball featured in the opening credits of The Man with Two Brains (1983).
A plasma ball's light output, with the glass envelope filtered out was used to depict the alien Chocky in the 1984 British science fiction series of the same name.
In March 1985, a plasma ball was featured as the aliens' "Doomsday Weapon" on the TV sci-fi series V: The Series episode "War of Illusions".
A plasma ball or "gizmo" was part of the primary plot as the time and space-warping engine of an alien spacecraft in the science fiction movie My Science Project released in August 1985.
The Matthew Broderick movie Ferris Bueller's Day Off (1986) featured a plasma ball in Cameron's (played by Alan Ruck) bedroom early in the movie.
In the science-fiction TV show, Primeval, a minor character uses a plasma lamp in his room to fight off a Gorgonopsid
In one episode of the show Newhart, Larry, Darryl, and Darryl become rich. "Darryl" buys a plasma ball and spends most of the episode staring into it.
In the UK, the late Kenny Everett, had a plasma ball in front of him when he presented Brainstorm, a television science quiz programme for the BBC. The programme was not particularly successful and did not last more than one season.
In at least one Doctor Who episode, a plasma ball was used as a "time controller" for a group of Daleks (Remembrance of the Daleks).
A plasma lamp exhibit was a feature at World Expo '88, where a range of commercial units were available at a cost of many thousands of dollars. Just a few years later, novelty shops began selling significantly cheaper and more portable units.
Commercially available units (lightning plates) are prominently depicted as part of Borg technology in the series Star Trek: Voyager. A plasma lamp was used as a part of the engine of the USS Dauntless in the Voyager episode "Hope and Fear".
Plasma balls feature in the opening sequences of The X-Files.
The Futurama episode Insane in the Mainframe features a robot with a plasma lamp for a head.
On the popular ESPN sports talk show Pardon the Interruption, a plasma lamp is used as a crystal ball by host Tony Kornheiser during the PTI Psychic Hotline segment.
In the 2005 film Boogeyman, Tim Jensen, the main protagonist, had a plasma ball in his room when he was a kid, and it was one of the things that sparked his fear that went into the Boogeyman.
In the 1993 season of the popular Japanese children's Super Sentai series "Gosei Sentai Dairanger", plasma balls were used as "Chi Power Conductors" to help activate and control "Ryuu-Sei-Oh". Each ranger placed one hand upon their respective plasma ball and thus activated the conductant.
[edit] See also
[edit] External links
- POWERLABS.org — Plasma Globes
- Science Hobbyist: Plasma globes without glass or vacuum
- See a plasma lamp in action ! (Videos and pictures)
- Detailed plan to building your own plasma globe
- A gallery of photographs featuring extremely large plasma globes and museum displays
- PLASMA ART
- YouTube video showing a plasma lamp with added special effects
- YouTube video showing an extremely large and slow-moving plasma ball
- YouTube video showing a very fast-moving plasma effect inside a 2 foot wide globe.
- Scott Bogard's Plasma Globe webpage.
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