Plasma globe: Difference between revisions
Snafflekid (talk | contribs) →Description: fact check of citation needed |
|||
| Line 11: | Line 11: | ||
Most commonly, plasma globes are available in spheres or cylinders. Although many variations exist, a plasma lamp is usually a clear glass orb filled with a mixture of various gases—most commonly [[helium]] and [[neon]], but sometimes also [[xenon]] and [[krypton]]—at low pressure (below 0.01 atmosphere)<ref>{{cite web |url=http://www.powerlabs.org/plasmaglobes.htm#%C2%A0PRINCIPLE%20OF%20OPERATION: |title=PowerLabs Plasma Globes Page |first=Sam |last=Barros |year=2002 |accessdate=Nov. 16, 2009 |section=Principle of operation}}</ref> and driven by high-frequency [[alternating current]] at approximately 35 [[hertz|kHz]], 2–5 [[volt|kV]], generated by a high-voltage [[transformer]]. A much smaller orb in its center serves as an [[electrode]]. [[Plasma (physics)|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|date=February 2008}} |
Most commonly, plasma globes are available in spheres or cylinders. Although many variations exist, a plasma lamp is usually a clear glass orb filled with a mixture of various gases—most commonly [[helium]] and [[neon]], but sometimes also [[xenon]] and [[krypton]]—at low pressure (below 0.01 atmosphere)<ref>{{cite web |url=http://www.powerlabs.org/plasmaglobes.htm#%C2%A0PRINCIPLE%20OF%20OPERATION: |title=PowerLabs Plasma Globes Page |first=Sam |last=Barros |year=2002 |accessdate=Nov. 16, 2009 |section=Principle of operation}}</ref> and driven by high-frequency [[alternating current]] at approximately 35 [[hertz|kHz]], 2–5 [[volt|kV]], generated by a high-voltage [[transformer]]. A much smaller orb in its center serves as an [[electrode]]. [[Plasma (physics)|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|date=February 2008}} |
||
Placing a hand near the glass alters the high-frequency [[electric field]], causing a single beam to migrate from the inner ball to the point of contact.{{Citation needed|date=February 2008}} |
Placing a hand near the glass alters the high-frequency [[electric field]], causing a single beam to migrate from the inner ball to the point of contact.{{Citation needed|date=February 2008}} A small 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. The glass acts as a [[dielectric]] in a [[capacitor]] formed between the ionized gas and the hand. |
||
==Potential hazards== |
==Potential hazards== |
||
Revision as of 06:42, 16 February 2010
 | This article needs additional citations for verification. (October 2006) |
Plasma globes, or plasma lamps (also called plasma balls, domes, spheres, tubes or orbs, depending on shape), are novelty items that 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, but the modern versions were first designed by Bill Parker.[1] Tesla called this invention an inert gas discharge tube[citation needed].
Description
Most commonly, plasma globes are available in spheres or cylinders. Although many variations exist, a plasma lamp is usually a clear glass orb filled with a mixture of various gases—most commonly helium and neon, but sometimes also xenon and krypton—at low pressure (below 0.01 atmosphere)[2] and driven by high-frequency alternating current at approximately 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, causing a single beam to migrate from the inner ball to the point of contact.[citation needed] A small 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. The glass acts as a dielectric in a capacitor formed between the ionized gas and the hand.
Potential hazards
Caution should be made when placing electronic devices 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 touchpads used on laptop computers, digital audio players, cell phones, and other similar devices. Some types can radiate sufficient RFI to interfere with cordless telephones and Wi-Fi devices several feet away. Additionally, when a metal object (such as a coin) 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.[citation needed] If the orb becomes wet or is covered in a metallic substance, such as a coin or tinfoil, arc burning becomes much less difficult.
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 a higher rate if a hand or metal object is placed on the glass.
Since the plasma ball also releases electromagnetic radiation, a person with a pacemaker or other internal electrical medical device should not touch the ball. In extremely rare instances, electromagnetic radiation interferes with implanted electronic devices.[citation needed]
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 used an incandescent-type lamp globe with a single internal conductive element and excited the element with high voltage currents from a Tesla coil, thus creating the brush discharge emanation. He gained patent protection on a particular form 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 called this invention the single terminal lamp, or, later, the "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.
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 school's laboratory equipment for demonstration purposes. They are not usually employed for general lighting. However, as of recent years, some novelty stores have begun selling a nightlight plasma lamp that can fit into any standard light socket.
See also
References
- ^ Gache, Gabriel (January 31, 2008). "How do plasma lamps work?". Softpedia. Retrieved Nov. 16, 2009.
{{cite web}}: Check date values in:|accessdate=(help) - ^ Barros, Sam (2002). "PowerLabs Plasma Globes Page". Retrieved Nov. 16, 2009.
{{cite web}}:|section=ignored (help); Check date values in:|accessdate=(help)