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DISPONIBILI
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ARTICLES IN THE BOOK

  1. AAAA battery
  2. AAA battery
  3. AA battery
  4. A battery
  5. Absorbent glass mat
  6. Alessandro Volta
  7. Alkaline battery
  8. Alkaline fuel cell
  9. Aluminium battery
  10. Ampere
  11. Atomic battery
  12. Backup battery
  13. Baghdad Battery
  14. Batteries
  15. Battery charger
  16. B battery
  17. Bernard S. Baker
  18. Beta-alumina solid electrolyte
  19. Betavoltaics
  20. Bio-nano generator
  21. Blue energy
  22. Bunsen cell
  23. Car battery
  24. C battery
  25. Clark cell
  26. Concentration cell
  27. Coulomb
  28. 2CR5
  29. Daniell cell
  30. Direct borohydride fuel cell
  31. Direct-ethanol fuel cell
  32. Direct methanol fuel cell
  33. Dry cell
  34. Dry pile
  35. Duracell
  36. Duracell Bunny
  37. Earth battery
  38. Electric charge
  39. Electric current
  40. Electricity
  41. Electrochemical cell
  42. Electrochemical potential
  43. Electro-galvanic fuel cell
  44. Electrolysis
  45. Electrolyte
  46. Electrolytic cell
  47. Electromagnetism
  48. Electromotive force
  49. Energizer Bunny
  50. Energy
  51. Energy density
  52. Energy storage
  53. Flashlight
  54. Float charging
  55. Flow Battery
  56. Formic acid fuel cell
  57. Fuel cell
  58. Fuel cell bus trial
  59. Galvanic cell
  60. Gel battery
  61. Grove cell
  62. Half cell
  63. History of the battery
  64. Hybrid vehicle
  65. Lead-acid battery
  66. Leclanché cell
  67. Lemon battery
  68. List of battery sizes
  69. List of battery types
  70. List of fuel cell vehicles
  71. Lithium battery
  72. Lithium ion batteries
  73. Lithium iron phosphate battery
  74. Lithium polymer cell
  75. LR44 battery
  76. Luigi Galvani
  77. Manganese dioxide
  78. Memory effect
  79. Mercury battery
  80. Metal hydride fuel cell
  81. Methane reformer
  82. Methanol reformer
  83. Michael Faraday
  84. Microbial fuel cell
  85. Molten carbonate fuel cell
  86. Molten salt battery
  87. Nickel-cadmium battery
  88. Nickel-iron battery
  89. Nickel metal hydride
  90. Nickel-zinc battery
  91. Open-circuit voltage
  92. Optoelectric nuclear battery
  93. Organic radical battery
  94. Oxyride battery
  95. Panasonic EV Energy Co
  96. Peukert's law
  97. Phosphoric acid fuel cell
  98. Photoelectrochemical cell
  99. Polymer-based battery
  100. Power density
  101. Power management
  102. Power outage
  103. PP3 battery
  104. Primary cell
  105. Prius
  106. Proton exchange membrane
  107. Proton exchange membrane fuel cell
  108. Protonic ceramic fuel cell
  109. Radioisotope piezoelectric generator
  110. Ragone chart
  111. RCR-V3
  112. Rechargeable alkaline battery
  113. Reverse charging
  114. Reversible fuel cell
  115. Searchlight
  116. Secondary cell
  117. Short circuit
  118. Silver-oxide battery
  119. Smart Battery Data
  120. Smart battery system
  121. Sodium-sulfur battery
  122. Solid oxide fuel cell
  123. Super iron battery
  124. Thermionic converter
  125. Trickle charging
  126. Vanadium redox battery
  127. Volt
  128. Voltage
  129. Voltaic pile
  130. Watch battery
  131. Water-activated battery
  132. Weston cell
  133. Wet cell
  134. Zinc-air battery
  135. Zinc-bromine flow battery
  136. Zinc-carbon battery
 



BATTERIES
This article is from:
http://en.wikipedia.org/wiki/Flashlight

All text is available under the terms of the GNU Free Documentation License: http://en.wikipedia.org/wiki/Wikipedia:Text_of_the_GNU_Free_Documentation_License 

Flashlight

From Wikipedia, the free encyclopedia

 
A high power torch
A high power torch
Green flashlight
Green flashlight
" Flashlight" is also the NATO designation for the Yakovlev Yak-25 Soviet military jet.

A flashlight or torch is a hand-held portable electric spotlight. It is known as a flashlight mainly in the United States and Canada and as a torch or electric torch in most Commonwealth countries.

History

Main article: History of the flashlight
An 1899 Eveready flashlight, one of the earliest flashlight models.
An 1899 Eveready flashlight, one of the earliest flashlight models.

In 1896, Joshua Lionel Cowen invented a decorative lighting fixture for potted plants which consisted of a metal tube housing a light bulb and a dry cell battery. It failed commercially, and so Cowen sold his company and patents to Conrad Hubert that same year and turned his attention to building and selling model trains. Hubert renamed Cowen's company the American Electrical Novelty & Manufacturing Company and, recognizing the true potential of Cowen's invention, hired David Misell to produce a tubular flashlight for portable use. They donated some models to the New York City police, who responded favorably to it.[1] These early flashlights ran on zinc-carbon batteries, which were poor at providing sustained currents; they would run down after a while and needed to rest before being useable again.[2] Since these early flashlights also used energy-inefficient carbon filament bulbs, this happened rather quickly, and consequently they could only be used in brief flashes (hence their name).

General information

A typical flashlight consists of a small incandescent lightbulb with associated parabolic reflector, powered by electric batteries, and with an electric power switch. The components are mounted in a housing that contains the necessary electric circuit and provides ease of handling, a means of access to the batteries for replacement, and a clear covering over the lightbulb for its protection.

Although a relatively simple device, its invention did not occur until the late 19th century because it depended upon the earlier invention of the electric battery and incandescent light bulb.

LED flashlights

Electronically regulated, variable output LED flashlight
Electronically regulated, variable output LED flashlight

Recently, flashlights which use light-emitting diodes (LEDs) instead of conventional lightbulbs have become available. LEDs have existed for decades, mainly as low-power indicator lights. In 1999, Lumileds Corporation of San Jose, CA, introduced the Luxeon LED, a high-power white-light emitter. For the first time this made possible LED flashlights with power and running time better than some incandescent lights. The first Luxeon LED flashlight was the Arc LS in 2001.

LEDs can be significantly more efficient at lower power levels, hence use less battery energy than normal lightbulbs. Such flashlights have longer battery lifetimes, in some cases hundreds of hours, although the LED efficiency advantage diminishes at higher power levels. LEDs also survive sharp blows that often break conventional lightbulbs.

LED flashlights are often electronically regulated to maintain constant light output as the batteries fade. By contrast a non-regulated flashlight becomes progressively dimmer, sometimes spending much of the total running time below 50 percent brightness level.

A common misconception about LED-based flashlights is that they generate no heat. While lower-power LED flashlights generate little heat, more powerful LED lights do generate significant amounts of heat – although not as radiant energy – as the semiconductor junction inherently dissipates heat. For this reason higher-powered LED flashlights usually have aluminum bodies and can become quite warm during use. The use of aluminum is largely due to its thermal properties, acting as a heatsink for the high-power LED. Very few high-output LED flashlights use a plastic body due to plastic being a thermal insulator rather than a conductor.

Other flashlight designs

A headlamp is a flashlight worn on the head for hands-free operation. Powerful headlamps mounted on helmets have been used in mining for decades, but general-purpose ones with fabric straps are now also available.

Sometimes a light is mounted to a handgun or rifle.[3][4] See also Streamlight and Surefire.

Most flashlights are cylindrical in design, with the lamp assembly attached to one end. However, early designs came in a variety of shapes. Many resembled lanterns of the day, consisting largely of a box with a handle and the lamp attached to the front. Some others were made to have a similar appearance to candles. It is possible that future developments of battery and LED technology will bring interesting new designs. For instance, one very small light consists of a few LEDs with a switch, designed to be an endcap for a 9-volt battery.

High-quality flashlights go for as much as several hundreds of dollars. Such flashlights are very advanced, using special batteries, have adjustable brightness levels, dive-depth waterproof ratings, interchangeable optics, and are very bright.

Other power sources

Dynamo light
Dynamo light

Since batteries can be a burdensome cost in developed countries, let alone in the third world, the development of self-powered flashlights is a welcome advance. Some use solar panels to recharge their batteries during the day.

Mechanical power

Main article: Mechanically powered flashlight

Some flashlights have an electrical generator built into them. Dynamo-powered flashlights have a winding crank connected to a stepper motor that feeds several diode bridges with their outputs connected in parallel feeding a field effect transistor that charges a capacitor that connects to one or more LEDs. Others generate electricity using electromagnetic induction. They use a strong permanent magnet that can freely slide up and down a tube, passing through a coil of wire as it does. Shaking the flashlight will charge a capacitor or a rechargeable battery that supplies a current to a light source, typically a light-emitting diode or, more rarely, an incandescent light bulb.

Gallery

References

  1. ^ Steve Hathcock. Give Me a Light. Island Breeze. Retrieved on 2007-02-05.
  2. ^ Brooke Schumm. Nonrechargeable Batteries. The Electrochemistry Encyclopedia. Retrieved on 2007-02-05.
  3. ^ http://www.handgunsmag.com/tactics_training/lights_072804/
  4. ^ http://www.policeone.com/writers/columnists/JohnMeyer/articles/98209/

See also

Wikimedia Commons has media related to:
Flashlight
  • Dyno torch
  • Maglite
  • Penlight
  • Surefire
  • Streamlight
  • Arc Flashlight
  • Philips Lumileds Lighting Company

External links

  • http://www.flashlightmuseum.com/ — flashlight Museum
  • http://www.ledmuseum.org/ — review website for lights
  • http://www.flashlightreviews.com/ — review website for lights
  • http://www.flashlightnews.org/ — flashlight industry news
Retrieved from "http://en.wikipedia.org/wiki/Flashlight"

 


 

 
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