Light Bulbs

tufailIncandescent lamps are often considered the least energy efficient type of electric lighting commonly found in residential buildings. Although inefficient, incandescent lamps possess a number of key advantages–they are inexpensive to buy, turn on instantly, are available in a huge array of sizes and shapes and provide a pleasant, warm light with excellent color rendition.
However, because of their relative inefficiency and short life spans, they are more expensive to operate than newer lighting types such as compact fluorescent lamps (CFLs) and light-emitting diodes (LEDs).
Types of Incandescent Lamps
There are three common types of incandescent lamps (called A-line lamps) used in residential applications:
•    Standard incandescent or pear-shaped A-19 lamps
•    Energy-saving or halogen A-19 lamps
•    Reflector or parabolic reflector (PAR) lamps, sometimes called “flood” or “spot” lamps
Standard Incandescent A-Line Lamps
Commonly known as the screw-in “A”-type lamp that use a medium Edison (E-26) base, standard incandescent bulbs are the least efficient light source commonly found in homes. These lamps produce visible light by heating a tiny coil or filament of tungsten wire that glows when it is heated by an electrical current.
“Long-life” lamps are an example of lamps with thicker, stronger filaments that can last much longer than a standard service lamp, but they are less energy efficient.
New efficiency standards for lighting require lamps to use about 25% less energy. These standards began taking effect starting in January 2012 and the phase-in will be complete as of January 1, 2014, after which time traditional incandescent general service lamps such as the common A-19 will not be available in most stores. Learn more about the new lighting standards.
Energy-Saving Incandescent (or Halogen) Lightbulbs
A halogen lamp is a type of incandescent lamp with a capsule that holds a special halogen gas composition around the heated filament to increase the efficacy of the incandescence. They are more energy efficient than standard incandescent bulbs but somewhat more costly. Halogen lamps may also have a special inner coating that reflects heat back into the capsule to further improve efficacy by “recycling” the otherwise wasted heat. Together, the filling and coating recycle heat to keep the filament hot with less electricity. They also provide excellent color rendition.

Halogens are a little more expensive than standard incandescent lamps, but are less expensive to operate because of their higher efficacy and longer life expectancy. They are commonly used in reflector lamps such as indoor and outdoor flood or spot lighting, indoor recessed and track fixtures, and floor and desk lamps.
Some halogen bulbs are dimmable, as indicated on the package, and are compatible with timers and other lighting controls.
Reflector Lamps
Reflector bulbs (Type R) spread and direct light over specific areas. They are used mainly for floodlighting, spotlighting, and down lighting applications both indoor and outdoor.
There are two types of reflector lamps:
•    Parabolic aluminized reflector lamps (Type PAR) are used for a number of applications, including outdoor floodlighting.
•    Ellipsoidal reflector lamps (Type ER) focus light beams about 2 inches in front of its enclosure, projecting light down from recessed fixtures. Ellipsoidal reflectors are twice as energy efficient as parabolic reflectors for recessed fixtures.
The first incandescent electric light was made in 1800 by Humphry Davy, an English scientist. He experimented with electricity and invented an electric battery. When he connected wires to his battery and a piece of carbon, the carbon glowed, producing light. This is called an electric arc.
Much later, in 1860, the English physicist Sir Joseph Wilson Swan (1828-1914) was determined to devise a practical, long-lasting electric light. He found that a carbon paper filament worked well, but burned up quickly. In 1878, he demonstrated his new electric lamps in Newcastle, England.
The inventor Thomas Alva Edison (in the USA) experimented with thousands of different filaments to find just the right materials to glow well and be long-lasting. In 1879, Edison discovered that a carbon filament in an oxygen-free bulb glowed but did not burn up for 40 hours. Edison eventually produced a bulb that could glow for over 1500 hours.
Lewis Howard Latimer (1848-1928) improved the light bulb by inventing a carbon filament (patented in 1881); Latimer was a member of Edison’s research team, which was called “Edison’s Pioneers.” In 1882, Latimer developed and patented a method of manufacturing his carbon filaments.
In 1903, Willis R. Whitney invented a treatment for the filament so that it wouldn’t darken the inside of the bulb as it glowed. In 1910, William David Coolidge (1873-1975) invented a tungsten filament which lasted even longer than the older filaments. The incandescent bulb revolutionized the world.


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