Electric Lighting - Most countries today are lit by Electric Lights which we use both in day and night. Electric lights are mostly used during night time which enables our infrastructure to be well lit. Without electric lights, production would cease at night because humans are only capable of seeing well during the daytime. Some electric lights run from electric grid, some run on generators and others are battery operated. Portable battery powered lights are commonly available in the forum of flashlights or torches. They are designed for mobility and portability. There are also emergency lanterns which run on lead acid batteries; emergency lanterns have a step-up transform which increases the voltage of the battery up to several thousand volts. Electric lights operate on different principles, they come on various shapes and sizes, each light has their own unique electromagnetic spectrum ( Color ) and some electric lights are short lived while others can run continously up to several years.
Types of Electric Light
1. Incandescent light - The incandescent lamp was invented by Thomas Edison and it uses a filament that gives off light when it was heated by electric current. Edison originally used carbon filaments but today we use tungsten filaments. Incandescent lamps produces a yellowish-white light and it also gives off a lot of heat. The heat generated by incandescent lamp is considered a waste product that is why incandescent lamps are not very efficient in producing light. Environmentalist suggest the phasing out of incandescent light bulbs because there are more efficient light bulbs that can be used such as the CFL or Compact Flourescent Lamp.
2. Arc lamp - These are lamps that produce light coming from an electric arc. Electric arc light consists of two electrodes separated by a gas. The gas can be any of the following neon, argon, xenon, krypton, sodium, metal halide, and mercury. We can consider lightning as a "naturally occuring arc lamp" where high voltage ionizes and excites the air. The temperature of an arc light can reach several thousand degrees centigrade and one should be careful when servicing an arc lamp.The concept of arc lighting was demonstrated by Sir Humphry Davy in the early 19th century when created an arc using Charcoal sticks and a 2,000 cell battery.
3. Gas-Discharge lamp - The operating principle of gas-discharge lamp is similar to arc lights. Gas discharge lamps consists of a glass envelope which encloses two electrodes and a gas fill. The gas fill can be neon, argon, xenon, sodium, metal halide, and mercury. The most common gas discharge lamp that we can find at home is the Fluorescent lamp and the Sodium Vapor lamp. Gas discharge lamps typically use a ballast to limit the amount of current to safe levels, this ensures the longer operating life of the lamp.
4. Light Emitting Diodes - Light emitting diodes are made up of Gallium Arsenide, a semiconductor that gives of light whenever electric current pass through it. The main advantage of LED compared with other lighting is its very long life. Indicator LEDs can be operated for as long as 100,000 hours. LEDs does not generate high amounts of heat, does not consume high amounts of electricity and can be turned on/off instantaneously. Today, LEDs are not used in applications where you need 10 Watts or more. High power LEDs are still very expensive and is not cost effective.
5. Sulfur Lamp - The Sulphur lamp was invented by Michael Ury in 1986-1990, the reason for his interest in the sulfur lamp is that the spectral distribution of its energy is very closely to the spectral sensitivity of the human eye. Sulfur lamps do not have an electrode because Sulfur would attack any metal electode that was placed inside it. Power is applied to the lamp by using microwave energy coming from a Magnetron. The efficiency of Sulfur lamp is about 70 % .The spectral output peaks at 510nm, imparting a distinctly greenish hue to the illuminated environment The spectral output of Sulfur lamp peaks at 510nm which impartis a distinctly greenish hue to the illuminated environment.
