History
The electric light bulb was invented in 1879 by the prolific American inventor Thomas Edison. There had been many attempts to produce a workable form of electric lighting over quite a period of years prior to that, with varying degrees of success, but Edison’s was the first practical and commercially viable light bulb.
The basic principle is the passing of an electric current through a thin filament of wire, which results in the wire glowing red hot, then white hot, the heat being the source of the light produced.
Oxidation of the metal of the filament is prevented by encasing it in an envelope of glass, usually in the shape of a flower bulb, hence the name light bulb. The glass excludes oxygen, which would be required for the oxidation process, otherwise the life of a filament would be very short indeed.
Apart from developments of the shape and composition of the metal of the filament, the basic design of the light remained unchanged for many years, the first main alternative being the fluorescent tube, which was used mainly in commercial applications in offices, shops and factories, with some limited household use, usually for kitchen lighting.
It is only relatively recently that we have seen major progress, first with the energy saving bulbs, otherwise known as compact fluorescent lamps, which was really only an electronic development of the flourescent tube, with the tube being produced in the form of a spiral, to keep it small enough to fit in standard household light fittings, table lamps, etc., and modern electronics being used to enhance the light output and most importantly, the smooth and fast startup of the lamp when it is switched on, which has really boosted sales and use of the energy saving bulbs over the past few years, fuelled by the latest thinking and concerns over energy economy and the possible effect of energy use on climate change.
The most recent development has been the use of light emitting diodes (LEDs). These have been around for quite a few years in electronic applications, particularly as warning lights on instrument panels, on/off lights for television sets and household appliances, etc.
However, development is progressing at a very fast pace and LEDs are now being used in car brake lights, indicators, etc and they are becoming very useful in home applications. With further development LEDs will be used in most areas where standard incandescent bulbs are used today and they will quickly also replace compact fluorescent lamps as they are so much more energy efficient even than the lamps we have been calling energy saving bulbs!