Why is the light on?
Times when all the light bulbslooked almost identical, already gone. If twenty years ago at the word "light bulb" any person immediately imagined a classical glass pear with a spiral inside, now the old kind light bulb has lost its former popularity, giving way to new, more economical and durable lamps. The whole modern range of electric lamps, depending on the principle of their operation, can be divided into three large groups:
- incandescent lamps;
- discharge lamps;
- LED lamp.
Why the incandescent lamp is on
In incandescent lamps, the light emits a conductor,heated by passing an electric current through it. After the electrical circuit is closed, the filament warms up to 3000 * C and begins to radiate energy in the visible part of the spectrum.
The construction of an incandescent lamp
The design of this light bulb is very simple. The lamp consists of:
- glass bulb;
As a material for making filamentin modern light bulbs use tungsten - a very refractory and relatively inexpensive metal. Of tungsten, the finest wire is made, which, in order to reduce the size of the filament, is wound into a spiral. Sometimes this spiral is twisted into a second-level spiral to increase the power of the lamp. Lamps in which such a double helix is installed are called bispiral.
The tungsten helix is fixed inside the flask by hooks - holders made of molybdenum. The ends of the helix are soldered to the electrodes, which are output to the lamp cap.
The glass bulb is sealed. Before sealing, air is completely evacuated from the flask. This is done in order to extend the life of the filament, since in air, tungsten is very rapidly oxidized, as a result of which the filament is destroyed and the lamp burns out. In low-power lamps, vacuum is created in the flasks, in more powerful lamps, the flask is filled with an inert gas (in cheap models a mixture of argon with nitrogen, in expensive models - with xenon or krypton). About the power consumption of electric lamps read in our article How much a light bulb consumes.
On the soldered end of the flask is attached a galvanized base with thread, soldered to the terminals of the electrodes, a ceramic insulation is applied to the tail of the cap.
The lamp is screwed into the cartridge, to which theelectricity. After the electricity is connected, the current will go through a tungsten spiral, the spiral will instantly warm up and the light will light up. Part of the energy consumed by the light bulb converts into visible by the human eye radiation, the other, most of it will dissipate in the form of heat.
Halogen lamps work on the same principle. The only difference from conventional incandescent lamps is that fluorine, chlorine, bromine or iodine halogens are added to the inert gas filling the flask, which partially regenerate the filament, thus prolonging the life of the lamp.
How Gas Discharge Lamps Work
Gas-discharge lamps work much more efficiently,than incandescent lamps. Their efficiency reaches thirty, and in some models, even forty percent, in contrast to the maximum ten percent inherent in incandescent lamps.
Discharge lamps are good for everyoneknown fluorescent lamps. The bulb of the fluorescent lamp is made in the form of a long, hermetically sealed glass tube filled with an inert gas and a small amount of mercury. In such a lamp, not a filament glows, but a thin layer of a powdery luminous substance-a phosphor deposited on the inner walls of a glass tube. The glow of the phosphor occurs as a result of continuous electrical discharges occurring in mercury vapor filling the flask.
Such popular nowadays energy-saving lamps are also among the gas-discharge fluorescent lamps, being their compact improved version.
In addition to energy-saving lamps, this large group includes neon lamps, mainly used in light advertising, and sodium lamps used for street lighting.
How LED Lamps Work
In LED lamps, the photon of light emitsa semiconductor crystal enclosed in a plastic protective flask simultaneously serving as a scattering lens. These are the newest and most promising lamps. Their only drawback for today is a rather high price. On the advantages of LED lamps, and how to choose a light bulb is written in the article How to choose a lamp.