An incandescent lamp ( also called incandescent light bulb, or incandescent light globe) is a lighting device, a source of artificial light, emitted from a wire heated by an electric current passing through it.
This type of lamp was created by A. Lodygin in 1872. It was a glass bulb filled with air, with two thick copper wires soldered and connected to each other through a charcoal stick. When current flows through the lamp, the carbon rod emits light for no more than half an hour and then burns. In 1875 Thomas Edison drew the air from the bulb and thus prolonged its life. Later, in 1890, A. Lodygin improved the light bulb by placing tungsten filament wire and filling the bulb with nitrogen. Incandescent lamps are divided into two basic types: with nitrogen and with halogen gas. The first ones are the well-known conventional lamps in all varieties, and the latter are halogen lamps, which have recently strengthened their position thanks to their advantages, such as longer life and 20-30 % energy efficiency.
In incandescent lamps we use the effect of heating a wire with high impedance (usually a tungsten alloy), when electrical current flows through it. To obtain visible emission of light, it is necessary to raise the temperature up to several thousand degrees.
Only a small part of the emitted light is visible to the human eye spectrum and the main part is infrared radiation. Part of the consumed energy is „wasted“ in the processes of heat and thermal conductivity. To increase the so-called „white“ light, it is necessary to increase the temperature of heating of the wire – that is why metals with a high melting point are used – in most cases tungsten (3410 ° C) and sometimes osmium (3045 ° C).
In air conditions at such temperature of heating the tungsten would become oxide (i.e. it would burn out), that is why the wire has to be protected in a glass bulb. The originally used bulbs were vacuumed, which caused evaporation of the metal, rapidly thinning filament and darkening of the glass of the bulb. Therefore, the bulbs began to be filled with a noble gas, usually argon. Vacuum bulbs are used nowadays, but only in lamps with low power.
Some types of incandescent lamps
Lamp sockets E27 and E14
These lamps were until recently the only major source of artificial light. The light they emit has a color temperature of 2700K (warm white light), and if you need a colored light, the glass bulb can be painted in the required color. These lamps are used in wall lamps, chandeliers, ceiling light, reading lamps, etc. Reading lamps are often directed in order to concentrate the emitted light to the required area.
Assembly and disassembly are performed through a bulb-holder to the corresponding lamp (desk lamps, wall lamps, etc.). Most light fixtures have indications showing the maximum power of the lamp, which can be mounted to them. This is necessary because incandescent bulbs emit most of the consumed energy in the form of heat, and if you put a more powerful lamp, it would damage the structure of the luminaire.
These lamps are produced in two versions – with one or two legs. The filament is located along the entire length of the lamp. Linear lamps are mostly used for decoration as additional lighting. They are mounted through the two legs of the lamp.
Principle of operation of halogen incandescent lamps
Halogen lamp, also known as a tungsten halogen lamp or quartz iodine lamp is an incandescent bulb, which has a small amount of halogen such as iodine or bromine. The combination of the halogen gas and the tungsten filament leads to a halogen cyclic chemical reaction in which the evaporated tungsten is re-deposited on the filament, increasing its life and maintaining the cleanliness of the casing. Therefore, a halogen lamp, compared to a standard lamp filled with gas, can function at a higher temperature, with similar power and similar exploitation durability, producing light with higher illumination efficiency and color temperature. The small size of halogen lamps allows their use in compact optical systems for projectors and lighting.
Some types of halogen lamps.
Lamps with sockets E27 and E14
These lamps are substitutes for conventional incandescent lamps, exceeding them in energy efficiency, rated life and brightness. Since conventional incandescent lamps have been phased out, their halogen substitutes are successfully gaining ground on the market. They have completely identical parameters with standard incandescent lamps, but they have many advantages as well. Thanks to this identity it is not necessary to transform the luminaire when the conventional lamp is replaced with its analogous halogen lamp.
Lamps with sockets G4, G9 and G6.35 halogen ampoules
These lamps are used mainly for suspended ceilings as downlights for basic or additional lighting. Halogen ampoules with G4 sockets are mostly 12 V (there are other voltages as well, but they are for special or medical purposes). Lamps with G9 sockets are only 220 VAC, and lamps with G6.35 sockets can be 12 and 220 VAC. As they are halogen and reach high temperature during operation, it is required not to touch them with hands during their mounting, but to place them with the help of nylon or paper, so that there is no direct contact with the skin. The contact of the skin with the bulb would lead to leaving greasy fingerprints on the lamp, which in turn would considerably shorten its life.
Lamps with sockets G4, GU10 and G6.35 with downlight reflector
These lamps are used mainly for suspended ceilings as downlights for basic or additional lighting. Lamps with G4 sockets are mostly 12 V (there are other voltages as well, but they are for special or medical purposes). Lamps with GU10 sockets are only 220 VAC, and lamps with G6.35 sockets can be 12 and 220 VAC. They emit directed light at about 120 °, and are suitable for the illumination of sites.
Halogen PAR lamps
These lamps are used mainly for directed illumination of sites. They have different sockets, supply voltage and colors. They are suitable for directed garden lighting, for illuminating statues, trees, etc.
These lamps are very popular due to their application as lighting of indoor and outdoor spaces such as warehouses, playgrounds, walkways, gardens, and parks. The illumination they provide is weaker than that of metal halogen lamps, but their price is much lower. Like all halogen lamps, they should not be touched without a protective film or paper.