Describe how incandescent lamps emit light

Incandescent lamps are mainly composed of glass bulbs, filaments, wires, sensing columns, lamp caps, etc. The glass bulb is made into a spherical shape, and the material is heat-resistant glass, which isolates the filament from the air, which not only transmits light but also protects. When the incandescent lamp is working, the temperature of the glass bulb can reach up to about 100 ℃. The filament is made of tungsten wire, which is much thinner than human hair, in a spiral shape. It seems that the filament is very short, but in fact, this very thin spiral tungsten wire is drawn into a straight line, and the straight line is more than 1 meter long. The two wires of the wire are very simple on the surface, but actually consist of three parts: the inner wire, the Dumet wire and the outer wire. The inner wire is used to conduct electricity and fix the filament, and it is made of copper wire or nickel-plated iron wire; a very short red metal wire in the middle is called Dumet wire, which is required to be closely combined with the glass without leaking; the outer wire is copper wire, the task It is to connect the lamp head to power on. Sensing column A horn-shaped glass part is the sensing column, which is connected to the glass bulb and plays the role of fixing metal parts. The exhaust pipe is used to draw out the air in the glass bulb, and then the lower end is welded and sealed, so that the lamp will not leak air. The lamp holder is a metal piece that connects the lamp holder and the power supply, and is bonded to the glass bulb with welding mud. The filament is especially needed here, because it is by it that electric lamps emit light. Like carbon filaments, tungsten filaments in incandescent lamps are afraid of air. If the glass bulb is filled with air, after the power is turned on, the temperature of the tungsten wire will rise to more than 2000 ℃, and the air will attack it mercilessly, making it burn out quickly, and at the same time generate a yellow-white trioxide Tungsten, attached to the inner wall of the glass bulb and the inner parts of the lamp. If there is less air left in the glass bulb, the process described above will proceed slower, and tungsten combines with the oxygen in the air to form a thin layer of blue mixture of tungsten trioxide and tungsten oxide. Incandescent lamps These are all tricks of the air - the oxygen in the air oxidizes the hot tungsten filaments. Therefore, the tungsten bulb should be evacuated to remove all the air. Sometimes I am afraid that the exhauster will not be able to pump cleanly, so I even put a little red phosphorus on the sensor column of the bulb. Red phosphorus will become white phosphorus when heated, and white phosphorus can easily react with oxygen to form solid phosphorus pentoxide, which eats up the oxygen. In this way, the residual oxygen in the glass bulb is also eliminated. However, this has not solved all the problems. Incandescent bulbs will turn black over time and burn out after a while. Do you know why? Indeed, tungsten filaments evaporate much more slowly in a vacuum than carbon filaments. However, the evaporation of tungsten is still very serious when the temperature of the incandescent lamp is very high. The long-term high temperature causes the tungsten atoms on the surface of the tungsten wire to evaporate and diffuse continuously like water vapor, and then deposit layer by layer on the inner surface of the glass bulb, making the glass bulb gradually blacken and become more and more opaque. The evaporation of tungsten also makes the tungsten wire thinner and thinner, and finally burns out. The higher the operating temperature of the filament, the faster the evaporation of tungsten, and the shorter the life of the incandescent lamp. Company: Shanghai CHZ Changhui Lighting Technology Co., Ltd. Website: www.chz-lighting.com