The incandescent lamp blackens after being used for a long time because the tungsten wire sublimates and evaporates. It needs to be replaced as soon as possible.
It is a common phenomenon that incandescent lamps will blacken after being used for a long time. The blackening of incandescent lamps not only affects lighting, but also makes people worry about its safety.
In the incandescent lamp, the tungsten filament is lit. The tungsten filament can be kept stable at a very high temperature without melting, but it can be directly sublimated into gas. When the lamp is turned off, the temperature drops, and the tungsten gas is again sublimated into a solid and covered on the inner wall of the bulb. Because tungsten is a black solid, after the incandescent lamp has been used for a long time, tungsten accumulates repeatedly on the inner wall of the lamp, and the bulb will become black.
Incandescent lamps have a life span. Generally, after blackening, the life span will not be long. Black bulbs will affect the lighting quality and are not beautiful. Therefore, it is better to replace the blackened bulbs that have been used for too long. Especially in prominent positions, where good lighting is needed, they should be replaced as soon as possible to avoid the bulb suddenly breaking down without a spare bulb, which will affect the normal lighting and life, Causes various inconveniences.
The life of an incandescent lamp is related to the temperature of the filament, because the higher the temperature is, the easier the filament will sublimate (tungsten will directly become tungsten gas). When the tungsten filament sublimates to a relatively thin size, it is easy to burn off after being powered on, thus ending the life of the lamp. Therefore, the greater the power (wattage) of the incandescent lamp, the shorter the life.