Views: 9 Author: Site Editor Publish Time: 2022-05-27 Origin: Site
The visible light emitted by the heating of the tungsten filament of a vacuum incandescent lamp is emitted when heated by resistance. The filament acts as a resistive electrical, applying times of current through the filament proportional to the power dissipated. Raising the power level beyond 1000 degrees Kelvin is sufficient to produce visible light. Due to the power loss and the increase in light, the amount of light at the peak wavelength shifts to blue. Typical vacuum filament temperatures range from 1800 to 2700 Kelvin. Low temperature lamps have a reddish-yellow appearance, while high temperature lamps have a white appearance.
The rate at which the tungsten filament evaporates increases as the temperature of the filament increases. Evaporated tungsten particles tend to deposit on the glass bulb, resulting in increased light absorption over time. Depending on the application, the light output obstruction may not be high enough, reducing the life of the bulb. Eventually the filament will evaporate and break, rendering the bulb useless. These all depend on the temperature of the filament, which is why vacuum lamps with long lifespans tend to operate at the low end of the temperature range and have a yellowish appearance.
The resistance of a tungsten wire at room temperature is quite low. When electricity is first applied to the lamp, large inrush currents can cause rapid heating of the filament. The resistance value of the filament increases five to ten times the cold resistance, resulting in a stable current flow and stable light output. Depending on the size of the wire, it can be from tens of milliseconds to hundreds of milliseconds during busy periods. This in busy current regulations should take into account the choice of power supply in a particular lamp application.
All in all, tungsten filament can increase the life of the bulb, in a vacuum environment, can prevent the oxidation of tungsten filament, reduce the thermal expansion of tungsten filament, improve the brightness of the bulb, and reduce power loss.
