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Why Is The Bulb In A Vacuum Bright?
May 14, 2018

The structure of the bulb is very simple. There are two metal contacts at the bottom, which are used to connect electricity. Metal contact points have two wires touching a thin metal filament. The filament is located in the center of the bulb and is supported by a glass. The wires and filament are wrapped in a glass bulb filled with inert gas, usually argon inert gas when the bulb is connected to the bulb, and the current flows from one point of contact to another point and then flow to the wire and filament. A large number of free electrons in the solid conductor line move from the negative charged region to the positive charged region. The hopping electrons in vibrational atoms may temporarily be pushed to a higher energy position.

When they fall back to the original normal position, electrons will release extra energy in the form of photons. Metal atoms release most of the infrared visible photons, and people's eyes are visible. But if they are heated to about 4000 Fahrenheit, the bulb will emit a lot of visible light. Tungsten is used in almost all incandescent bulbs because it is the ideal filament material. Metals must be heated to a very high temperature before emitting useful visible light.

In fact, most metals melt before reaching this temperature, while tungsten wires have an unusual high melting temperature. But the tungsten wire fires at such a high temperature. If the condition is allowed, the two chemicals will produce a reaction between them and cause combustion. The filament in the bulb is covered with a sealed, oxygen free space to prevent combustion. The air in the bulb is sucked out to create a vacuum close to the vacuum - that is, there is no substance in it. Since there is hardly any special gas in it, the material will not burn. The problem with this method is the evaporation of tungsten atoms.

At such a high temperature, in a vacuum bulb, free tungsten atoms are emitted in a straight line. As more and more atoms evaporate, the filament begins to decay and the glass begins to darken. This greatly reduces the life of the bulb.