Why Do All Kinds Of Electric Light Sources Work In A Vacuum

- May 27, 2020-

Why do all kinds of electric light sources work in a vacuum

A vacuum is not a space where there is no air at all, but a space where the pressure is lower than the ambient (atmospheric) pressure. Vacuum pumps are now used to obtain a vacuum at pressures ranging from less than 760 to 10-3 liters (1 liter is equal to 1 millimeter of mercury, and 1 atmosphere is 760 liters).
Even at 10-3 liters of ultra-high vacuum, there are 3,480 gas molecules per cubic centimeter (2.7 x 1,019 gas molecules per cubic centimeter at atmospheric pressure).
The pressure in a vacuum is very low, and there is a pressure difference between it and the atmosphere. With the decrease of pressure (10-3 to below), the number of gas molecules decreases, and the heat conduction and convection capacity of air decreases obviously, thus effectively preventing the heat transfer.

In a high vacuum (pressure below 10-4 torr), the gas is quite thin and clean, and the air molecules are not strong enough to react with any luminescent and hot materials (including active metals). In such a space, gas molecules, electrons and ions can fly freely and rarely collide with each other.
In vacuum, the filament of an incandescent lamp will not be oxidized and burned by high temperature. Neon lights, filled with tiny amounts of different gases, can emit colorful light. The picture tube will not be distorted due to the collision and deflection of the electron beam and other particles.

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