Vacuum Technology
. Vacuum Technology, in physics and engineering, processes and equipment based on the principle that, when the quantity of oppressive gas such as air in a closed vessel is removed, the remaining molecules, atoms, or any electrically charged particles that are derived from them, such as ions and electrons, can move about more freely (see Vacuum ). This freedom is proportional to the reduction in the gas pressure. See Atom ; Electron ; Ion ; Molecule ; Pressure . Low and medium vacuums have been commonly used in such household equipment as vacuum bottles and vacuum cleaners since the late 19th century. The distillation of lubricating oils from petroleum residues and the removal of atmospheric oxygen from electric light bulbs also employ vacuum technology. Before World War II, however, high-vacuum techniques, achieving near-complete vacuum conditions, were mainly used in research laboratories, the one exception being radio-tube production (see Vacuum Tubes ). During the war, techniques