DICT.TW Dictionary Taiwan
Vac·u·um n.; pl. E. Vacuums L. Vacua
1. Physics A space entirely devoid of matter (called also, by way of distinction, absolute vacuum); hence, in a more general sense, a space, as the interior of a closed vessel, which has been exhausted to a high or the highest degree by an air pump or other artificial means; as, water boils at a reduced temperature in a vacuum.
2. The condition of rarefaction, or reduction of pressure below that of the atmosphere, in a vessel, as the condenser of a steam engine, which is nearly exhausted of air or steam, etc.; as, a vacuum of 26 inches of mercury, or 13 pounds per square inch.
Vacuum brake, a kind of continuous brake operated by exhausting the air from some appliance under each car, and so causing the pressure of the atmosphere to apply the brakes.
Vacuum pan Technol., a kind of large closed metallic retort used in sugar making for boiling down sirup. It is so connected with an exhausting apparatus that a partial vacuum is formed within. This allows the evaporation and concentration to take place at a lower atmospheric pressure and hence also at a lower temperature, which largely obviates the danger of burning the sugar, and shortens the process.
Vacuum pump. Same as Pulsometer, 1.
Vacuum tube Phys., (a) a glass tube provided with platinum electrodes and exhausted, for the passage of the electrical discharge; a Geissler tube. (a) any tube used in electronic devices, containing a vacuum and used to control the flow of electrons in a circuit, as a vacuum diode, triode, tetrode, or pentode.
Vacuum valve, a safety valve opening inward to admit air to a vessel in which the pressure is less than that of the atmosphere, in order to prevent collapse.
Torricellian vacuum. See under Torricellian.
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vacuum
n 1: the absence of matter [syn: vacuity]
2: an empty area or space; "the huge desert voids"; "the
emptiness of outer space"; "without their support he'll be
ruling in a vacuum" [syn: void, vacancy, emptiness]
3: a region empty of matter [syn: vacuity]
4: an electrical home appliance that cleans by suction [syn: vacuum
cleaner]
v : clean with a vacuum cleaner; "vacuum the carpets" [syn: vacuum-clean,
hoover]
[also: vacua (pl)]