Bell jar

Bell jar

Infobox Laboratory equipment
name = Bell Jar

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caption = Bell Jar Apparatus during low-pressure test
uses = Enclosing objects or containing gases or a vacuum

A bell jar is a piece of laboratory glassware similar in shape to a bell. A bell jar is placed on a base which is vented to a hose fitting, which can be connected via a hose to a vacuum pump. By pumping the air out of the bell jar, a vacuum is formed.

Bell jars are generally used for classroom demonstrations or by hobbyists, when only a relatively low-quality vacuum is required. Cutting-edge research that needs an ultra high vacuum requires a more sophisticated form of vacuum chamber.

An example classroom science experiment involving a bell jar is to place a ringing alarm clock under the bell jar. As the air is pumped out of the sealed bell jar, the noise of the alarm clock fades, thus demonstrating that the propagation of sound is mediated by the air. Deprived of its medium, the sound cannot travel.


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Look at other dictionaries:

  • Bell jar — Jar Jar (j[aum]r), n. [F. jarre, Sp. jarra, from Ar. jarrah ewer; cf. Pers. jarrah.] 1. A deep, broad mouthed vessel of earthenware or glass, for holding fruit, preserves, etc., or for ornamental purposes; as, a jar of honey; a rose jar. Dryden.… …   The Collaborative International Dictionary of English

  • Bell jar — (Phys.) A glass vessel, varying in size, open at the bottom and closed at the top like a bell, and having a knob or handle at the top for lifting it. It is used for a great variety of purposes; as, with the air pump, and for holding gases, also… …   The Collaborative International Dictionary of English

  • bell jar — bel .jär n a bell shaped usu. glass vessel designed to cover objects or to contain gases or a vacuum * * * a glass vessel, closed at top, open at bottom, used in laboratory vacuum experiments …   Medical dictionary

  • bell jar — n. a bell shaped container or cover made of glass, used to keep gases, air, moisture, etc. in or out: also bell glass …   English World dictionary

  • bell jar — bell′ jar n. chem. a bell shaped glass cover designed esp. for protecting objects or for containing gases or a vacuum in chemical experiments …   From formal English to slang

  • bell jar — noun a bell shaped glass cover used to protect and display delicate objects or to cover scientific apparatus or to contain gases • Syn: ↑bell glass • Hypernyms: ↑protective covering, ↑protective cover, ↑protection * * * noun : a bell shaped… …   Useful english dictionary

  • bell jar — UK / US noun [countable] Word forms bell jar : singular bell jar plural bell jars science a piece of equipment that is made of glass and shaped like a bell, used to surround other equipment during scientific experiments …   English dictionary

  • bell jar — a bell shaped glass jar or cover for protecting delicate instruments, bric a brac, or the like, or for containing gases or a vacuum in chemical experiments. Also called bell glass. [1875 80] * * * …   Universalium

  • bell jar — n. bell shaped glass jar or cover for displaying and protecting delicate objects; bell shaped glass container (closed at top and open at bottom) used in laboratories for keeping gases or vacuum under control during vacuum and chemical experiments …   English contemporary dictionary

  • bell jar — /ˈbɛl dʒa / (say bel jah) noun a bell shaped glass vessel or cover, as for protecting delicate instruments, bric a brac, etc., or for holding gases in chemical operations. Also, bell glass …  

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