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Bell jar

 
Bell Jar

 
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Bell jar
 
 
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A bell jar is a piece of laboratory glassware
Laboratory glassware

Laboratory glassware refers to a variety of equipment, traditionally made of glass, used for scientific experiments and other work in science, especially in chemistry and biology laboratory....
 similar in shape to a bell
Bell (instrument)

A bell is a simple sound-making device. The bell is a percussion instrument and an idiophone. Its form is usually an open-ended hollow drum which resonates upon being struck....
. 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
Vacuum pump

A vacuum pump is a device that removes gas molecules from a sealed volume in order to leave behind a partial vacuum. The vacuum pump was invented in 1650 by Otto von Guericke....
. By pumping the air out of the bell jar, a vacuum
Vacuum

A vacuum is a volume of space that is essentially empty of matter, such that its gaseous pressure is much less than atmospheric pressure. The word comes from the Latin term for "empty," but in reality, no volume of space can ever be perfectly empty....
 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
Ultra high vacuum

Ultra high vacuum is the vacuum regime characterised by pressures lower than about 10-7 pascal or 100 nanopascals . UHV requires the use of special materials in creating the vacuum system, extreme cleanliness to maintain the vacuum system, and baking of the entire system to remove water and other trace gases that adsorb on the su...
 requires a more sophisticated form of vacuum chamber
Vacuum chamber

A vacuum chamber is a rigid enclosure from which air and other gases are removed by a vacuum pump. The resulting low pressure, commonly referred to as a vacuum, allows researchers to conduct physical experiments or to test mechanical devices which must operate in outer space ....
.

An example classroom science experiment
Experiment

In scientific inquiry, an experiment is a method of investigating causal relationships among variables. An experiment is a cornerstone of the empiricism approach to acquiring data about the world and is used in both natural sciences and social sciences....
 involving a bell jar is to place a ringing alarm clock
Alarm clock

File:Clock radio.jpgAn alarm clock is a clock that is designed to make a loud sound at a specific date and/or time. The primary use of these clocks is to Awake people from their sleep in order to start their days in the mornings, but they are sometimes used for other reminders as well....
 under the bell jar.






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Encyclopedia


A bell jar is a piece of laboratory glassware
Laboratory glassware

Laboratory glassware refers to a variety of equipment, traditionally made of glass, used for scientific experiments and other work in science, especially in chemistry and biology laboratory....
 similar in shape to a bell
Bell (instrument)

A bell is a simple sound-making device. The bell is a percussion instrument and an idiophone. Its form is usually an open-ended hollow drum which resonates upon being struck....
. 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
Vacuum pump

A vacuum pump is a device that removes gas molecules from a sealed volume in order to leave behind a partial vacuum. The vacuum pump was invented in 1650 by Otto von Guericke....
. By pumping the air out of the bell jar, a vacuum
Vacuum

A vacuum is a volume of space that is essentially empty of matter, such that its gaseous pressure is much less than atmospheric pressure. The word comes from the Latin term for "empty," but in reality, no volume of space can ever be perfectly empty....
 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
Ultra high vacuum

Ultra high vacuum is the vacuum regime characterised by pressures lower than about 10-7 pascal or 100 nanopascals . UHV requires the use of special materials in creating the vacuum system, extreme cleanliness to maintain the vacuum system, and baking of the entire system to remove water and other trace gases that adsorb on the su...
 requires a more sophisticated form of vacuum chamber
Vacuum chamber

A vacuum chamber is a rigid enclosure from which air and other gases are removed by a vacuum pump. The resulting low pressure, commonly referred to as a vacuum, allows researchers to conduct physical experiments or to test mechanical devices which must operate in outer space ....
.

An example classroom science experiment
Experiment

In scientific inquiry, an experiment is a method of investigating causal relationships among variables. An experiment is a cornerstone of the empiricism approach to acquiring data about the world and is used in both natural sciences and social sciences....
 involving a bell jar is to place a ringing alarm clock
Alarm clock

File:Clock radio.jpgAn alarm clock is a clock that is designed to make a loud sound at a specific date and/or time. The primary use of these clocks is to Awake people from their sleep in order to start their days in the mornings, but they are sometimes used for other reminders as well....
 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
Sound

Sound is vibration transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a threshold of hearing to be heard, or the sensation stimulated in organs of hearing by such vibrations....
 is mediated by the air. Deprived of its medium
Transmission medium

A transmission medium is a material substance which can wave propagation energy waves. For example, the transmission medium for sound received by the ears is usually air, but solids and liquids may also act as transmission media for sound....
, the sound cannot travel.