Pressure in liquids and gases

Calculation of atmospheric pressure in various units

Calculation of atmospheric pressure in various units For ordinary laboratory purposes, atmospheric pressure is measured in mmHg by a Fortin barometer (page 113). The average value of the barometeric height at sea-level over a long period is 760 mmHg, and this has been taken as a unit of pressure and called standard atmospheric pressure or one atmosphere. The unit …

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Pressure in relation to diving and aviation

Pressure in relation to diving and aviation It should be clear from the previous paragraph that for every 10.3 m (approx. 10 m in sea-water) a diver descends the pressure on his body increases by one atmosphere. The aqualung diving-suit incorporates a rubber helmet fitted with a circular window and supplied with air from compressed-air cylinders carried on …

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The aneroid barometer and altimeter

The aneroid barometer and altimeter Barometers of the aneroid (without liquid) type are commonly used as weather glasses, the idea being that low pressure, or a sudden fall in pressure, generally indicates unsettled weather while a rising barometer or high pressure is associated with fine weather. The essential part of an aneroid barometer is a flat cylindrical metal box …

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Pascal’s’ experiments with barometers

Pascal’s’ experiments with barometers Torricelli died a few years after the barometer experiment had been performed, an did not live to see his explanation of it, in terms of atmospheric pressure, generally accepted among scientists. After Torricelli’s death Pascal repeated the experiment in France and set up two barometers. The first of these was placed at the foot of …

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Torricelli’s experiment. Simple barometer

Torricelli’s experiment. Simple barometer About the middle of the seventeenth century an Italian scientist named Torricelli, living at Pisa, suggested an experiment to discount the theory that nature abhorred a vacuum. Torricelli believed that nature’s supposed horror of a vacuum was caused simply by atmospheric pressure. In a famous experiment, first performed in 1643, he set up the first …

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Measurement of gas pressure by the manometer

Measurement of gas pressure by the manometer Earlier in this chapter it was stated that the pressure of the atmosphere was about 100 kNzm? (or kPa). Before explaining how this is measured let us make a study of the manometer, an instrument for measuring the pressure of gas. The manometer consists of a U-tube containing water. When both …

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