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| 17.6 Temperature Scales
Daniel Gabriel Fahrenheit (1686 – 1736) gave his name to the temperature scale which is still used in some weather reports. Fahrenheit was a scientific- instrument- maker from Holland. Here is a belief that one day a cold winter wind came through the window of his room and froze his tea with milk on the table. This made him think of artificial mixtures of low temperatures. The lowest temperature Fahrenheit could produce in his experiments was with a freezing mixture: the scientists mixed ice and ammonium chloride. He called this temperature 0 0 F (0 degree Fahrenheit) on his temperature scale. Ice melted at 32 0 F and normal human blood temperature was 96 0 F. The improved modern version of the Fahrenheit scale uses 32 0 F and 212 0 F, as the lowest and highest points on the scale. The scale became popular both in Britain and through out the English-speaking world. Actually, the Celsius temperature scale is taught in all modern schools today. It was introduced in 1742 by the Swedish astronomer Anders Celsius (1701 – 1744), who chose the melting point of the ice as 0 0 C and the boiling point of water as 90 100 0 C. The scale in between these points was divided into 100 equal degrees and was called a Centigrade or the Celsius scale. The scale was simpler than Fahrenheit’s, and was soon adopted by scientists throughout the world. In 1948 it became officially known as the Celsius scale, which is now part of the International System of Units. Another temperature scale was made in 1848 by Scottish physicist William Thomson-Lord Kelvin (1824 – 1907). Kelvin knew that when oxygen and other gases were cooled, their volume became smaller. The lower the t 0 , the smaller the volume. Experiments proved that at certain t 0 the molecules do not move, and their energy becomes zero. That represented the lowest possible temperature, and was called absolute zero on the Kelvin temperature scale. On the Celsius scale absolute zero is - 273,15 0 C. жүктеу/скачать 2.09 Mb. Достарыңызбен бөлісу:
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