Английский язык. Ильичева Н.А - 34 стр.

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with mercury or with alcohol coloured with a red dye to make it visible. 3
The glass also expands but the liquid expands much more. Thermometers are
calibrated so that numerical values can be assigned to different temperatures.
The calibration requires two reference points and a choice of unit. Two
common reference points for a temperature scale are the ice and steam points of
water. The steam point is the temperature at which pure water boils at one
atmosphere of pressure. 4
       Two common temperature scales are the Fahrenheit and Celsius scales.
The Fahrenheit scale has an ice point of 32° (read “32 degrees”) and a steam
point of 212°. The interval between the ice and steam points is evenly divided
into 180 units. The Celsius scale is based on an ice point of 0° and a steam point
of 100°. There are 100 equal units or divisions between these points. So a
degree Celsius is almost twice as large as a degree Fahrenheit. At one time the
Celsius scale was commonly called the “centigrade” scale. 5
       The scale is now referred to correctly as the Celsius scale.

        There is no known upper limit of temperature; however, there is a lower
limit. The lower limit occurs at about – 273° C or – 460° F, and it is called
absolute zero. Another temperature scale, called the Kelvin scale, has its zero
temperature at this absolute limit. The scale is sometimes called the absolute
temperature scale. The unit of the Kelvin scale is the kelvin, abbreviated K and
it has the same magnitude as a degree Celsius. Notice that since the Kelvin scale
has absolute zero at its lowest reading, there can be no negative Kelvin or
absolute temperatures.

      Because the Kelvin and degree Celsius are equal intervals we can easily
convert from the Celsius scale to the Kelvin scale. 5
      In equation form we have Tk = Tc + 273. For example, a temperature of 0°
C equals 273 K, and a Celsius temperature of 27° C is equal to 300 K (Tk = Tc +
273 = 27 + 273 = 300 K).

       Converting from Fahrenheit to Celsius and vice versa is also quite easy.
The formulas for these conversions are
      9
T f = (Tc +32) (Celsius Tc to Fahrenheit Tf);
      5
and
     5
Tc = (T f −32) (Fahrenheit Tf to Celsius Tc).
     9
       For example, suppose it is very chilly 5° F outside. This value is
equivalent to a temperature of – 15° C. (Use the second equation to verify this
result).