Scales of temperature measurement

To measure temperature two fixed points are taken on each thermometer. One of the fixed points is the freezing point or water or ice as lower fixed point (LFP). The other fixed point is the boiling point of water or steam as upper fixed print (UFP).

The temperatures of these fixed points; the no. of fundamental interval between the two fixed points on different temperature scales is shown by the table given below:

 

	Celsius	Fahrenheit	Reaumur	Kelvin	Rankine
UFP	100˚C	212˚F	80˚F	373.15k	672˚Ra
No. of fundamental interval	100	180	80	100	180
LFP	0˚C	32˚F	0˚R	273.15K	492˚Ra
Absolute zero	-273.15˚C	-459.6˚F	-218.4˚R	ok	0˚Ra

Relation between Temperatures on different scales

C-0 / 100   = F-32 /180 =   R-0 /80   = K-273/ 100    = Ra-492   /180

Celsius was initially known as centigrade.

While expressing temperature on Kelvin scale˚ (degree) is not used.

Freezing point (F.P) of mercury is -39˚C. Hence to measure temperature below this temperature, alcohol thermometer is used F.P. of alcohol is -115˚C.