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Thermometry is the branch of physics concerned with temperature measurement. It is the study of making and using thermometers. Since its inception, thermometry has been linked to medicine. Technical advancements have aided the growth of thermometry and its contributions to medicine, and the reverse is also true.
Temperature also indicates the movement of heat or thermal energy, which goes down a thermal gradient from a hotter to a cooler body. The hot body will lose thermal energy to the cool body during this process.
What is a Thermometer?
The word thermometer is derived from the Greek words’ thermos (meaning “hot”) and metron (meaning “measure”). Any instrument that measures temperature is referred to as a thermometer. The multiplicity of thermometer types attests that any temperature-dependent parameter can serve as the basis for a thermometer.
Because there are so many temperature-dependent characteristics, much engineering time is spent removing temperature sensitivity from equipment.
The thermometer has evolved over time rather than being unchanging. Philo of Byzantium (280-220 BC) recognised that air expands and contracts in response to temperature variations and provided a demonstration that Galileo later evolved into his air thermometer or thermoscope in roughly 1600.
The Cricket as a Thermometer
The relation between air temperature and the rate at which crickets chirp is described by Dolbear’s law. Amos Dolbear proposed it in an article titled, “The Cricket as a Thermometer,” published in 1897. The sound of chirping crickets is associated with summer for many people. Males only stridulate, which is a scientific term for chirping, in order to attract a female.
Amos Dolbear found that the frequency of chirping of the narrow-winged tree cricket Oecanthus niveus was affected by air temperature and published his law connecting temperature T to the number of chirps per minute N in 1897 as,
T = 10 + (N – 40)/7
Temperature Scales
Temperature scales allow quantifying and measuring how hot or cold a substance is. Celsius and Fahrenheit are generally employed in ordinary, around house measures, although a complete zero-basis Rankine and Kelvin scale is more commonly utilised in business and sciences.
There are four different types of temperature scales:
- Celsius Scale
- Fahrenheit Scale
- Kelvin Scale
- Rankine Scale
Celsius Scale
In the early eighteenth century, two variants of (C) scale were developed: first by Swedish scientist Anders Celsius and then another by Frenchman Pierre Cristin.
The centigrade scale is also known as the Celsius scale. The temperature scale based on 100° for the boiling point and 0° for the freezing point of water is known as the Celsius scale. Anders Celsius, a Swedish physicist, engineer, and astronomer, was the first to introduce and name this scale.
The celsius scale was first used to indicate the boiling point of water at 0° and the freezing point of water at 1000°. The freezing point and boiling point of water were inverted to 0° and 100°, respectively. This sort of Celsius scale became very popular.
Fahrenheit Scale
The British physicist William Thompson, afterward Lord Kelvin, converted the Celsius scale into the Kelvin scale in the 19th century. Kelvin was created with the goal of setting the temperature scale’s zero point at zero. As a result, absolute zero is 0 K, as Kelvin does not employ a degree in notation.
By multiplying a Celsius temperature by 273.15, it can be converted to Kelvin. The H2O freezes at 273.150-degree kelvin and boils at 373.15 degrees Celsius. Kelvin temperature is extensively utilised in the scientific equation and calculation because of its direct relationship to absolute zero. The gas law, for example, employs Kelvin as its standard unit to depict the relationship between temperature, pressure, mass, and volume.
Kelvin Scale
A temperature scale with an absolute zero below which no temperatures exist is known as the Kelvin temperature scale. Absolute zero, or 0°K, is the temperature at which molecular energy is at its lowest, corresponding to a temperature of 273.15° Celsius.
Because the Kelvin degree has the same magnitude as the Celsius degree, the freezing point of water (0°C) and the boiling point of water (100°C) are 273.15°K and 373.15°K, respectively.
By multiplying a Celsius temperature by 273.15, it can be converted to Kelvin. Water freezes at 273.15 degrees Celsius and boils at 373.15 degrees Celsius. Kelvin temperature is extensively utilised in scientific equations and calculations because of its direct relationship to absolute zero. The ideal gas law, for example, employs Kelvin as its standard unit to depict the relationship between mass, pressure, temperature, and volume.
Rankine Scale
W.J.M. Rankine (1820–72), a Scottish physicist, was the inspiration for the Rankine temperature scale. The scale is set up so that zero degrees Rankine (marked by 0°R) represents absolute zero, and a 1°R interval equals one degree Fahrenheit.
The relationship between the Rankine and Fahrenheit scales is akin to that between the Celsius and Kelvin scales in this sense. Temperatures in Fahrenheit can be translated to Rankine by multiplying by 459.67. As a result, absolute zero is found at 0 degrees Rankine. Water has a freezing point of 491.67 degrees Fahrenheit and a boiling point of 671.67 degrees Fahrenheit.
Conclusion
In this article, we learned about various concepts related to thermometry and the different scales at which a temperature can be measured.
There are three types of scales, mainly at which the temperature is measured. The first one is the Celsius scale, the Rankin scale, and the Kelvin scale.
