Temperature and Scale of Temperature

Temperature Temperature is defined as tee degree of hotness or coldness of a body. T natural flow of heat is from higher temperature...

Temperature

Temperature is defined as tee degree of hotness or coldness of a body. T natural flow of heat is from higher temperature to lower temperature.

Two bodies are said to be in thermal equilibrium with each other, when no heat flow from one body to other. That is when both the bodies are at same temperature.

• Temperature is one of the seven fundamental quantities with dimension (Ɵ). It is a scalar quantity with S.I. unit Kelvin.
• When heat is given to a body and its state does not change the temperature of the body rises and if heat taken from a body its temperature falls i.e. temperature can be regarded as the effect of cause “heat”.
• According to kinetic theory of gasses, temperature (macroscopic physics quantity) is a measure of average transnational kinetic energy of a molecule (microscopic physical quantity).
• Although the temperature of a body can be raised already without limit, it cannot be lowered without limit and theoretically limiting is taken to be zero of the Kelvin scale
• Highest possible temperature in laboratory is about 18⁸ K while lowest possible temperature is 18⁻⁸ K.
• Temperature of the core of the sun is 10⁷ while that of its surface 6000 K.
• Normal temperature of human body is 310.15 K (37˚C=98.6˚F)
• NTP or STP implies 273.15 K (0˚32˚F)
  
  
  
  
  Scale of Temperature

  

  
  

  
  

  The centigrade (˚c), Fahrenheit (˚f), Kelvin (K), Reaumer (R), Rankine (Rɑ) are commonly used temperature scales.

  (1)   To construct a scale of temperature, two fixed points are taken. First fixed point is the freezing point (ice point) of water, it is called lower fixed point (LPF) the second fixed point is the boiling point (steam point) of water, it is called upper fixed limit point (UFP).

  Different measuring scales

  Scale	Symbol for each scale	LFP	UFP	Number of division on the scale
  Celsius	˚C	0˚C	100˚C	100
  Fahrenheit	˚F	32˚F	212˚F	180
  Reaumer	˚R	0˚R	˚80	80
  Rankine	˚Rɑ	460 Rɑ	627Rɑ	212
  Kelvin	K	273.15K	373.15 K	100

  
  

  (2) Celsius scale, also known as the centigrade scale, is an SI scale and unit of measurement for temperature. As an SI derived unit, it is used by most countries in the world. It is named after the Swedish astronomer Anders Celsius (1701–1744). The Celsius scale was based on 0 °C for the freezing point of water and 100 °C for the boiling point of water at 1 atm pressure.

  (3) Fahrenheit scale, is a temperature scale based on one proposed in 1724 by Amsterdam-based physicist Daniel Gabriel Fahrenheit (1686–1736). It uses the degree Fahrenheit (symbol: °F) as the unit. The lower defining point, 0 °F, was established as the temperature of a solution of brine made from equal parts of ice and salt. Further limits were established as the melting point of ice (32 °F) and his best estimate of the average human body temperature (96 °F, about 2.6 °F less than the modern value due to a later redefinition of the scale). The scale is now usually defined by two fixed points: the temperature at which water freezes into ice is defined as 32 °F, and the boiling point of water is defined to be 212 °F, a 180 °F separation, as defined at sea level and standard atmospheric pressure.

  (4) Kelvin scale is an absolute thermodynamic temperature scale using as its null point absolute zero. The kelvin (symbol: K) is the base unit of temperature in the International System of Units (SI). The kelvin is defined as the fraction  ¹⁄_273.16 of the thermodynamic temperature of the triple point of water (exactly 0.01 °C or 32.018 °F).In other words, it is defined such that the triple point of water is exactly 273.16 K. The Kelvin is the primary unit of temperature measurement in the physical sciences, but is often used in conjunction with the degree Celsius, which has the same magnitude. The definition implies that absolute zero (0 K) is equivalent to −273.15 °C (−459.67 °F).

  (5)           the triple point of a substance is the temperature and pressure at which the three phases (gas, liquid, and solid) of that substance coexist.

  (6)  Temperature on one scale can be convert in to other scale by using the following identity.

  Reading on any scale—LFP   =  Constant for all scale

               UFP-LFP

  (7)  All temperature are related to each other by the following relationship