Temperature, in physics, is a quality of physical entities that indicates both whether heat will flow between them and in which direction it will flow. The concept of temperature comes from the idea of measuring relative hotness and coldness, and from the observation that the addition of heat to an object leads to an increase in temperature as long as no melting or boiling occurs.
Temperature is a quality of an object
Temperature and heat, although interrelated, are different concepts. Temperature is a quality of an object; heat is an energy flow to or from an object because of a temperature difference. Temperature changes must be measured in terms of other changes in a substance. The conventional mercury thermometer measures the expansion of a mercury column in a glass tube. The change in length of the column shows temperature change.
The Fahrenheit scale, invented by German physicist Gabriel Fahrenheit, assigns a value of 32°F to the freezing point and 212°F to the boiling point of water. The centigrade, or Celsius scale, invented by Swedish astronomer Anders Celsius assigns a value of 0°C to the freezing point and 100°C to the boiling point. In science, the absolute or Kelvin scale, invented by British mathematician and physicist William Thompson, 1st Baron Kelvin, is most widely used. In this scale, absolute zero is at -273.16°C, which is zero K. A scientific temperature scale based on the Kelvin scale was adopted in 1933.
Comparison of Temperature Scales
Boiling Point of Water
Freezing Point of Water
Sensing Temperature Background Information
Temperature is one of the most common physical measures taken. Many industrial processes must be undertaken within critical temperature ranges. Temperature will affect chemical reactions, reaction rates, energy consumption and industrial plant life. There are a number of technologies that can be employed to measure temperature. Simple liquid in glass, thermocouples, resistance thermometers (RTDs), thermistors, infrared and quartz crystals are among the methods used.