Thermodynamics

Thermodynamics States About Energy Conversion Thermodynamics is the branch of science that embodies the principles of energy transformation in macroscopic systems. The general restrictions which experience has shown to apply to all such transformations are known as the laws of thermodynamics. These laws are primitive; they cannot be derived from anything more basic. The first law of thermodynamics states that energy is conserved; that, although it can be altered in form and transferred from one place to another, the total quantity remains constant. Thus, the first law of thermodynamics depends on the concept of energy; but, conversely, energy is an essential thermodynamic function because it allows the first law to be formulated. This coupling is characteristic of the primitive concepts of thermodynamics. The words system and surroundings are similarly coupled. A system is taken to be any object, any quantity of matter, any region, and so on, selected for study and set apart (men

Measuring Temperature

The human ability to perceive temperature i.e. the ability to evaluate thermal stimuli is very rudimentary. Changes of the properties of material under the influence of heat such as expansion, electrical phenomena, incandescence, radiation, melting make it possible to construct accurate instruments for measuring temperature. Temperature unit system as the SI Unit standard is Kelvin but for general measuring people often use Celcius or Fahrenheit.

Thermometers
Thermometers are base on the principle that liquid and solid expand when heated. Mercury and alcohol expand uniformly. Hence mercury and alcohol thermometer, When heat supplied, the volume of the liquid in the container of thermometer is increases as a result of which the liquid rises up the capillary tube welded to the container. The bimetallic thermometers consist of metal with different coefficients of expansion, e.g. a steel containing 20% nickel and one containing 36% nickel. The bimetal twisted into a spiral which curls when the temperature rises, because the 36% nickel steel undergoes a greater expansion.

Thermoelectric Pyrometer
Thermoelectric pyrometer or thermocouple element, if the soldering point between wires of different metals is heated a contact voltage is generated (thermoelectric effect). The voltage depends upon the temperature difference between the hot measuring point and the cold and of the wire.

The electron in some metals are bound more strongly than in others. This leads to an exchange of electrons which depends upon the temperature. As a result, one metal becomes positive by losing electron, and the other negative by accepting them. As electric current flows. Thermocouple elements are constructed of copper and constanian (up to 600oC) or of platinum and platinum rhodium (up to 1600oC).

Radiation Pyrometers
Radiation pyrometers are used to measure the temperature of red hot metals or of melts up to around 3000oC. These concentrate thermal rays through an optical lens and focus them onto a thermo element. The scale of the ammeter is calibrated in degrees Celsius or Kelvin.