Showing posts with label evaporation. Show all posts
Showing posts with label evaporation. Show all posts


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The “ether” is a hypothetically predicted matter to explain the phenomena of light, and to account for the flow of energy across empty space. The existence of which was not proved till date experimentally.

Euclidean Geometry

The study of plane and solid figures on the basis of axioms and theorems employed by Greek mathematician Euclid.


Process by which atoms or molecules of liquid gain sufficient energy and gets converted to gaseous state. There is no boiling involved.

Even-even Nucleus

Nucleus having even no. of neutrons and protons.

Even-odd Nucleus

Nucleus having even no. of protons and odd no. of neutrons.


A given point (x,y,z,t) in space time is called event.   


Prefix in the metric system denoting 1018 of a given base unit.

Excitation Energy

Energy required for exciting electron from lower energy state to particular higher energy state.


Process of transferring electrons or atoms from lower energy states to higher energy states.

Excited State

An electron energy state, not normally occupied to which an electron may be promoted by the absorption of some type of energy.


It is a bound state of an electron and hole which are attracted to each other by electrostatic Coulomb force. It is an electrically neutral quasi particle. It is regarded as an elementary excitation of condensed matter that can transport energy without transporting net electric charge.


See exothermic.


The outermost region of earth’s atmosphere, beginning at an altitude of approximately 550 km to 700 km and merging with interplanetary medium at around 10000 km. The exosphere consist chiefly Hydrogen and Helium at extremely low densities. Temperatures in earth’s atmosphere remain constant with altitude, averaging about 1500 K. The earth’s exosphere contains the Hydrogen, Geo corona and Van Allen radiation belts.

Exothermic Process

Chemical reaction in which there is release of energy in the form of heat, light or sound. These processes occur spontaneously. They result in high randomness of entropy of the system. They are denoted by a negative heat flow (heat lost to the surroundings) and decrease in enthalpy.

Exponential Function

An Exponential Function is a function of the form y = abx, where both a and b are greater than 0 and b is not equal to 1.


It is defined by ICRU (1980), as “the quotient of dQ by dm, where the value of dQ is absolute value of total charge of the ions of one sign produced in air when all the electrons liberated by photons in air of mass ‘dm’ are completely stopped in air (or) In simple terms, it is defined as total electric charge of the ions generated by the gamma radiation per given mass of air.

External Work

When the force is exerted by the system on its surroundings leading to displacement, then the work done is called external work.


It means attenuation of incident electromagnetic wave due to absorption by medium or attenuation by medium.

Extraordinary Ray

One of the two refracted rays from double refracting crystals which don’t obey laws of refraction is called as extra ordinary ray.


Extrapolation is an estimation of a value based on extending a known sequence of values or facts beyond the area that is certainly known.

Extrinsic Semiconductor

The semiconductors for which the electrical behavior is determined by impurities, which when present in even minute concentrations, introduce excess electrons or holes.


A forming technique where by a material is formed by compression through a die or orifice.

Eye Piece

Combination of Two lenses used in optical instruments such as microscope or telescope etc., to obtain image free from aberrations.


It is type of optical lens placed in optical devices near focal point of objective to magnify image. It is so named as it is usually closest to eye of observer using the optical device. 


Refrigerating machines are of two types 1) Vapour compression machine (Frigidaire)" and 2) "Vapour absorption machine". 


The liquid which on evaporation produces cooling is called refrigerant. Some examples are Ammonia(NH₃), Sulphur dioxide, Freon.

Properties of Refrigerant:

  1. It should have low boiling point & melting point
  2. It should be vapor at normal temperature and pressure.
  3. It should have high thermal conductivity
  4. "Latent heat of vaporization" of the refrigerant must be large.  
  5.  The specific volume should be small in order to reduce the size of compressors. 

The evaporation of liquid under reduced pressure is a cooling process. The reason is that when a substance changes from liquid to vapor phase, it is associated with absorption of heat. If this heat is not taken from any external source, the necessary heat for phase exchange is taken from itself which therefore cools.

Vapor Compression Machine

Production of temperature by making a liquid evaporate rapidly under reduced pressure and circulating evaporating liquid around enclosure.

Difference between evaporation and vaporization

Vaporization of an element or compound is a phase transition from the liquid phase to gas phase. There are two sorts of vaporization: evaporation and boiling.

Evaporation is a phase transition from the liquid phase to gas phase that occurs at temperatures below the boiling temperature at a given pressure.

Boiling is a phase transition from the liquid phase to gas phase that occurs at or above the temperature the boiling temperature.