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Classification Of Lubricants: According to the state of lubricant there are classified into the following classes: (i)                  Liquid lubricants or Lubricating oils (ii)                Semi-solid Lubricants, and (iii)              Solid Lubricants These are describing below one by one. (i)                  Liquid Lubricants:                                 The main function of lubricating oils is to reduce friction or wear between two moving metallic surfaces by providing a continuous film in between them. Liquid lubricants are further classified as:- (1)    Animal Oils and Vegetable Oils (2)    Minerals Oils(Petroleum oil) (3)    Blended Oils(Compounded Oil), and (4)    Emulsions (1)        Animal Oils and Vegetable Oils:                           Animal and vegetable oils are very important having good oiliness and obtained from the animal and vegetable kingdom contain glycerides of higher fatty acids. Before developing the petroleum

Lubricants:-                         Those substance which is applied between two moving or sliding surface in order to reduce the frictional resistance called lubricant. Function of Lubricant:-        I.             It reduce the frictional forces between two rubbing surfaces.     II.             It reduces the cost of maintenance of the machines and tools.   III.             It acts as a cleaning agent to wash off the solid carbon.   IV.             It acts as a seal and prevents the entry of moisture i.e leakage of gases under high pressure.     V.             The Lubricant prevents rusting and corrosion.   VI.             It act as a Coolant. Lubrication:-                             The process of reducing frictional resistance between moving surface using lubricants in between them is called Lubrication. Friction:-                     Due to mutual rubbing of one part against another, a resistance is developed which tends to retards the mot

Law Of Friction: (i)                 Anonton’s First Law:-     According to this Law, the friction between two solids is independent of the area of contact.   For example   a Bricks slides over a flat surface than the friction will be same whether it is sliding on its end or its side or its base, because the actual area of contact is always smaller than the apparent area. (ii)              Anonton’s Second Law:-   According to this Law, the friction force is proportional to the load exerted by one surface over the another . For example- If a brick is placed on the Top of the another brick the friction will be doubled and the another brick is placed on the second brick, than the friction will get trebled and so on.                          f α w                                 f= Kw                 K or µ= coefficient of friction             µ or K= f/w          f= friction, w=weight(load)  

Einstein’s Coefficients:                                             Possibility of laser action:   Consider an atomic medium like a monoatomic gas, sealed in an enclosure. Let the e closure be maintained at a constant temperature, T. Let us define two energy states of Energies E 1 and E 2 , such that E 2 >E 1 . Let N 1 and N 2 = number of atoms in lower and upper energy states i.e. E 1 and E 2 respectively. When an atom is in the lower energy state E 1 , it would be in a position to absorb a photon of energy, E 2 -E 1 =hv. Let the enclosure be irradiated with an isotropic radiation of frequency, v or angular frequency w . Where, w =2 π v.                          [where h =h/2 π; h= Plank’s constant] Let U(w)= Radiation density such that, U( w ) d w is radiation density in frequency range w and ( w +d w ) Therefore,     {The rate of absorption of radiation, per unit time, per unit volume}∞ N 1 and U( w ) ð   [Number of photon absorptions per

Mechanism of Lubrication: (i)                 Fluid-film or thick-film or Hydrodynamic Lubrication (ii)              Boundary Lubrication or thin-film lubrication (iii)            Extreme Pressure Lubrication All parts are described below one by one. (i)                 Fluid-film or thick-film or Hydrodynamic Lubrication:                                                                                                                                      In this the moving surface are separated from each other by a thick-film of fluid(at least 1000A º thick), So   that the direct contact of two surfaces of metals or   junket may be minimized. As a result wearing and tearing of metals get minimized due to less friction.    The lubrication film fins the irregularities of the moving surfaces and forms a thick layer in-between them, So that there are no direct contact between the metal surfaces. Hydrodynamic friction occurs in case of a shaft running at a fair speed as w