Viscosity
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Coefficient of viscosity :

“ It is the tangential force acting on a unit area to produce a unit change in velocity between two liquid layers at unit normal distance a part from each other”.

* To keep the plate moving with constant velocity, a force “F” is required, this force (F):

1. F a V                (V: velocity).

 2. F a A                (A: area of moving plate).

 3. F a 1/S             (S: the distance between the two plates).

4. F  depends on the kind of the liquid.

F   a   A.V/S

 F   =   constant x A.V/S

F   =       h.A.V/S          (h: the coefficient of viscosity).     

Unit of coefficient of viscosity:

1.                  N .S. m^-2

2.                  Kg .m^-1. Sec^-1

The dimensional formula of coefficient of viscosity:

        ·          M .L^-1. T^-1

The factors affecting coefficient of viscosity:

1.                  Kind of fluid.

2.                  The temperature.

Application of the viscosity:

1.                  Viscosity for liquids:

        ·          The lubrication process is accomplished by using

   special oils characterized by high viscosity.

        ·          The lubrication process leads to:

1.      Reduction of heat quantity generated by friction.

2.      Protecting the machine parts from wearing.

3.      Increase the efficiency of the machine.