Saturday, June 18, 2011


It is well known that all liquids do not flow with the same speed. Some liquids like water, alcohol, ether etc. flow very rapidly while some liquids like glycerine, honey, castor oil etc. flow slowly .This indicates that every liquid has some internal resistance to flow.
This internal resistance to the flow possessed by a liquid is known as its Viscosity.           
To understand the nature of internal resistance or friction existing within a liquid. It has been observed that liquid flows in layers. The layer which is in contact with the wall of tube through which it flows is almost stationary. As we move towards higher level, the speed increases. In other words, every layer offers some resistance or friction to the layers flowing over it. Thus viscosity may also be defined as,
 “The force of friction or resistance offered by a layer of liquid to the other layer flowing over it.”

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