Viscosity In Chemistry With Example

What is Viscosity - Most fluids offer some resistance to motion, and we call this resistance “viscosity.” Viscosity arises when there is relative motion between layers of the fluid.

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Unit of Viscosity - The SI unit of viscosity is poiseiulle (PI). Its other units are the newton-second per square meter (N s m-2) or the pascal-second (Pa s). The dimensional formula for viscosity is [ML-1T-1].

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Viscosity Formula - Viscosity is measured in terms of a ratio of shearing stress to the velocity gradient in a fluid.

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Viscosity Types - There are two ways to measure the fluid’s viscosity as 1) Dynamic Viscosity (Absolute Viscosity) and 2) Kinematic Viscosity.

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Dynamic Viscosity - One way is to measure the fluid’s resistance to flow when an external force is applied. This is known as Dynamic Viscosity.

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Kinematic Viscosity - The other way is to measure the resistive flow of a fluid under the weight of gravity. We call this measure of fluid viscosity kinematic viscosity.

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Viscosity Measurement -

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The elementary way of measuring viscosity is to allow a sphere, such as a metal ball, to drop through a fluid and time the fall of the metal ball.

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The slower the sphere falls, the greater the viscosity. But, a more accurate measure of viscosity is given by the viscometer.

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U-Tube Viscometer - U-tube viscometers are also known as glass capillary viscometers or Ostwald viscometers.

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