Question

discuss the vvariation of viscosity with temperature and pressure​

Answer 1

Answer:

The former effect causes a decrease in the shear stress while the latter causes it to increase. The result is that liquids show a reduction in viscosity with increasing temperature. With high temperatures, viscosity increases in gases and decreases in liquids, the drag force will do the same.

Answer 2

$\red{\bold{\underline{{ Answer \: with\: Explanation \: :}}}}$

Effects of Temperature on Viscosity :-

When a liquid is heated the kinetic energy of its molecule increases and the intermolecular attraction become weaker. Hence the viscosity of an liquid decreases with the increase in its temperature.

Stole's empirical formula for the variation of viscosity of a Liquid with the temperature is :-

$\orange{\large{\bold{\sf\:\eta\:=\:\dfrac{\eta_0}{1\:+\:\alpha\:t\:+\:\beta\:t^2}}}}$

where ή is the Coefficient of Viscosity at 1° C and 0° C respectively , and α and β are the constants.

Viscosity of a gases is due to the diffusion of molecules from one moving layer to another.

But the rate of diffusion is directly proportional to the square root of its absolute temperature so viscousity of a gas inferases with temperature as :-

• ή ∝ $\large\red{\bold{\sqrt{T}}}$

Effect of Pressure :-

Except water the viscosity of liquids increases with the increase in pressure. In case of water, viscosity decreases with increase in pressure for the first few hundred atmosphere of pressure. The Viscosity of gases is independent of Pressure.