MCQ
With increase in temperature, the viscosity of:
- AGases decreases.
- BLiquids increases.
- ✓$A$ and $B$
- Dliquids decreases.
✓
Answer
Correct option: C.
$A$ and $B$
The viscosity of gases increases with increase of temperature, because on increasing temperature the rate of diffusion increases.
The viscosity of liquid decreases with increase of temperature, because the cohesive force between the liquid molecules decreases with increase of temperature.
Relation between coefficient of viscosity and temperature (Andrade formula)
$\eta=\frac{\text{Ae}^{\frac{\text{C}\rho}{\text{T}}}}{\rho^{\frac{-1}{3}}}$
where $T =$ Absolute temperature of liquid, $p =$ density of liquid, $A$ and $C$ are constants.
Important point: With increase in temperature, the coefficient of viscosity of liquids decreases but that of gases increases. The reason is that as temperature rises, the atoms of the liquid become more mobile, whereas in case of a gas, the collision frequency of atoms increases as their motion becomes more random.
The viscosity of liquid decreases with increase of temperature, because the cohesive force between the liquid molecules decreases with increase of temperature.
Relation between coefficient of viscosity and temperature (Andrade formula)
$\eta=\frac{\text{Ae}^{\frac{\text{C}\rho}{\text{T}}}}{\rho^{\frac{-1}{3}}}$
where $T =$ Absolute temperature of liquid, $p =$ density of liquid, $A$ and $C$ are constants.
Important point: With increase in temperature, the coefficient of viscosity of liquids decreases but that of gases increases. The reason is that as temperature rises, the atoms of the liquid become more mobile, whereas in case of a gas, the collision frequency of atoms increases as their motion becomes more random.
Need a full question paper?
Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.
Explore more
Similar questions
A particle moving in a circle of radius $R$ with uniform speed takes time $\mathrm{T}$ to complete one revolution. If this particle is projected with the same speed at an angle $\theta$ to the horizontal, the maximum height attained by it is equal to $4 R$. The angle of projection $\theta$ is then given by :
→A stationary sound source $'s'$ of frequency $334\,\, Hz$ and a stationary observer $'O'$ are placed near a reflecting surface moving away from the source with velocity $2\,\, m/sec$ as shown in the figure. If the velocity of the sound waves is air is $V = 330\,\, m/sec$, the apparent frequency of the echo is ... $Hz$
→The average degree of freedom per molecule of a gas is $6$. The gas performs $25\ J$ work, while expanding at constant pressure. The heat absorbed by the gas is .... $J$
→On a $TP$ diagram, two moles of ideal gas perform process $AB$ and $CD$. If the work done by the gas in the process $AB$ is two times the work done in the process $CD$ then what is the value of $T_1/T_2$?
→A thin liquid film formed between a $U-$ shaped wire and a light slider supports a weight of $1.5 \times 10^{-2}\ N$ (see figure). The length of the slider is $30\ cm$ and its weight are negligible. The surface tension of the liquid film is
→A travelling wave is described by the equation $y(x, t)=[0.05 \sin (8 x-4 t] \;m$
→The velocity of the wave is $.....ms ^{-1}$ [all the quantities are in SI unit]
A source of sound $A$ emitting waves of frequency $1800\,Hz$ is falling towards ground with a terminal speed $v.$ The observer $B$ on the ground directly beneath the source receives waves of frequency $2150\,Hz.$ The source $A$ receives waves, reflected from ground of frequency nearly ..... $Hz$ (Speed of sound $= 343\,m/s$ )
→A spherical asteroid having the same density as that of earth is floating in free space. A small pebble is revolving around the asteroid under the influence of gravity near the surface of the asteroid. What is the approximate time period of the pebble?
Infinite springs with force constant $k$, $2k$, $4k$ and $8k$.... respectively are connected in series. The effective force constant of the spring will be
→Why are drops and bubbles spherical?