Tag: fluids

Quizzes (14) Questions (63)

Questions Related to fluids

Multiple choice various types of barometer fluids physics

If two identical mercury drops are combined to form a single drop,then its temperature will

  1. decrease

  2. increase

  3. remains the same

  4. none of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

There will be a very small increase in temperature$.$ The surface area of the combined drop will be smaller than the original combined surface area of the two drops$.$ There is a small amount of work done by the surface tension as it pulls in the excess surface$.$ 

Since the system is adiabatic by your definition$.$ then the energy has to remain within the mercury$.$ At first$,$ the drop will jiggle around$.$ but eventually$,$ that motion will damp out to the viscosity in the mercury$.$ That will raise the temperature a very  tiny amount$.$
Hence$,$ option $(B)$ is correct$.$ 

Multiple choice various types of barometer fluids physics
Which of the following is not an advantage of using mercury as a barometric liquid.

  1. It does not affect the barometric height

  2. It gives correct reading

  3. It is easily seen due to its shiny appearance

  4. All the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The surface of mercury is shiny and opaque. Therefore it is easily seen while taking the observation. The vapor pressure of mercury is negligible. Hence the barometric height is not affected. The mercury neither sticks nor wets the glass tube.

Multiple choice various types of barometer fluids physics
Mercury .......... under vacuum conditions.

  1. Evaporates

  2. Does not evaporate

  3. No relation of evaporation with mercury

  4. All the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Mercury does not evaporate under vacuum conditions, whereas water does. Hence water is not used in barometers due to this effect whereas mercury is highly preferred.

Multiple choice various types of barometer fluids physics
Mercury is the densest liquid known. What is the advantage of this property?

  1. It can record the true pressure.

  2. It can be easily seen while taking observation.

  3. It does not affect the barometric height.

  4. Short column of it can counter balance the atmospheric pressure.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The atmospheric pressure measured by mercury barometer is the pressure equal to that at the bottom of the mercury column given by $h\rho g$.

Due to high value of $\rho$ the same pressure can be measured for smaller value of $h$.

Multiple choice various types of barometer fluids physics
Which of the following is not a property of mercury?

  1. It is the densest liquid known.

  2. It can be easily obtained in pure form.

  3. By using it the sides of the tube does not get wet.

  4. None
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

All the given properties of mercury shown are true.

Due to highest density, the same pressure can be measured using relatively shorter column of mercury.
Mercury can easily be obtained in pure form. Hence one can record the true atmospheric pressure as the pressure is directly proportional to the density of the liquid.

Multiple choice various types of barometer fluids physics

Vapour pressure of mercury is

  1. highest among all liquids

  2. negligible

  3. infinity

  4. None
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The vapor pressure of mercury is negligible. Thus the barometric height of a simple barometer or a mercury barometer is not affected.

Multiple choice various types of barometer fluids physics

An aluminum can of cylindrical shape contains $V _{0}\ cm^{3}$ of water. The area of the linear cross-section of the can is $A _{0}\ cm^{2}$. (All measurement refer to $T _{0}^\circ C$). Find the rise in the water level, if the temperature increases to $T _{1}C(T _{1}^\circ C > T _{0}$) $\alpha _{Al}$ and $\gamma _{water}$ are given

  1. $\dfrac { { V } _{ 0 }\left( { T } _{ 1 }-{ T } _{ 0 } \right) \left( { \gamma } _{ w }-2{ \alpha } _{ Al } \right) }{ { A } _{ 0 } } $
  2. $\dfrac { { V } _{ 0 }\left( { T } _{ 1 }-{ T } _{ 0 } \right) \left( { \gamma } _{ w }-2{ \alpha } _{ Al } \right) }{ {2A } _{ 0 } } $
  3. $\dfrac { { V } _{ 0 }\left( { T } _{ 1 }-{ T } _{ 0 } \right) \left( { \gamma } _{ w }-2{ 3\alpha } _{ Al } \right) }{ { A } _{ 0 } } $
  4. $\dfrac { { V } _{ 0 }\left( { T } _{ 1 }-{ T } _{ 0 } \right) \left( { \gamma } _{ w }-2{ 3\alpha } _{ Al } \right) }{ { 2A } _{ 0 } } $
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The volume of water at T1 is V1 = V0(1 + gamma_w * dT). The area of the can at T1 is A1 = A0(1 + 2 * alpha_Al * dT). The new height h1 = V1 / A1. The rise in level is h1 - h0 = (V0/A0) * [(1 + gamma_w * dT) / (1 + 2 * alpha_Al * dT) - 1]. Using binomial approximation (1+x)^-1 approx 1-x, this simplifies to (V0/A0) * dT * (gamma_w - 2 * alpha_Al).

Multiple choice various types of barometer fluids physics
Mercury can be obtained in its pure form. What is its advantage?

  1. True atmospheric pressure can be recorded.

  2. Mercury does not affect the barometric height.

  3. It is easily seen while taking observation.

  4. All the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Mercury can be easily obtained in its pure state and one can record the true atmospheric pressure as the pressure is directly proportional to the density of the liquid.
Multiple choice various types of barometer fluids physics

If the compressibility of water is $\sigma$ per unit atmospheric pressure, then the decrease in volume $V$ due to atmospheric pressure $p$ will be

  1. $\sigma p/V$
  2. $\sigma pV$
  3. $\sigma /pV$
  4. $\sigma V/p$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Compressibility sigma = -(1/V) * (dV/dp). Therefore, dV = -sigma * V * dp. For a pressure change p, the magnitude of volume decrease is sigma * V * p.

Multiple choice various types of barometer fluids physics

A faulty barometer shows 72cm and the air column is 10cm when the true pressure is 76cm of Hg. The barometer reading will be, when the length of air column is 5cm.

  1. 76cm of Hg

  2. 71.5 Hg

  3. 68gm of Hg

  4. 72.5gm of Hg
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Using Boyle's Law (P1V1 = P2V2) for the trapped air: (76-72) * 10 = (76-x) * 5. Thus, 4 * 10 = (76-x) * 5, so 8 = 76-x, which means x = 68 cm.