Tag: physics

Questions Related to physics

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

  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

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Correct Option: D
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.

Vapour pressure of mercury is

various types of barometer fluids physics

  1. highest among all liquids

  2. negligible

  3. infinity

  4. None

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Correct Option: B
Explanation:

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

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

various types of barometer fluids physics

  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 } } $

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Correct Option: C
Mercury can be obtained in its pure form. What is its advantage?
various types of barometer fluids physics
  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

Show answer
Correct Option: A
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.

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

various types of barometer fluids physics

  1. $\sigma p/V$

  2. $\sigma pV$

  3. $\sigma /pV$

  4. $\sigma V/p$

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Correct Option: B

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.

various types of barometer fluids physics

  1. 76cm of Hg

  2. 71.5 Hg

  3. 68gm of Hg

  4. 72.5gm of Hg

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Correct Option: C

In the bottom of a vessel with mercury of density $\rho$ there is a round hole of radius $r$. At what maximum height of the mercury layer will the liquid still not flow out through this hole. (Surface tension = $T$) 

various types of barometer fluids physics

  1. $\dfrac T {rpg}$

  2. $\dfrac T {2rpg}$

  3. $\dfrac {2T} {rpg}$

  4. $\dfrac{4T} {rpg}$

Show answer
Correct Option: A
Explanation:

Given,


$r=$ radius of the hole


$p=$ density of mercury liquid

$g=$ acceleration due to gravity

$T=$ Surface tension

$h=$ maximum height

The liquid can not penetrate until the hydro-static pressure is greater than excess pressure.

Limiting condition,

$pgh=\dfrac{2T}{r}$

$h=\dfrac{2T}{rpg}$

The correct option is C.

The height of a mercury barometer is 75 cm at sea level and 50 cm at the top of a hill. Ratio of density of mercury to that of air  is $10 ^ { 4 }$ The height of the hill is

various types of barometer fluids physics

  1. 250 m

  2. 2.5 km

  3. 1 .25 km

  4. 750 m

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Correct Option: C

The brass scale of a barometer gives correct reading at $10^{ o }C$. The barometer reads 75 cm at $30^{ o }C$. What is the atmospheric pressure at $8^{ o }C$(in cm Hg)

various types of barometer fluids physics

  1. 74.8

  2. 75.03

  3. 70

  4. 60

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Correct Option: C

The lengths of air column are 10 and 8 cm in a faulty barometer when it shows 72 and 71 cm. The atmospheric pressure is 

various types of barometer fluids physics

  1. 76 cm of Hg

  2. 75 cm of Hg

  3. 64.4 cm of Hg

  4. None

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Correct Option: C