Tag: pressure exerted by air

Questions Related to pressure exerted by air

The correct relationship between gauge pressure, atmospheric pressure and absolute pressure is 

physics fluid pressure pressure in air introduction to atmospheric pressure pressure exerted by air devices to measure pressure

  1. Gauge pressure = Atmospheric pressure - Absolute pressure

  2. Gauge pressure = Atmospheric pressure + Absolute pressure

  3. Absolute pressure = Atmospheric pressure + Gauge pressure

  4. None of the above

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Correct Option: C
Explanation:

Absolute pressure: It uses absolute zero (pressure in vacuum) as its zero point.

Gauge pressure: It uses atmospheric pressure  as its zero point.
Therefore, Absolute pressure = Atmospheric pressure + Gauge pressure 

If one newton force is applied to unit crossesctional area (in $m^2$)  of any subject then the amount of pressure applied is

physics fluid pressure pressure in air introduction to atmospheric pressure pressure exerted by air devices to measure pressure

  1. one pascal

  2. one atmospheric pressure

  3. one gauge pressure

  4. none of the above

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Correct Option: A
Explanation:

Pressure is defined as force per unit area applied on a surface.

$P=\dfrac{F}{A}$ 
In SI units, pressure has unit $N/m^2$ which is equivalent to $Pa$(Pascal).

The amount by which the pressure measured in a fluid exceeds that of the atmosphere is known as 

physics fluid pressure pressure in air introduction to atmospheric pressure pressure exerted by air devices to measure pressure

  1. atmospheric pressure

  2. gauge pressure

  3. absolute pressure

  4. none of the above

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Correct Option: B
Explanation:

Gauge Pressure uses a reference to the atmosphere around the sensor. Because the sensing element has a deflection due to a pressure change, a reference point is needed to know exactly what pressure is being measured. Pressure sensors that use gauge pressure—typically seen in PSIG, BARG, and kPaG —have some type of vent. This vent can be built in to the sensor or even through a tube in the electrical connection. The vent is positioned to use atmospheric pressure as a reference point for the sensor to measure the media. One common reason for using gauge pressure is to ensure that with any location throughout the world, the sensor will always reference the location in which it is installed.

One atmospheric pressure at sea level is equal to 760 cm of Hg.

physics fluid pressure pressure in air introduction to atmospheric pressure pressure exerted by air devices to measure pressure

  1. True

  2. False

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Correct Option: B
Explanation:

1 atm = 76 cm of Hg 

so given statement is false 
hence option (B) is correct.

A bubble is at the bottom of a lake of depth $h$. As the bubble comes to the sea level, its radius increase three times. If atmospheric pressure is equal to $l$ metre of a water column, then $h$ is equal to

physics fluid pressure pressure in air introduction to atmospheric pressure pressure exerted by air devices to measure pressure

  1. $26\ l$

  2. $l$

  3. $25\ l$

  4. $30\ l$

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Correct Option: A

If a given mass of gas occupies a volume of 10 cc at 1 atmospheric pressure and a temperature of ${ 100 }^{ 0 }$C (373.15 k). What will be its volume at 4 atmospheric pressure; the temperature being the same 

physics fluid pressure pressure in air introduction to atmospheric pressure pressure exerted by air devices to measure pressure

  1. 100 cc

  2. 400 cc

    1. cc

  4. 104 cc

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Correct Option: C

A narrow glass tube, $80$ cm long and opens at both ends, is half immersed in mercury, now the top of the tube is closed and is taken out of mercury A column of mercury $20$ cm long remains in the tube. Find the atmospheric pressure

physics fluid pressure pressure in air introduction to atmospheric pressure pressure exerted by air devices to measure pressure

  1. $20$ cm of air column

  2. $60$ cm of Hg column

  3. $60$ cm of air column

  4. $20$ cm of Hg column

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Correct Option: C

Find pressure on swimmer at a depth of $10 m$ in water

physics fluid pressure pressure in air introduction to atmospheric pressure pressure exerted by air devices to measure pressure

  1. $2$ atm

  2. $1$ atm

  3. $3$ atm

  4. $4$ atm

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Correct Option: B

A brass scale, correct at $0^\circ C$, registers the height of a mercury barometer at 76.5 cm at $30^\circ c$. What is the actual height of the barometer? [Linear expansivity for brass=$1.9\times10^{-5} K^{-1}$]

physics fluid pressure pressure in air introduction to atmospheric pressure pressure exerted by air devices to measure pressure

  1. 70.88cm

  2. 72.45cm

  3. 71.25cm

  4. 76.46 cm

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Correct Option: D

A barometer is carried from the $1^{st}$ floor to the $20^{th}$ floor of a building. Why does the reading on the barometer fall?

physics fluid pressure pressure in air introduction to atmospheric pressure pressure exerted by air devices to measure pressure

  1. Air pressure has increased

  2. Gravity has decreased

  3. Temperature has increased

  4. There is less air above the barometer

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Correct Option: D
Explanation:

Answer is D.

The air pressure decreases as the we go up the atmosphere. Therefore, when a  barometer is carried from the 1st floor to the 20th floor of a building, the air pressure decreases and hence the reading on the barometer falls down.