Tag: pressure in air

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Questions Related to pressure in air

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

Atmospheric pressure can be measured by which of the following instruments

  1. doctor's thermometer

  2. mercury barometer

  3. speedometer

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

Speedometre is an instrument which is used to measure the speed of a vehicle.

Doctor's thermometre is used to measure the temperature of the body of the patient.
Mercury thermometre is used for measuring the atmospheric pressure.

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

'The atmospheric pressure at a place is $76  cm$ of $Hg$? State its value in $bar$.

  1. $1.013\times{10}^{5}$ $bar$
  2. $1 bar$
  3. $1.013\times{10}^{-5}$ $bar$

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

$1atm$ is the standard atmospheric pressure. 
In terms of length of mercury it is $76cm $ of Hg.

In SI units, the atmospheric pressure is $1atm=1.01325\times 10^{5}Nm^{-2}= 1 bar$

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

A measurement referenced to the atmospheric pressure and it varies from the measurement of barometric reading and manometer reading is called as 

  1. gauge pressure

  2. absolute pressure

  3. atmospheric pressure

  4. none of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
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
A barometer reads the atmospheric pressure and a manometer reads absolute pressure (when closed from one end), therefore a measurement referenced to the atmospheric pressure varying from barometer reading and manometer is called as gauge pressure.

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

1 pascal (Pa) is equal to 

  1. $1 \times 10^{5} $ bar
  2. $1 \times 10^{3} $ bar
  3. $1 \times 10^{-3} $ bar
  4. $1 \times 10^{-5} $ bar
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

We have,

               $1 atm=1\times10^{5}Pa$ ,
and         $1atm=1bar$ ,
hence,   $1bar=1\times10^{5}Pa$ 
or            $1Pa=1\times10^{-5}bar$