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Questions Related to physics

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            $1Pa=1\times10^{-5}bar$

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

Increase in height of mercury column indicates:

  1. decrease in atmospheric pressure

  2. increase in atmospheric pressure

  3. no change in atmospheric pressure

  4. increase in humidity in air
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The pressure at the bottom of mercury column tries to equate the atmospheric pressure outside. 
When the compensating height of mercury column increases, it means that the atmospheric pressure has indeed increased.