The top of the barometer is filled with nothing (vacuum) because
the mercury must have the space to expand and contract without any other force affecting it
; a gas or liquid in the top would have its own pressure against the mercury and give inaccurate readings.
Why vacuum is created in barometer?
The mercurial barometer consists of a glass tube, sealed at one end and filled with pure mercury. … After being heated to expel the air, it is inverted in a small cup of mercury called the cistern.
The mercury in the tube sinks slightly
, creating above it a vacuum (the Torricellian vacuum).
Is there a vacuum in a mercury barometer?
When the finger is removed, the level of the mercury inside the tube drops until the pressure at the bottom of the column of mercury is equal to the pressure exerted by the surrounding air. Since no air was allowed to enter the tube,
the empty space above the mercury column is a vacuum
.
What is the name given to the vacuum above the surface of mercury in a barometer?
The space above mercury is a vacuum. This empty space is called ‘
Torricellian vacuum
‘. This can be shown by tilting the tube till the mercury fills the tube completely. Again when the mercury column becomes stationary, the empty space is created above the mercury column.
What is in the space above the HG in a barometer?
The space would be occupied by the mercury vapour and the pressure would equal to the vapour pressure of mercury at its existing temperature. This almost vacuum condition above the mercury in the barometer is known as
Torricellian vacuum
.
Is the top of a barometer a vacuum?
The top of the
barometer is filled with nothing (vacuum)
because the mercury must have the space to expand and contract without any other force affecting it; a gas or liquid in the top would have its own pressure against the mercury and give inaccurate readings.
How many types of barometer are there?
There are
two main types
of barometers: mercury and aneroid. In the mercury barometer, atmospheric pressure balances a column of mercury, the height of which can be precisely measured.
What keeps the mercury in the tube?
The mercury is in a long glass tube with an open reservoir at the bottom:
higher atmospheric pressure exerts a downward force on the mercury
in the reservoir – and pushes the mercury up the tube.
Why does mercury rise in a barometer?
A traditional mercury barometer consists of an evacuated tube immersed in a container of mercury. Air molecules push down on the surface of the mercury.
Because the inside of the tube is a vacuum
, the mercury rises inside the tube.
What will happen to the barometric height of mercury if water is introduced in the vacuum above mercury in the tube in a simple barometer justify your answer?
The
barometric height is decreased in
this case. So, vacuum is present on top of the mercury inside the tube.
What are the two factors which affect the atmospheric pressure as we go up?
- Temperature.
- Altitude or Elevation.
- Moisture ow water vapour.
What height of water is atmospheric pressure?
Standard atmospheric pressure supports
33.0 ft
of water and 760 mm of mercury.
Why does pressure decrease with altitude?
As altitude rises, air pressure drops. … As altitude increases,
the amount of gas molecules in the air decreases
—the air becomes less dense than air nearer to sea level. This is what meteorologists and mountaineers mean by “thin air.” Thin air exerts less pressure than air at a lower altitude.
How much does air pressure drop with altitude?
Since more than half of the atmosphere's molecules are located below an altitude of 5.5 km, atmospheric pressure decreases roughly
50%
(to around 500 mb) within the lowest 5.5 km. Above 5.5 km, the pressure continues to decrease but at an increasingly slower rate.
What is the normal range of barometric pressure?
Know what represents reasonable barometer readings
Normal is 29.9; range
~29.6 – 30.2 inches Hg (752-767 mm Hg)
… at SEA LEVEL! Rarely (at sea level) do readings exceed 30.4 inches Hg (773 mm Hg)… except for occasional arctic highs in January.
