Question

Pressure exerted by a 76cm high column of mercury is equal to _______ pressure.
A. 1 atmospheric
B. 2 atmospheric
C. 3 atmospheric
D. 4 atmospheric

Answer 1

Hint: To answer this question, consider a barometer which is an instrument to measure air pressure in certain environments. It is a tube sealed at one end which is marked as zero i.e. zero pressure. While the other end is open to the atmosphere. It has a column of mercury fixed in it. The difference in the pressure is proportional to the height of the mercury column. At atmospheric pressure, the mercury column rises to a height of 76 cm from the closed end.

Complete answer:
The scientific instrument used to measure the atmospheric pressure in a certain environment is the Barometer. It measures the atmospheric pressure in terms of height of the mercury column. Mercury is commonly used in the barometers because of its high density. Under normal atmospheric pressure, the mercury column shows a height of 76cm. Gravitational force of the earth is responsible for the decreasing atmospheric pressure with increasing altitude.
Hence, the pressure exerted by a 76cm high column of mercury is equal to 1 atmospheric pressure.

So, the correct answer is “Option A”.

Note:
The atmospheric pressure is also known as barometric pressure. Greater the atmospheric pressure, higher the mercury column rises. The barometric pressure is typically measured in either inches of mercury i.e. in Hg or millibars. Atmospheric pressure varies from place to place and time to time. This variation depends on the altitude or elevation, temperature, water pressure and rotation of the earth. If we want to use water instead of mercury, then a much taller barometer will be required because mercury is much denser than the water.