Question

Atmospheric pressure can be measured by which of the following instruments
(A) Doctor’s thermometer
(B) Mercury barometer
(C) Speedometer
(D) None of these

Answer 1

Hint:First let us see what atmospheric pressure is:
Atmospheric pressure is the force exerted on the ground by the air above it when it is attracted to earth by gravity. Usually atmospheric pressure is measured with a barometer. It is represented by the unit atmosphere. It can also be visualised on the earth’s surface as a column above the surface, reaching all the way to the top of the atmosphere.

Complete step by step answer:
The pressure exerted by air in the atmosphere at the earth’s surface is maximum and reduces as the altitude increases. The explanation for this is that at sea level the density and volume of the atmosphere is highest and decreases with rising altitude. Also, the air molecules are less in number at a high altitude as compared to air molecules at low altitude.
Barometric height is used as a measurement to express the atmospheric pressure and air pressure retaining mercury in the container, so mercury height is used as a unit to reflect the atmospheric pressure.
$P = \rho gh$
Where $P = $pressure, $\rho = $density of liquid, $g = $gravity and $h = $height. This expression is used to measure barometric pressure or height. We can compute the height by understanding the atmospheric pressure. A mercury barometer is a device that measures barometric pressure using the physical properties of mercury in a tube.
So, option B is correct.

Note: We can also calculate atmosphere from the given formula. Also we should not be confused by pressure and atmospheric pressure as the units for pressure and atmospheric pressure are different. While calculating barometer height it is important to note that we should not use mercury barometer as it is heavy and poisonous. An aneroid barometer can be used in place of mercury barometer.