Question

Which of the following instruments is used to measure the atmospheric pressure?
A) Doctor’s thermometer
B) Speedometer
C) Mercury barometer
D) All of the above

Answer 1

Atmospheric pressure refers to the force exerted on a surface by the air present above that surface. Atmospheric pressure is also known as barometric pressure and is usually expressed in units of Pascals. It can also be expressed as mm Hg.

Complete step by step solution:
Step 1: Explain mercury barometer with an appropriate diagram.

The above diagram represents a mercury barometer. The mercury barometer consists of a glass tube which is open at one end and closed at the other. The tube is dipped in an open vessel containing mercury. The high force exerted on the vessel by the air above its surface forces mercury to rise in the glass tube. The rise of mercury in the tube will thus be in correspondence with the atmospheric pressure. The height of mercury from the surface of the vessel gives the atmospheric pressure and it is expressed in millimetres of mercury.

The atmospheric pressure can thus be measured using the mercury barometer. It can also be used to determine the altitude of a place and also finds many applications in fluid mechanics.

Therefore, the correct option is C.

Additional information: The doctor’s thermometer also known as the medical thermometer is used to measure the temperature of a body (human body or animal body). The speedometer is an instrument that is used to measure the speed of a vehicle. It simply determines how fast an automobile is moving at any instant of time.

Note: If the atmospheric pressure is low, the mercury in the tube will drop. If the atmospheric pressure is high, the mercury in the tube will rise. At the sea level, the atmospheric pressure is maximum. The atmospheric pressure decreases with an increase in altitude from the surface of the Earth.