Question

Which of the following instruments is used for measuring gauge pressure?
A. Thermometer
B. Barometer
C. Manometer
D. Hydrometer

Answer 1

Hint: Try to understand the definitions of gauge pressure and Learn the basics of the instruments given in the question which are thermometer, barometer, manometer and the hydrometer and find out what is the purpose of these instruments.

Complete Step-by-Step solution:
Thermometer is a temperature measuring instrument which is used to measure temperature. It is used in medical processes to measure human body temperature or in laboratories. Thermometers have units of temperature degree Celsius.
Barometer is an instrument that is used to measure the atmospheric pressure, which is also called the barometric pressure. Barometer measures atmospheric pressure in terms of bars or atmosphere.
Manometer is an instrument which is used to measure the gas pressure. Here, manometer is an U-shape tube with its one end connected to the source where the pressure is to be measured and the other end is open to the atmosphere. It measures the pressure of the source with respect to the atmospheric pressure.
Hydrometer is an instrument used to measure the density of liquids.
Gauge pressure can be defined as a relative pressure which is measured relative to atmospheric pressure.
Compared with the instruments above, we can say that a manometer is used to measure the gauge pressure. So the correct option is C.

Note: In the manometer the two ends of the instrument are connected to different systems. The liquid inside the tube will rise towards the source if the pressure is lower than the atmospheric pressure or fall if the pressure is greater than the atmospheric pressure. The difference between the liquid levels in two sides of the tube gives us the measure of the pressure.