A manometer is an instrument that is commonly used in laboratories and industry to measure which physical quantity?

Introduction / Context:
Many industrial and laboratory processes require accurate measurement of pressure in gases and liquids. Devices that use columns of liquid or mechanical sensors to compare pressures are called manometers. Understanding what a manometer measures is essential in fluid mechanics, chemistry, and engineering practice. This question asks you to identify the physical quantity that a manometer is designed to measure.

Given Data / Assumptions:

• The instrument considered is a manometer.
• Typical manometers include U tube manometers and inclined tube manometers.
• The listed options include earthquake vibrations, pressure, temperature, and density of solids.
• We assume standard usage in fluid systems and laboratories.

Concept / Approach:
A manometer consists of a tube, often U shaped, partially filled with a liquid such as mercury or water. When connected to a system where pressure is to be measured, the difference in liquid column heights indicates the pressure difference between the system and a reference, often atmospheric pressure. The height difference is proportional to pressure difference, given by delta P = rho * g * h. Therefore, the primary physical quantity measured by a manometer is pressure, not temperature, density of solids, or ground motion.

Step-by-Step Solution:
Step 1: Recall that manometers are frequently mentioned in context with gas pressure measurement in chemistry labs and in fluid mechanics problems. Step 2: Understand that they use a liquid column whose height difference corresponds to pressure difference via the relation delta P = rho * g * h. Step 3: Note that earthquake vibrations are measured by seismometers, not by manometers. Step 4: Temperature is measured by thermometers, thermocouples, or other temperature sensors, not by manometers. Step 5: Density of solids is determined by other methods such as Archimedes principle or direct mass and volume measurements, not by manometers.

Verification / Alternative check:
In fluid mechanics laboratories, manometers are connected to pipelines, Venturi meters, or orifice meters to determine pressure differences across components. In chemistry, gas collection experiments use manometers to compare gas pressure with atmospheric pressure. These uses consistently involve pressure measurement. Manuals and textbooks describe manometers as pressure measuring instruments, confirming the correct association.

Why Other Options Are Wrong:
Earthquake vibrations: Recorded by seismographs or seismometers, not by manometers. Temperature: Measured by thermometers and similar instruments, not by liquid columns calibrated for pressure. Density of solids: Determined using mass and volume methods or dedicated density meters, not by manometers.

Common Pitfalls:
Students can confuse manometers with other instruments because many scientific devices end with the suffix meter. It is helpful to associate the root word mano, related to pressure, with this instrument. Remember that barometers and manometers are both pressure instruments, with barometers measuring atmospheric pressure and manometers measuring general pressure differences in fluids.

Final Answer:
A manometer is used to measure pressure.