Concept:A manometer measures the pressure of fluids by comparing it with the pressure exerted by a liquid column.
Explanation:A common manometer is a U-shaped tube containing a liquid such as mercury, water, or oil.
One limb is connected to the liquid or gas whose pressure is being measured, while the other limb is open to the atmosphere.
The pressure of the fluid acts on the liquid surface and causes the column levels to shift.
At equilibrium, the difference in liquid levels between the two limbs is read directly.
This height difference is related to the pressure by
P=hρg, where
h is the height difference,
ρ is the density of the liquid, and
g is the acceleration due to gravity.
Hence, the instrument measures pressure in liquids and gases, not relative density, humidity, or atmospheric pressure alone.
Answer:B. Pressure in liquids and gases