Question

Name the device used for measuring the pressure exerted by liquids. Also, state its working principle.

Answer 1

Hint: A manometer is used for measuring the pressure exerted by liquids. It works on the principle of hydrostatic equilibrium. According to hydrostatic equilibrium, the excess pressure exerted at a point inside a liquid is equal to the weight of the liquid column above that point.

Complete step by step solution:
We know that there are many devices used for measuring the pressure of liquid as well as of gas.
But according to the concept of hydrostatic equilibrium.
Device: - A manometer is the device used for measuring the pressure exerted by liquids.

Working principle: - Hydrostatic equilibrium is the basic principle of working of a manometer.
Hydrostatic Equilibrium means Hydrostatic made up of two words Hydro and static that is when the liquid is in static equilibrium.
According to it, the pressure at any point on a fluid at static condition is always equal to the value of the weight of the overlying fluid.
Generally, a manometer is U-shaped in which an incompressible fluid like water and mercury is filled. After that when a liquid is put in it then the difference between the raise and depression in the liquid height of the U-tube of the manometer is used to measure pressure.
The formula for pressure difference is given by
$$\text{P = }{\rho }_{\text{2}}g{h}_{\text{2}}-{\rho }_{\text{1}}g{h}_{\text{1}}$$
Where
${\rho }_{\text{2}}$= Density of heavy liquid
${\text{h}}_{\text{2}}$ = Height of heavy liquid above reference line
${\rho }_{\text{1}}$ = Density of light liquid
$h_1$ = Height of light liquid above the reference line.
On the basis of this formula, we easily determine the required pressure that a liquid exerts.

Note:
Hydrostatic equilibrium can be best represented by U-tube. Pressure, as determined by hydrostatic barometers, is often measured by determining the height of the liquid in the barometer column, thus the torr as a unit of pressure, but can be used to determine the pressure in SI units. Hydrostatic based barometers most commonly use water or mercury as the static liquid.