Barometer And Manometer MCQ - Practice Questions with Answers

Barometer-

Mercury Barometer was invented by Torricelli and it is a device used for measuring pressure.

Below is a figure showing the  Mercury Barometer device

From the figure we can say that

At Point C only atmospheric pressure is there.

$$
\mathrm{so}_{\mathrm{o}} P_C=P_0
$$

Ans since $B$ and $C$ are at the same horizontal level
${ }_{\mathrm{s}} P_C=P_B=P_A+\rho g h=0+\rho g h=\rho g h=P_0=$ Atmospheric pressure
For mercury barometer $\mathrm{h}=76 \mathrm{~cm}$ and
And using $\rho=13.6 * 10^3 \mathrm{~kg} / \mathrm{m}^3$
We get $P_0=1.013 * 10^5 \mathrm{~N} / \mathrm{m}^2=1 \mathrm{~atm}=76 \mathrm{~cm}$ of Hg

Manometer-

Manometers are the devices used for measuring gauge pressure of fluids.

Simple Manometer-

The figure of Simple Manometer is given below

And from the figure we can say that

The gauge pressure at point A in the vessel is 

$$
P_A=\rho g h
$$

Where $\rho=$ density of the liquid

U-tube Manometer-

Figure of U-tube manometer is given below

And from the figure we can say that

$$
P_A=P_B
$$

And The gauge pressure at point $A$ is given by

$$
P_A=\rho g h
$$

Where
$\rho_{=\text {density of the liquid }}$