Question

A device used to measure atmospheric pressure is called
A. Manometer
B. Barometer
C. Hydraulic brakes
D. All

Answer 1

Hint: Find out the meaning of each device given in the options and check the uses of the devices. One point may help that all of the devices given work on the mechanics of fluids. The substance used in each is a fluid.

Complete step-by-step answer:

The device used to measure atmospheric pressure is called a barometer. The common use of a barometer is to check the rise or fall in the pressure of the atmosphere. This is how weather conditions are predicted. Barometer also helps in understanding the nature of storms.
A classical barometer consists of a glass tube with one end sealed and other end open. This tube is filled with mercury and placed upside down in a bigger container called a reservoir. Even the reservoir contains mercury. When the tube is placed inside the reservoir, due to pressure difference the mercury level in the glass tube decreases creating vacuum at the top of the tube.
A barometer works on Pascal's law. The pressure in a fluid at a certain horizontal level is the same at every point on this level, irrespective of the size of the container.
We know to calculate the pressure in a mercury column. If we know the pressure of mercury at a certain level, it will be the same at any other point on this level. The pressure of air just above the reservoir is equal to the pressure in the mercury column at the same level.
Therefore, when the mercury level rises, it means that the atmospheric pressure is high. When the mercury level comes down, it tells us that the pressure of the atmosphere is low. This is how the weather forecasts are shown.

Note: Let us see what the options given are used for.
Manometer is a simple device used to measure gauge pressure of fluids. Gauge pressure is the pressure measured at a point relative to the local atmospheric pressure. In other words, it does not include the contribution of atmospheric pressure.
Hydraulic brakes are used in vehicles. These brakes work on the principle of Pascal’s law for fluids.