Tag: pressure in liquids and gases

Answer is C.

The mercury level in the tube of the barometer falls until it is about $76 cm (760 mm)$ vertically above the mercury level. It is the atmospheric pressure acting on the surface of the mercury in the trough that supports the vertical mercury column.
The atmospheric pressure is therefore specified by so many millimetres of mercury. For example, the atmospheric pressure is $760 mm$ Hg at sea level.
Hence, The vertical height of mercury which a simple barometer can support at sea level is less than 76 cm. 

A barometer is an instrument that is used to measure pressure.

A barometer is a device used for measuring atmospheric pressure.

A classic mercury barometer is constructed from a 3-foot glass tube that is open at one end and sealed at the opposite end. The glass tube is filled with liquid mercury and rests upside-down in a reservoir of mercury. As the mercury moves down the glass tube, a vacuum is created. When the atmospheric pressure above the reservoir increases, the mercury inside the tube rises. As atmospheric pressure decreases the mercury moves down the tube, into the reservoir.The change in the mercury level in the glass tube is equal to the pressure exerted by the air above the reservoir and is measured using the scale marked on the glass tube. 

A manometer is any device used to measure pressure. However, the word manometer is commonly used to mean a pressure sensor which detects pressure change by means of liquid in a tube.
Manometers are differential pressure sensors. A differential pressure sensor measures the difference between a pressure being applied to it and a reference pressure (often atmospheric pressure). 

Answer is A.

A barometer is a scientific instrument used in meteorology to measure atmospheric pressure. A simple barometer consists of a long glass tube (closed at one end, open at the other) filled with mercury and turned upside down into a container of mercury. The barometer works by balancing the mercury in the glass tube against the outside air pressure, just like a set of scales. As air pressure increasesthat is, as the air becomes heavierit pushes more of the mercury up into the tube. As air pressure decreases, more of the mercury drains from the tube. So the level of mercury in the tube provides a precise measure of air pressure.

• The mercury Barometre was invented by Torricelli.

The tube in a simple barometer is 'completely' filled with mercury so that no air bubble is left inside the tube. 

The height to which mercury rises in simple barometer is $76cm$.

A mercury barometer was discovered by Torricelli in the year 1643.