The Existence of Atmospheric Pressure

Atmospheric pressure is as a result of the weight of this layer of gases, the act at atmospheric pressure is surrounded the layer of air consisting of a mixture of gases.

Note. The atmospheric pressure on the earth's surface and objects on the earth is a approximately
1.01x105N/m2.


Umbler experiment

The experiment which demonstrate the existence of atmospheric pressure.



When you fill a glass timber with cord and gentle turned upside down. It will be seen that water will not poured down.


Plunger
Pulling the plunger is not easy. This is so because all the air is squeezed out from the table when
the surrounding pressure being high the plunger sticks.



Crushed bottle 
When putting hot water in, the bottle is cooled under cold water the steam condenses; leaving partial vacuum inside the bottle consequently the greater atmospheric pressure outside the bottle crushes it in wards.


Applications of Atmospheric Pressure


A siphon

A siphon is applied in areas and devices that we use everyday



1. It is used in the toilet flushing cisterns (chain and ball tank). The flush is triggered by a handle that operates a simple diaphragm like piston pump that lifts enough water.

2. It is used in special rain gauges called siphon rain gauge which are able to automatically drain out excess water.

3. A siphon cup is a reservoir attached to a gum.

4. It is used is some drainage systems to drain water to one point.


The lift pump
A lift pump is used to raise water from underground sources. This is a pump that is used to lift the liquid, rather than force liquid up.

A syringe is a simple piston pump that lifts a tube. The plunger that lifts can be pulled and pushed through inside a cylindrical tube or barrel. This enables the syringe to take in or expel fluid through the opening (nozzle) at the end of the tube.



Syringe



Uses of syringe:

1. They can be fitted with hypodermic needles and used to administer injections.

2. They are used to measure liquids and gases in a laboratory.

3. They are used to apply certain compounds such as a glue or lubricant.


Bicycle pump
This is a type of force pump that consists of a hollow metal cylinder and a movable piston.



Measuring Atmospheric Pressure

Atmospheric pressure is measured by using barometer;



Types of barometer:


i. The simple barometer

A simple barometer is the most fundamental of the other types of barometer. The barometric liquid used is mercury.
A simple barometer consists of a hard glass tube closed at one end.


ii. Fortin barometer

A Fortin barometer is a modified simple barometer. It consists of an inverted tube closed at its upper end with the lower open end immersed in a reserve of mercury. The atmospheric pressure is measured in terms of the height of the column of mercury.


Disadvantages of Fortin barometer:

1. Mercury is very expensive to use and is very toxic. For these reasons, an aneroid barometer is usually preferred.

2. It is not portable as it is generally big and contains liquid.

3. It must be mounted in a vertical position.

iii. Aneroid barometer

This is a type of force pump that consists of a hollow metal cylinder and a movable piston.