Tools of pressure

Manometer

Barometer

The application of straw

Pressure gauge

What is pressure ?

Pressure is the ratio between the force

exerted upon specific area

P = ــــــــــــــــ

Pressure has the unit of N/M2 this unit is

called Pascal in the SI system of units

pressure may also use unit of Ib/in2

F

A

The manometer

Manometer is a tool for measuring the

pressure

Figure.1 Figure.2

Manometer depends on 3 factors;

1. the Height of the column of the fluid

[H]

2. The density of the fluid [ρ]

3. The gravitaional constant [g] which

equal 9.81 m/s2

So the pressure in manometer = H x ρ x

g

The barometer Measurement tool for pressure of gases

[atmospheric pressure]

It depends on the direct proportional

between the pressure of the air

[atmospheric pressure] and the

height of the column of the mercury.

The straw

The straw depends on the idea of the

barometer that;

[as the atmospheric pressure decreases

the height of the column of liquid

increases]

1. When you take a smell by opening your lungs;

2. You increase the volume where the same air is separated,

3. Then the density of air is increasing.

4. The pressure of the air is decreasing and the air transport from high pressure to law.

5. The pressure in the straw get smaller. It makes the height of the liquid’s column increases

Pressure gauge

Measurement tool for pressure

The measured fluid flow through the

pump to make the needle to move.

Where the needle stops, the read value

is the value of the pressure

Gauge pressure Vs total

pressure Total pressure =

the pressure on the surface of the liquid

+ the atmospheric pressure [gauge

pressure]

Gauge pressure =

total pressure – the pressure on the

surface of the liquid

Problems