Pressure - Volume Correction

Pressure correction :

 We all are very much friendly with these words pressure and volume . When I say pressure, suddenly one picture comes in your mind is application of force on any surface area. OK, you are correct, but you know actually what is pressure and what is mechanism of developing pressure ..???
Pressure is nothing but the excitement of molecule which is present inside the air. If I heat the air inside a container at say 60 degree, the molecule of air is started exciting. Firstly when air is at N.T.P. condition the air molecule flows smoothly and that haven't that much energy, but when it is heated at some temperature the molecule are charging its own energy. And after getting some amount of energy to each molecule, they started travelling very fast and hit the container wall with some force. We can also say the molecule become mad and dashed the wall with stored energy. Once it hits the wall it destroy its energy. Once again it recharges its own energy and try to dashed against wall.
The addition of this all small small force make one big force and it create pressure by adding all forces upon the area on which it acts.

Pressure = force / area

Now the question comes what is pressure correction
Suppose is we consider a rectangular box with full of pressurised air and one pressure gauge is mounted on that box and take reading for pressure. Say pressure is 5 bar. But if we go towards CG of body, we get pressure some what 4.96 bar. This is called pressure correction.
Theoretically we say that the pressure is constant throughout the box but in actually its not constant. This is called pressure correction. This is because the hitting of molecule against wall. At surface, molecule get one face to hit. But at C.G. no surface is present. Due to this phenomena pressure correction comes in picture.

Volume correction :

Volume is another major parameter in engineering calculation. When I say volume, you all are started thing about multiplication of length x width x thickness. But you know what is actual meaning of volume ??

Let us take one square container in which the air is present at N.T.P. condition. Volume of that container in general terms is l x b x w. but in engineering language this is not a definition of volume. volume is nothing but a space in which one molecule of air can travel. in above example, air molecule can travel in whole container. That's why volume of container is l x b x w.
now the question rises, what is volume correction ?? if you read above five lines carefully then you also understand the correction factor. let us take same example of container. The volume, in which the molecule can travel is (l x b x w) - (self volume of that molecule). this is what volume correction. it means molecule cannot travel in whole container, i.e. l x b x w.  it can travel only in (l x b x w) - (self volume).  


Thank You.