Education and Career Forum

Please tell me difference in pressure and vaccum with all related formule and conversion of units etc.

Differences:
To get the difference between pressure and vaccum , one must use both the terms in a common situation. So to clear this, have an example of piston-bottle arrangement(very much like the case in reciprocating or cylinder engine).

So in this case whenever user applies a pressure over it, the inner air gets densed and in the other end, if user tries to take piston out , in the same condition, the inner air gets less denser. Means by the second activity , a VACCUM is going to create in between the bottle.
So we can deduce that vaccum is reciprocal to pressure, means

• more the pressure => more the air density in between => No longer Vaccum Exist

but

• Negating the Pressure => Less the air density in between => Vaccum is established.

Such thing can be observed in Injections, if you block the needle end and try to elongate the other end by akichning it.

Formulaes:
There are many formulaes so one must have to constraint himself upto a limit:

• Boyle's Law: P1/P2 = V2/V1
• Cay Lussac Law: V2 / V1 = T2 / T1 = CONSTANT
• Charles law: P1 / P2 = T1 / T2
• Average Free lift: λ＝(5×10-3)/P (cm)
• Suction capacity：S＝dv/dt (L/s) or Q＝Flow volume(Torr·L/s) P＝Pressure Intensity(Torr) S＝Q/P V＝Volume(L) t＝Time(s)
• Pumping time of vacuum:

The calculation formula of the pumping time from ATM to 1Torr : t＝8V/S (experience formula)
V represents the volume，S reprensents the suction capacity，the "t" is usally selected during the 5~10
minutes.

• Rough vacuum pump's suction capacity selection：

S＝Q1/P Pre (l/s)
S=2.3V·lg(Pa/P Pre)/t
S－the efficient suction capacity of the chemical pump
Q1－the vacuum system leakage rate(Torr·L/s)
P Pre－need reach to the preparation vacuum (Torr)
V－vacuum system volume(L)
t－the expending time to reach at the preparation pressure
Pa－ATM(Torr）

ETC.

difference betwen pressure and vacuum