A gas pressure difference is applied to the legs of a U-tube manometer filled with a liquid with specific gravity of 1.7. The manometer reading is 320 mm. What is the pressure difference

Answer : pressure difference is Δp=5,32pa

Explanation : the expression for pressure difference at the top of the manometer can be given as

P1-P2=Rg (ρm-ρs) ... 1

For gases, ρs is negligibly small when compared to ρm. So substitute zero for in equation (1) and re-write the final expression

Δp=Rg (ρm)

Here,

Δp is the differential pressure applied to manometer in Pa or psi

R is the difference in the levels of the two interfaces in meters 320mm

To metre = 0.320m

g is the acceleration of gravity

ρm is the manometer liquid density in 9.81m/s²

Specific gravity (sg) of liquid 1.7

Density of water is 997 kg/m³

Sg=density of substance/density of water

1.7=density of substance/997

Density of substance=1.7*997

=1694.9kg/m³

Hence solving for pressure difference

Δp=Rg (ρm)

=0.320*9.81*1694.9

Δp=5,32pa

5320.6 Pascal

Explanation:

Manometer is a pressure measuring device use to measure gas pressure.

Pressure difference in Manometer is a function of density, gravity and the height difference of the liquid.

Pressure difference = density x acceleration due to gravity x difference in height of liquid

Density of liquid = specific gravity of object x density of water.

Density of water = 997 kg/m^3

Specific gravity of liquid = 1.7

Density of liquid = 997 x 1.7 = 1694.9kg/m^3

g = 9.81 m/s^2

h = 320mm = 0.320m

Pressure difference = 1694.9 x 9.81 x 0.320 = 5320.6 Pascal