Find out the correct pressure difference if the level of the liquid

[zorro]

Homework Statement

The limbs of a manometer consist of uniform capillary tubes of radii 1.4 x 10^-3 m and 7.2 x 10^-4 m. Find out the correct pressure difference if the level of the liquid (density 10^3 kg/m^3 and surface tension 72 x 10^-3 N/m) in narrower tube stands 0.2 m above that in the broader tube.

Homework Equations

The Attempt at a Solution

Please explain me the meaning of this question. Why is there a false pressure difference?
The manometer measures the pressure of a gas. So it ought to show the correct pressure.

 

[rl.bhat]

The difference between the liquid levels is due to pressure difference due to the liquid and surface tension.
So 0.2 m = ρ*g*h + 2*T/ρ*g*r.

Hence correct pressure difference = ρ*g*h = 0.2 - 2*T/ρ*g*r.

 

[zorro]

so the only error is due to surface tension?

 

[rl.bhat]

so the only error is due to surface tension?

Yes.