Question

The limbs of a mono meter consist of uniform capillary tubes of radii 1.4 × 10 ^–3 m and 7.2 × 10 ^–4 m. Find out the correct pressure difference if the level of the liquid (density 10³ kg/m³ ,surface tension 72 × 10 ^–3 N/m) in narrower tube stands 0.2 m above that in the broader tube.

Answer 1

If p¹ and p² are the pressures in the broader and narrower tubes of radii r₁ and r₂ respectively, the pressure just below the meniscus in the respective tubes will be

Assuming the angle of contact to be zero, i.e., radius of meniscus equal to that of capillary,