2015 AIPMT-II Mechanical Properties of FluidsCapillarity Medium Question 32 of 34 in Mechanical Properties of Fluids

Water rises to height 'h' in capillary tube. If the length of capillary tube above the surface of water is made less than 'h', then

A water does not rise at all
B water rises upto the tip of capillary tube and then starts overflowing like a fountain
C water rises upto the top of capillary tube and stays there without overflowing
D water rises upto a point a little below the top and stays there

The answer is C.

Solution

Capillary rise: $h = \frac{2T\cos\theta}{r\rho g}$, so $hR$ = constant, where R is the radius of the meniscus.
When the tube is shorter than h, water reaches the top and the meniscus flattens (R increases) until $h'R' = hR$ is satisfied.
So the water rises to the top and stays there without overflowing.

Concept Insufficient capillary length

Mechanical Properties of Fluids in past papers

34 questions from this chapter have appeared across 14 exam years.