Water rises to a height h in capillary tube. If the length of capillary tube above the surface of water is made less than h, then (a) water rises upto a point a little below the top and stays there. (b) water does not rise at all. (c) water rises upto the tip of capillary tube and then starts overflowing like a fountain. (d) water rises upto the top of capillary tube and stays there without overflowing.

Answer: (d). hR = (2T)/(ρ g) is constant, where R is the meniscus radius. If the tube length h' R. No extra force pushes water out, so there is no overflow. So the answer is (d) water rises to the top and stays there without overflowing.

Water rises to a height h in capillary tube. If the length of… | NEET 2015 (AIPMT)

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Angle of Contact & Capillarity

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

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Answer: (d)

$hR = \frac{2T}{\rho g}$ is constant, where $R$ is the meniscus radius.
If the tube length $h' < h$ , water reaches the top and the meniscus flattens so that $R' = \frac{hR}{h'} > R$ .
No extra force pushes water out, so there is no overflow.
So the answer is (d) water rises to the top and stays there without overflowing.

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