Question

Water rises to height h in the 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 up to the tip of the capillary tube and then starts overflowing like a fountain.
(C) Water rises up to the top of the capillary tube and stays there without overflowing.
(D) Water rises up to a point a little below the top and stays there.

Answer 1

Hint: Know the relation between height of water in a capillary tube and the radius of the capillarity. Apply the given question condition with the relation and find the suitable solution.

Complete step by step Solution:
 The given statement says that the water rises to a height of h in a capillary tube, when it is in contact with the fluid surface. So, at a normal condition, water height h is given as \[h = \dfrac{{2S}}{{\rho gR}}\], where R is radius of capillarity, g is gravity constant and \[\rho \] is liquid density.
 Now consider the second statement, if the length of the capillary tube is made less than h,
It is clear that, Height h is inversely proportional to the capillary radius R. So, it is understandable that, when height above the surface is decreased, there won’t be any motion as the water rises till height h and stays put.
 Overflowing of water is impossible because there isn’t any external pull experienced by the water molecules that cause it to overflow from the capillary tube. If the force is increased then, there are chances that water levels might witness an overflow. At the given height, the water present inside the column balances the upward force, thus making it stay inside the tube.

Hence, Option (c) is the right answer

Note:
Capillary rise of fluid is defined as the ability of fluids to flow through narrow spaces. When a capillary tube is placed on a fluid containing a tank, the liquid on the surface begins to flow inside the walls of the capillary tube, which rises against the gravity. The liquid rises due to the adhesion, cohesion and surface tension it experiences due to the contact with the tube surface.