A glass capillary sealed at the upper end is of length 0.11 m and internal diameter . The tube is immersed vertically into a liquid of surface tension . To what length has the capillary to be immersed so that the liquid level inside and outside the capillary becomes the same? What will happen to the water level inside the capillary if the seal is now broken?


Correct option is


If A is the cross-sectional area of the tube and L its length, the initial volume of air inside it will be V1 = AL while pressure p1 = p0 = atmospheric pressure.

Now when the tube is immersed in water wit

h its length x in water, the level of water inside and outside is same; so the volume of air in the tube will beV2 = A(L – x). Further if p2 is the pressure of gas in the tube, 


Now if temperature is constant, 





If the seal is broken the pressure inside the capillary will become atmospheric, i.e., p0 while capillary will take place and the rise will be    


However, the length of the tube outside the water is 0.11 – 0.01 = 0.1 m; so the tube will be of insufficient length and so the liquid will rise to the top of the tube and will stay there with radius of meniscus, 






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