Water rises higher in narrower tubes than in the broader tubes. Why? 

The height to which the liquid rises in capillary tube is inversely proportional to the radius of the tube. Therefore, water rises higher in narrower tubes than in the broader tubes. 
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Define angle of contact. Is it constant for liquid?

Angle of contact is the angle between the tangents drawn at the point of contact, one along the free surface and second along the solid surface inside the liquid. 
Angle of contact is not fixed for a given liquid but depends upon the solid surface in contact with liquid and media which exists above the free surface of liquid. 

 
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How does the surface tension help in skating?

We know that, with increase of pressure, melting point of ice decreases. Under the skater, ice melts and small tiny water droplets are formed. Due to the small size of water droplets, the excess pressure inside the droplets is sufficiently high and the drops remain spherical in shape. Thus, under the pressure of the skater, drops remain spherical in shape and acts as a ball bearing. Hence, the skater rolls over the drops. 



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What happens if the capillary tube is of insufficient height?

The ascent formula is given by,

                      h=2TRpg  Rh=2Tρg=constant                   

where,
R is the radius of meniscus, and
h is the height to which the liquid rises.

If tube is of insufficient height, the liquid will rise to the top of the tube and spread over the brim. Thus, the radius of meniscus will adjust to a new value so that Rh remains constant. 
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How is the rise of liquid affected if the top of capillary tube is closed?


If the top of the capillary tube is closed, the liquid will rise to lesser height as compared to ordinary condition. This is because the air gets compressed and the pressure will increase. Thus, the top end of the tube being closed will affect the rise of a liquid. 
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