Question

1. A capillary tube is dipped vertically in a liquid. If the
liquid surface is hemispherical, then the angle of contact
is given by
(a) O = 90°
(b) 0 =0°
(c) 0 > 90°
(d) < 90° but not 0°
​

Answer 1

Explanation:

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Answer 2

Explanation:

Consider a capillary tube of radius r immersed in a liquid of surface tension T and density ρ. The height to which the liquid will rise in the capillary tube is given as

rρg

2Tcosθ

=

Rρg

2T

or

hR=

ρg

2T

which is a constant.

Thus we get

h

1

R

1

=h

2

R

2

When the tube is pushed down we are increasing the h, thereby reducing the radius R of the of the liquid meniscus. Thus as h increases, the level of the liquid becomes more and more flat but does not overflow