Properties Of Solids And Liquids Question 162
Question: Two parallel glass plates are dipped partly in the liquid of density ’d’ keeping them vertical. If the distance between the plates is ‘x’, surface tension for liquids is T and angle of contact is $ \theta $ , then rise of liquid between the plates due to capillary will be[NCERT 1981]
Options:
A) $ \frac{T\cos \theta }{xd} $
B) $ \frac{2T\cos \theta }{xdg} $
C) $ \frac{2T}{xdg\cos \theta } $
D)$ \frac{T\cos \theta }{xdg} $
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Answer:
Correct Answer: B
Solution:
Let the width of each plate is b and due to surface tension liquid will rise upto height h then upward force due to surface tension = $ 2Tb\cos \theta $ -(i)
Weight of the liquid rises in between the plates = $ Vdg=(bxh)dg $ -(ii)
Equating (i) and (ii) we get ,$ 2T\cos \theta =bxhdg $
$ \therefore h=\frac{2T\cos \theta }{xdg} $
