Question

A 10.0 cm column of air is trapped by a column of $Hg$ and a liquid as shown in the figure in a capillary tube of uniform diameter when the tube is held horizontally in a room at 1 atm pressure. The length of the air column when the tube is held vertically with the open end up is: (The relative density of the liquid with respect to $Hg$ is 0.5)

• A. 9.50 cm
• B. 10.52 cm
• C. 3.53 cm
• D. 4.61 cm

Answer 1

The correct option is A 9.50 cm

When column is horizontal pressure of air in column = 1 atm = 76 cm of $Hg$ When column is vertical pressure of air in column $=76+1+\frac{4}{2}+1=80$ cm of $Hg$.
So, $P_1{V}_1=P_2{V}_2$
$\Rightarrow 76\times 10\times A=80\times l\times A$ $\Rightarrow l=9.5cm$