One end of a uniform glass capillary tube of radius r = 0.025 cm is immersed vertically in water to a depth h = 1cm. The excess pressure (in `Nm^(-2)`) required to blow an air bubble out of the tube (Given , surface tension of water `= 7 xx 10^(-2) Nm^(-1)`, density of water `= 10^(-3) k gm^(-3)` and acceleration due to gravity `= 10 ms^(-2)`)

Options

A. `0.0048 xx 10^(5)`
B. `0.0066 xx 10^(5)`
C. `1.0048 xx 10^(5)`
D. `1.0066 xx 10^(5)`

Answer

B

Explanation

Excess pressure, `p = hdg + h' dg = dg (h+h')`
where, h is capillary rise `= (2S)/(rdg) = (2 xx 7 xx 10^(-2))/(25 xx 10^(-5) xx 10^(3) xx 10)`
= 0.056 m
`:. p = 10^(3) xx 10[0.056 + 0.01]`
`= 0.066 xx 10^(4) = 0.0066 xx 10^(5) Nm^(-2)`