One end ofauniform glass capillary tube of radius r = 0.025 cm is immersed vertically in water to a depth h= 1 cm. The excess pressure in Nm required to blow an air bubble out of the tube (Surface tension of water =`7xx10^-2 N m^-1` Density of water `10^-3 kg m^-3` Acceleration due to gravity =`10 ms^-2`)

Options

A. `0.0048xx10^5`
B. `0.0066xx10^5`
C. `1.0048xx10^5`
D. `1.0066xx10^5`

Answer

B

Explanation

Excess pressure, `P=hdg + h^(')dg = dg (h+ h^('))`
Where,
Capillary rise, `h= (2T)/(rdg) = (2xx7xx10^(-2))/(25xx10^(-5)xx10^(3) xx10) =0.056m`
`therefore P=10^(3) xx 10(0.056 +0.01) = 0.0066 xx 10^(5) N//m^(2)`