The lower end of a capillary tube is dipped into water and it is seen that water rises through 7.5 cm in the capillary. Given surface tension of water is `7.5 xx 10^(-2) N//m` and angle of contact between water and glass capillary tube is zero, What will be diameter of the capillary tube ? (Given, `g = 10 ms^(-2)`)

Options

A. 0.2 mm
B. 0.33 mm
C. 0.4 mm
D. 0.5 mm

Answer

C

Explanation

Given, `h=7.5 cm`
`=7.5 xx10^(-2) m implies S=7.5xx10^(-2) Nm^(-1)`
`theta=0^(@), 2r =?`
`h=(2S cos theta)/(r rho g)implies 2r=(4s cos theta)/(h rho g)`
`D=(4xx7.5xx10^(-2)xxcos theta)/(7.5xx10^(-2)xx10^(3)xx10)`
`D=4xx10^(-4) m`
The diameter of the capillary tube, `D=0.4` mm