Question

When a capillary tube is immersed in ethyl alcohol whose surface tension is $20dynec{m}^{-1}$,the liquid rises to a height of $10cm$. Density of the liquid is $0.8g-c{m}^{-3}$. If $g=10m{s}^{-2}$, the radius of the capillary tube is $......mm.$ (Angle of contact of ethyl alcohol w.r.t. glass is ${60}^o$).

• A. $0.0025$
• B. $0.025$
• C. $0.25$
• D. $2.5$

Answer 1

Answer: (B)

$0.025$

$T=20dyne/cm$
$=0.02N/m$

By using formula for radius, $r=\frac{2Tcos\theta }{h\rho g}$

$r=\frac{2\times 0.02\times \cos 60}{0.1\times 1000\times 10}$

$=0.02mm$