Question

If one end of capilary tubes is dipped into water then water rises up to 3cm. If the surface tension of water is $75\times {10}^{-3}N/m$ then the diameter of capillary will be :-

• A. 0.1 mm
• B. 0.5 mm
• C. 1 mm
• D. 2 mm

Answer 1

The correct option is C 1 mm

The capillary rise in a tube is given by the expression,

$H=\frac{2Tcos\theta }{\rho gr}$

Given, T = 0.075 N/m

H = 0.03 m

$\rho =1000kg/m^3$

$g=10m/s^2$

$\theta =0$ for water

Substituting the values in the equation, $r=0.5$mm

Therefore the diameter of the tube is $2r=1$ mm