Question

Water rises in a capillary tube to a certain height such that the upward force due to surface tension is balanced by $75\times {10}^{-4}\text{N}$ force due to the weight of the liquid. If the surface tension of water is $6\times {10}^{-2}\text{N/m}$, the inner circumference of the capillary tube must be: (Take $\theta =0^{\circ })$

• A. $1.25\times {10}^{-2}\text{m}$
• B. $0.50\times {10}^{-2}\text{m}$
• C. $6.5\times {10}^{-2}\text{m}$
• D. $12.5\times {10}^{-2}\text{m}$

Answer 1

The correct option is D $12.5\times {10}^{-2}\text{m}$

Given: Weight of liquid column = Upward force due to surface tension
$W=\left(2\pi r\right)\times T$
For water $\theta =0^{\circ }$,
$\therefore$ Inner circumference,
$2\pi r=\frac{W}{T}=\frac{75\times {10}^{-4}}{6\times {10}^{-2}}=12.5\times {10}^{-2}\text{m}$