Question

A capillary tube of radius r is dipped in a liquid f density $\rho$ and surface tension S. If the angle of contact is $\theta$, the pressure difference between the two surfaces in the beaker and the capillary.

• A. $\frac{S}{r}cos\theta$
• B. $\frac{2S}{r}cos\theta$
• C. $\frac{S}{rcos\theta }$
• D. $\frac{2S}{rcos\theta }$

Answer 1

The correct option is B $\frac{2S}{r}cos\theta$

As we know,

$S=\frac{rhdg}{2\cos \theta }$

$\Rightarrow$ Pressure difference $=hdg=\frac{2S}{r}\cos \theta$