Figure shows a capillary tube of radius r dipped integralo w... | Physics - Surface Tension and Capillary Action | SolveeIt | Solveeit

Today, August 19

Question

Figure shows a capillary tube of radius r dipped into water. If the atmospheric pressure is $P_0$ , the pressure at point A is

Visual representation for Physics

A

$P_0$

B

$P_0 + \frac{2S}{r}$

C

$P_0 - \frac{2S}{r}$

D

$P_0 - \frac{4S}{r}$

Answer

$P_0 - \frac{2S}{r}

Explanation

Solution

Using Laplace’s equation, the pressure difference across a curved surface is

\Delta P = \frac{2S}{r}

Since the meniscus is concave, the pressure inside the liquid at point A is less than the atmospheric pressure by this amount. Thus,

P_A = P_0 - \frac{2S}{r}