Question

In a device designed by Academician Rebinder the surface tension is determined from the pressure difference required to form a bubble of air at the end of a capillary immersed in the liquid being investigated. Calculate the surface tension if the radius of the capillary is r = 1 mm and the difference in the pressures during bubble formation is $\Delta$P = 14 mm of water column. The end of the capillary is near the surface of the liquid.

Answer 1

0.070 N/m

Answer 2

The excess pressure ($\Delta P$) inside a bubble of radius $r$ is related to surface tension ($\gamma$) by $\Delta P = \frac{2\gamma}{r}$. The given pressure difference of 14 mm of water column is converted to Pascals using $\Delta P = \rho_{water}gh$, assuming $\rho_{water} = 1000 \text{ kg/m}^3$ and $g = 10 \text{ m/s}^2$. Substituting the converted $\Delta P$ and the given radius $r$ (in meters) into the formula and solving for $\gamma$ yields the surface tension.