In a device designed by Academician Rebinder the surface tension is determnined from the pressure difference required to form a bubble of air at the end of a capillary immersed in the liquid being investigated (fig). Calculated the surface tension if the radius of the capillary is `r = 1 mm` and the difference in the pressures during bubble formation is `DeltaP = 14 mm` of water column. The end of the capillary is near the surface of the liquid.

Answer

`70 "dyne"//cm`

Explanation

`2T sin theta = s (R. 2theta) xx 2 `, for small `theta sintheta = theta`
`T = 2SR = 2 xx .030 xx (6.28 xx 10^(-2))/(2 xx 3.14) = 6 xx 10^(-4) N`