Question

A capillary tube of inner radius `0.5 mm` is dipped keeping it vertical in a mercury of soecific gravity 13.6, surface tension `545 dyn e//cm` and angle of contact `135^(@)` . Find the depression or elevation of liquid in the tube.

Answer 1

Here, `r=0.5//2 = 0.25 mm = 0.0025 cm`,
Density of mercury , `rho =` specific . gravity `xx` density ofwater` = 13.6 xx 1 = 13.6 g//c c`
Surface tension , `S=545 dyn e//cm`, angle of contact `theta= 135^(@)`. The height of liquid in tube is
`h=(2S cos theta)/(r rho g) = (2 xx 545 xx cos 135^(@))/((0.025)xx13.6 xx 980) = (2xx545xx(-1//sqrt(2)))/(0.025xx13.6xx980)=-2.31 cm`.