On heating water, bubbles being formed at the bottom of the vessel detach and rise. Take the bubbles to be spheres of radius R and making a circular contact of radius r with the bottom of the vessel. If `rlt ltR` and the surface tension of water is T, value of r just before bubbles detach is: (density of water is `rho_w`)

Explanation

The bubble will detach if,

Buoyant force`ge` Surface tension force
`(4)/(3) pi R^(3) rho_(w)g geint T xxdl sin theta`
`(rho_(w)) ((4)/(3) pi R^(3))gge(T)(2pir )sin theta`
Here, `sin theta = (r)/(R)`
Solving,` r=sqrt((2rho_(w)R^(4)g)/(3T))=R^(2)sqrt((2rho_(w)g)/(3T))`
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