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1. Surface Energy
Surface energy = Surface tension ´ surface area
2. Rise of Liquid in a Capillary
h =
2 T cos q
, where T is the surface tension of the liquid, q
r r g
is the angle of contact, r is the radius of the capillary bore and r the density of the liquid.
3. Free Surface Energy
For a drop, E = 4pr^{2}T
For a bubble, E = 2 ´ 4pr^{2}T, since a bubble has two free surfaces.
4. Capillary Rise
Difference in heights in the two limbs of a U tube capillary, which is vertical, is
a.
b.
given by, h =
2 T COsq
1

, where r_{1} and r_{2} are the radii of the two limbs of the capillary.
r g
r_{1}
r_{2}
For two different capillaries: (same liquid) h_{1}r_{1} = h_{2}r_{2}
5. Total Surface Area of a Soap Bubble
Total surface area of a soap bubble = 2 ´ surface area
6. Angle of Contact for Water and Glass
For water, angle of contact = q = 0° \ COsq = 1
r = 1 gm/cc : T =
hrg
2
7. Work Done in Breaking a Liquid Drop
If a liquid drop breaks into number of spherical droplets, Work done = T ´ increase in surface area
8. Energy Released During Formation of a Liquid Drop
If liquid drops coalesce to form a single drop, Decrease in surface energy = T ´ decrease in surface area
9. Work Done in Increasing the Radius of a Soap Bubble
Work done in increasing the radius of a soap bubble = T ´ 2 ´ increase in surface area