For a droplet of liquid in equilibrium p i g \u03c0 R 2 \u03c3 2 \u03c0 R 0 p i g is the

# For a droplet of liquid in equilibrium p i g π r 2

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For a droplet of liquid in equilibrium, -( p i ) g ( π R 2 ) + σ (2 π R ) = 0 ( p i ) g is the inside pressure in the droplet above that of the atmosphere. ( p i ) g = 2 σ / R
8 For a bubble of liquid in equilibrium, -( p i ) g ( π R 2 ) + 2 [ σ (2 π R )] = 0 ( p i ) g is the inside gage pressure. ( p i ) g = 4 σ / R For a liquid in contact with a solid, if the adhesion of the liquid to the solid exceeds the cohesion in the liquids, then the liquid will rise curving upward toward the solid. If the adhesion to the solid is less than the cohesion in the liquid, then the liquid will be depressed curving downward. These effects are called capillary effects . The capillary distance, h , depends for a given liquid and solid on the curvature measured by the contact angle θ , which in turn depends on the internal diameter. σ ( π D ) cos θ - ρ g ( π R 2 ) h = 0 The pressure jump across an interface is Δ p = σ (1/ R 1 + 1/ R 2 )

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