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Capillary rise
Intermediate
Liquid climbs in narrow tubes.
h = 2T cosθ/ρgrIn a narrow tube a liquid rises by h = 2T cosθ/(ρgr) if it wets the wall and falls if not. It helps water move up plants and in paper towels.
Water in a 0.5 mm radius tube: about 3 cm.
Narrower tubes give larger rise.
In more detail
Capillary rise occurs when a liquid climbs a narrow tube because of surface tension and wetting. The height is h = 2γcosθ/(ρgr), where r is the tube radius.
Real-world uses
- Plants draw water up through narrow xylem vessels by capillary action.
- Paper towels absorb liquid through capillary effects.
- Plants draw water up through narrow xylem vessels, a process explained by capillary action.
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Frequently asked questions
Why does a narrower tube rise higher?
Because the pressure difference from surface tension is larger for a smaller radius.
Does mass matter?
Only through density; the rise depends on the liquid density, not the tube mass.
Why does water rise in a thin tube?
Surface tension pulls the liquid up the walls, and the narrower the tube, the higher the column rises.
Related topics in Fluids & Elasticity
Surface energy · Excess pressure in drops and bubbles · Angle of contact · Cohesion and adhesion · Elasticity · Stress