Capillary Action

Liquid & surface Tube radius r: 0.50 mm Contact angle θ: 0° Temperature: 20 °C Gravity

Earth

Moon

Show 3 tubes (compare 1/r) Force-balance diagram

Readout

γ surface tension—

ρ density—

θ contact angle—

r tube radius—

g gravity—

h rise (Jurin)—

verify 2γcosθ/ρgr—

Jurin's law: h = 2γ·cosθ / (ρ·g·r). Surface tension pulls a wetting liquid (θ<90°) up the tube; a non-wetting liquid like mercury (θ>90°) is pushed down. Rise scales as 1/r — halve the radius and the column doubles.