# Jurin's law

Capillary rise or fall in a tube.

Jurin's law describes the rise and fall of a liquid within a thin capillary tube. Named after its discoverer James Jurin.

This law is expressed as:

$\qquad h = \frac{2\gamma \cos\theta}{r\rho g}$

where

• h is the liquid height ;
• γ is the liquid surface tension ;
• θ is the contact angle of the liquid on the tube wall ;
• ρ is the liquid density ;
• r is the tube radius ;
• g is the gravitational acceleration.

This law is valid if the tube radius is smaller than the capillary length.