Capillarity
Capillarity - or capillary action - is the ability of a narrow tube to draw a liquid upwards against the force of gravity. Calculate the height of liquid in a tube due to capillary action using the formula: h = 2 σ cos(θ) / (ρ g r)
About Capillarity
Capillarity is the ability of a narrow tube to draw a liquid upwards against the force of gravity. The height of liquid in a tube due to capillarity is calculated using:
h = 2 σ cos(θ) / (ρ g r)
Where:
- h = height of liquid (m)
- σ = surface tension (N/m)
- θ = contact angle (0° for clean tube)
- ρ = density of liquid (kg/m³)
- g = acceleration of gravity (9.81 m/s²)
- r = radius of tube (m)
Example
For a clean glass tube with 2 mm diameter containing water at 20°C (density 1000 kg/m³):
- h = 2 (0.0728 N/m) cos(0°) / ((1000 kg/m³)(9.81 m/s²)(0.001 m))
- h = 0.0074 m = 7.4 mm