To demonstrate the shape of capillary rise in a wedge-shaped gap between two glass sheets and in capillary tubes of different radius.
Angle of contact
Surface of liquid near plane of contact with another medium is curved. Angle between tangent to the liquid at point of contact and solid surface inside the liquid is angle of contact.
θ is the angle of contact
When capillary tube immerses in liquid if angle of contact is acute liquid rises through capillary tube. This is known as capillary rise.
s = surface tension of liquid
θ = angle of contact
ρ = density of liquid
r = radius of capillary tube
g = acceleration due to gravity
If cosθ is negative liquid in capillary tube will be lower.
For water cosθ = 1
Capillary rise will be high for the capillary tubes of small radius.