Our Objective

To demonstrate the shape of capillary rise in a wedge-shaped gap between two glass sheets and in capillary tubes of different radius.

 

The Theory 

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 

Capillary rise 

When capillary tube immerses in liquid if angle of contact is acute liquid rises through capillary tube. This is known as capillary rise. 

                                                    

• Capillary rise (h) = 2s cosθ/ρrg

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 (h) = 2s/ρrg

Capillary rise will be high for the capillary tubes of small radius. 

 

Learning Outcomes 

• Students can understand the concept of capillary rise. 
• Students can understand the relationship between the capillary rise(h) and the radius of capillary tube(r).