A capillary tube of internal radius r is dipped vertically into a liquid of density ρ, surface tension S and contact angle θ. Neglect the weight of the meniscus. What is the equilibrium capillary rise h?
Options

Question

A capillary tube of internal radius r is dipped vertically into a liquid of density ρ, surface tension S and contact angle θ. Neglect the weight of the meniscus. What is the equilibrium capillary rise h?

Options

G1 Physics · Accepted Answer

The upward vertical component of surface tension around the circumference is F(up) = 2πrS cosθ. The weight of the liquid column of height h is W = πr²hρg. At equilibrium, 2πrS cosθ = πr²hρg. Cancel πr: 2S cosθ = r h ρg. Therefore, h = [2S cosθ] / [ρgr]. Correct option: B.