A liquid is placed in a narrow capillary tube. Which statement correctly describes the role of the contact angle θ in capillary rise or depression?
Options

Question

A liquid is placed in a narrow capillary tube. Which statement correctly describes the role of the contact angle θ in capillary rise or depression?

G1 Physics · Accepted Answer

The ideal capillary-height relation is h = [2S cosθ] / [ρgr]. If θ < 90°, then cosθ > 0, so the liquid rises. If θ > 90°, then cosθ < 0, so h is negative and the liquid surface is depressed. At θ = 90°, cosθ = 0, so there is no ideal capillary rise or depression. Correct option: B.