Capillary rise and angle of contactकेशिका उन्नयन और स्पर्श कोण

NCERT Fig 9.15, 9.18 · interactive diagram

Parts and their functions

• Water in a beaker (बीकर में जल) — Outside level.
• Capillary tube, concave meniscus (केशिका नली, अवतल मेनिस्कस) — Pressure just below the curved surface is lower by 2S/r (for θ ≈ 0), so water is pushed up.
• Rise h (उन्नयन h) — h = 2S cos θ/(ρgr): narrower tube ⇒ higher rise. Mercury (θ > 90°) is depressed.
• Tube radius r (नली की त्रिज्या r) — Halving r doubles h.
• Acute angle of contact (न्यून स्पर्श कोण) — Water–glass: adhesion > cohesion, θ < 90°, the liquid spreads and wets. Detergents reduce θ further.
• Obtuse angle of contact (अधिक स्पर्श कोण) — Mercury–glass: cohesion > adhesion, θ > 90°, drops form; the surface is not wetted.

Original diagram drawn by Simple Learning Hub, based on NCERT Fig 9.15, 9.18. Report a mistake