When a long glass capillary tube of radius 0.015 cm is dipped in a liquid, the liquid rises to a height of 15 cm within it. If the contact angle between the liquid and glass to close to 0°, the surface tension of the liquid, in milli Newton m?¹, is [ρ(liquid) = 900kgm?³, g = 10 ms?²] (Give answer in closest integer)
When a long glass capillary tube of radius 0.015 cm is dipped in a liquid, the liquid rises to a height of 15 cm within it. If the contact angle between the liquid and glass to close to 0°, the surface tension of the liquid, in milli Newton m?¹, is [ρ(liquid) = 900kgm?³, g = 10 ms?²] (Give answer in closest integer)
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1 Answer
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The height of capillary rise is given by the formula:
h = (2T cosθ) / (rρg)
Given: h = 15 cm = 0.15 m, r = 0.015 cm = 1.5 × 10? m, ρ = 900 kg/m ³, g = 10 m/s², and θ ≈ 0° (so cosθ ≈ 1).
We need to find the surface tension, T.
T = (h r ρ g) / (2 cosθ)
T = (0.15 * 1.5 × 10? * 900 * 10) / 2
T = 0.10125 N/m
The answer is required in milliNewton m? ¹, so we multiply by 1000.
T = 101.25 mN/m.
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