What is the minimum size of glass tube
Civil UPSC ESE Exam Solution 2021
UPSC ESE Exam Solution 2021 for Civil Engineering UPSC ESE 2021 GS Paper 1 download exam paper from telegram https://telegram.me/civil_experiences
What is the minimum size of a glass tube that can be used to measure water level if the capillary rise in the tube is to be restricted to 2 mm?
Take surface tension of water in contact with air as 0.073575 N/m
Correct answer for What is the minimum size of glass tube is 1.5 cm.
Detailed Solution for Civil Engineering Exam
Capillary rise = [(4 σ cosθ) / (γ * d)] = h
if h less than or equal to 2 mm
(4 σ cosθ)/(γw * d ) ≤ 2 mm
d ≥ (4 σ cos θ) / (γw * 2 mm)
dmin = (4 σ cos θ)/(γw * 2 mm)
for water glass contact, θ = 0
dmin = (4 σ)//(γw * 2 mm)
dmin = 4 * 0.073575 N/m/(9810 N/m3 * 2 * 10-3 m)
dmin = 0.015 m = 15 mm = 1.5 cm