Question

The following observations were taken for determining surface tension T of water by capillary method: diameter of capillary, $D = 1.25 \times 10^{-2} \, m$rise of water, $h = 1.45 \times 10^{-2} m$. Using $g = 9.80 \, m/s^2$ and the simplified relation $T = \frac{rhg}{2} \times 10^3 \, N/m$ , the possible error in surface tension is closest to:

• A. $0.15\%$
• B. $1.5\%$
• C. $2.4\%$
• D. $10\%$

Answer 1

Answer: (B)

$1.5\%$

Answer 2

$\frac{\Delta T}{T} \times100 = \frac{\Delta D}{D} \times100 + \frac{\Delta h}{h} \times100$

$= \frac{0.01}{1.25} \times100 + \frac{0.01}{1.45} \times100$

$= \frac{100}{125} + \frac{100}{145}$

$= 0.8 + 0.689$

$= 1.489$ $\simeq 1.5 \%$