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Question: Water rises in a capillary tube when its one end is dipped vertically in it, is 3 cm. If the surface...

Water rises in a capillary tube when its one end is dipped vertically in it, is 3 cm. If the surface tension of water is 75 × 10-3 N/m, then the diameter of capillary will be

A

0.1 mm

B

0.5 mm

C

1.0 mm

D

2.0 mm

Answer

1.0 mm

Explanation

Solution

T=rhρg2⇒75×10−3=3×10−2×r×103×9.82T = \frac { r h \rho g } { 2 } \Rightarrow 75 \times 10 ^ { - 3 } = \frac { 3 \times 10 ^ { - 2 } \times r \times 10 ^ { 3 } \times 9.8 } { 2 }

⇒r=12mm\Rightarrow r = \frac { 1 } { 2 } m m ∴D=2r=1 mm\therefore D = 2 r = 1 \mathrm {~mm}