When one end of the capillary is dipped in water, the height of water column is ‘h’. The upward force of 105 dyne due to surface tension is balanced by the force due to the weight of water column. The inner circumference of the capillary is (Surface tension of water = 7 × 10-2 N/m)

Question

When one end of the capillary is dipped in water, the height of water column is ‘h’. The upward force of 105 dyne due to surface tension is balanced by the force due to the weight of water column. The inner circumference of the capillary is (Surface tension of water = 7 × 10-2 N/m) (A) 1.5 cm (B) 2 cm (C) 2.5 cm (D) 3 cm

Tardigrade Admin · Accepted Answer

Upward force acting F =105 dyne =105 × 10-5 N Surface tension of water T =7 × 10-2 N / m Surface tension acts at the circumference C of the capillary tube. ∴ F = CT Or 105 × 10-5= C × 7 × 10-2 Or C =15 × 10-3 m ⇒ C =15 × 10-1 cm =1.5 cm

Q. When one end of the capillary is dipped in water, the height of water column is ‘h’. The upward force of 105 dyne due to surface tension is balanced by the force due to the weight of water column. The inner circumference of the capillary is (Surface tension of water = 7×10−2N/m)

1.5 cm

2 cm

2.5 cm

3 cm

Upward force acting F=105 dyne =105×10−5N Surface tension of water T=7×10−2N/m Surface tension acts at the circumference C of the capillary tube. ∴F=CT Or 105×10−5=C×7×10−2 Or C=15×10−3m ⇒C=15×10−1cm=1.5cm