Prelims 2012 · archive
MediumConsider the following statements:
If there were no phenomenon of capillarity
- 1.it would be difficult to use a kerosene lamp
- 2.one would not be able to use a straw to consume a soft drink
- 3.the blotting paper would fail to function
- 4.the big trees that we see around would not have grown on the Earth
Which of the statements given above are correct?
Answer & explanation
Answer: (b) 1, 3 and 4 only
Capillarity is the rise of a liquid through narrow spaces such as fibres, wicks and fine tubes. It feeds the kerosene lamp wick, makes blotting paper absorb ink, and aids the rise of water in plants. A straw works differently: sucking lowers the pressure inside it, and atmospheric pressure on the drink's surface pushes the liquid up. So statements 1, 3 and 4 are correct.
- ✓ 1. Kerosene climbs the cotton wick through the tiny gaps between its fibres by capillary rise. Without capillarity the flame would get no fuel.
- ✗ 2. A straw works by suction. Sucking lowers the pressure inside the straw, and atmospheric pressure on the drink's surface pushes the liquid up. This would work even if capillarity did not exist.
- ✓ 3. Blotting paper is a mass of fine pores between fibres. Ink is drawn into these pores by capillary action. Without capillarity it would not absorb.
- ✓ 4. Water rises to the top of trees through very narrow xylem vessels. Transpiration creates a pull in the xylem. The water column can be pulled up unbroken only because water molecules cling to the vessel walls (adhesion) and to each other (cohesion). These are the same forces behind capillarity. Without them, water could not reach the crowns of tall trees.
Remember · Capillarity explains wicks, blotting paper, soil moisture and water rise in plants. Drinking through a straw is atmospheric pressure at work, not capillarity.
📘 Read it in NCERT: Class 11 Fundamentals of Physical Geography, Ch 5 (practise this chapter) · Class 9 Exploration, Ch 3 (practise this chapter)
Sources
- NCERT Class 11 · Fundamentals of Physical Geography, Chapter 5 “ground water is brought up to the surface by capillary action and in the process the water evaporates leaving behind salts in the soil”
- NCERT Class 9 · Exploration, Chapter 3 “transpiration helps in water transportation by creating a transpiration pull in xylem.”
Question: UPSC Civil Services (Preliminary) 2012, General Studies paper. Explanation: Minimalist IAS, checked 25 Oct 2026 (how we verify). ·