NEET UG - Applications of surface tension including drops, bubbles and capillary rise Question Bank with Options

1. When a liquid surface is concave, the pressure in the liquid just below the surface is:

A) Higher than the pressure just above the surface

B) Lower than the pressure just above the surface

C) Equal to the pressure just above the surface

D) Zero

2. The capillary rise method is used to determine:

A) The density of the liquid

B) The viscosity of the liquid

C) The surface tension of the liquid

D) The angle of contact

3. The formation of spherical raindrops is a direct consequence of:

A) Gravitational force minimizing potential energy

B) Surface tension minimizing surface area

C) Air resistance shaping the drop

D) Evaporation causing contraction

4. Which of the following statements about surface tension is incorrect?

A) It is a surface phenomenon.

B) It is directly proportional to cohesive forces.

C) It decreases with an increase in temperature.

D) It is measured in units of force per unit area.

5. The pressure difference across a curved liquid surface is given by:

A) Laplace's pressure formula

B) Young's equation

C) Archimedes' principle

D) Bernoulli's equation

6. In a capillary tube, the pressure at the level of the liquid surface outside the tube is:

A) Equal to the pressure inside the liquid at the same level

B) Less than the pressure inside the liquid at the same level

C) Greater than the pressure inside the liquid at the same level

D) Zero

7. The phenomenon of a water strider walking on water is an example of:

A) Buoyancy

B) Surface tension

C) Viscosity

D) Adhesion

8. If the surface tension of water is 0.07 N/m, and it rises 2 cm in a capillary tube of radius 0.5 mm, what is the approximate angle of contact?

A) 0 degrees

B) 30 degrees

C) 60 degrees

D) 90 degrees

9. What is the term for the force of attraction between molecules of the same substance?

A) Adhesion

B) Cohesion

C) Surface tension

D) Capillarity

10. The rise of water in the narrow pores of soil is primarily due to:

A) Evaporation

B) Capillary action

C) Osmosis

D) Diffusion

11. Why do painters prefer brushes with fine bristles?

A) To increase surface tension of the paint

B) To decrease surface tension of the paint for better spreading

C) To increase adhesion between bristles

D) To reduce the viscosity of the paint

12. The energy required to increase the surface area of a liquid by a unit amount is equal to:

A) Surface tension

B) Surface energy

C) Cohesive force

D) Adhesive force

13. If the angle of contact is 90 degrees, the liquid level in the capillary tube will be:

A) Higher than the surrounding liquid

B) Lower than the surrounding liquid

C) At the same level as the surrounding liquid

D) Zero height

14. Surface tension is a property of:

A) Liquids only

B) Gases only

C) Solids only

D) Liquids and gases

15. The shape of a liquid surface in contact with the atmosphere where adhesive forces are stronger than cohesive forces is:

A) Convex

B) Concave

C) Flat

D) Spherical

16. Which factor does NOT affect the height of capillary rise?

A) Radius of the capillary tube

B) Surface tension of the liquid

C) Density of the liquid

D) Volume of the liquid

17. The excess pressure inside a liquid drop is less than that of a soap bubble of the same radius because:

A) A drop has two free surfaces, while a bubble has one

B) A bubble has two free surfaces, while a drop has one

C) The liquid in a drop is denser

D) The surface tension of a bubble is lower

18. A very fine hole in a boat can cause it to sink because:

A) The weight of the water entering increases the boat's weight

B) Surface tension of water inside the hole is greater than the buoyancy

C) The hole allows water to enter, increasing the boat's density

D) The capillary action pulls water into the boat

19. The ability of a liquid to rise or fall in a narrow tube due to surface tension and adhesion is called:

A) Viscosity

B) Capillarity

C) Surface tension

D) Density

20. Why does a hot liquid have lower surface tension than a cold liquid?

A) Increased cohesive forces at higher temperatures

B) Decreased cohesive forces at higher temperatures

C) Increased adhesive forces at higher temperatures

D) Decreased density at higher temperatures

21. In the context of capillary rise, 'ρ' represents:

A) Surface tension

B) Radius of the tube

C) Density of the liquid

D) Acceleration due to gravity

22. The force of surface tension acts:

A) Perpendicular to the surface and inwards

B) Parallel to the surface and tangential to the surface

C) Perpendicular to the surface and outwards

D) Randomly within the liquid

23. If two soap bubbles of different radii are joined by a tube, air will flow:

A) From the larger bubble to the smaller bubble

B) From the smaller bubble to the larger bubble

C) There will be no flow

D) The flow will be bidirectional

24. Which property explains why water forms beads on a waxed surface?

A) High cohesion, low adhesion

B) Low cohesion, high adhesion

C) High surface tension

D) Low viscosity

25. The excess pressure in a bubble is due to:

A) The weight of the liquid

B) The cohesive forces between liquid molecules

C) The surface tension of the liquid film

D) The atmospheric pressure acting on the bubble

26. In which scenario would capillary depression be observed?

A) Water in a glass tube

B) Mercury in a glass tube

C) Alcohol in a metal tube

D) Oil in a plastic tube

27. The phenomenon that allows a needle to float on the surface of water if placed carefully is:

A) Buoyancy

B) Surface tension

C) Density difference

D) Adhesion

28. Why do aeroplane wings often have a coating to repel water?

A) To increase surface tension

B) To decrease surface tension and improve aerodynamics

C) To increase adhesion to the wing

D) To reduce air resistance

29. If the surface tension of a liquid is 'S' and the radius of a capillary tube is 'r', and the angle of contact is 'θ', the height of capillary rise 'h' is given by:

A) h = 2S cos(θ) / (ρgr)

B) h = S cos(θ) / (2ρgr)

C) h = S sin(θ) / (ρgr)

D) h = 2S sin(θ) / (ρgr)

30. The term 'wetting' in surface tension refers to:

A) The ability of a liquid to form bubbles

B) The tendency of a liquid to spread over a solid surface

C) The resistance of a liquid to flow

D) The force required to break a liquid surface

31. What is the role of detergents in washing clothes?

A) They increase the surface tension of water

B) They decrease the surface tension of water, allowing it to penetrate fabrics better

C) They increase the viscosity of water

D) They cause the dirt to stick more firmly to the fabric

32. The height 'h' of capillary rise is inversely proportional to:

A) Surface tension (S)

B) Radius of the tube (r)

C) Density of the liquid (ρ)

D) Angle of contact (θ)

33. Which of the following liquids exhibits the highest surface tension at room temperature?

A) Alcohol

B) Water

C) Mercury

D) Kerosene

34. If a liquid has a high surface tension, it means:

A) Its molecules are weakly attracted to each other

B) It requires less energy to increase its surface area

C) Its molecules have strong cohesive forces

D) It spreads out easily on a surface

35. A soap bubble has two free surfaces, while a liquid drop has only one. Therefore, the excess pressure inside a soap bubble is:

A) Half that of a liquid drop of the same radius

B) Twice that of a liquid drop of the same radius

C) Equal to that of a liquid drop of the same radius

D) Independent of the type of surface

36. The phenomenon of capillary action is utilized in:

A) Pressure cookers

B) Barometers

C) Lamps (wick action)

D) Hydrometers

37. Which force is dominant in holding a water droplet to a leaf?

A) Gravitational force

B) Electrostatic force

C) Surface tension (adhesion)

D) Viscous force

38. What happens to the surface tension of a liquid when its temperature is increased?

A) It increases

B) It decreases

C) It remains constant

D) It becomes zero

39. In the case of capillary rise, the upward force due to surface tension is balanced by:

A) The weight of the liquid column

B) The viscosity of the liquid

C) The density of the liquid

D) The atmospheric pressure

40. The unit of surface tension is:

A) Newton per meter (N/m)

B) Joule per meter (J/m)

C) Newton meter (N·m)

D) Joule per square meter (J/m²)

41. Surface tension of a liquid is defined as:

A) Force per unit area

B) Energy per unit volume

C) Force per unit length acting parallel to the surface

D) Pressure difference across the surface

42. Capillary depression occurs when the angle of contact is:

A) Acute

B) Right

C) Obtuse

D) Zero

43. When a liquid does not wet the surface, the meniscus in a capillary tube is:

A) Concave

B) Convex

C) Flat

D) Cylindrical

44. The excess pressure inside a liquid drop is given by the formula:

A) 2S/r

B) 4S/r

C) S/r

D) 6S/r

45. Which of the following is NOT an application of surface tension?

A) Formation of dew drops

B) Capillary action in plants

C) Buoyancy of a ship

D) Movement of water through soil

46. If the radius of a capillary tube is doubled, the rise of liquid in the capillary due to surface tension will be:

A) Doubled

B) Halved

C) Quadrupled

D) Unchanged

47. For a liquid that wets the surface, the meniscus in a capillary tube is:

A) Convex

B) Concave

C) Flat

D) Irregular

48. The excess pressure inside a soap bubble is given by the formula:

A) 2S/r

B) 4S/r

C) S/r

D) 6S/r

49. In capillary rise, the liquid rises in a capillary tube if the angle of contact between the liquid and the tube wall is:

A) Obtuse (greater than 90 degrees)

B) Right (equal to 90 degrees)

C) Acute (less than 90 degrees)

D) Zero

50. What causes the formation of a liquid film in a soap bubble?

A) Gravitational pull

B) Cohesive forces between liquid molecules

C) Surface tension of the soap solution

D) Evaporation rate

Applications of surface tension including drops, bubbles and capillary rise - Question Bank