81 model questions from Surface tension - Scientific officer Police forensic / Kerala PSC College Lecturer in Physics / SET - Higher secondary teacher

SURFACE TENSION for Kerala PSC Scientific Officer / Lecturer / SET / Higher secondary teacher - Physics

1. One end of a towel dips into a bucket full of water and other end hangs over the bucket. It is found that after some time the towel becomes fully wet. It happens ...

(a) Because viscosity of eater is high

(b) Because of the capillary action of cotton threads

(c) Because of gravitational force

(d) Because of evaporation of water.

2. For tap water and clean glass, the angle of contact is

(a) 0° (b) 90°

(c) 140° (d) 8°

3.  Water rises up to a height h1 in a capillary tube of radius r. the mass of the water lifted in the capillary tube is M. if the radius of the capillary tube is doubled, the mass of water that will rise in the capillary tube will be

(a) M (b) 2M

(c) (d) 4M

4. Water rises through a height h in a capillary tube of internal radius (r). if T is the S.T. of water, then the pressure difference between the liquid level in the container and the lowest point of the concave meniscus is

(a) (b) (c) (d) 5.  A number of small drops of mercury coalesce adiabatically to form a single drop. The temperature of drop

(a) Increases

(b) Is infinite

(c) Remains unchanged

(d) May decrease or increase depending upon size

6. The angle of contact between a glass capillary tube of length 10 cm and a liquid is 90°. If the capillary tube is dipped vertically in the liquid, then the liquid

(a) Will rise in the tube

(b) Will get depressed in the tube

(c) Will rise up to 10 cm in the tube and will over flow

(d) Will neither rise nor fall in the tube

7. When there are no external forces, the shape of a liquid drop is determined by

(a) Surface tension of the liquid

(b) Density of liquid

(c) Viscosity of liquid

(d) Temperature of air only

8. Choose the wrong statement from the following.

(a) Small droplets of a liquid are spherical due to surface tension

(b) Oil rises through the wick due to capillarity

(c) In drinking the cold drinks through a straw, we use the phenomenon of capillarity

(d) Gum is used to stick two surfaces. In this process we use the property of Adhesion

9. If the surface of a liquid is plane, then the angle of contact of the liquid with the walls of container is

(a) Acute angle (b) Obtuse angle

(c) 90° (d) 0°

10. A capillary tube when immersed vertically in a liquid records a rise of 3 cm. if the tube is immersed in the liquid at an angle of 60° with the vertical, then length of the liquid column along the tube will be

(a) 2 cm (b) 3 cm

(c) 6 cm (d) 9 cm

11. If soap bubbles of different radii are in communication with each other

(a) Air flow from the larger bubble into the smaller one until the two bubbles are of equal size

(b) The sizes of the bubbles remain unchanged.

(c) Air flows from the smaller into the larger on and lager bubble grows at the expense of the smaller one

(d) Air flows from the larger into the smaller one becomes equal to that of the larger one and the large one equal to that of the smaller one.

12. A capillary tube of radius r can support a liquid of weight 6.28 × 10-4 N. if the surface tension of the liquid is 5 × 10-2 N/m. the radius of capillary must be

(a) 2.5 × 10-3 m (b) 2.0 × 10-4 m

(c) 1.5 × 10-3 m (d) 2.0 × 10-3 m

13. The work done in blowing a soap bubble of radius R is W1 and that to a radius 3R is W2. the ratio of work done is

(a) 1:3 (b) 3:1

(c) 1:9 (d) 9:1

14. When the angle of contact between a solid and a liquid is 90°, then

(a) Cohesive force > Adhesive force

(b) Cohesive force < Adhesive force

(c) Cohesive force = Adhesive force

(d) Cohesive force >> Adhesive force

15. Rain drops are spherical in shape because of

(a) Surface tension

(b) Capillary

(c) Downward motion

(d) Acceleration due to gravity

16.  A sheet can be made water proof by coating it with a substance that changes the angle of contact

(a) (b) To zero

(c) From acute to obtuse

(d) From obtuse to acute

17. Which of the following is not based one the principle of capillarity

(a) Floating of wood on eater surface

(b) Ploughing of soil

(c) Rise of oil in wick of lantern

(d) Soaking of ink by bloating paper

18. The rise of a liquid in a capillary tube does not depend upon

(a) Angle of contact

(b) Density of the liquid

(c) Radius of the capillary tube

(d) Atmospheric pressure

19. The height of water in a capillary tube of radius 2 cm is 4 cm. what should be the radius of capillary, if the water rises to 8 cm in tube?

(a) 1 cm (b) 0.1 cm

(c) 2 cm (d) 4 cm

20. The work done to get ‘n’ smaller equal size spherical drops from a bigger size spherical size drop of water is proportional to

(a) (b) (c) (d) 21. For a liquid, which is rising in a capillary tube, the angle of contact is

(a) 90° (b) 180°

(c) Acute (d) Obtuse

22. W is the work done, when a bubble of volume V is formed from a solution. How much work is required to be done to form a bubble of volume 2V?

(a) 2 W (b) W

(c) 21/3 W (d) 41/3 W

23. Two soap bubbles have radii in the ratio of 4:3. What is the ratio of work done to below these bubbles?

(a) 4:3 (b) 16:9

(c) 9:16 (d) 3:4

24. In a surface tension experiment with a capillary tube water rises up to 0.1 m. if the same experiment is repeated on an artificial satellite which is revolving around the earth. The rise of water in a capillary tube will be

(a) 0.1 m

(b) 9.8 m

(c) 0.98

(d) Full length of capillary tube

25. At critical temperature, the surface tension of a liquid

(a) Is zero

(b) Is infinity

(c) Is the same as that at any other temperature

(d) Can not be determined

26. Out of the following. Which one is not an example of capillary action?

(a) Ploughing of the field

(b) Absorption of ink in a blotting paper

(c) Floating of wood on the surface of water

(d) Rise of oil in the wick of a lamp

27. A capillary tube is placed vertically in a liquid. If the cohesive force is less than the adhesive force, then

(a) The meniscus will be convex upwards

(b) The liquid will wet the solid

(c) The angle of contact will be obtuse

(d) The liquid will drip in the capillary tube

28. If the surface of a liquid is plane, then the angle of contact of the liquid with the walls of container is

(a) Acute angle (b) Obtuse angle

(c) 90° (d) 0°

29. The surface of water in contact with glass wall is

(a) Plane (b) concave

(c) convex (d) Both ‘b’ and ‘c’

30. Water rises to a height of 10 cm in a capillary tube, and mercury falls to a depth of 3.42 cm in the same capillary tube. If the density of mercury is 13.6 gm/cm3 and the angle of contact is 135°, the ratio of surface tension for water and mercury is

(a) 1:0.5 (b) 1:3

(c) 1:6.5 (d) 1.5:1

31. Surface tension may be defined as

(a) The work done per unit area in increasing the surface area of a liquid under isothermal condition

(b) The work done per unit area in increasing the surface area of a liquid under adiabatic condition

(c) The work done per unit area in increasing the surface is of a liquid under both isothermal and adiabatic conditions.

(d) Free surface energy per init volume

32. The surface tension for pure water in a capillary tube experiment is

(a) (b) (c) (d) 34. A liquid is kept in a glass vessel. If the liquid solid adhesive force between the liquid and the vessel is very weak as compared to the cohesive force in the liquid, then the shape of the liquid surface near the solid should be

(a) Concave (b) Convex

(c) Horizontal (d) Almost vertical

35. The height of a liquid in a fine capillary tube

(a) Increases with an increase in the density of a liquid

(b) Decreases with a decrease in the diameter of the tube

(c) Decreases with an increase in the surface tension

(d) Increases as the effective value of acceleration due to gravity is decreased

36. When a soap bubble is charged

(a) It contracts

(b) It expands

(c) It does not undergo any change in size

(d) None of these

37. If common salt is dissolved in water, then the Surface Tension of salt water is

(a) Increased

(b) Decreased

(c) Not changed

(d) First decreases and then increases

38. In a capillary tube, fall of liquid is possible when angle of contact is

(a) Acute angle (b) Right angle

(c) Obtuse angle (d) None of these

39. One thousand small water droplets of equal size combine to form a big drop. The ratio of the final surface energy to the initial surface energy is

(Surface tension of water = 70 dyne/cm)

(a) 10:1 (b) 1000:1

(c) 1:10 (d) 1:1000

40. Water can rise up to a height of 12 cm in a capillary tube. If the tube is lowered to keep only 9 cm above the water level then the water at the upper end of the capillary will

(a) Overflow

(b) From a convex surface

(c) From a flat surface

(d) From a concave surface

41. A square frame of length L is immersed in soap solution and taken out. The force experienced by the square plate is
(a) TL (b) 2TL

(c) 4TL (d) 8TL

42. A drop of oil is placed on the surface of water. Which of the following statement is correct?

(a) It will remain on it as a sphere

(b) It will spread as a thin layer

(c) It will partly be as spherical droplets and partly as thin film

(d) It will float as distorted drop on the water surface.

43. Plants get water through the roots because of

(a) Capillarity (b) Viscosity

(c) Gravity (d) Elasticity

44. A liquid does not wet the surface of a solid if the angle of contact is

(a) Zero (b) An acute one

(c) 45° (d) An obtuse one

45. The pressure just below the meniscus of water

(a) Is greater than just above it

(b) Is less than just above it

(c) Is same as just above it

(d) Is always equal to atmospheric pressure.

46. 5 g of water rises in the bore of capillary tube when it is dipped in water. If the radius of bore capillary tube is doubled, the mass of water that rises in the capillary tube above the outside water level is

(a) 1.5 g (b) 10 g

(c) 5 g (d) 15 g

47. When a capillary tube is immersed vertically in water the capillary rise is 3 cm. if the same capillary tube is inclined at angle of 60° to the vertical, the length of the water column in the capillary tube above that of the outside level is (MHT CET 2003)

(a) 6 cm (b) 1 cm

(c) 8 cm (d) Zero

48. Water rises up to a height of 5 cm in a capillary tube of radius 2 mm. what is the radius of the radius of the capillary tube if the water rises up to a height of 10 cm in another capillary?

(a) 4 mm (b) 1 mm

(c) 3 mm (d) 1 cm

49. Water rises up to a height of 4 cm, in a capillary tube immersed vertically in water. What will be the length of water column in the capillary tube, if the tube is immersed in water, at an angle of 60° with the vertical?

(a) 4 cm (b) 6 cm

(c) 8 cm (d) 2 cm

50. Work done in blowing a liquid drop to radius R is W1 and that to radius 3R is W2. the ratio of work done is

(a) 1:3 (b) 1:4

(c) 1:2 (d) 1:9

51. Potential energy of a molecule on the surface of a liquid is as compare to another molecule inside of the liquid is

(a) More (b) Less

(c) Both ‘a’ and ‘b’ (d) None of these

52. Rain drops are spherical because of

(a) Gravitational force

(b) Surface tension

(c) Air resistance

(d) Low viscosity of water

53. Pressure inside two soap bubbles is 1.01 and 1.02 atmospheres. ratio between their volume is

(a) 102:101 (b) (102)3:(101)3

(c) 8:1 (d) 2:1

54. Excess pressure inside a bubble of radius r and of a liquid of surface tension T is

(a) (b) (c) (d) 55. A square frame of side l is dipped in a liquid soap when it is taken out of the liquid, a film is formed on it. If surface tension is T then force acting on it is

(a) 2T l (b) 8T l

(c) 4T l (d) 16T l

56. Two soap bubbles with radii 3 cm and 4 cm combine to form a bubble of large radius R, under isothermal condition. Then R is approximately equal to

(a) (33 + 43)1/3 cm (b) (33 + 43)1/2 cm

(c) (32 + 42)1/2 cm (d) (33 + 42)1/3 cm

57. Meniscus of mercury in capillary is (PMT MP 88)

(a) Concave (b) Convex

(c) Plane (d) Cylindrical

58. Surface tension of liquid is independent of the

(a) Temperature of the liquid

(b) Area of the liquid surface

(c) Nature of the liquid

(d) Impurities present in the liquid

59. For a liquid which is rising in a capillary, he angle of contact is

(a) Obtuse (b) Acute

(c) 180° (d) 90°

60. Two capillary tubes of the same material but of different radii are dipped in a liquid. The heights to which the liquid rises in the two tubes are 2.2 cm and 6.6 cm. the ratio of radii of the tubes will be

(a) 1:9 (b) 1:3

(c) 9:1 (d) 3:1

61. Two soap bubbles have radii in the ratio 2:1. What is the ratio excess of pressure inside them?

(a) 1:2 (b) 2:1

(c) 1:4 (d) 4:1

62. Water rises to a height of 2 cm in a capillary tube held vertically. When the tube is tilted 60° from the vertical, the length of the water column in the tube will be

(a) 2 CM (b) 1 CM

(c) 3 CM (d) 4 CM

63. Find the difference of air pressure between the inside and out side of a soap bubble of 5 mm diameter, if the surface tension is 1.6 N/m

(a) 2560 N/m2 (b) 3720 N/m2

(c) 1208 N/m2 (d) 10132 N/m2

64. For a water does not wet a glass rod, the angle of contact is

(a) Obtuse (b) Acute

(c) 0° (d) 90°

65. The S.T. of soap solution is 25 ×10-3 N/m. the excess of pressure inside a soap bubble of diameter 1 cm is

(a) 10 Pa (b) 20 Pa

(c) 5 Pa (d) None of these

66. when a liquid rises inside a capillary tube, the weight of the liquid in the capillary tube is supported

(a) Entirely by atmospheric pressure

(b) Entirely by the force due to surface tension

(c) Partly by the force due to surface tension and partly by atmospheric pressure

(d) Entirely due to the upward component of the reaction (R) to the surface tension

67. A liquid is kept in a glass beaker. Which molecules of the liquid have the highest potential energy?

(a) Molecules at the bottom of the beaker

(b) Molecules near the centre of the liquid

(c) Molecules lying at half the depth of the liquid and touching the walls of the beaker

(d) Molecules lying in the surface film

68. Kerosene in the wick of lantern rises up because

(a) Of negligible viscosity

(b) The diffusion of the oil through the wick

(c) Of the surface tension of the oil

(d) Wick attracts the kerosene

69. Two soap bubbles of radii 4 cm and 3 cm respectively coalesce under isothermal conditions to form a single bubble. What is the radius of the new single bubble?

(a) 3 cm (b) 4 cm

(c) 5 cm (d) 6 cm

70. At the boiling point of water, its surface tension

(a) Is infinite

(b) Is zero

(c) Is the same as that at room temperature

(d) Is maximum

71. The surface tension of a liquid is 108 dyne/cm2. it is equivalent to

(a) 107 N/m (b) 106 N/m

(c) 105 N/m (d) 104 N/m

72. Nacl dissolved (added) in to water than it surface tension is

(a) Decreases (b) Increases

(c) Remains same (d) All of these

73. Out of the following, which is not an example of capillary action

(a) Absorption of ink in blotting paper

(b) Floating of wood on water surface

(c) Rise of oil wick of a lamp

(d) Ploughing of the field

75. The surface of water in contact with glass wall is

(a) Plane

(b) Convex

(c) Concave

(d) Either convex or concave

76. Water rises to a height of 16.3 cm in a capillary tube of height 18 cm above the water level. If the tube is cut at a height of 12 cm

(a) Water will come out in the form of fountain from the capillary tube

(b) Water will stay at height of 12 cm in the capillary

(c) The height of water in the capillary will be 10.3 cm

(d) Water will flow down the sides of capillary tube

77. More liquid rises in a thin tube because of

(b) Larger value of surface tension

(c) Smaller value of S.T.

78. Excess pressure inside a soap bubble is

(a) Inversely proportional to its radius

(b) Directly proportional to its radius

(c) Directly proportional to square roots of its radius

79. When a liquid rises inside a capillary tube, the weight of the liquid in the tube is supported

(a) By atmospheric pressure

(b) Partly by atmospheric pressure and partly by surface tension

(c) Entirely by the force due to surface tension

(d) Partly by the force due to surface tension

80. When two capillary tube of different diameters are dipped vertically the rise of the liquid is

(a) Same in both the tubes

(b) More in tube of larger diameter.

(c) Less in tube of smaller diameter

(d) More in the tube of smaller diameter

81. Two drops of a liquid are merged to from a single drop. In this process

(a) Energy is released

(b) Energy is absorbed

(c) Energy is remains constant

(d) First ‘B’ then ‘C’