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14. A capillary tube made of glass is dipped into mercury. Then

(a) Mercury rises in the capillary tube (b) Mercury rises and flows out of the capillary tube (c) Mercury descends in the capillary tube (d) Mercury neither rises nor descends in the capillary tube Ans. c (8)

13. Water rises in a capillary tube when its one end is dipped vertically

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) …

12. A vessel, whose bottom has round holes with diameter of 0.1mm, is filled with water. The maximum height to which the water can be filled without leakage is (S.T. of water =75 dyne/cm, g =1000 cm/s2)

(a) 100 cm (b) 75 cm (c) 50 cm (d) 30 cm Ans. d (42)

10. When a capillary is dipped in water, water rises to a height h . If the length of the capillary is made less than h , then

(a) The water will come out (b) The water will not come out (c) The water will not rise (d) The water will rise but less than height of capillary Ans. b (24)

9. Two capillaries made of the same material with

(a) 7.5 cm (b) 60 cm (c) 15 cm (d) 120 cm Ans. c (13)

4. Two parallel glass plates are dipped partly in the liquid of density ‘d’ keeping them vertical. If the distance between the plates is ‘x’, surface tension for liquids is T and angle of contact is θ, then rise of liquid between the plates due to capillary will be

(a) T cosθ/xd (b) 2T cosθ/xdg (c) 2T/xdg cosθ …

5. water rises in a capillary tube to a certain height such that the upward force due to surface

Water rises in a capillary tube to a certain height such that the upward force due to surface tension is balanced by 75 X 10-4 N force due to the weight of the liquid. If the surface tension of water …

3. In the state of weightlessness, a capillary tube is dipped in water, then water

(a) Will not rise at all (b) Will rise to same height as at atmospheric pressure (c) Will rise to less height than at atmospheric pressure (d) Will rise up to the upper end of the capillary tube of any …

8. Two capillaries made of same material but of different radii are dipped in a liquid. The rise of liquid in one capillary is 2.2 cm and that in the other is 6.6 cm. The ratio of their radii is

(a) 9 : 1 (b) 1 : 9 (c) 3 : 1 (d) 1 : 3 Ans. c (11)

7. Two capillary tubes P and Q are dipped in water. The height of water level in capillary P is 2/3 to the height in Q capillary. The ratio of their diameters is

(a) 2 : 3 (b) 3 : 2 (c) 3 : 4 (d) 4 : 3 Ans. b (10)

6. It is not possible to write directly on blotting paper or newspaper with ink pen

(a) Because of viscosity (b) Because of inertia (c) Because of friction (d) Because of capillarity Ans. d (44)

2. A large number of water drops each of radius r combine to have a drop of radius R. If the surface tension is T and the mechanical equivalent of heat is J, then the rise in temperature will be

(a) 2T/rJ (b) 3T/RJ (c) 3T/J[(1/R )-(1/R)] (d) 2T/J[(1/r)-(1/R)] Ans. c (30)

1. There is a horizontal film of soap solution. On it a thread is placed in the form of a loop. The film is pierced inside the loop and the thread becomes a circular loop of radius R. If the surface tension of the loop be T, then what will be the tension in the thread

(a) πR2/T (b) πR2T (c) 2πRT (d) 2RT Ans. d (21)

2. Due to capillary action, a liquid will rise in a tube, if the angle of contact is

(a) Acute (b) Obtuse (c) 90° (d) Zero Ans. a (3)

1. When two capillary tubes of different diameters are dipped vertically, the rise of the liquid is

(a) Same in both the tubes (b) More in the tube of larger diameter (c) Less in the tube of smaller diameter (d) More in the tube of smaller diameter Ans. d (35)

4. In a surface tension experiment with a capillary tube water rises upto 0.1 m. If the same experiment is repeated on an artificial satellite, which is revolving around the earth, water will rise in the capillary tube upto a height of

(a) 0.1 m (b) 0.2 m (c) 0.98 m (d) Full length of the capillary tube Ans. (d) In the satellite, the weight of the liquid column is zero. So the liquid will rise up to the top of the …

3. An air bubble in a water tank rises from the bottom to the top. Which of the following statements are true

(a) Bubble rises upwards because pressure at the bottom is less than that at the top. (b) Bubble rises upwards because pressure at the bottom is greater than that at the top. (c) As the bubble rises, its size increases …

2. Assertion : It is better to wash the clothes in cold soap solution. Reason : The surface tension of cold solution is more than the surface tension of hot solution.

Read the assertion and reason carefully to mark the correct option out of the options given below: (a) If both assertion and reason are true and the reason is the correct explanation of the assertion. (b) If both assertion and …

3. Which graph represents the variation of surface tension with temperature over small temperature ranges for water

Ans. b (7)

2. A soap bubble is blown with the help of a mechanical pump at the mouth of a tube. The pump produces a certain increase per minute in the volume of the bubble, irrespective of its internal pressure. The graph between the pressure inside the soap bubble and time t will be-

Ans. a (12)

1. The correct curve between the height or depression h of liquid in a capillary tube and its radius is

Ans. b (14)

4. Assertion : A needle placed carefully on the surface of water may float, whereas a ball of the same material will always sink. Reason : The buoyancy of an object depends both on the material and shape of the object.

14. Assertion : The shape of a liquid drop is spherical. Reason : The pressure inside the drop is greater than that of outside.

13. Assertion : Hot soup tastes better than the cold soup. Reason : Hot soup has high surface tension and it does not spread properly on our tongue.

3. Assertion : When height of a tube is less than liquid rise in the capillary tube, the liquid does not overflow. Reason : Product of radius of meniscus and height of liquid in capillary tube always remains constant.

1. Assertion : It is easier to spray water in which some soap is dissolved. Reason : Soap is easier to spread.

12. Assertion : The water rises higher in a capillary tube of small diameter than in the capillary tube of large diameter. Reason : Height through which liquid rises in a capillary tube is inversely proportional to the diameter of the capillary tube.

11. Assertion : Tiny drops of liquid resist deforming forces better than bigger drops. Reason : Excess pressure inside a drop is directly proportional to surface tension.

10. Assertion : A large soap bubble expands while a small bubble shrinks, when they are connected to each other by a capillary tube. Reason : The excess pressure inside bubble (or drop) is inversely proportional to the radius.

9. Assertion : At critical temperature, surface tension of a liquid becomes zero. Reason : At this temperature, intermolecular forces for liquids and gases become equal. Liquid can expand without any restriction.

8. Assertion : The concept of surface tension is held only for liquids. Reason : Surface tension does not hold for gases.

7. Assertion : The angle of contact of a liquid decrease with increase in temperature. Reason : With increase in temperature, the surface tension of liquid increase.

6. Assertion : The impurities always decrease the surface tension of a liquid. Reason : The change in surface tension of the liquid depends upon the degree of contamination of the impurity.

5. Assertion : A large force is required to draw apart normally two glass plate5. Assertion : A large force is required to draw apart normally two glass plates enclosing a thin water film. Reason : Water works as glue and sticks two glass plates. s enclosing a thin water film. Reason : Water works as glue and sticks two glass plates.

46. 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 …

45. The force required to take away a flat circular plate of radius 2 cm from the surface of water, will be (the surface tension of water is 70 dyne/cm)

(a) 280 π dyne (b) 250 π dyne (c) 140 π dyne (d) 210 π dyne Ans. a (37)

44. A thread is tied slightly loose to a wire frame as in figure and the frame is dipped into a soap solution and taken out. The frame is completely covered with the film. When the portion A punctured with a pin, the thread.

(a) Becomes concave toward A (b) Becomes convex towards A (c) Remains in the initial position (d) Either (a) or (b) depending on the size of A w.r.t. B Ans. a (15)

43. A wooden stick 2m long is floating on the surface of water. The surface tension of water 0.07 N/m. By putting soap solution on one side of the sticks the surface tension is reduced to 0.06 N/m. The net force on the stick will

(a) 0.07 N (b) 0.06 N (c) 0.01 N (d) 0.02 N Ans. d (11)

42. The dimensions of surface tension are

(a) MLT-1 (b) ML2 T-2 (c) ML0 T-2 (d) ML-1T-2 Ans. c (9)

41. The property utilized in the manufacture of lead shots is

(a) Specific weight of liquid lead (b) Specific gravity of liquid lead (c) Compressibility of liquid lead (d) Surface tension of liquid lead Ans. d (6)

Ajneesh

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