NEET Physics Surface Tension Surface Energy and Capillarity MCQs Set A

Question.  A water film is formed between two straight parallel wires of 10 cm length 0.5 cm apart. If the distance between wires is increased by 1 mm. What will be the work done ? (surface tension of water = 72 dyne/cm)
(a) 144 erg
(b) 72 erg
(c) 288 erg
(d) 36 erg

Answer: A

Question.  The work done in increasing the size of a soap film from 10 cm × 6 cm to 10 cm × 11 cm is 3 × 10^–4J. The surface tension of the film is
(a) 3 × 10^–2 N/m
(b) 11 × 10^–2 N/m
(c) 6 × 10^–2 N/m
(d) 1.5 × 10^–2 N/m

Answer: A

Question. A mercury drop of radius 1 cm is sprayed into 106 drops of equal size. The energy expressed in joule is (surface tension of Mercury is 460 × 10^–3 N/m)
(a) 0.057
(b) 5.7
(c) 5.7 × 10^–4
(d) 5.7 × 10^–6

Answer: A

Question.  A 20 cm long capillary tube is dipped in water. The water rises up to 8 cm. If the entire arrangement is put in a freely falling elevator the length of water column in the capillary tube will be
(a) 20 cm
(b) 4 cm
(c) 8 cm
(d) 10 cm

Answer: A

Question. In a capillary tube, water rises to 3 mm. The height of water that will rise in another capillary tube having one-third radius of the first is
(a) 9 mm
(b) 6 mm
(c) 3 mm
(d) 1 mm

Answer: A

Question.  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) full length of the capillary tube
(b) 0.98 m
(c) 0.2 m
(d) 0.1 m

Answer: A

Question.  Water rises in a capillary tube to a certain height such that the upward force due to surface tension is balanced by 7.5 × 10^–4N force due to the weight of the liquid. If the surface tension of water is 6 × 10^–2Nm^–1, the inner circumference of the capillary tube must be
(a)   1.25 × 10^–2m
(b) 0.50 × 10^–2m
(c) 12.5 × 10^–2m
(d) 6.5 × 10^–2m

Answer: C

Question.  Radius of a capillary tube is 2 × 10^–3m. A liquid of weight 6.28 × 10^–4 N may remain in the capillary then the surface tension of liquid will be
(a) 5 × 10^–2 N/m
(b) 50 N/m
(c) 5 N/m
(d) 5 × 10³ N/m

Answer: A

Question. Two capillary tubes A and B of diameter 1 mm and 2 mm respectively are dipped vertically in a liquid. If the capillary rise in A is 6 cm, then the capillary rise in B is
(a) 3 cm
(b) 4 cm
(c) 6 cm
(d) 2 cm

Answer: A

Question.  Water rises to a height of 10 cm in capillary tube and mercury falls to a depth of 3.1 cm in the same capillary tube. If the density of mercury is 13.6 and the angle of contact for mercury is 135°, the approximate ratio of surface tensions of water and mercury is
(a) 1 : 6
(b) 1.5 : 1
(c) 1 : 3
(d) 1 : 0.15

Answer: A

Question.  In a capillary rise experiment, the water level rises to a height of 5 cm. If the same capillary tube is placed in water such that only 3 cm of the tube projects outside the water level, then
(a) angle of contact increases
(b) the meniscus completely vanishes
(c) angle of contact decreases
(d) water will begin to overflow through the capillary

Answer: A

Question. Surface tension of a liquid is due to
(a) cohesive force between molecules
(b) adhesive force between molecules
(c) electrical force between molecules
(d) gravitational force between molecules

Answer: A

Question.  If a soap bubble formed at the end of the tube is blown very slowly, then the graph between excess pressure inside the bubble with time will be a
(a) parabolic curve sloping down
(b) parabolic curve sloping up
(c) straight line sloping down
(d) straight line sloping up

Answer: A

Question.  Surface tension may be defined as
(a) the work done per unit area in increasing the surface area of a liquid under isothermal conditions
(b) the work done per unit area in increasing the surface area of a liquid under adiabatic conditions
(d) free surface energy per unit volume

Answer: A

Question.  At critical temperature, the surface tension of a liquid is
(a) zero
(b) infinity
(c) the same as that at any other temperature
(d) None of these

Answer: A

Question.   If two soap bubbles of different radii are in communication with each other then
(a) air flows from the smaller bubble into the larger one and the larger one grows at the expense of the smaller one
(b) the air flows from the larger into the smaller bubble until the radius of the smaller one becomes equal to that of the larger one and of the larger one equal to that of the smaller one.
(c) the size of the bubbles remains the same
(d) air flows from the larger bubble into the smaller one until the two bubbles are of equal size

Answer: A

Question.  Two water droplets merge with each other to form a larger droplet. In this process
(a) energy is liberated
(b) energy is absorbed
(c) energy is neither liberated nor absorbed
(d) some mass is converted into energy

Answer: A

Question.  Consider the following statements and select the true statement(s)?
I. A large soap bubble shrinks while a small soap bubble expands when they are connected to each other by a capillary tube, in order to gain equilibrium
II. The raindrops fall on the surface of earth with the same constant velocity
III. A hydrogen filled balloon stops rising after it has attained a certain height in the sky
(a) III only
(b) I & III
(c) II only
(d) I only

Answer: A

Question.  For a given volume which of the following will have minimum energy?
(a) Sphere
(b) Cube
(c) Cone
(d) All have same energy

Answer: A

Question.  When a pinch of salt or any other salt which is soluble in water is added to water, its surface tension
(a) increases
(b) decreases
(c) may increase or decrease depending upon salt
(d) None of these

Answer: A

Question. If more air is pushed in a soap bubble, the pressure in it
(a) becomes zero
(b) increases
(c) decreases
(d) remains same

Answer: A

Question. A drop of oil is placed on the surface of water. Which of the following is correct?
(a) It will spread as a thin layer
(b) It will partly be a spherical droplet and partly a thin film
(c) It will float as a distorted drop on the water surface
(d) It will remain on it as a sphere

Answer: A

Question. Kerosene oil rises up in a wick of a lantern because of
(a) capillary action
(b) buoyant force of air
(c) the gravitational pull of the wick
(d) diffusion of the oil through the wick

Answer: A

Question. Assertion : Surface tension of all lubricating oils and paints is kept high.
Reason : Due to high value of surface tension the fluids don't get damaged.
(a) Assertion is incorrect, reason is correct
(b) Assertion is correct, reason is incorrect
(c) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
(d) Assertion is correct, reason is correct; reason is a correct explanation for assertion

Answer: A

Question.  With the increase in temperature, the angle of contact
(a) decreases
(b) increases
(c) remains constant
(d) sometimes increases and sometimes decreases

Answer: A

Question. Due to capillary action, a liquid will rise in a tube if angle of contact is
(a) acute
(b) obtuse
(c) 90º
(d) zero

Answer: A

Question.  Select the false statement(s) about surface tension from the following?
I. Surface tension is the extra energy that the molecules at the interface have as compared to the molecules in the interior
II. The value of surface tension is independent of the temperature
III. Surface tension causes capillary action
(a) II only
(b) I & II
(c) I, II & III
(d) I only

Answer: A

Question. A glass capillary tube of inner diameter 0.28 mm is lowered vertically into water in a vessel. The pressure to be applied on the water in the tube so that water level in the tube is same as that in the vessel in N/m² is (surface tension of water = 0.07 N/m, atmospheric pressure = 10⁵ N/m²)
(a) 99 × 10³
(b) 100 × 10³
(c) 101 × 10³
(d) 10³

Answer: A

Question. Assertion : Smaller the droplets of water, spherical they are.
Reason : Force of surface tension is equal, and opposite to force of gravity.
(a) Assertion is correct, reason is incorrect
(b) Assertion is incorrect, reason is correct
(c) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
(d) Assertion is correct, reason is correct; reason is a correct explanation for assertion

Answer: A