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InterviewSolution
This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
Pressure inside two soap bubbles are `1.01` and `1.02` atmospheres. Ratio between their volumes isA. `2:1`B. `1:2`C. `8:1`D. `1:8` |
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Answer» Correct Answer - C Excess pressure `P_(1) = 1.01 -1 = 0.01 ` atm Excess pressure `P_(2) = 1.02 - 1 = 0.02 ` atm As ` P prop 1/r " " :. (r_(1))/(r_(2)) = (P_(2))/(P_(1))= 0.02/0.01 = 2/1 ` ` (v_(1))/(v_(2)) = (r_(1)^(3))/(r_(2)^(3)) = (2^(3))/(1^(3)) = 8/1 ` |
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| 2. |
Pressure inside two soap bubble are 1.02 and 1.03 atm . Then ratio of their volumes isA. `8 :27`B. `27:8`C. `(1.02)^(3) :(1.03)^(2)`D. `(1.03)^(3):(1.02)^(2)` |
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Answer» Correct Answer - B ` (V_(1))/(V_(2)) = ((P_(2))/(P_(1)))= ((0.03)/0.02 )^(3)= (3)^(2) : (2)^(3) = 27 : 8 ` |
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| 3. |
If the surface tension of water is ` 7.3 xx 10^(-2)` N/m then the excess pressure inside a spherical drop of water of radius ` 1 xx 10^(-3)` m formed will beA. `14.6 N//m^(2)`B. `146 N//m^(2)`C. `1460 N//m^(2)`D. ` 14600 N//m^(2)` |
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Answer» Correct Answer - B ` P = (2T)/r = (2 xx 7. 3 xx 10^(-2))/(1 xx 10^(-3)) = 146 " N/m"^(2)` |
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| 4. |
A capillary of internal radius `4 mm`, is dipped in water. To how much height, will the water rise in the capillary. (`T_(water) = 70 xx 10^(-3) N//m, g = 10 m//sec^(2), rho_(water) 10^(3) kg//m^(3)`, contact angle `theta rarr 0`) |
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Answer» Capillary rise `h = (2T)/(rhoPR)costheta = (2 xx 70 xx 10^(-3))/(10^(3) xx 10 xx 4 xx 10^(-3)) …(1)` `h = 3.5 mm` |
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| 5. |
Internal pressure inside a liquid drop of radius r and surface tension T isA. `(2T)/r-P_(0)`B. `(4T)/r + P_(0)`C. `P_(0)+(2T)/r`D. `T/(4r)-P_(0)` |
| Answer» Correct Answer - C | |
| 6. |
Let `T_(1)` be surface tension between solid and air, `T_(2)` be the surface tension between solid and liquid and T be the surface tension between liquid and air. Then in equilibrium, for a drop of liquid on a clean glass plate, the correct relation is (`theta` is angle of contact) A. ` cos theta = T/(T_(1)+T_(2))`B. ` cos theta = T /(T_(1)-T_(2))`C. ` cos theta = (T_(1)+T_(2))/T`D. ` cos theta = (t_(1) - T_(2))/T` |
| Answer» Correct Answer - D | |
| 7. |
Surface tension of a liquid is found to be influenced byA. It increases with the increase of temperatureB. Nature of the liquid in contactC. Presence of soap that increases itD. Its variation with the concentration of the liquid |
| Answer» Correct Answer - D | |
| 8. |
Water does not wet an oily glass becauseA. cohesive force of oil `gt ` adhesive force between oil and glassB. cohesive force of oil `lt` cohesive force of waterC. oil repels waterD. cohesive force of water `gt` adhesive force between water and oil molecules |
| Answer» Correct Answer - D | |
| 9. |
Mercury does not wet glass, wood or iron becauseA. Cohesive force is less than adhesive forceB. Cohesive force is greater than adhesive forceC. Angle of contact is less than `90^(@)C`D. Cohesive force is equal to adhesive force |
| Answer» Correct Answer - B | |
| 10. |
Mercury does not wet wood . It indicates that its cohesive force isA. greater than its adhesive forceB. equal to its adhesive forceC. less than its adhesive forceD. none of these |
| Answer» Correct Answer - A | |
| 11. |
If the cohesive force is greater than the adhesive force , the liquid surface will beA. planeB. concaveC. convexD. horizontal |
| Answer» Correct Answer - C | |
| 12. |
The liquid which completely wets the solid , the cohesive forces areA. very weak compared to the adhesive forceB. very strong compared to the adhesive forceC. equal to the adhesive forceD. can not be predicted |
| Answer» Correct Answer - A | |
| 13. |
Consider a liquid contained in a vessel. The liquid solid adhesive force is very weak as compared to the cohesive force in the liquid. The shape of the liquid surface near the solid shall beA. HorizontalB. Almost verticalC. ConcaveD. Convex |
| Answer» Correct Answer - D | |
| 14. |
Two capillary tubes of same diameter are put vertically one each in two liquids whose relative densities are 0.8 and 0.6 and surface tensions are 60 dyne/cm and 50 dyne/cm respectively. Ratio of heights of liquids in the two tubes `(h_(1))/(h_(2))` isA. `(10)/(9)`B. `(10)/(3)`C. `(10)/(3)`D. `(9)/(10)` |
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Answer» Correct Answer - D `h = (2T cos theta)/(rdg)` `:. (h_(1))/(h_(2)) = (T_(1))/(T_(2)) xx (d_(2))/(d_(1))` `= (60)/(50) xx (0.6)/(0.8) = (9)/(10)` |
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| 15. |
The potential energy of molecule on the surface of a liquid as compared to in side the liquid isA. zeroB. lesserC. equalD. greater |
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Answer» Correct Answer - D The potential energy of the molecules lying in the surface is greater than than of the molecules in the interior of the liquid. |
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| 16. |
Angle of contact of a liquid with a solid depends onA. solid onlyB. liquid onlyC. both solid and liquidD. orientation of the solid surface in liquid |
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Answer» Correct Answer - C Angle of contact is defined as the angle inside the liquid between the tangent to the solid surface and the tangent to the liquid surface at the point contact. It depends on nature of liquid and solid in contact. |
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| 17. |
On the surface of the liquid in equilibrium , molecules of the liquid possessA. maximum potential energyB. minimum potential energyC. maximum kinetic energyD. minimum kinetic energy |
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Answer» Correct Answer - A On the surface of the liquid in equilibrium, molecules of the liquid possess maximum potential energy. |
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| 18. |
A liquid will not wet the surface of a solid if the angle of contact isA. zeroB. equal to `45^(@)`C. smaller than `90^(@)`D. greater than `90^(@)` |
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Answer» Correct Answer - D A liquid does not wet the solid surface if the angle of contact is obtuse, i.e., greater than `90^(@)`. In this case, cohesive forces will be greater than adhesive forces. |
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| 19. |
A liquid will not wet the surface of a solid if the angle of contact isA. ZeroB. Obtuse (More than `90^(@)`)C. Acute (Less than `90^(@)`)D. `90^(@)` |
| Answer» Correct Answer - B | |
| 20. |
Molecules on the surface of the liquid haveA. maximum kinetic energyB. maximum potential energyC. minimum kinetic energyD. minimum potential energy |
| Answer» Correct Answer - B | |
| 21. |
A liquid will not wet the surface of a solid if the angle of contact isA. acuteB. unityC. obtuseD. zero |
| Answer» Correct Answer - C | |
| 22. |
The force of attraction between molecules of different substances isA. adhesive forceB. molecular forceC. cohesive forceD. intermolecular force |
| Answer» Correct Answer - A | |
| 23. |
When a liquid is in contact with a solid the angle between the surface of the solid and the tangent drawn to the surface of the liquid at the point of contact , measured in the side of the liquid isA. acute angleB. obtuse angleC. angle of contact for liquid pairD. solid angle |
| Answer» Correct Answer - C | |
| 24. |
An imaginary sphere drawn with a radius equal to the range of molecular attraction is calledA. range of molecular attractionB. sphere of influence of that moleculeC. diameter of that moleculeD. radius of molecular attraction |
| Answer» Correct Answer - B | |
| 25. |
The tangential force per unit length an imaginary line drawn on the surface of a liquid , isA. surface energyB. surface tensionC. free surface energyD. work done |
| Answer» Correct Answer - B | |
| 26. |
Calculate the force required to separate the glass plates of area `10^(-2)m^(2)` with a film of water 0.05 mm thickness between them (surface tension of water `=70xx10^(-3)N//m)`)A. 28 NB. 14 NC. 50 ND. 38 N |
| Answer» Correct Answer - A | |
| 27. |
An imaginary line is a drawn in a liquid surface . At what angle with the line , the surface tension acts ? |
| Answer» Correct Answer - A | |
| 28. |
If a water drop is kept between two glass plates, then its shape isA. B. C. D. |
| Answer» Correct Answer - C | |
| 29. |
When a shaving brush is taken out of water its hair cling together, why?A. Force of attraction between hairB. Surface tensionC. Viscosity of waterD. Characteristic property of hairs |
| Answer» Correct Answer - B | |
| 30. |
Small droplets of a liquid are usually more spherical in shape than larger drops of the same liquid becauseA. force of surface tension is equal and opposite to force of gravityB. force of surface tension predominates the force of gravityC. force gravity predominates the force of surface tensionD. force of gravity and surface tension are equal and in same direction |
| Answer» Correct Answer - B | |
| 31. |
Small droplets of a liquid are usually more spherical in shape than larger drops of the same liquid becauseA. Force of surface tension is equal and opposite to the force of gravityB. Force of surface tension predominates the force of gravityC. Force of gravity predominates the force of surface tensionD. Force of gravity and force of surface tension act in the same direction and are equal |
| Answer» Correct Answer - B | |
| 32. |
Small droplets of a liquid are usually more spherical in shape than larger drops of the same liquid becauseA. of the gravitational force acting on the dropB. of the atmospheric pressureC. volume of a spherical drop is minimumD. the liquid surface tends to have a minimum surface area |
| Answer» Correct Answer - D | |
| 33. |
A drop of water is broken into two droplets . The sum of which property of the two drops is equal to that of the single one ?A. surface energyB. radius of the moleculeC. volumeD. surface tension |
| Answer» Correct Answer - C | |
| 34. |
Two pieces of glass plate one upon the other with a little water between them cannot be separated easily because ofA. InertiaB. PressureC. Surface tensionD. Viscocity |
| Answer» Correct Answer - C | |
| 35. |
Small droplets of a liquid are usually more spherical in shape than larger drops of the same liquid becauseA. Atmospheric pressure exerts a force on a liquid dropB. Volume of a spherical drop is minimumC. Gravitational force acts upon the dropD. Liquid tends to have the minimum surface area due to surface tension |
| Answer» Correct Answer - D | |
| 36. |
The surface energy of a soap film formed on a frame of area ` 2 xx 10^(-3) m^(2) is (T= 40 xx 10^(-3)` N/m)A. `16 xx 10^(-5)`JB. `32 xx 10^(-5)`JC. `16 xx 10^(-4)`JD. `32 xx 10^(4)`J |
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Answer» Correct Answer - A `E = T xx 2xxA` ` 40 xx 10^(-3) xx2 xx 10^(-3)` ` = 16xx10^(-5)` J |
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| 37. |
A thin metal disc of radius `r` floats on water surface and bends the surface downwards along the perimeter making an angle `theta` with vertical edge of the disc of the disc. If the disc dispplaces a weight of water `W` and surface tension of water is `T`, then the weight of metal disc isA. `2pir T+W`B. `2pirTcos theta-W`C. `2pirTcos theta+W`D. `W-2pirTcos theta` |
| Answer» Correct Answer - C | |
| 38. |
A needle made up of iron floats on the water surface due toA. surface tension of water is greater than the weightB. free surface energy of water surfaceC. surface energy of water surfaceD. viscus force of water |
| Answer» Correct Answer - A | |
| 39. |
In a capillary tube, water rises by `1.2mm`. The height of water that will rise in another capillary tube having half the radius of the first, isA. 1.2 mmB. 2.4 mmC. 0.6 mmD. 0.4 mm |
| Answer» Correct Answer - B | |
| 40. |
A soap film in formed on a frame of area `4xx10^(-3)m^(2)`. If the area of the film in reduced to half, then the change in the potential energy of the film is (surface tension of soap solution`=40xx10^(-3)N//m)`A. `160 `JB. `160 xx 10^(-5)`JC. `80 xx 10^(-6)`JD. `1.6 xx 10^(-4)`J |
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Answer» Correct Answer - D `W= S.T xx 2 `dA ` = 40 xx10^(-3) xx2 xx2xx10^(-3) = 6.4 xx10^(-4)` J |
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| 41. |
A thin metal disc of radius `r` floats on water surface and bends the surface downwards along the perimeter making an angle `theta` with vertical edge of the disc. If the disc displaces a weight of water `W` and surface tension of water is `T`, then the weight of metal disc is :A. `2pirT + W`B. `2pirT costheta - W`C. `2pirT costheta + W`D. `W - 2pirT costheta` |
| Answer» Correct Answer - C | |
| 42. |
The surface tension of a liquid is 0.5 N/m . If a liquid film is formed on a ring of area 0.02 `m^(2)` then its surface energy will beA. `0.01 ` JB. `0.02 `JC. ` 0.03`JD. `0.04` J |
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Answer» Correct Answer - B `E= T xx 2A =0.5xx2 xx0.02 = 0.02` J |
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| 43. |
The surface tension of a liquid is `5` Newton per metre. If a film is held on a ring of area `0.02 metres^(2)`, its surface energy is about :A. `5 xx 10^(-2) J`B. `2.5 xx 10^(-2) J`C. `2 xx 10^(-1) J`D. `3 xx 10^(-1) J` |
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Answer» Correct Answer - C We know that surfaces energy `U_(s) = T xx Area`. Hence. As `2` films are formed because of ring. So `U_(s) = T xx 2 xx (A)` `= 5 (N)/(m) xx 2 xx 0.02 m^(2) = 0.2 J` |
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| 44. |
The diameter of one drop of water is 0.2 cm. The work done in breaking one drop into 1000 droplets will be (Given, `S_("water") = 7 xx 10^(-2) Nm^(-1)`)A. `7.9 xx 10^(-6) J`B. `5.92 xx 10^(-6) J`C. `2.92 xx 10^(-6) J`D. `1.92 xx 10^(-6)J` |
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Answer» Correct Answer - A Let R and r be the radii of big drop and each smaller drop, respectively `:.` Volume of big drop = Volume of smaller drops `(4)/(3)pi R^(3) = 1000 xx (4)/(3) pi xx r^(3)` `rArr r = (R)/(10) = (0.1 xx 10^(-2))/(10) = 0.1 xx 10^(-4) m` (`because R = 0.1 xx 10^(-2) m`) The work done in breaking the big drop into 100 small droplets is `W = S(1000 xx 4pi r^(2) - 4pi R^(2))` `= S xx 4pi (1000 xx 10^(-8) - 10^(-6)) = 7.9 xx 10^(-6) J` |
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| 45. |
The surface tension of liquid is 0.5 N / m . If a film is held on a ring of area 0.02 m 2, its surface energy isA. `5xx10` jouleB. `2.0xx10` jouleC. `4xx10` jouleD. `0.8 xx10` joule |
| Answer» Correct Answer - B | |
| 46. |
The surface tension of a liquid is `5` Newton per metre. If a film is held on a ring of area `0.02 metres^(2)`, its surface energy is about :A. `2 xx 10^(-2) J`B. `2.5 xx 10^(-3) J`C. `2 xx 10^(-1) J`D. `3 xx 10^(-1) J` |
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Answer» Correct Answer - C Surface energy is related to the surface tension by the relation, `U = Delta A` Given, `T = 5 Nm^(-1)` `Delta A = 2A = 2 xx 0.02 = 0.04 m^(2)` `:. U = 5 xx 0.04 = 0.20 J = 2 xx 10^(-1) J` |
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| 47. |
Two capillaries made of the same material with radii `r_(1) =1mm` and `r_(2)=2mm` . The rise of the liquid in one capillary ( `r_(1)=mm`) is 30 cm , then the rise in the other will beA. 7.5 cmB. 60 cmC. 15 cmD. 120 cm |
| Answer» Correct Answer - C | |
| 48. |
A water film is formed between two parallel wires of 10 cm length. The distance of 0.5 cm between the wires is increased by 1mm. What will be the work done ? (Given, surface tension of water of `72 Nm^(-1)`)A. 288 ergB. 144 ergC. 72 ergD. 36 erg |
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Answer» Correct Answer - B Work done, `W = 2 xx S xx Delta A` `= 2 xx 72 xx (0.6 - 0.5) xx10 = 144` erg |
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| 49. |
A film of water is formed between two straight parallel wires of length 10 cm each separated by `0.5cm` If their separation is increased by `1mm` while still maintaining their parallelism, how much work will have to be done (Surface tension of water `=7.2xx10^-2(N)/(m)`)A. `7.22xx10^(-6)` jouleB. `1.44xx10^(-5) ` jouleC. `2.88xx10^(-5) ` jouleD. `5.76xx10^(-5) ` joule |
| Answer» Correct Answer - B | |
| 50. |
A soap bubble has radius `R` and surface tension `S`, How much energy is required to double the radius with out change of temperature . |
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Answer» Correct Answer - `24piR^(2)S` On doubling the radius, `DeltaA = 4pi (2R)^(2) - 4 piR^(2) = 12piR^(2)` but `DeltaW = (2 xx DeltaA) xx S = 24 piR^(2)S`. |
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