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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.
| 251. |
If the surface tension of a soap water is 0.04 N/m Then excess pressure inside a 10 mm diameter soap bubble in `N//m^(2)` will beA. 4B. 16C. 8D. 32 |
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Answer» Correct Answer - D ` P_(i)- P_(0)= (4T)/r ` ` = (4xx 0.04)/(5 xx 10^(-3))= 16/5 xx 10 = 160/5 = 32 ` |
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| 252. |
If two soap bubbles of different radii are connected by a tubeA. Internal pressure of the smaller bubble is higher than the internal pressure of the larger bubbleB. Pressure of the larger bubble is higher than the smaller bubbleC. Both bubbles have the same internal pressureD. None of the above |
| Answer» Correct Answer - A | |
| 253. |
If work `W` is done in blowing a bubble of radius `R` from a soap solution. Then the work done is blowing a bubble of radius `2R` from the same solution isA. W/2B. 2WC. 4WD. `2 1/3 W` |
| Answer» Correct Answer - C | |
| 254. |
Surface tension of soap solution is `2 xx 10^(-2) N//m` . The work done in producing a soap bubble of radius 2 cm isA. `64pi xx 10^(-6) J`B. `32pi xx 10^(-6) J`C. `16 pi xx 10^(-6) J`D. `8 pi xx 10^(-6) J` |
| Answer» Correct Answer - A | |
| 255. |
A bubble of 8 mm diameter is formed in the air. The surface tension of soap solution is 30 dynes/cm . The excess pressure inside the bubble isA. 150 dynes/cmB. 300 dynes/cmC. `3 xx 10^(-3) "dynes"//cm`D. 12 dynes/cm |
| Answer» Correct Answer - B | |
| 256. |
The pressure of air in a soap bubble of 0.7 cm diameter is 8 mm of water above the atmospheric pressure calculate the surface tension of soap solution. (take `g=980cm//sec^(2))`A. 100 dyne /cmB. 68.66 dyne /cmC. 137 dyne/cmD. 150 dyne /cm |
| Answer» Correct Answer - B | |
| 257. |
Two soap bubbles have radii in the ratio of `4:3` . What is the ratio of work done to blow these bubbles ?A. `4:3`B. `16:9`C. `9:16`D. `3:4` |
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Answer» Correct Answer - B `(W_(1))/(W_(2)) = ((R_(1))/(R_(2)))^(2)=(4/3)^(2) = 16:9` |
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| 258. |
Work `W` is required to form a bubble of volume `V` from a given solution. What amount of work is required to be done to form a bubble of volume `2V` ?A. WB. `2^(1//3)W`C. 2 WD. `4^(1//3)W` |
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Answer» Correct Answer - D `W = Txx 2 dA` ` = 40 xx10^(-3) xx2 xx 2xx 10^(-3)=16xx10^(-5)`J |
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| 259. |
A soap bubble has radius R and thickness of its wall is a. Calculate the apparent weight `(= true weight - Buoyancy)` of the bubble if surface tension of soap solution and its density are T and d respectively. The atmospheric pressure is `P_(0)` and density of atmospheric air is `rho_(0)`. By assuming `a = 10^(–6) m, R = 10 cm, P_(0) = 10^(5) Nm^(–2), rho_(0) = 1.2 kg m^(–3), d = 10^(3) kg m^(–3), T = 0.04 Nm^(–1)`, show that the weight of the bubble is mainly because of water in the skin. What is weight of the bubble? |
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Answer» Correct Answer - `(16pi)/3 (R^(2)rho_(o))/P_(o) g+4piR^(2)` a.d.g |
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| 260. |
Amount of energy required to blow a bubble radius 5 cm , isA. 1.88 JB. `1.88 xx 10^(-1)`JC. `1.88 xx 10^(-2)` JD. `1.88 xx 10` J |
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Answer» Correct Answer - C ` dW = 4pi r^(2)T xx 2 ` ` = 8pi xx 25 xx 10^(-4) xx 30 xx 10^(-2) xx 2 ` ` = 200 pi xx 30 xx 10^(-6)` ` = 1.884 xx 10^(-2)` J |
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| 261. |
What is the shape when a non-wetting liquid is placed in a capillary tubeA. Concave upwardB. Convex upwardC. Concave downwardD. Convex downward |
| Answer» Correct Answer - B | |
| 262. |
A frame made of a metallic wire enclosing a surface area A is covered with a soap film . If the area of the frame of metallic wire will be changed byA. 1B. 0.5C. 0.75D. 0.25 |
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Answer» Correct Answer - B `(E_(2))/(E_(1)) = (A_(2))/(A_(2)) = 50/100 = 0.5` `E_(2) = 50 ` % E |
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| 263. |
A soap bubble is blown at the end of a capillary tube of radius a and length L. When the other end is left open, the bubble begins to deflate. Write the radius of the bubble as a function of time if the initial radius of the bubble was `R_(0)`. Surface tension of soap solution is T. It is known that volume flow rate through a tube of radius a and length L is given by Poiseuille’s equation- `Q=(pia^(4)DeltaP)/(8ne L)` Where `DeltaP` is pressure difference at the two ends of the tube and `ne` is coefficient of viscosity. Assume that the bubble remains spherical. |
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Answer» Correct Answer - `R=R_(0)[1-(a^(4)Tt)/(2neLR_(0)^(4))]^(1//4)` |
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| 264. |
A soap bubble of radius R is blown. After heating the solution a second bubble of radius 2 R is blown. The work required to blow the second bubble in comparison to that required for the first bubble isA. DoubleB. Slightly less than doubleC. Slightly less than four timesD. Slightly more than four times |
| Answer» Correct Answer - C | |
| 265. |
A frame made of metallic wire enclosing a surface area A is covered with a soap film. If the area of the frame of metallic wire is reduced by 25%, the energy of the soap film will be changed byA. 1B. 0.75C. 0.5D. 0.25 |
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Answer» Correct Answer - D Surface energy = Surface tension `xx` Surface area `E = T xx 2A` New surface energy, `E_(1) = T xx 2((A)/(4)) = T xx (A)/(2)` % decrease in surface energy `= (E xx E_(1))/(E) xx 100 = (2TA - TA//2)/(2TA) xx 100 = 75%` |
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| 266. |
In the glass capillary tube, the shape of the surface of the liquid depends uponA. Only on the cohesive force of liquid moleculesB. Only on the adhesive force between the molecules of glass and liquidC. Only on relative cohesive and adhesive force between the atomsD. Neither on cohesive nor on adhesive force |
| Answer» Correct Answer - C | |
| 267. |
A glass tube of radius R is covered with a liquid film at its one end. Air is blown slowly into the tube to gradually increase the pressure inside. What is the maximum pressure that the air inside the tube can have? Assume that the liquid film does not leave the surface (whatever its size) and it does not get punctured. Surface tension of the liquid is T and atmospheric pressure is `P_(o)`. |
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Answer» Correct Answer - `P_(o)+(4T)/R` |
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| 268. |
In a horizontal capillary tube, the rate of capillary flow depends on the surface tension force as well as the viscous force. Lueas and washburn showed that the length `(x)` of liquid penetration in a horizontal capillary depends on a factor `(k)` apart from time (t). The factor is given by`k = [(rTcos theta)/(2ne)]^(1//2)`, where r, T, `theta` and `ne` are radiusof the capillary tube, surface tension, contact angle and coefficient of viscosity respectively. If the length of liquid in the capillary grows from zero to `x_(0)` in time `t_(0), how much time will be needed for the length to increases from `x_(0) to 4x_(0)`. |
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Answer» Correct Answer - `15 t_(0)` |
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| 269. |
If the radius of a soap bubble is four times that of another, then the ratio of their pressures will beA. `1:4`B. `4:1`C. `16:1`D. `1:16` |
| Answer» Correct Answer - A | |
| 270. |
When a large bubble rises from the bottom of a lake to the surface its radius doubles. If atmospheric pressure is equal to that of column of water height H then the depth of lake isA. HB. 2HC. 7HD. 8H |
| Answer» Correct Answer - C | |
| 271. |
The volume of an air bubble becomes three times as it rises from the bottom of a lake to its surface. Assuming atmospheric pressure to be 75 cm of Hg and the density of water to be `1//10` of the density of mercury, the depth of the lake isA. 5 mB. 10 mC. 15 mD. 20 m |
| Answer» Correct Answer - C | |
| 272. |
A soap bubble in vacuum has a radius of `3 cm` and another soap bubble in vacuum has a radius of `4 cm`. If the two bubbles coalesce under isothermal conditions then the radius of the new bubble is :A. 12 cmB. 16 cmC. 25 cmD. 5 cm |
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Answer» Correct Answer - D ` r _(1) = sqrt(r_(1)^(2)+r_(1)^(2))` |
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| 273. |
A soap bubble in vacuum has a radius of `3 cm` and another soap bubble in vacuum has a radius of `4 cm`. If the two bubbles coalesce under isothermal conditions then the radius of the new bubble is :A. `2.3 cm`B. `4.5 cm`C. `5 cm`D. `7 cm` |
| Answer» Correct Answer - C | |
| 274. |
Two soap bubbles of radius `R_(1) and R_(2) (lt R_(1))` are joined by a straw. Air flows from one bubble to another and a single bubble of radius `R_(3)` remains. (a) From which bubble does the air flow out ? (b) Assuming no temperature change and atmospheric pressure to be `P_(o), find the surface tension of the soap solution. |
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Answer» Correct Answer - (a) From smaller bubble (b) `T=(P_(o)(R_(3)^(3)-R_(1)^(3)-R_(2)^(3))/(4(R_(1)^(2)+R_(2)^(2)-R_(3)^(2))` |
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| 275. |
Out of the following , which is not an example of capillary actionA. absorption of ink in blotting paperB. floating of wood on water surfaceC. rise of oil in wick of a lampD. ploughing of the field |
| Answer» Correct Answer - B | |
| 276. |
Two identical soaop bubbles each of radius `r` and of the same surface tension `T` combine to form a new soap bubble od radius `R`. The two bubbles contain air at the same temperature. If the atmospheric pressure is `p_(0)` then find the surface tension `T` of the soap solution in terms of `p_(0), r` and `R`. Assume process is isothermal. |
| Answer» Correct Answer - `T = (p_(0)(2r^(3) - R^(3)))/(4(R^(2) - 2r^(2)))` | |
| 277. |
Two soap bubble of radii 3 mm and 4 mm are in contact radius of curvature of interface between those two bubbles isA. 1 mmB. 7 mmC. 12 mmD. 12/7 mm |
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Answer» Correct Answer - C ` r = (r_(1)r_(2))/(r_(2)-r_(1)) = ( 3 xx 4 xx 10^(-6))/(10^(-3)(4-3))= 12` mm |
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| 278. |
Two soap bubbles of radii `r_(1)` and `r_(2)` equal to 4 cm and 5 cm are touching each other over a common surface `S_(1)S_(2)` (shown in figure). Its radius will be A. 4 cmB. 20 cmC. 5 cmD. 4.5 cm |
| Answer» Correct Answer - B | |
| 279. |
In capillary pressure below the curved surface of water will beA. Equal to atmosphericB. Equal to upper side pressureC. More than upper side pressureD. Lesser than upper side pressure |
| Answer» Correct Answer - D | |
| 280. |
Two soap bubbles of radii `r_(1) and r_(2)` are attached as shown. Find the radius of curvature of the common film ACB. |
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Answer» Correct Answer - `(r_(1)r_(2))/(r_(1)-r_(2))` |
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| 281. |
Select the correct statement , if a liquid surface is curvedA. the pressure on the concave side is less than that on the convex sideB. the pressure on the concave side is equal to pressure on convex sideC. the pressure on concave side is more than that on convex sideD. the pressure on the comvex side is atmospheric pressure |
| Answer» Correct Answer - C | |
| 282. |
A capillary is dipped into a liquid which does not wet , the liquid levelA. remains the same in capillary as normal liquid levelB. changes in the capillaryC. rises in he capillary than normal liquidD. fall in the capillary than normal liquid level |
| Answer» Correct Answer - D | |
| 283. |
A curved liquid surface has radius of curvature `R_(1) and R_(2)` in two perpendicular directions as shown in figure. Surface tension of the liquid is `T`. Find the difference in pressure on the concave side and the convex side of the liquid surface. |
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Answer» Correct Answer - `DeltaP=T(1/R_(1)+1/R_(2))` |
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| 284. |
A wire of length `L` metres, made of a material of specific gravity 8 is floating horizontally on the surface of water. If it is not wet by water, the maximum diameter of the wire (in mm) upto which it can continue to float is (surface tension of water is `T=70xx10^(-3)Nm^(-1)`)A. 0.75 mmB. 1.5 mmC. 1.5 cmD. 1.5 m |
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Answer» Correct Answer - B F= 2l mg= 2T l `rho pi r^(2) Lg = 2 TL` `r^(2) = (2TL)/(rhopiLG) = (2T)/(rho pi g)` ` r = sqrt((2T)/(rho pi g))` ` d = 2r = 2 sqrt((2xx70)/(8xx22/7xx980))` ` = 2 xx 7 sqrt((1)/(4xx22xx49xx2))` ` = 2/2 sqrt(1/44)=sqrt(0.022)` ` d = sqrt(2.2xx10^(-2))= 1.5 xx10^(-1)` cm d = 1.5 mm. |
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| 285. |
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 beA. 0.07 NB. 0.06 NC. 0.01 ND. 0.02 N |
| Answer» Correct Answer - D | |
| 286. |
A liquid having surface tension `T` and density `rho` is in contact with a vertical solid wall. The liquid surface gets curved as shown in the figure. At the bottom the liquid surface is flat. The atmospheric pressure is `P_(o)`. (i) Find the pressure in the liquid at the top of the meniscus (i.e. at A) (ii) Calculate the difference in height `(h)` between the bottom and top of the meniscus. |
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Answer» Correct Answer - (1)`P_(o)-rhogh` (2) `sqrt((2T)/(rhog)` |
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| 287. |
Two wooden sticks of negliable weight are floating parallel to each other very closely . If a hot metal wire is placed between the two sticks without touching themA. the two sticks move apartB. come closerC. they remain at the same as beforeD. they stand erect |
| Answer» Correct Answer - B | |
| 288. |
A 10 cm long wire is placed horizontal on the surface of water and is gently pulled up with a force of `2xx10^(2)` N to keep the wire in equilibrium. The surface tension, in `Nm^(-1)` of water isA. `0.002`B. `0.001`C. `0.2`D. `0.1` |
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Answer» Correct Answer - D We have, 2Sl = F `rArr S = F/2l = (2 xx 10^(-2))//2 xx 0.10 = 0.1 Nm^(-1)` |
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| 289. |
Eight droplets of water each of radius 0.5 mm when coalesce into single drop , then the change in surface energy will be ,A. `4pi T xx 10^(-5)` JB. ` 4 pi T xx 10^(7)` JC. ` 4pi T xx 10^(-6)` JD. ` 4 pi T xx 10^(-8)` J |
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Answer» Correct Answer - C `Delta E = E (n^(1//3)-1)= T 4piR^(2)(n^(1//3)-1)` |
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| 290. |
The dimensions of surface tension areA. `[MLT^(-1)]`B. `[ML^(2)T^(-2)]`C. `[ML^(0)T^(-2)]`D. `[ML^(-1)T^(-2)]` |
| Answer» Correct Answer - C | |
| 291. |
Statement-1: The angle of contact of a liquid decrease with increase in temeperature Statement-2: With increase in temperature the surface tension of liquid increase.A. If both assertion and reason are true and the reason is the correct explanation of the assertion.B. If both assertion and reason are true but reason is not the correct explanation of the assertion.C. If assertion is true but reason is falseD. If the assertion and reason both are false |
| Answer» Correct Answer - C | |
| 292. |
The surface tension of molten cadmium with increase of temperature generallyA. increasesB. is infinityC. remains constantD. decreases |
| Answer» Correct Answer - A | |
| 293. |
A spherical liquid drop of radius `R` is divided into eight equal droplets. If the surface tension is `T`, then the work done in this process will beA. `8piR^(2)T`B. `3pi R^(2)T`C. `4piR^(2)T`D. `2piRT^(2)` |
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Answer» Correct Answer - C `dw = 4 pi R^(2) T (n^(1//3)-1) and R = n^(1//3)r` |
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| 294. |
A sphere liquid drop of radius R is divided into eight equal droplets. If surface tension is S, then the work done in this process will beA. `2pi R^(2)S`B. `3pi R^(2)S`C. `4pi R^(2)S`D. `2pi RS^(2)` |
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Answer» Correct Answer - C Volume of big drop = Volume of 8 small droplets `(4)/(3)pi R^(3) = 8 xx (4)/(3)pi R^(3) rArr r = R//2` Work done `= S xx (4pi r^(2) xx 8 - 4pi R^(2))` `= S xx 4pi ((R^(2))/(4) xx 8 - R^(2)) = 4pi R^(2)S` |
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| 295. |
A water drop is divided into eight equal droplets. The pressure difference between inner and outer sides of big drop isA. same as for smaller dropletB. `1//2` of that for smaller dropletC. `1//4` of that for smaller dropletD. twice that for smaller droplet |
| Answer» Correct Answer - B | |
| 296. |
The dimensions of surface tension areA. ` [L " M "T^(-1)]`B. ` [ L^(2) " M "T^(-2)]`C. ` [ L^(0)" M "T^(-2)]`D. ` [ L^(-1)" M "T^(-2)]` |
| Answer» Correct Answer - C | |
| 297. |
The force due to surface tension isA. normal to free surfaceB. normal to free surface downwardsC. along the free surfaceD. at an angle of `60^(@)` with free surface |
| Answer» Correct Answer - C | |
| 298. |
A spherical liquid drop of radius `R` is divided into eight equal droplets. If the surface tension is `T`, then the work done in this process will beA. `8piR^(2)T`B. `3 piR^(2)T`C. `4piR^(2)T`D. `2piRT^(2)` |
| Answer» Correct Answer - C | |
| 299. |
S.I. Unit of surface tension is:A. m/NB. dyne/cmC. `J/m^(2)`D. J/m |
| Answer» Correct Answer - C | |
| 300. |
On mixing the salt in water, the surface tension of water willA. increasesB. decreasesC. may increase or decrease depending upon saltD. None of the above |
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Answer» Correct Answer - A When a highly soluble salt (like sodium chloride) is dissolved in water, the surface tension of water increases. |
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