InterviewSolution
Saved Bookmarks
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.
| 201. |
A solid cube and a solid sphere of the same material have equal surface area. Both are at the same temperature `120^(@)C`, thenA. Both the cube and the sphere cool down at the same rateB. The cube cools down faster than sphereC. The sphere cools down faster than the cubeD. Whichever is having more mass will cool down faster |
|
Answer» Correct Answer - B |
|
| 202. |
Two identical objects A and B are at temperature `T_(A)` and `T_(B)` respectively. Both objects are placed in a room with perfectly absorbing walls maintained at temperature `T(T_(A)gt TgtT_(B))` Statement-1: The objects A and B attain the temperature T eventually. Statement-2: A only emits radiation while B only absorbs until radiation both attain the temperature TA. ‘ A ’ only emits radiations while B only absorbs them until both attain temperatureB. A loses more radiations than it absorbs while B absorbs more radiations that it emits until temperature T is attainedC. Both A and B only absorb radiations until they attain temperature TD. Both A and B only emit radiations until they attain temperature T |
|
Answer» Correct Answer - B |
|
| 203. |
Two identical objects A and B are at temperatures `T_A` and `T_B`. Respectively. Both objects are placed in a room with perfectly absorbing walls maintained at a temperature `T(T_AgtTgtT_B)`. The objects A and B attain the temperature T eventually. Select the correct statements from the following:A. A only emits radiation while `B` only absorbs it untilboth attain the temperatures `T` .B. A loses more heat by radiation than it absorbs, while `B` absords more radiation than it emits until they attain the temperature `T`C. Both `A` and `B` only absorb radiation but do not emit it they attain the temperature `T` .D. Each object continous to emit and absorb radiation even after attaiing the temperature `T` . |
|
Answer» Correct Answer - B::D `B,D` Every object emits and absorbs the radiation simultaneously If energy emitted is more than energy absorded, temperature falls and vice versa . |
|
| 204. |
The plots of intensity versus wavelength for three black bodies at temperature `T_1,T_2 and T_3` respectively are as shown. Their temperatures are such that A. `T _(1) gt T _(2) gt T_(3)`B. `T _(1 ) gt T _(3) gt T_(2)`C. `T_(2) gt T_(3) gt T_(1)`D. `T_(3) gt T_(2) gt T _(1)` |
|
Answer» Correct Answer - B |
|
| 205. |
Assertion : All black coloured objects are considered black bodies. Reason : Black colour is a good absorber of heatA. 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 assertionC. If assertion is true reason is falseD. If assertion is false but reason is true. |
|
Answer» Correct Answer - D |
|
| 206. |
Liquid water coats an active (growing) icicle and extends up a short, narrow tube along the central axis. Because the water-ice interface must have a temperature of `0^(@)`C, the water in the tube cannot lose energy through the sides of the icicle or down through the tip because there is no temperature change in those directions . It can lose energy and freeze only by sending energy up(through distance L) to the top of the icicle, where the temperature `T_(r)` can be below `0^(@)`C. Take L=0.10m and `T_(r)`=`-5^(@)`C.Assume that the central tube and the upward conduction path both have crosse-sectional area A=0.5`m^(2)`. The thermal conductivity of ice is 0.40 W`//mcdotK`, latent heat of fusion is `L_(F)=4.0xx10^(5) J//K` and the density of liquid water is 1000 kg`//m^(3)`. At what rate does the top of the tube move downward because of water freezing there?A. `5xx10^(-8) m//s`B. `2.5xx10^(-3) m//s`C. `2.5xx10^(-8) m//s`D. `4.5xx10^(-2) m//s` |
|
Answer» Correct Answer - C |
|
| 207. |
A room has a window fixed with a pane of area `1.2m^(s)` The glass has thickness `2.2mm` If the temperature outside the room is `36^(@)C` and the temperature inside is `26^(@)C` (a) calculate the heat flowing into the room every hour (b) If the same single pane window is replaced by double paned window with an air gap of `0.50cm` between the two panes calculate the heat flowing into the room every hour `K_(g) =0.80 Wm^(-1)K^(-1),K_(air)=0.0234Wm^(-1)K^(-1)` . |
|
Answer» We assume the one side of the pane is at `36^(@)C` and the other side (inside the room) is at `26^(@)C` Given Thickness of the window pane `d = 2.2mm = 2.2 xx 10^(-3)m` Area of window pane ` A =1.2m^(2)` `(Q)/(t)=K(A(theta_(2)-theta_(1)))/(d)= (0.8xx1.2xx10)/(2.2xx10^(-3)) =4364J//s` Therefore heat flown into the room per hour is `Q = 4364 xx 3600 =1.57 xx 10^(2)J` (b) When single pane widow is replaced by a duble paned widow we have two layers of glss and one layer of air between them Thermal resistacne for glass `R_(a) =(d_(a))/(K_(a)A_(a)) = (0.5xx10^(-2))/(0.0234xx1.2) =178xx10^(3)K//W` Net thermal resistance `R_(T) =R_(g) +R_(a)+R_(g)` ` =(2.29 xx 10^(-3)+178 xx 10^(-3)+2.29 xx 10^(-3))` `=182.6 xx 10^(-3)K//W` `P=(Deltatheta)/(R_(T)) = (10)/(182.6xx10^(-3)) =55J//5` Therefore heat flown into the room per hour is `Q =P xx t =1.98 xx 10^(5) J` . |
|
| 208. |
The temperature drop through each layer of a two layer furnace wall is shown in Assume that the external temperature `T_(10` and `T_(3)` are mainitained constant and `T_(1)gtT_(3)` If the thichness of the layers `x_(1)` and `x_(2)` are the same which of the following statements are correct .A. `k_(1)gtk_(2)`B. `k_(1)ltk_(2)`C. `k_(1)=k_(2)` but heat flow through material (1) is less then through (2) .D. `k_(1)=k_(2)` but heat flow through material (1) is less then through (2) . |
|
Answer» Correct Answer - A `(dQ)/(dt) =KA(d theta)/(dx0` `(d theta)/(dx) =` slope of graph `alpha (1)/(K)` . |
|
| 209. |
The rates of cooling of two different liquids put in exactly similar calorimeters and kept in identical surroundings are the same ifA. The masses of the liquids are equalB. Equal masses of the liquids at the same temperature are takenC. Different volumes of the liquids at the same temperature are takenD. Equal volumes of the liquids at the same temperature are taken |
|
Answer» Correct Answer - D |
|
| 210. |
The temperature of a liquid drops from 365 K to 361 K in 2 minutes . Find the time during which temperature of the liquid drops from 344 K to 342 K.Temperature of room is 293 KA. 84 secB. 72 secC. 66 secD. 60 sec |
|
Answer» Correct Answer - A |
|
| 211. |
Assertion : The absorbance of a perfect black body is unity. Reason : A perfect black body when heated emits radiations of all possible wavelengths at that temperature.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 assertionC. If assertion is true reason is falseD. If the assertion and reason both are false. |
|
Answer» Correct Answer - B |
|
| 212. |
The maximum wavelength of radiation emitted at K 2000 K is `4mu m` . What will be the maximum wavelength of radiation emitted atA. `3.33 mu m`B. `0.66 mu m`C. `1 mu m`D. 1 m |
|
Answer» Correct Answer - A |
|
| 213. |
If wavelengths of maximum intensity of radiations emitted by the sun and the moon are `0.5xx10^(-6)m " and " 10^(-4)`m respectively, the ratio of their temperature is …………… |
|
Answer» Correct Answer - 200 |
|
| 214. |
If wavelengths of maximum intensity of radiations emitted by the sun and the moon are `0.5xx 10^(-6)m` and `10^(-4)m` respectively, the ratio of their temperatures isA. 1/100B. 1/200C. 100D. 200 |
|
Answer» Correct Answer - D |
|
| 215. |
The maximum wavelength of radiations emitted at 900 K is `4mu m` . What will be the maximum wavelength of radiations emitted at 1200 KA. `3 mu m`B. `0.3 mu m`C. `1 mu m`D. 1m |
|
Answer» Correct Answer - A |
|
| 216. |
The absolute temperatures of two black bodies are 2000 K and 3000 K respectively. The ratio of wavelengths corresponding to maximum emission of radiation by them will beA. `2 : 3`B. `3 : 2`C. `9 : 4`D. `4 : 9` |
|
Answer» Correct Answer - B |
|
| 217. |
What will be the ratio of temperatures of sun and moon if the wavelengths of their maximum emission radiations rates are `140A^(@)` and `4200A^(@)` respectively .A. `1 : 30`B. `30 : 1`C. `42 : 14`D. `14 : 42` |
|
Answer» Correct Answer - B |
|
| 218. |
What will be the ratio of temperatures of sun and moon if the wavelengths of their maximum emission radiations rates are `140A^(@)` and `4200A^(@)` respectively .A. `1:30`B. `30:1`C. `42 :14`D. `14 :42` |
|
Answer» Correct Answer - B `lambda_(m) T =` constant `rArr lambda_(1) T_(1) = lambda_(2) T_(2)` |
|
| 219. |
The reflectance and emittance of a perfectly black body are rspectivelyA. `0,1`B. `1,0`C. `0.5,0.5`D. 0,0 |
| Answer» Correct Answer - A | |
| 220. |
In the figure, the distribution of energy density of the radiation emitted by a black body at a given temperature is shown. The possible temperature of the black body is A. 1500 KB. 2000 KC. 2500 KD. 3000 K |
|
Answer» Correct Answer - B |
|
| 221. |
The amount of radiation emitted by a perfectly black body is proportional to .A. Temperature on ideal gas scaleB. Fourth root of temperature on ideal gas scaleC. Fourth power of temperature on ideal gas scaleD. Source of temperature on ideal gas scale |
|
Answer» Correct Answer - C |
|
| 222. |
A star behaves like a perfectly black body emitting radiant energy The ratio of radiant energy per second by this star to that emitted by another star having 8 times the radius of former, but having temperature, one-fourth that of the former in Kelvin is .A. `1:4`B. `1:16`C. `4:1`D. `16:1` |
|
Answer» Correct Answer - C `P =sigma AT^(4) rArr P =sigma4 pi R^(2)T^(4)` `:.(P_(1))/(P_(2))=((R_(1))/(R_(2)))^(2)((T_(1))/(T_(2)))^(4)` . |
|
| 223. |
Which of the following is the `v_(m)` = T graph for a perfectly black body ( `v_(m)` =maximum frequency of radiation) A. AB. BC. CD. D |
|
Answer» Correct Answer - B |
|
| 224. |
Which of the following graphs correctly represents the relation between ln E and ln T where E is the amount of radiation emitted per unit time from unit area of a body and T is the absolute temperatureA. B. C. D. |
|
Answer» Correct Answer - D |
|
| 225. |
The amount of radiation emitted by a perfectly black body is proportional to .A. temperature on ideal gas scaleB. fourth root of temperature on ideal gas scaleC. fourth power of temperature on ideal gas scaleD. source of temperature on ideal scale |
| Answer» Correct Answer - C | |
| 226. |
The temperature of a body is increased by `50%`. The amount of radiation emitted by it would be nearlyA. `50%`B. `100%`C. `225%`D. `406.25%` |
|
Answer» Correct Answer - D `E=sigmaT^(4),(E_(2)-E_(1))/(E_(1))xx100=[((T_(2))/(T_(1)))^(4)-1]xx100` |
|
| 227. |
The rectangular surface of area `8 cm xx 4 cm` of a black body at temperature `127^(@)C` emits energy `E` per section if length and breadth are reduced to half of the initial value and the temperature is raised to `327^(@)C`, the ratio of emission of energy becomes |
|
Answer» Correct Answer - `(81)/(64)E` |
|
| 228. |
The temperature of the two outer surfaces of a composite slab, consisting of two materials having coefficients of two materials having coefficients of thermal conductivity K and 2K and thickness x and 4x, respectively, are `T_2 and T_1(T_1gtT_1)`. The rate of heat transfer through the slab, in a steady state is `((A(T_2-T_1)K)/2)f`, with f equal to A. 1B. `(1)/(2)`C. `(2)/(3)`D. `(1)/(3)` |
|
Answer» Correct Answer - D |
|
| 229. |
A composite metal bar of uniform section is made up of length 25 cm of copper, 10 cm of nickel and 15 cm of aluminium. Each part being in perfect thermal contact with the adjoining part. The copper end of the composite rod is maintained at `100^(@)"C"` and the aluminium end at `0^(@)"C"`. The whole rod is covered with belt so that there is no heat loss occurs at the sides. If `K_(Cu) = 2K_(Al)" and" " K"_(Al) = 3"K"_(Ni)`, then what will be the temperatures of `Cu- Ni` and `Ni -Al` junctions respectively A. `23.33^(@)C` and `78.8^(@)C`B. `83.33^(@)C` and `20^(@)C`C. `50^(@)C` and `30^(@)C`D. `30^(@)C` and `50^(@)C` |
|
Answer» Correct Answer - B |
|
| 230. |
The three rods of same meterial and crosssectional area from the sides of a triangle `ABC` The points `A,B` and `C` are maintained at temperature `T T sqrt2` and `(3T)/((sqrt2 +1))` respectively Assuming that only heat conducting takes place the system is in steady state, find the angle at `B` The temperature difference per unit length along `SB` and `CA` is equal .A. `30^(@)`B. `45^(@)`C. `60^(@)`D. `90^(@)` |
|
Answer» Correct Answer - D `T_(B) gt T_(A)` heat will flow from `B` to `A` and from `C` to `B` to remain in steady state. The conduction formula is `(DeltaQ)/(DeltaT) = (KA)/(L) DeltaT` `(T_(C))/(T_(A))=(3)/(sqrt2+T_(A))` and `T_(A)-T_(c) =sqrt2 (T_(C) - T_(A)sqrt2)` `(T_(A)-T_(c))/(Lsqrt2)=((T_(c)-T_(A)sqrt2))/(L) = (T_(C)-T_(B))/(L)` from this we can find that `L_(CB) = L, L_(AC) = L sqrt2` and for which `L_(AB) = L :. haTB = 90^(@)` . |
|
| 231. |
A body is kept inside a container the temperature of the body is `T_(1)` and the temperature of the container is `T_(2)` the rate at which body absorbs the energy is `alpha` The emissivity of the body is The radiation striking the body is either absorbed or reflected At what rate of body will absorb the radiant energy .A. `alpha," but " alpha!=e`B. `(T_(1)-T_(2))//t`, where t is the timeC. e, but e = `alpha`D. None of above |
|
Answer» Correct Answer - C |
|
| 232. |
A body is kept inside a container the temperature of the body is `T_(1)` and the temperature of the container is `T_(2)` the rate at which body absorbs the energy is `alpha` The emissivity of the body is The radiation striking the body is either absorbed or reflected A good absorber is .A. good reflectorB. poor reflectorC. average reflectorD. assessment not possible |
| Answer» Correct Answer - B | |
| 233. |
Two rods `A` and `B` of same cross sectional are `A` and length l connected in series between a source `(T_(1) =100^(@)C)` and a sink `(T_(2) =0^(@)C)` as shown in The rod is laterally insulated The ratio of thermal resistance of the rod is .A. `(R_(A))/(R_(B))=(1)/(3)`B. `(R_(A))/(R_(B)) =3`C. `(R_(A))/(R_(B)) =(3)/(4)`D. `(4)/(3)` |
| Answer» Correct Answer - A | |
| 234. |
Two rods `A` and `B` of same cross sectional are `A` and length l connected in series between a source `(T_(1) =100^(@)C)` and a sink `(T_(2) =0^(@)C)` as shown in The rod is laterally insulated If `A_(A)` and `T_(B)` are the temperature drops across temperature gradients the rod `A` and `B` then .A. `(T_(A))/(A_(B)) =(3)/(1)`B. `(T_(A))/(T_(B)) =(1)/(3)`C. `(T_(A))/(T_(B)) =(3)/(4)`D. `(T_(A))/(T_(B)) =(4)/(3)` |
| Answer» Correct Answer - B | |
| 235. |
Two conducting rods A and B of same length and cross-sectional area are connected (i) In series (ii) In parallel as shown. In both combination a temperature difference of `100° C` is maintained. If thermal conductivity of A is 3 K and that of B is K then the ratio of heat current flowing in parallel combination to that flowing in series combination is A. `(16)/(3)`B. `(3)/(16)`C. `(1)/(1)`D. `(1)/(3)` |
|
Answer» Correct Answer - A |
|
| 236. |
The rates of coling of a body at tempeerature `100^(@)C` and `80^(@)C` are `x_(1)` and `x_(2)` respectively, when placed in a room of tmpeerature `40^(@)C` then `(x_(1))/(x_(2))` is .A. `4//5`B. `5//4`C. `3//2`D. `2//3` |
|
Answer» Correct Answer - C `(dtheta)/(dt) prop (0 -theta_(0)) rArr R prop theta - theta_(0)` |
|
| 237. |
A ring consisting of two parts `ADB` and `ACB` of same conductivity k carries an amount of heat `H` The `ADB` part is now replaced with another metal keeping the temperature `T_91)` and `T_(2)` constant The heat carried increases to `2H` What should be the conductivity of the new `ADB` Given `(ACB)/(ADB)=3` .A. `(7)/(3)K`B. `2K`C. `(5)/(2)K`D. `3K` |
|
Answer» Correct Answer - A `(dQ)/(dt) = (KA d theta)/("arc length")` . |
|
| 238. |
If the initial temperatures of metallic sphere and disc, of the same mass, radius and nature are equal, then the ratio of their rate of cooling in same environment will beA. `1 : 4`B. `4 : 1`C. `1 : 2`D. `2 : 1` |
|
Answer» Correct Answer - D |
|
| 239. |
A sphere at temperature `600 K` is placed in an enviroment to temperature is `200 K`. Its cooling rate is `H`. If its temperature reduced to `400 K` then cooling rate in same enviorment will becomeA. `(3//16) H`B. `(16//3)H`C. `(9//27)H`D. `(1//16)H` |
|
Answer» Correct Answer - A |
|
| 240. |
A blackbody does notA. emit radiationB. absorb radiationC. reflect and refract radiationD. All the above |
| Answer» Correct Answer - C | |
| 241. |
Two spheres of the same materical have radii `1m` and `4m` nad temperature `4000K` and `2000K` respectively The energy radiated per second by the first sphere is .A. greater than that of the secondB. Less than that of the secondC. equal in both casesD. the information is incomplete to draw any conclusion |
|
Answer» Correct Answer - C `p=sigmaAT^(4)=sigma4pir^(2)T^(4)rArr(P_(1))/(P_(2))=((r_(1))/(r_(2)))xx((T_(1))/(T_(2)))^(4)` |
|
| 242. |
The emissive power of a black body at `T=300K` is `100Watt//m^(2)` consider a body B of area `A=10m^(2)` coefficient of reflectivity `r=0.3` and coefficient of transmission `t=0.5` its temperature is 300 K. then which of the followin is correct:A. The emissive power of `b` is `20W//m^(2)`B. The emissive power of `b` is `200W//m^(2)`C. The power emitted by `B` is `20W`D. The power emitted by `B` is `180W` |
|
Answer» Correct Answer - A For body `A` emissivity =absorptivity `= 0.2` So from Kirchhoft,s law `(E)/(a)|._("black body")=(E)/(a)|_(B)` `rArr (100)/(1) = (E)/(0.2) rArr E = 20W//m^(2)` Emitted power by `B` is `p = EA = 200W` . |
|
| 243. |
The amount of heat energy radiated per second by a surface depends upon .A. Depends upon nature of the meterial of the bodyB. Difference of temperature between the surface and its surroundingsC. Nature of the surfaceD. All the above |
| Answer» Correct Answer - D | |
| 244. |
The spectral emissive power `E_(lambda)` for a body at temperature `T_(1)` is poltted againist the wavelenght and area under the curve is found to be `A.At` a different temperature `T_(2)` the area is found to be A then `lambda_(1)//lambda_(2)=` .A. 3B. `1//3`C. `1//sqrt3`D. `sqrt3` |
|
Answer» Correct Answer - D Area of graph `=E` `E alpha T^(4)` and `lambda alpha (1)/(T) rArr E alpha (1)/(lambda^(4))` Area `alpha (1)/(lambda^(4))` . |
|
| 245. |
The spectral energy distribution of star is maximum at twice temperature as that of sun. The total energy radiated by star isA. Twice as that of the sunB. Same as that of the sunC. Sixteen times as that of the sunD. One sixteenth of sun |
|
Answer» Correct Answer - C |
|
| 246. |
The adjoining diagram shows the spectral energy density distribution `E_(lambda)` of a black body at two different temperatures. If the areas under the curves are in the ratio 16 : 1, the value of temperature T is A. 32,000 KB. 16,000 KC. 8,000 KD. 4,000 K |
|
Answer» Correct Answer - D |
|
| 247. |
Four pieces of iron are heated to different are respectively red, yellow orange and white respectively The one that is heated to the highest temperature will exhibit the colour .A. WhiteB. YellowC. OrangeD. Red |
|
Answer» Correct Answer - A |
|
| 248. |
Which of the following cylindrical rods will conduct most heat, when their ends are maintained at the same steady temperatureA. Length 1 m , radius 1 cmB. Length 2 m , radius 1 cmC. Length 2 m , radius 2 cmD. Length 1 m , radius 2 cm |
|
Answer» Correct Answer - D |
|
| 249. |
Four pieces of iron are heated to different are respectively red, yellow orange and white respectively The one that is heated to the highest temperature will exhibit the colour .A. `WhiteB. YellowC. RedD. Orange |
| Answer» Correct Answer - A | |
| 250. |
The energy distribution E with the wavelength `(lambda)` for the black body radiation at temperature Kelvin T is shown in the figure. As the temperature is increased the maxima will A. Shift towards left and become higherB. Rise high but will not shiftC. Shift towards right and become higherD. Shift towards left and the curve will become broader |
|
Answer» Correct Answer - A |
|