Thermodynamics PYQs Set 10 (PDF)

Set 10 of 16 · Questions 271-300 of 459

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Mere Teacher · Previous Year Questions NEET Physics · Thermodynamics · Set 10 (Q271-300)
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271. $Temperature of a cold reservoir of a Carnot engine is 127^{\circ} C . If the efficiency of the Carnot engine is 20 %, then the temperature of the hot reservoir is$ (1) $500^{\circ} C$ (2) $227^{\circ} C$ (3) $273^{\circ} C$ (4) $400^{\circ} C$ 272. $A gas is compressed at a constant pressure of 50 N / m^{2} from a volume of 10 m^{3} to a volume of 4 m^{3} . Energy of 100 J is then added to the gas by heating. Its internal energy is$ (1) $increased by 400 J$ (2) $increased by 200 I$ (3) $increased by 100 J$ (4) $decreased by 200 I$ 273. $For which combination of working temperatures of source and sink, the efficiency of Carnot's heat engine is maximum?$ (1) $600 K, 400 K$ (2) $500 K, 300 K$ (3) $400 K, 200 K$ (4) $300 K, 100 K$ 274. $To find out degree of freedom, the expression is$ (1) $f = \frac{2}{γ - 1}$ (2) $f = \frac{γ + 1}{2}$ (3) $f = \frac{2}{γ + 1}$ (4) $f = \frac{1}{γ + 1} .$ 275. $A Carnot's engine working between 400 K and 800 K has a work output of 1200 J per cycle. The amount ofheat energy supplied to the engine from the source in each cycle is:$ (1) $3200 J$ (2) $1800 J$ (3) $1600 J$ (4) $2400 J$ 276. $Consider the sound wave travelling in ideal gases of He, CH_{4}, and CO_{2} . All the gases have the same ratio \frac{P}{ρ}, where P is the pressure and ρ is the density. The ratio of the speed of sound through the gases V_{He} : V_{CH_{4}} : V_{CO_{2}} is given by$ (1) $\frac{7}{5} : \frac{5}{3} : \frac{4}{3}$ (2) $\frac{5}{3} : \frac{4}{3} : \frac{4}{3}$ (3) $\frac{5}{3} : \frac{4}{3} : \frac{7}{5}$ (4) $\frac{4}{3} : \frac{5}{3} : \frac{7}{5}$ 277. $A gas is compressed adiabatically, which one of the following statement is NOT true?$ (1) $There is no heat supplied to the system$ (2) $There is no change in the internal energy$ (3) $The temperature of the gas increases$ (4) $The change in the internal energy is equal to the work done on the gas$ 278. $For which combination of working temperatures, the efficiency of 'Carnot's engine' is the least?$ (1) $40 K, 20 K$ (2) $60 K, 40 K$ (3) $100 K, 80 K$ (4) $80 K, 60 K$ 279. $A steel rod at 25^{\circ} C is observed to be 1 m long when measured by another metal scale which is correct at 0^{\circ} C . The exact length of steel rod at 0^{\circ} C is (α_{steel} = 12 \times 10^{- 6} /° C and α_{metal} = 20 \times 10^{- 6} /° C)$ (1) $1.00002 m$ (2) $1.0002 m$ (3) $0.998 m$ (4) $0.9998 m$ 280. $The relation between volume (V) and absolute temperature (T) of a gas in an adiabatic process is$ (1) $TV^{γ} = constant$ (2) $VT^{γ} = constant$ (3) $TV^{1 - γ} = constant$ (4) $TV^{γ - 1} = constant$ 281. $An Ideal gas heat engine operated in a carnot's cycle between 227° C and 127° C. It absorbs 6 \times 1 0^{4} J at high temperature. The amount of heat converted into work is$ (1) $4.8 \times 104 J$ (2) $3.5 \times 1 0^{4} J$ (3) $1.6 \times 1 0^{4} J$ (4) $1.2 \times 104 J$ 282. $Steam at 100^{\circ} C is passed into 1 kg of water contained in a calorimeter at 9^{\circ} C till the temperature of water and calorimeter is increased to 90^{\circ} C . The mass of the steam condensed is nearly (water equivalent of calorimeter = 0.1 kg, specific heat of water = 1 calg^{- 1} ° C^{- 1} and latent heat of vaporisation = 540 calg^{- 1})$ (1) $81 g$ (2) $162 g$ (3) $243 g$ (4) $486 g$ 283. $One mole of a gas expands such that its volume ' V' changes with absolute temperature ' T' in accordance with the relation V = K T^{2} where ' K' is a constant. If the temperature of the gas changes by 60^{\circ} C, then work done by the gas is (R is universal gas constant).$ (1) $KRln 60$ (2) $Rln 60$ (3) $40 KR$ (4) $120 R$ 284. $A Carnot working between 300K and 600K has work output of 800 J per cycle. What is amount of heat energy supplied to the engine form source per cycle$ (1) $1800 J/cycle$ (2) $1000 J/cycle$ (3) $2000 J/cycle$ (4) $1600 J/cycle$ 285. $According to law of equipartition of energy the molar specific heat of a diatomic gas at constant volume where the molecule has one additional vibrational mode is:-$ (1) $\frac{9}{2} R$ (2) $\frac{5}{2} R$ (3) $\frac{3}{2} R$ (4) $\frac{7}{2} R$ 286. $In a thermodynamic process if ' Δ W^{’} and ' Δ U^{’}' are the work done and change in the internal energy of a system respectively, then$ (1) $Δ U = Δ W in adiabatic process$ (2) $Δ U = Δ W in isothermal process$ (3) $Δ U = - Δ W in isothermal process$ (4) $Δ U = - Δ W in adiabatic process$ 287. $“Heat cannot by itself flow from a body at lower temperature to a body at higher temperature” is a statement or consequence of$ (1) $Second law of thermodynamics$ (2) $Conservation of momentum$ (3) $Conservation of mass$ (4) $First law of thermodynamics$ 288. $Two moles of a gas is expanded to double its volume by two different processes. One is isobaric and the other is isothermal. If W_{1} and W_{2} are the works done, respectively then$ (1) $W_{2} = \frac{W _{1}}{log e ^{2}}$ (2) $W_{2} = W_{1}$ (3) $W_{2} = W_{1} log e^{2}$ (4) $W_{2} = W_{1} log_{e} (2)$ 289. $For an adiabatic expansion of an ideal gas, the fractional change in its pressure is equal to (where is the ratio of specific heats):$ (1) $- γ \frac{dV}{V}$ (2) $- γ \frac{V}{dV}$ (3) $- \frac{1}{γ} \frac{dV}{V}$ (4) $\frac{dV}{V}$ 290. $An ideal heat engine has an efficiency η . The coefficient of performance of the engine when driven backward will be$ (1) $1 - (\frac{1}{η})$ (2) $η - (\frac{1}{η})$ (3) $(\frac{1}{η}) - 1$ (4) $\frac{1}{1 - η}$ 291. $The amount of heat energy required to raise the temperature of 1 g ofHelium at NTP, from T_{1} K to T_{2} K is$ (1) $\frac{3}{4} N_{a} k_{B} (T_{2} - T_{1})$ (2) $\frac{3}{4} N_{a} k_{B} (\frac{T _{2}}{T _{1}})$ (3) $\frac{3}{8} N_{a} k_{B} (T_{2} - T_{1})$ (4) $\frac{3}{2} N_{a} k_{B} (T_{2} - T_{1})$ 292. $The change in density of mercury, when it is heated from 10^{\circ} C to 60^{\circ} C is (The coefficient of volume expansion of mercury is 18.2 \times 10^{- 5} K^{- 1}).$ (1) $1.82 %$ (2) $0.91 %$ (3) $9.1 %$ (4) $0.45 %$ 293. $A scientist says that the efficiency of his heat engine which operates at source temperature 127°C and sink temperature 27° C is 26% then$ (1) $It is impossible$ (2) $It is possible but less probable$ (3) $It is quite probable$ (4) $Data are incomplete$ 294. $The entropy of any system is given by S = α^{2} β ln (\frac{μkR}{J β ^{2}} + 3) where α and β are the constants. μ, J, k and R are no. of moles, mechanical equivalent of heat, Boltzmann constant and gas constant respectively. (TakeS = \frac{dQ}{T}) Choose the incorrect option from the following:$ (1) $α and J have the same dimensions.$ (2) $S, β, k and μR have the same dimensions.$ (3) $S and α have different dimensions.$ (4) $α and k have the same dimensions.$ 295. $A meter scale made of steel, reads accurately at 25^{\circ} C . Suppose in an experiment an accuracy of 0.06 mm in 1 m is reqnired, the range of temperature in which the experiment can be performed with this meter scale is (Coefficient of linear expansion of steel is 11 \times 10^{- 6} /° C)$ (1) $19^{\circ} C to 31^{\circ} C$ (2) $25^{\circ} C to 32^{\circ} C$ (3) $18^{\circ} C to 25^{\circ} C$ (4) $18^{\circ} C to 32^{\circ} C$ 296. $An ideal gas heat engine, exhausting heat at 77° C has a 30% efficiency. It must take heat at$ (1) $127° C$ (2) $227 ° C$ (3) $327° C$ (4) $673°C$ 297. $Statement (I): A device in which heat measurement can be made is called calorimeter. Statement (II): Skating is possible on snow due to the formation of water below the skates. Water is formed due to the increase of temperature and ice melts. Statement (III): Two bodies at different temperature are mixed in a calorimeter. Total internal energy of the two bodies remains conserved. Which of the following is correct?$ (1) $Statements I, II and III are true$ (2) $Statement I is true, but statements II and III are false$ (3) $Both statements I and II are true, but statement III is false$ (4) $Both statements I, III are true, but statement II is false$ 298. $Steam at 100^{\circ} C is added to 150 g water to increase its temperature from 20^{\circ} C to 40^{\circ} C . The total mass of the water at 40^{\circ} C is (specific heat capacity of water = 1 cal g^{- 1} ° C^{- 1} and latent heat of steam = 540 cal g^{- 1})$ (1) $155 g$ (2) $150 g$ (3) $145 g$ (4) $5 g$ 299. $If the co-efficient of performance of a refrigerator is 5 and operates at the room temperature 27°C, the temperature inside the refrigerator is$ (1) $240 K$ (2) $250 K$ (3) $230 K$ (4) $260 K$ 300. $A carnot engine takes 900 kcal of heat from a reservoir at 723°C and exhausts it to a sink at 30°C. The work done by the engine is$ (1) $2.73 \times 1 0^{6} Cal$ (2) $3.73 \times 1 0^{6} Cal$ (3) $6.27 \times 1 0^{5} Cal$ (4) $3.73 \times 1 0^{5} Cal$