Thermodynamics PYQs Set 14 (PDF)

Set 14 of 16 · Questions 391-420 of 459

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Mere Teacher · Previous Year Questions NEET Physics · Thermodynamics · Set 14 (Q391-420)
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391. $The temperature-entropy diagram of a reversible engine cycle is given in the figure. Its efficiency is:$ (1) $\frac{1}{2}$ (2) $\frac{1}{4}$ (3) $\frac{1}{3}$ (4) $\frac{2}{3}$ 392. $The volume (V) of a monatomic gas varies with its temperature (T), as shown in the graph. The ratio of work done by the gas, to the heat absorbed by it, when it undergoes a change from state A to state B, is$ (1) $\frac{2}{5}$ (2) $\frac{2}{3}$ (3) $\frac{1}{3}$ (4) $\frac{2}{7}$ 393. $Consider a heat engine as shown in figure Q1 and Q2 are heat added to heat bath T_{1} and heat taken from T_{2} in one cycle of engine. W is the mechanical work done on the engine. If W > 0, then possibilities are (i) Q1 > Q2 > 0 (ii) Q2 > Q1 > 0 (iii) Q2 < Q1 < 0 (iv) Q1 < 0, Q2 > 0$ (1) $(i) and (ii)$ (2) $(i) and (iii)$ (3) $(ii) and (iii)$ (4) $(ii) and (iv)$ 394. $The magnitude of heat exchanged by a system for the given cyclic process ABCA (as shown in figure) is (in SI unit):$ (1) $5 π$ (2) $40 π$ (3) $10 π$ (4) $zero$ 395. $A sample of gas expands from volume V_{1} to V_{2} . The amount of work done by the gas is greatest, when the expansion is$ (1) $adiabatic$ (2) $equal in all cases$ (3) $isothermal$ (4) $isobaric.$ 396. $An ideal gas is taken through the cycle A \to B \to C \to A as shown in the figure. If the net heat supplied to the gas in the cycle is 5 J . The magnitude of work done during the process C \to A is$ (1) $5 J$ (2) $10 J$ (3) $15 J$ (4) $20 J$ 397. $A Carnot engine whose heat sinks at 27°C, has an efficiency of 25%. By how many degrees should the temperature of the source be changed to increase the efficiency by 100% of the original efficiency?$ (1) $Increases by 18°C$ (2) $Increase by 200°C$ (3) $Increase by 120°C$ (4) $Increase by 73°$ 398. $The graph between two temperature scales P and Q is shown in the figure. Between upper fixed point and lower fixed point there are 150 equal divisions of scale P and 100 divisions on scale Q. The relationship for conversion between the two scales is given by:$ (1) $\frac{t _{Q}}{150} = \frac{t _{P} - 180}{100}$ (2) $_\frac{t _{Q}}{100} = \frac{t _{P} - 30}{150}$ (3) $\frac{t _{P}}{180} = \frac{t _{Q} - 40}{100}$ (4) $\frac{t _{P}}{100} = \frac{t _{Q} - 180}{150}$ 399. $A gas is compressed isothermally to half its initial volume. The same gas is compressed separately through an adiabatic process until its volume is again reduced to half. Then$ (1) $Compressing the gas isothermally or adiabatically will require the same amount of work.$ (2) $Which of the case (whether compression through isothermal or through adiabatic process) requires more work will depend upon the atomicity of the gas.$ (3) $Compressing the gas isothermally will require more work to be done.$ (4) $Compressing the gas through adiabatic process will require more work to be done.$ 400. $In the given triple point curve as shown in fig. the curves AO, BO, CO represents$ (1) $AO = Sublimation curve, BO = fusion curve, CO = Vaporization curve$ (2) $AO = Fusion curve, BO = Sublimation curve, CO = Vaporization curve$ (3) $AO = Fusion curve, BO = Vaporization curve, CO = Sublimation curve$ (4) $AO = Vaporization curve, BO = fusion curve, CO = Sublimation curve$ 401. $A gas system is taken through the thermodynamic cyclic process 1 \to 2 \to 3 \to 1 as shown below. The amount of heat released by the system is$ (1) $- P \frac{V}{2}$ (2) $PV$ (3) $\frac{PV}{2}$ (4) $\frac{- 3 PV}{2}$ 402. $If c_{p} and c_{v} denote the specific heats (per unit mass) of an ideal gas of molecular weight M, then where R is the molar gas constant.$ (1) $c_{p} - c_{v} = R / M^{2}$ (2) $c_{p} - c_{v} = R$ (3) $c_{p} - c_{v} = R / M$ (4) $c_{p} - c_{v} = M R$ 403. $A hypothetical gas expands adiabatically such that its volume changes from 8 liters to 27 liters. If the ratio of final pressure of the gas to initial pressure of the gas is \frac{16}{81} . Then the ratio of \frac{C _{P}}{C _{V}} will be.$ (1) $\frac{4}{3}$ (2) $\frac{3}{1}$ (3) $\frac{1}{2}$ (4) $\frac{3}{2}$ 404. $When 1 kg of ice at 0^{\circ} C melts to water at 0^{\circ} C, the resulting change in its entropy, taking latent heat of ice to be 80 cal/g, is$ (1) $273 cal / K$ (2) $8 \times 1 0^{4} cal / K$ (3) $80 cal / K$ (4) $293 cal / K$ 405. $In a vessel, the gas is at pressure P . Ifthe mass of all the molecules is halved and their speed is doubled, then the resultant pressure will be$ (1) $2 P$ (2) $P$ (3) $\frac{P}{2}$ (4) $4 P$ 406. $A carnot engine absorbs 750 J of heat energy from a reservoir at 137°C and rejects 500 J of heat during each cycle, then the temperature of sink is$ (1) $0.25°C$ (2) $0.34°C$ (3) $0.44°C$ (4) $0.54°C$ 407. $The ratio energies of emitted radiation by a black body at 600 K and 900 K when the surrounding temperature is 300 K$ (1) $\frac{5}{16}$ (2) $\frac{7}{16}$ (3) $\frac{3}{16}$ (4) $\frac{9}{16}$ 408. $Which of the following relations does not give the equation of an adiabatic process, where terms have their usual meaning?$ (1) $P^{1 - γ} T^{γ} = constant$ (2) $P V^{γ} = constant$ (3) $T V^{γ - 1} = constant$ (4) $P^{γ} T^{1 - γ} = constant$ 409. $Two containers A and B are partly filled with water and closed. The volume of A is twice that of B and it contains half the amount of water in B . If both are at the same temperature, the water vapour in the containers will have pressure in the ratio of$ (1) $1: 2$ (2) $1 : 1$ (3) $2 : 1$ (4) $4 : 1$ 410. $If the ratio of specific heat of a gas at constant pressure to that at constant volume is γ, the change in internal energy of a mass of gas, when the volume changes from V to 2 V at constant pressure P, is$ (1) $\frac{P V}{γ - 1}$ (2) $PV$ (3) $\frac{R}{( γ - 1 )}$ (4) $\frac{γ P V}{γ - 1}$ 411. $Match the temperatures of the source and sink (T_{1} and T_{2} respectively) of a Carnot heat engine given in List-I with the corresponding efficiencies given in List-II. List-I (A) T_{1} = 500 K, T_{2} = 300 K (B) T_{1} = 500 K, T_{2} = 350 K (C) T_{1} = 800 K, T_{2} = 400 K (D) T_{1} = 450 K, T_{2} = 360 K List-II (i) 0.2 (ii) 0.3 (iii) 0.4 (iv) 0.5 The correct match is$ (1) $A-(iii), B-(iv), C-(ii), D-(i)$ (2) $A-(iv), B-(iii), C-(ii), D-(i)$ (3) $A-(iii), B-(i), C-(iv), D-(ii)$ (4) $A-(iii), B-(ii), C-(iv), D-(i)$ 412. $Which statement is incorrect?$ (1) $All reversible cycles have same efficiency$ (2) $Reversible cycle has more efficiency than an irreversible one$ (3) $Carnot cycle is a reversible one$ (4) $Carnot cycle has the maximum efficiency in all cycles$ 413. $A metal rod of length 10 cm and area of cross-section 2.8. \times 10^{- 4} m^{2} is covered with a non-conducting substance/ One end of it is maintained at 80^{\circ} C, while the other end is put in ice at 0^{\circ} C . It is found that 20 gm of ice melts in 5 min . The thermal conductivity of the metal in Js^{- 1} m^{- 1} K^{- 1} is (Latent heat of ice is 80 cal g^{- 1} .)$ (1) $70$ (2) $80$ (3) $90$ (4) $100$ 414. $An ideal gas goes from an initial state to final state. During the process, the pressure of gas increases linearly with temperature. A. The work done by gas during the process is zero. B. The heat added to gas is different from change in its internal energy. C. The volume of the gas is increased. D. The internal energy of the gas is increased. E. The process is isochoric (constant volume process) Choose the correct answer from the options given below:$ (1) $E Only$ (2) $A, B, C, D Only$ (3) $A, D, E Only$ (4) $A, C Only$ 415. $Efficiency of Carnot engine is 100% if$ (1) $T_{2} = 273 K$ (2) $T_{2} = 0 K$ (3) $T_{1} = 273 K$ (4) $T_{1} = 0 K$ 416. $Identify the characteristics of an adiabatic process in a monoatomic gas. (A)Internal energy is constant. (B)Work done in the process is equal to the change in internal energy. (C)The product of temperature and volume is a constant. (D)The product of pressure and volume is a constant. (E) The work done to change the temperature from T_{1} to T_{2} is proportional to (T_{2} - T_{1}) . Choose the correct answer from the options given below:$ (1) $(B), (D)only$ (2) $(B), (E) only$ (3) $(A), (C), (E) only$ (4) $(A), (C), (D)only$ 417. $Three containers of the same volume contain three different gases. The masses of the molecules are m_{1}, m_{2} and m_{3} and the number of molecules in their respective containers are N_{1}, N_{2} and N_{3} . The gas pressure in the containers are P_{1}, P_{2} and P_{3} respectively. All the gases are now mixed and put in one ofthese containers. The pressure P of the mixture will be$ (1) $P < (P_{1} + P_{2} + P_{3})$ (2) $P = P_{1} + P_{2} + P_{3} 3$ (3) $P = P_{1} + P_{2} + P_{3}$ (4) $P > (P_{1} + P_{2} + P_{3})$ 418. $An electric heater with constant heat supply rate is used to convert a certain amount of liquid ammonia to saturated vapour at high pressure. The heater takes 14 minutes to bring the liquid at 15^{\circ} C to the boiling point of 50^{\circ} C and 92 minutes to convert the liquid at the boiling point wholly to vapour. If the specific heat capacity of liquid ammonia is 4.9 kJ / kgK, the latent heat of vaporisation of ammonia in kJ / kg is$ (1) $557$ (2) $981$ (3) $1127$ (4) $2250$ 419. $In thermodynamics, heat and work are:$ (1) $Path functions$ (2) $Intensive thermodynamic state variables$ (3) $Extensive thermodynamic state variables$ (4) $Point functions$ 420. $Wein's displacement law states$ (1) $λ_{m} T = constant$ (2) $\frac{λ _{m}}{T} = constant$ (3) $\frac{T}{λ _{m}} = constant$ (4) $λ_{m} + T = constant$