Thermodynamics PYQs Set 15 (PDF)

Set 15 of 16 · Questions 421-450 of 459

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Mere Teacher · Previous Year Questions NEET Physics · Thermodynamics · Set 15 (Q421-450)
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421. $A Carnot engine operates between 227° C and 27°C. Efficiency of the engine will be$ (1) $\frac{1}{3}$ (2) $\frac{2}{5}$ (3) $\frac{3}{4}$ (4) $\frac{3}{5}$ 422. $The work done by a gas is maximum when it expands from a volume V_{1} to V_{2}, then the expansion is$ (1) $Isothermal expansion$ (2) $Adiabatic expansion$ (3) $Isobaric expansion$ (4) $Free expansion$ 423. $The number of translational degrees of freedom for a diatomic gas is$ (1) $2$ (2) $3$ (3) $5$ (4) $6$ 424. $The coefficient of performance of a carnot refrigerator working between 30° C and 0° C is$ (1) $10$ (2) $1$ (3) $9$ (4) $0$ 425. $A Carnot engine operates between 22 7^{o} C and 2 7^{o} C . Efficiency of the engine will be$ (1) $\frac{1}{3}$ (2) $\frac{2}{5}$ (3) $\frac{3}{4}$ (4) $\frac{3}{5}$ 426. $Which of the following parameters does not characterize the thermodynamic state of matter?$ (1) $Temperature$ (2) $Pressure$ (3) $Work$ (4) $Volume$ 427. $A block of steel of mass 2 kg slides down a rough inclined plane of inclination of sin^{- 1} (\frac{3}{5}) at a constant speed. The temperature of the block as it slides through 80 cm, assuming that the mechanical energy lost is used to increase the temperature of the block is nearly (Specific heat capacity of steel = 420 Jkg^{- 1} K^{- 1} and Acceleration due to gravity = 10 ms^{- 2})$ (1) $0.0190^{\circ} C$ (2) $0.0114^{\circ} C$ (3) $0.0152^{\circ} C$ (4) $0.0952^{\circ} C$ 428. $A piston of mass M is hung from a massless spring whose restoring force law goes as F = - k x^{3}, where k is the spring constant of appropriate dimension. The piston separates the vertical chamber into two parts, where the bottom part is filled with ' n' moles of an ideal gas. An external work is done on the gas isothermally (at a constant temperature T ) with the help of a heating filament (with negligible volume) mounted in lower part of the chamber, so that the piston goes up from a height L_{0} to L_{1}, the total energy delivered by the filament is: (Assume spring to be in its natural length before heating)$ (1) $nRTln (\frac{L _{1}}{L _{0}}) + Mg (L_{1} - L_{0}) + \frac{3 k}{4} (L_{1}^{4}) (- L_{0}^{4})$ (2) $nRTln (\frac{L _{1}}{L _{0}}) + Mg (L_{1} - L_{0}) + \frac{k}{4} (L_{1}^{4} (- L_{0}^{4}))$ (3) $nRTln (\frac{L _{1}^{2}}{L _{0}^{2}}) + \frac{Mg}{2} (L_{1} - L_{0}) + \frac{k}{4} (L_{1}^{4} -) (L_{0}^{4})$ (4) $3 nRTln (\frac{L _{1}}{L _{0}}) + 2 Mg (L_{1} - L_{0}) + \frac{k}{3} (L (- L_{0}^{3})$ 429. $According to kinetic theory of gases, at absolute zero of temperature$ (1) $water freezes$ (2) $liquid helium freezes$ (3) $molecular motion stops$ (4) $liquid hydrogen freezes$ 430. $Which of the following graphs represent the behavior of an ideal gas? Symbols have their usual meaning.$ (1) (2) (3) (4) 431. $An ideal gas A and a real gas B have their volumes increased from V to 2 V under isothermal conditions. The increase in internal energy$ (1) $will be same in both A and B$ (2) $will be zero in both the gases$ (3) $of B will be more than that of A$ (4) $of A will be more than that of B$ 432. $A copper rod of length 75 cm and an iron rod of length 125 cm are joined together end to end. Both are of circular cross-section with diameter 2 cm . The free ends of the copper and iron are maintained at 100^{\circ} C and 0^{\circ} C respectively. The surfaces of the bars are insulated thermally. The temperature of the copper-iron junction is [Thermal conductivity of copper is 386.4 W / m - K and thermal conductivity of iron is 48.46 W / m - K]$ (1) $100^{\circ} C$ (2) $0^{\circ} C$ (3) $93^{\circ} C$ (4) $50^{\circ} C$ 433. $The relation between efficiency η of a heat engine and the coefficient of performance α of a refrigerator is$ (1) $η = \frac{1}{1 - α}$ (2) $η = \frac{1}{1 + α}$ (3) $η = 1 + α$ (4) $η = 1 - α$ 434. $At 0K which of the following properties of a gas will be zero?$ (1) $vibrational energy$ (2) $density$ (3) $kinetic energy$ (4) $potential energy.$ 435. $In a adiabatic process, relation between Δ U and Δ W is$ (1) $Δ U = Δ W$ (2) $Δ U = - Δ W$ (3) $Δ U = - Δ W + Δ Q$ (4) $Δ Q = Δ W$ 436. $A cycle tyre bursts suddenly. What is the type of this process?$ (1) $Isochoric$ (2) $Isothermal$ (3) $Isobaric$ (4) $Adiabatic$ 437. $Which of the following is not thermodynamically function?$ (1) $Enthalpy$ (2) $Work done$ (3) $Gibb’s energy$ (4) $Internal energy$ 438. $A thermodynamic process is shown in the figure. The pressure and volumes corresponding to some points in the figure are P_{A} = 3 \times 1 0^{4} Pa; V_{A} = 2 \times 1 0^{- 3} m^{3}; P_{B} = 8 \times 1 0^{4} Pa; V_{D} = 5 \times 1 0^{- 3} m^{3} . In the process AB, 600 J of heat is added to the system and in process BC, 200 J ofheat is added to the system. The change in internal energy of the system is process AC would be$ (1) $560 J$ (2) $800 J$ (3) $600 J$ (4) $640 J$ 439. $Isothermal process is the graph between$ (1) $pressure and temperature$ (2) $pressure and volume$ (3) $volume and temperature$ (4) $pV and temperature$ 440. $Which of the following processes described below is irreversible?$ (1) $The increase in temperature of an iron rod by hammering it.$ (2) $A gas in a small container at a temperature T_{1} is brought in contact with a big reservoir at a higher temperature T_{2} which increases the temperature of the gas.$ (3) $An ideal gas is enclosed in a piston cylinder arrangement with adiabatic walls.$ (4) $All of above$ 441. $The correct relation between γ = \frac{C _{p}}{C _{v}} and temperature T is:$ (1) $γ \propto \frac{1}{T}$ (2) $γ \propto T^{0}$ (3) $γ \propto \frac{1}{T}$ (4) $γ \propto T$ 442. $An ideal gas in a cylinder is separated by a piston in such a way that the entropy of one part is S_{1} and that ofthe other part is S_{2} . Given that S_{1} > S_{2} . If the piston is removed then the total entropy of the system will be:$ (1) $S_{1} \times S_{2}$ (2) $S_{1} - S_{2}$ (3) $\frac{S _{1}}{S _{2}}$ (4) $S_{1} + S_{2}$ 443. $Starting with the same initial conditions, an ideal gas expands from volume V_{1} to V_{2} in three different ways. The work done by the gas is W_{1} if the process is purely isothermal. W_{2} . if the process is purely adiabatic and W_{3} if the process is purely isobaric. Then, choose the coned option$ (1) $W_{1} < W_{2} < W_{3}$ (2) $W_{2} < W_{3} < W_{1}$ (3) $W_{3} < W_{1} < W_{2}$ (4) $W_{2} < W_{1} < W_{3}$ 444. $A thermodynamic system is taken from state A to B along ACB and is brought back to A along BDA as shown in the PV diagram. The net work done during the complete cycle is given by the area$ (1) $P_{1} ACB P_{2} P_{1}$ (2) $ACBB’A’A$ (3) $ACBDA$ (4) $ADBB’A’A$ 445. $A poly-atomic molecule (C_{V} = 3 R, C_{P} = 4 R, where R is gas constant) goes from phase space point A (P_{A} = 10^{5} Pa, V_{A} = 4 \times 10^{- 6} m^{3}) to point B (P_{B} = 5 \times 10^{4} Pa, V_{B} = 6 \times 10^{- 6} m^{3}) to point C (P_{C} = 10^{4}) (Pa, V_{C} = 8 \times 10^{- 6} m^{3}) . A to B is an adiabatic path and B to C is an isothermal path. The net heat absorbed per unit mole by the system is:$ (1) $500 R (ln 3 + ln 4)$ (2) $450 R (ln 4 - ln 3)$ (3) $500 R ln 2$ (4) $400 R ln 4$ 446. $Work done$ (1) $can only be positive$ (2) $can only be negative$ (3) $can either be positive or negative$ (4) $cannot be assigned a sign$ 447. $A measure of the degree of disorder of a system is known as$ (1) $Isobaric$ (2) $Isotropy$ (3) $Enthalpy$ (4) $Entropy$ 448. $First law of thermodynamics is consequence of conservation of$ (1) $work$ (2) $energy$ (3) $heat$ (4) $all of these$ 449. $The S.I. unit of specific heat capacity is$ (1) $J k g^{- 1} K^{- 1}$ (2) $J mol^{- 1} K^{- 1}$ (3) $J kg^{- 1}$ (4) $J K^{- 1}$ 450. $For hydrogen gas C_{P} - C_{\nabla} = a and for oxygen gas C_{P} - C_{\nabla} = b, so the relation between a and b is given by$ (1) $a = 16 b$ (2) $16 b = a$ (3) $a = 4 b$ (4) $a = b$