Title 13. Thermodyanmaics Medium.pdf ✅

1. A system is said to be in thermal equilibrium if (a) The macroscopic variables do not change in time (b) The microscopic variables do not change in time (c) The macroscopic variables change in time (d) The maicrosocpic variables changes in time. 2. “Two systems in thermal equilibrium with a third system separately are in thermal equilibrium with each other.” The above statement is (a) First law of thermodynamics (b) Second law of thermodynamics (c) Third law of thermodynamics (d) Zeroth law of thermodynamics 3. Internal energy of an ideal gas depends upon (a) Temperature only (b) Volume only (c) Both volume and temperature (d) Neither volume nor temperature 4. An ideal gas undergoing a change of state from A to B through four different paths I, II, III and IV as shown in the P-V diagram that lead to the same change of state, then the change in internal energy is (a) Is same in I and II but not in III and IV (b) Is same in III and IV but not in I and II (c) Is same in I, II and III but not in IV (d) Same in all the four cases 5. An electric heater supplies heat to a system at a rate of 120 W. If system performs work at a rate of 80 J s–1 , the rate of increase in internal energy is (a) 30 J s–1 (b) 40 J s–1 (c) 50 J s–1 (d) 60J s–1 6. Air is expanded from 50 litres to 150 litres at 2 atmospheric pressure. The external work done is (Given, 1 atm = 105 N m– 2 ) (a) 2 × 10–8 J (b) 2 × 104 J (c) 200 J (d) 2000 J 7. The possibility of increase in the temperature of a gas without adding heat to it happens in (a) Adiabatic expansion (b) Isothermal expansion (c) Adiabatic compression (d) Isothermal compression 8. Which of the following is not a path function? (a)  Q (b)  Q + DW (c)  W (d)  Q – DW 9. Which one of the following is not possible in a cyclic process? (a) Work done by the system is positive (b) Heat added to the system is positive (c) Work done on the system is positive (d) Heat removed from the system is negative 10. If a gas is compressed adiabatically by doing work of 150 J, the change in internal energy of the gas is (a) 100 J (b) 150 J (c) 200 J (d) 250 J 11. If R is universal gas constant, the amount of heat neaded to raise the temperature of 2 moles of an ideal monoatomic gas from 273 K to 373 K when no work is done is (a) 100 R (b) 150 R (c) 300 R (d) 500 R 12. In an adiabatic change the specific heat of gas is (a) Increase with increase in temperature (b) Decrease with increase in temperature (c) Not depend upon change in temperature (d) Always zero 13. Which one of the following graphs represents variation of specific heat capacity of water with temperature? (a) (b) (c) (d) 14. An ideal gas having molar specific heat capacity at constant volume 2 3 is R, the molar specific heat capacities at constant pressure is (a) 2 1 R (b) 2 5 R (c) 2 7 R (d) 2 9 R 15. Mayer’s formula for the relation between two principal specific heats CP and CV of a gas is given by (a) CV – CP = R (b) R C C V P = (c) CP – CV = R (d) R C C P V = 16. For a gas of molecular weight M specific heat capacity at constant pressure is          = V P C C (a) 1 R  − (b) 1 R  −  (c) M( 1) R  −  (d) ( 1) RM  −  17. Two moles of oxygen is mixed with eight moles helium. The effective specific heat of the mixture at constant volume is (a) 1.3 R (b) 1.4 R (c) 1.7 R (d) 1.9 R 18. One mole of an ideal monoatomic gas at temperature T0 expands slowly according to the law = V P constant. If the final temperature is 2T0 heat supplied to the gas is
(a) 2RT0 (b) RT0 (c) RT0 2 3 (d) RT0 2 1 19. Which is an intensive property? (a) Volume (b) Mass (c) Refractive index (d) Weight 20. Which of the following process is correct for given P-V diagram. (a) Adiabatic process (b) Isothermal process (c) Isobaric process (d) Isochoric process 21. The ideal gas equation for an adiabatic process is (a) PV  = constant (b) TV  +1 = constant (c) P(  +1) T = constant (d) P  +1T = constant 22. The isothermal diagram of a gas at three different temperatures T1 , T2 and T3 is shown in the given figure. Then, (a) T1 < T2 < T3 (b) T1 < T2 > T3 (c) T1 > T2 > T3 (d) T1 > T2 < T3 23. If an engine delivers 9.5 × 106 J of work per hour and absorbs 6.2 × 107 J of heat per hour, the amount of heat wasted per hour is (a) 6.95 × 107 J (b) 5.25 × 107 J (c) 8.55 × 107 J (d) 9.55 × 107 J 24. A thermodynamic process is carried out from an original state D to an intermediate state E by the linear process shown in figure The total work is done by the gas from D to E to F is (a) 100 J (b) 800 J (c) 300 J (d) 250 J 25. If an ideal gas undergoes isothermal process from some initial state i to the f, then the change in internal energy during this process is (a) dU = dQ (b) dU = –dW (c) dU = 0 (d) dU = dW 26. The relation between the slope of isothermal curve and slope of adiabatic curve (a) Slope of adiabatic curve =  times slope of isothermal curve (b) Slope of isothermal curve =  times slope of adiabatic curve (c) Slope of adiabatic curve =  2 times slope of isothermal curve (d) Slope of isothermal curve =  2 times slope of adiabatic curve 27. In a cyclic process, which of the following statement is not correct? (a) Change in internal energy is zero. (b) The system returns to its initial state and it is reversible (c) The total heat abosorbed by the system is equals to work done by the system. (d) Change in internal energy is not zero. 28. An ideal gas system undergoes an isothermal process, then the work done during the process is (a) nRTln 1 2 V V (b) nRTln 2 1 V V (c) 2nRTln 1 2 V V (d) 2nRTln         2 1 V V 29. One mole of an ideal gas goes from an initial state A to final state B via two processes : It first undergoes isothermal expansion from volume V to 3V and then its volume is reduced from 3V to V at constant pressure. The correct P-V diagram representing the two processes is (a) (b) (c) (d) 30. Pressure P, volume V and temperature T for a certain gas are related by P = V AT BT2 − , where A and B are constants. The work done by the gas as its temperature change from T1 to T2 while pressure remaining constant is (a) A – (T2 – T1 ) (b) A(T2 – T1 ) – B(T2 2 – T1 2 ) (c) (T2 2 – T1 2 ) – (T2 3 – T1 3 ) (d) A(T2 – T1 ) 2 – (T2 – T1 ) 3 31. 1 g mole of an ideal gas at STP is subjected of a reversible adiabatic expression to double its volume. The change in internal energy (  = 1.4) (a) 1169 J (b) 769 J (c) 1373 J (d) 969 K
32. An ideal gas at pressure P is adiabatically compressed so that its density becomes n times the initial value. The final pressure of the gas will be (a) n  P (b) (n –  )P (c) n(  – 1)P (d) n(1 –  )P 33. During an isothermal expansion, a confined ideal gas does – 150 J of work against its surroundings. This implies that (a) 150 J of heat has been removed from the gas (b) 300 J of heat has been added to the gas (c) No heat is transferred because the process is Isothermal (d) 150 J of heat has been added to the gas 34. The work done in adiabatic process is given by (a) ( )  R T1 −T2 n (b) ( ) 1 nR T1 T2  − − (c) ng(T1 – T2 )R (d) ( ) n  T1 −T2 R 35. Which of the following P-V diagram represent the graph of isometric process ? (a) (b) (c) (d) 36. A gas expands with temperature according to the relation V = KT2/3. Work done when the temperature changes by 60 K is (a) 0 R (b) 30 R (c) 40 R (d) 20 R 37. Match the column I with column II Type of processes Features (A) Isothermal (p)  Q = 0 (B) Isobaric (q) Volume constant (C) Isochoric (r) Pressure constant (D) Adiabatic (s) Temperature constant (a)(A)-(s), (B)-(r), (C)-(q), (D)-(p) (b)(A)-(p), (B)-(s), (C)-(r), (D)-(q) (c)(A)-(q), (B)-(r), (C)-(p), (D)-(s) (d) (A)-(r), (B)-(p), (C)-(q), (D)-(s) 38. Two moles of helium gas undergo a cyclic process as shown in figure. Assuming the gas to be ideal, the net work done by the gas is (a) 200Rln2 (b) 100Rln2 (c) 300Rln2 (d) 400Rln2 39. Two moles of an ideal monoatomic gas occupy a volume 2V at temperature 300 K, it expands to a volume 4V adiabatically, then the final temperature of gas is (a) 179 K (b) 189 K (c) 199 K (d) 219 K 40. The given P-V diagram expansion of gas. Which one of the following statement is true? (a) A is isothermal and B adiabatic process (b) A is adiabatic and B isothermal process (c) Both isothermal process (d) Both adiabatic process 41. The temperature of n moles of an ideal gas is increased from T to 4T through a process for which pressure P = aT–1 where a is a constant. Then, the work done by the gas is (a) nRT (b) 4nRT (c) 2nRT (d) 6Nrt 42. The pressure P1 and density d1 of a diatomic gas (  = 7/5) change to P2 and d2 during an adiabatic operation. If 1 2 d d = 32, then 1 2 P P is (a) 76 (b) 128 (c) 168 (d) 298 43. The fall in temperature of helium gas initially at 20°C when it is suddenly expanded to 8 times its original volume is        = 3 5 (a) 70.25 K (b) 71.25 K (c) 72.25 K (d) 73.25 K 44. In the question number 72, the heat exchanged by the engine with the surroundings for path D to A is (at constant pressure) (a) 2 5 PA (VD – VA ) (b) 2 5 PA (VA – VD ) (c) 2 3 PA (VD – VA ) (d) 2 1 PA (VD – VA ) 45. A one mole of an ideal gas expands adiabatically at constant pressure such that its temperature T V 1  The value of the adiabatic constant of gas is (a) 1.3 (b) 1.5 (c) 1.67 (d) 2.0 46. A Carnot cycle has the reversible processes in which of the following order. (a)Isothermal expansion, adiabatic expansion, isothermal compression and adiabatic compression (b) Isothermal compression, adiabatic expansion, isothermal expansion and adiabatic compression
(c) Isothermal expansion, adiabatic compression, isothermal compression and adiabatic expansion (d) Adiabatic expansion, isothermal expansion adiabatic compression and isothermal compression. 47. The conclusion of second law of thermodynamics is that (a) No heat engine can have efficiency  equal to zero. (b) No heat engine can have efficiency  equal to one. (c) No heat engine can have efficiency  greater than one. (d) No heat engine can have efficiency  less than one. 48. An engine has an efficiency of 0.25 when temperature of sink is reduced by 58°C, if its efficiency is doubled, then the temperature of the source is (a) 150°C (b) 222°C (c) 242°C (d) 232°C 49. Consider a Carnot cycle operating between source temperature 750 K and sink temperature 350 K producing 1.25 kJ of mechanical work per cycle, the heat transferred to the engine by the reservoirs (a) 1.34 kJ (b) 2.34 kJ (c) 3.34 kJ (d) 4.34 kJ 50. A heat engine has an efficiency  . Temperatures of source and sink are each decreased by 100 K. The efficiency of the engine (a) Increases (b) Decreases (c) Remains constant (d) Becomes 1 51. A refrigerator is to maintain eatables kept inside at 7°C. The coefficient of performance of refrigerator if room temperature is 38°C is (a) 15.5 (b) 16.3 (c) 20.1 (d) 9.03 52. When the door of a refrigerator is kept open then the room temperature starts (a) Cool down (b) Hot up (c) First cool down then hot up (d) Neither cool down nor hot up 53. 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 (a)240 K (b) 250 K (c) 230 K (d) 260 K 54. The coefficient of performance of refrigerator, whose efficiency is 25% is (a) 1 (b) 3 (c) 5 (d) 7 55. Consider a heat engine as shown in figure Q1 and Q2 are heat added to heat bath T1 and heat taken from T2 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 (a) (i) and (ii) (b) (i) and (iii) (c) (ii) and (iii) (d) (ii) and (iv) 56. A process is said to be reversible if (a) The system return to their original states (b)The surroundings return to their original states (c) Both the system as well as the surroundings return to their original states (d) Neither system nor surroundings return to their original states 57. A Carnot’s cycle operating between T1 = 600 K and T2 = 300 K producing 1.5 kJ of mechanical work per cycle. The heat transferred to the engine by the reservoirs (a) 2.5 kJ (b) 3 kJ (c) 3.5 kJ (d) 4 kJ 58. If a carnot engine is working between steam point and ice point, then its efficiency will be (a) 24.9 % (b) 25.7% (c) 26.8% (d) 28.8% 59. Carnot engine is (a) Reversible engine (b) Operating between two temperature T1 (source) and T2 (sink) have maximum efficiency (c) Consisting of two isothermal processes connected by two adiabatic processes (d) All of these 60. Air pressure in the tyers of a car during motion is (a) Increase (b) Decrease (c) Remain constant (d) First increase then decrease 61. A Carnot engine whose efficiency is 40%, takes in heat from a source maintained at a temperature of 500 K. It is desired to have an engine of efficiency 60%. Then, the intake temperature for the same exhaust (sink) temperature must be (a) 1200 K (b) 750 K (c) 600 K (d) 800 K 62. An ideal gas undergoes four different processes from the same initial state as sown in P-V diagram. Four processes are adiabatic, isothermal, isobaric and isochoric. Out of 1, 2, 3 and 4 which one is adiabatic ? (a) 4 (b) 3 (c) 2 (d) 1 63. If an average person jogs, he produces 14.5 × 104 cal min–1 . This is removed by the evaporation of sweat. The amount of sweat evaporated per minute (assuming 1 kg requires 580 × 103 cal for evaporation) is (a) 0.25 kg (b) 2.25 kg (c) 0.05 kg (d) 0.20 kg 64. Consider P-V diagram for an ideal gas shown in figure.