CBSE Class 11 Physics Thermodynamics Assignment

Question. A sample of 0.1 g of water at 100°C and normal pressure (1.013 × 105 N m^–2) requires 54 cal of heat energy to convert to steam at 100°C. If the volume of the steam produced is 167.1 cc, the change in internal energy of the sample, is
(a) 104.3 J
(b) 208.7 J
(c) 42.2 J
(d) 84.5 J
Answer. B

Question. The internal energy change in a system that has absorbed 2 kcal of heat and done 500 J of work is
(a) 6400 J
(b) 5400 J
(c) 7900 J
(d) 8900 J
Answer. C

Question. 110 joule of heat is added to a gaseous system whose internal energy is 40 J, then the amount of external work done is
(a) 150 J
(b) 70 J
(c) 110 J
(d) 40 J
Answer. B

Question. First law of thermodynamics is consequence of conservation of
(a) work
(b) energy
(c) heat
(d) all of these
Answer. B

Question. If c_p and c_v denote the specific heats per unit mass of an ideal gas of molecular weight M, then
(a) c_p – c_v = R/M²
(b) c_p – c_v = R
(c) c_p – c_v = R/M
(d) c_p – c_v = MR
Answer. C

Question. One mole of an ideal gas requires 207 J heat to rise the temperature by 10 K when heated at constant pressure. If the same gas is heated at constant volume to raise the temperature by the same 10 K, the heat required is (Given the gas constant R = 8.3 J/mole K)
(a) 198.7 J
(b) 29 J
(c) 215.3 J
(d) 124 J
Answer. D

Question. A cylinder contains hydrogen gas at pressure of 249 kPa and temperature 27°C. Its density is (R = 8.3 J mol^–1 K^–1)
(a) 0.5 kg/m³
(b) 0.2 kg/m³
(c) 0.1 kg/m³
(d) 0.02 kg/m³
Answer. B

Question. Which of the following is not thermodynamical function ?
(a) Enthalpy
(b) Work done
(c) Gibb’s energy
(d) Internal energy
Answer. B

Question. Two cylinders A and B of equal capacity are connected to each other via a stopcock. A contains an ideal gas at standard temperature and pressure. B is completely evacuated. The entire system is thermally insulated. The stopcock is suddenly opened. The process is
(a) isothermal
(b) adiabatic
(c) isochoric
(d) isobaric 
Answer. B

Question. In which of the following processes, heat is neither absorbed nor released by a system?
(a) isochoric
(b) isothermal
(c) adiabatic
(d) isobaric
Answer. C

Question. 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
(a) Compressing the gas isothermally or adiabatically will require the same amount of work.
(b) Which of the case (whether compression through isothermal or through adiabatic process) requires more work will depend upon the atomicity of the gas.
(c) Compressing the gas isothermally will require more work to be done.
(d) Compressing the gas through adiabatic process will require more work to be done.
Answer. D

Question. An ideal gas is compressed to half its initial volume by means of several processes. Which of the process results in the maximum work done on the gas?
(a) Isochoric
(b) Isothermal
(c) Adiabatic
(d) Isobaric
Answer. C

Question. 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. 
Answer. D

Question. A mass of diatomic gas (g = 1.4) at a pressure of 2 atmospheres is compressed adiabatically so that its temperature rises from 27°C to 927°C. The pressure of the gas in the final state is
(a) 8 atm
(b) 28 atm
(c) 68.7 atm
(d) 256 atm 
Answer. D

Question. If ΔU and ΔW represent the increase in internal energy and work done by the system respectively in a thermodynamical process, which of the following is true?
(a) ΔU = – ΔW, in an adiabatic process
(b) ΔU = ΔW, in an isothermal process
(c) ΔU = ΔW, in an adiabatic process
(d) ΔU = –ΔW, in an isothermal process
Answer. A

Question. A monatomic gas at pressure P₁ and volume V₁ is compressed adiabatically to 1/8th of its original volume. What is the final pressure of the gas?
(a) 64P₁
(b) P₁
(c) 16P₁
(d) 32P₁
Answer. D

Question. In thermodynamic processes which of the following statements is not true?
(a) In an isochoric process pressure remains constant.
(b) In an isothermal process the temperature remains constant.
(c) In an adiabatic process PVg = constant.
(d) In an adiabatic process the system is insulated from the surroundings. 
Answer. A

Question. If Q, E and W denote respectively the heat added, change in internal energy and the work done in a closed cyclic process, then
(a) E = 0
(b) Q = 0
(c) W = 0
(d) Q = W = 0
Answer. A

Question. One mole of an ideal gas at an initial temperature of T K does 6R joule of work adiabatically. If the ratio of specific heats of this gas at constant pressure and at constant volume is 5/3, the final temperature of gas will be
(a) (T + 2.4) K
(b) (T – 2.4) K
(c) (T + 4) K
(d) (T – 4) K 
Answer. D

Question. An ideal gas at 27°C is compressed adiabatically to 8/27 of its original volume. The rise in temperature is (Take g = 5/3)
(a) 275 K
(b) 375 K
(c) 475 K
(d) 175 K 
Answer. B

Question. We consider a thermodynamic system. If DU represents the increase in its internal energy and W the work done by the system, which of the following statements is true?
(a) DU = –W in an isothermal process
(b) DU = W in an isothermal process
(c) DU = –W in an adiabatic process
(d) DU = W in an adiabatic process 
Answer. C

Question. A sample of gas expands from volume V₁ to V₂. The amount of work done by the gas is greatest, when the expansion is
(a) adiabatic
(b) equal in all cases
(c) isothermal
(d) isobaric. 
Answer. D

Question. A diatomic gas initially at 18°C is compressed adiabatically to one eighth of its original volume.
The temperature after compression will be
(a) 395.4°C
(b) 144°C
(c) 18°C
(d) 887.4°C 
Answer. B

Question. In an adiabatic change, the pressure and temperature of a monatomic gas are related as P ∝ T^C, where C equals
(a) 3/5
(b) 5/3
(c) 2/5
(d) 5/2 
Answer. D

Question. An ideal gas A and a real gas B have their volumes increased from V to 2V under isothermal conditions.The increase in internal energy
(a) will be same in both A and B
(b) will be zero in both the gases
(c) of B will be more than that of A
(d) of A will be more than that of B.
Answer. B

Question. The efficiency of an ideal heat engine working between the freezing point and boiling point of water, is
(a) 26.8%
(b) 20%
(c) 6.25%
(d) 12.5%
Answer. A

Question. A refrigerator works between 4°C and 30°C. It is required to remove 600 calories of heat every second in order to keep the temperature of the refrigerated space constant. The power required is (Take 1 cal = 4.2 Joules)
(a) 236.5 W
(b) 2365 W
(c) 2.365 W
(d) 23.65 W 
Answer. A

Question. The coefficient of performance of a refrigerator is 5.If the temperature inside freezer is –20°C, the temperature of the surroundings to which it rejects heat is
(a) 11°C
(b) 21°C
(c) 31°C
(d) 41°C 
Answer. C

Question. Which of the following processes is reversible?
(a) Transfer of heat by conduction
(b) Transfer of heat by radiation
(c) Isothermal compression
(d) Electrical heating of a nichrome wire 
Answer. C

Question. A carnot engine having an efficiency of 1/10 as heat engine, is used as a refrigerator. If the work done on the system is 10 J, the amount of energy absorbed from the reservoir at lower temperature is
(a) 90 J
(b) 99 J
(c) 100 J
(d) 1 J
Answer. A

Question. An engine has an efficiency of 1/6. When the temperature of sink is reduced by 62°C, its efficiency is doubled. Temperatures of the source is
(a) 37°C
(b) 62°C
(c) 99°C
(d) 124°C 
Answer. C

Question. A Carnot engine whose sink is at 300 K has an efficiency of 40%. By how much should the temperature of source be increased so as to increase its efficiency by 50% of original efficiency?
(a) 380 K
(b) 275 K
(c) 325 K
(d) 250 K
Answer. D

Question. An ideal gas heat engine operates in Carnot cycle between 227°C and 127°C. It absorbs 6 × 10⁴ cal of heat at higher temperature. Amount of heat converted to work is
(a) 4.8 × 10⁴ cal
(b) 6 × 10⁴ cal
(c) 2.4 × 10⁴ cal
(d) 1.2 × 10⁴ cal
Answer. D

Question. An ideal gas heat engine operates in a Carnot cycle between 227°C and 127°C. It absorbs 6 kcal at the higher temperature. The amount of heat (in kcal) converted into work is equal to
(a) 4.8
(b) 3.5
(c) 1.6
(d) 1.2
Answer. D

Question. The efficiency of Carnot engine is 50% and temperature of sink is 500 K. If temperature of source is kept constant and its efficiency raised to 60%, then the required temperature of sink will be
(a) 100 K
(b) 600 K
(c) 400 K
(d) 500 K 
Answer. C

Question. A scientist says that the efficiency of his heat engine which work at source temperature 127°C and sink temperature 27°C is 26%, then
(a) it is impossible
(b) it is possible but less probable
(c) it is quite probable
(d) data are incomplete. 
Answer. A

Question. The (W/Q) of a Carnot engine is 1/6, now the temperature of sink is reduced by 62°C, then this ratio becomes twice, therefore the initial temperature of the sink and source are respectively
(a) 33°C, 67°C
(b) 37°C, 99°C
(c) 67°C, 33°C
(d) 97 K, 37 K
Answer. B

Question. An ideal Carnot engine, whose efficiency is 40%, receives heat at 500 K. If its efficiency is 50%, then the intake temperature for the same exhaust temperature is
(a) 800 K
(b) 900 K
(c) 600 K
(d) 700 K
Answer. C