# MCQs For NCERT Class 11 Physics Chapter 12 Thermodynamics

Please refer to the MCQ Questions for Class 11 Physics Chapter 12 Thermodynamics with Answers. The following Thermodynamics Class 11 Physics MCQ Questions have been designed based on the latest syllabus and examination pattern for Class 11. Our experts have designed MCQ Questions for Class 11 Physics with Answers for all chapters in your NCERT Class 11 Physics book.

## Thermodynamics Class 11 MCQ Questions with Answers

See below Thermodynamics Class 11 Physics MCQ Questions, solve the questions and compare your answers with the solutions provided below.

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.

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%

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

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

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

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

A

Question. Two Carnot engines A and B are operated in series. The engine A receives heat from the source at temperature T1 and rejects the heat to the sink at temperature T. The second engine B receives the heat at temperature T and rejects to its sink at temperature T2. For what value of T the efficiencies of the two engines are equal
(a) T1 – T2 /2
(b) T1 -T2
(c) √T1 -T2
(d)  T+ T2 /2

C

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

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

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

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

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

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.

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

B

Question. The efficiency of a Carnot engine operating with reservoir temperature of 100°C and –23°C will be
(a) 373 + 250 /373
(b) 373 – 250 /373
(c) 100 + 23 /100
(d) 100 – 23 /100

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

C

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

B

Question. A thermally insulted vessel contains 150 g of water at 0°C. Then the air from the vessel is pumped out adiabatically. A fraction of water turns into ice and the rest evaporates at 0°C itself. The mass of evaporated water will be closed to : (Latent heat of vaporization of water = 2.10 × 106 J kg–1 and Latent heat of Fusion of water = 3.36 × 105 J kg–1)
(a) 150 g
(b) 20 g
(c) 130 g
(d) 35 g

B

Question. An ideal heat engine works between temperatures T1 = 500 K and T2 = 375 K. If the engine absorbs 600J of heat from the source, then the amount of heat released to the sink is:
(a) 450 J
(b) 600 J
(c) 45 J
(d) 500 J

A

Question. In a Carnot engine, the temperature of reservoir is 927°C and that of sink is 27°C. If the work done by the engine when it transfers heat from reservoir to sink is 12.6 × 106J, the quantity of heat absorbed by the engine from the reservoir is
(a) 16.8 × 106 J
(b) 4 × 106 J
(c) 7.6 × 106 J
(d) 4.2 × 106 J

A

Question. A reversible engine converts one-sixth of the heat input into work. When the temperature of the sink is reduced by 62ºC, the efficiency of the engine is doubled. The temperatures of the source and sink are
(a) 99ºC, 37ºC
(b) 80ºC, 37ºC
(c) 95ºC, 37ºC
(d) 90ºC, 37ºC

A

Question. Two moles of helium gas (g = 5/3) are initially at temperature 27°C and occupy a volume of 20 litres. The gas is first expanded at constant pressure until the volume is doubled. Then, it undergoes and adiabatic change until the temperature returns to the initial value. What is the final volume of the gas?
(a) 112.4 lit.
(b) 115.2 lit
(c) 120 lit
(d) 125 lit

A

Question. The relation between U, P and V for an ideal gas in an adiabatic process is given by relation U = a + bP V. Find the value of adiabatic exponent (γ) of this gas.
(a) b+1/b
(b) b+1/a
(c) a+1/b
(d) a/a+b

A

Question. An ideal monatomic gas with pressure P, volume V and temperature T is expanded isothermally to a volume 2V and a final pressure Pi. If the same gas is expanded adiabatically to a volume 2V, the final pressure is Pa. The ratio Pa /Pi is
(a) 2-1/3
(b) 21/3
(c) 22/3
(d) 2-2/3

D

Question. A Carnot engine whose low temperature reservoir is at 7°C has an efficiency of 50%. It is desired to increase the efficiency to 70%. By how many degrees should the temperature of the high temperature reservoir be increased?
(a) 840 K
(b) 280 K
(c) 560 K
(d) 373 K

D

Question. Three samples of the same gas A, B and C (γ=3/2) have initially equal volume. Now the volume of each sample is double. The process is adiabatic for A, Isobaric for B and isothermal for C. If the finanl pressures are equal for all the three samples, the ratio of their initial pressure is
(a) 2√2 : 2 :1
(b) 2√2 :1: 2
(c) √2 :1: 2
(d) 2:1: √2

B

Question. Which of the following is incorrect regarding first law of thermodynamics?
(a) It is a restatement of principle of conservation of energy.
(b) It is applicable to cyclic processes
(c) It introduces the concept of entropy
(d) It introduces the concept of internal energy

C

Question Choose the incorrect statement related to an isobaric process.
(a) V /T = constant
(b) W = PDV
(c) Heat given to a system is used up in raising the temperature only.
(d) DQ > W

C

Question. The internal energy of an ideal gas does not depend upon
(a) temperature of the gas
(b) pressure of the gas
(c) atomicity of the gas
(d) number of moles of the gas.

B

Question. During isothermal expansion, the slope of P-V graph
(a) decreases
(b) increases
(c) remains same
(d) may increase or decrease

A

Question. The temperature at which speed of sound in air becomes  double of its value at 27° C is
(a) 54°C
(b) 327°C
(c) 927°C
(d) None of these

C

Question. 1 gm of water at a pressure of 1.01 × 105 Pa is converted into steam without any change of temperature. The volume of 1 g of steam is 1671 cc and the latent heat of evaporation is 540 cal. The change in internal energy due to evaporation of 1 gm of water is
(a) » 167 cal
(b) » 500 cal
(c) 540 cal
(d) 581 cal

B

Question. An ideal refrigerator has a freezer at a temperature of 13ºC.
The coefficient of performance of the engine is 5. The temperature of the air (to which heat is rejected) is
(a) 320ºC
(b) 39ºC
(c) 325 K
(d) 325ºC

B

Question. One mole of an ideal monoatomic gas is heated at a constant pressure of one atmosphere from 0ºC to 100ºC. Then the work done by the gas is
(a) 6.56 joule
(b) 8.32 × 102 joule
(c) 12.48 × 102 joule
(d) 20.8 × 102 joule

B

Question. The pressure inside a tyre is 4 times that of atmosphere. If the tyre bursts suddenly at temperature 300 K, what will be the new temperature?
(a) 300 (4)7/2
(b) 300 (4)2/7
(c) 300 (2)7/2
(d) 300 (4)–2/7

D

Question. A monatomic ideal gas expands at constant pressure, with heat Q supplied. The fraction of Q which goes as work done by the gas is
(a) 1
(b) 2/3
(c) 3/5
(d) 5/

D

Question. A carnot’s engine takes 300 calories of heat at 500 K and rejects 150 calories of heat to the sink. The temperature of the sink is
(a) 1000 K
(b) 750 K
(c) 250 K
(d) 125 K

B

Question. The source and sink temperatures of a Carnot engine are 400 K and 300 K, respectively. What is its efficiency?
(a) 100%
(b) 75%
(c) 33.3%
(d) 25%

D

Question. The volume of a gas is reduced adiabatically to 1/4 of its volume at 27ºC. If g = 1.4 the new temperature is
(a) (300) 20.4 K
(b) (300) 21.4 K
(c) 300 (4)0.4 K
(d) 300 (2)1.4 K