Choose Kelvin-Plank statement among the following

It is impossible to construct a device which, operating in a cycle will produce no effect other than the transfer of heat from a cooler to hotter body

It is impossible for a heat engine to produce net work in a complete cycle if it exchanges heat only with bodies at a single fixed temperature

It is impossible to construct a device which, operating in a cycle will produce no effect other than the transfer of heat from a cooler to hotter body

Entropy of universe is always increasing

According to Clausius statement

When two dissimilar metals are heated at one end and cooled at other end, e.m.f. is developed proportional to the difference of temperature at two ends.

It is impossible to construct a heat engine which operates in a cycle and receives a given amount of heat from a high temperature body and does equal amount of work

It is impossible to construct a device which operates in a cycle and produces no effect other than the transfer of heat from cooler body to hotter body

When two dissimilar metals are heated at one end and cooled at other end, e.m.f. is developed proportional to the difference of temperature at two ends.

Heat can be converted into work

In a reversible process, the entropy of a system _________.

first increases and then decreases

According to Carnot's theorem _________.

For different engines operating between the same temperature limit, every engine has an efficiency greater than Carnot cycle efficiency.

For different engines operating between the different temperature limits, no engine has an efficiency greater than Carnot cycle efficiency

For different engines operating between the same temperature limit, no engine has an efficiency greater than Carnot cycle efficiency.

A system undergo a state change from 1 to 2, according to second law of thermodynamics for the process to be feasible, the entropy change S2 – S1 of the system

Can be positive, negative or zero

One kg of air in a closed system undergoes an irreversible process from an initial state of p1 = 1 bar (absolute) and T1 = 27°C, to a final state of p2 = 3 bar (absolute) and T2 = 127°C. If the gas constant of air is 287 J/kg.K and the ratio of the specific heats γ = 1.4, then the change in the specific entropy (in J/kg.K) of the air in the process is

Indeterminate, as the process is irreversible

absolute temperature / heat change

heat change / absolute pressure

absolute pressure / heat change

heat change / absolute temperature

156 + Mcqs in Second Law Thermodynamics in Thermodynamics Page 2 McqOptions

51.	A Carnot engine rejects 50% of heat absorbed from a source to a sink at 27°C. What is the source temperature?
A.	54°C
B.	150°C
C.	327°C
D.	600°C
Answer» D. 600°C

52.	Ninety kilograms of ice at 0°C is completely melted. Find the entropy change, in kJ/K, if T2 = 0°C. (Latent heat of fusion is 318.5 kJ/kg)
A.	0
B.	45
C.	105
D.	85
Answer» D. 85

53.	A liquid of heat capacity 5 J/K in an insulated container is heated electrically from 300 K to 600 K. If, In 2 = 0.693, entropy generation of the universe would be
A.	6.93 J/K
B.	3.465 J/K
C.	34.65 J/K
D.	10.65 J/K
Answer» C. 34.65 J/K

54.	A Carnot engine operates between the temperatures of 300 K and 600 K. If engine produces 600 KJ of work, what is the entropy change during heat addition in KJ/K?
A.	1
B.	0.5
C.	1.5
D.	2
Answer» E.

55.	A Carnot engine receives 100 kJ of heat at 600 K. Heat is rejected at 300 K. the displacement volume is 0.2 m3. The mean effective pressure is
A.	2 bar
B.	2.5 bar
C.	3 bar
D.	3.5 bar
Answer» C. 3 bar

56.	Efficiency of Carnot cycle is the function of
A.	Absolute temperature range
B.	Absolute pressure
C.	Properties of air
D.	None of the above
Answer» B. Absolute pressure

58.	If the COP of Carnot refrigerator is 4, then the thermal efficiency of the Carnot engine would be ________.
A.	0.33
B.	0.25
C.	0.2
D.	0.18
Answer» D. 0.18

59.	If the air has to flow from station P to station Q, the maximum possible value of pressure in kPa at station Q is close to
A.	50
B.	87
C.	128
D.	150
Answer» C. 128

60.	For a heat engine operating on a Carnot cycle, the work output is 1/4th of the heat rejected to the sink. The thermal efficiency of the engine would be
A.	10%
B.	20%
C.	30%
D.	50%
Answer» C. 30%

62.	A heat transformer is a device that transfers a part of the heat, supplied to it at an intermediate temperature, to a high temperature reservoir while rejecting the remaining part to a low temperature heat sink. In such a heat transformer, 100 kJ of heat is supplied at 350 K. The maximum amount of heat in kJ that can be transferred to 400 K, when the rest is rejected to a heat sink at 300 K is
A.	12.5
B.	14.29
C.	33.33
D.	57.14
Answer» E.

63.	A reversible heat engine receives 2 kJ of heat from a reservoir at 1000 K and a certain amount of heat from a reservoir at 800 K. It rejects 1 kJ of heat to a reservoir at 400 K. The net work output (in kJ) of the cycle is
A.	0.8
B.	1
C.	1.4
D.	2
Answer» D. 2

66.	Kelvin-plank law deals with
A.	Conservation of Energy
B.	Conservation of heat
C.	Conservation of mass
D.	Conversion of heat into work
Answer» E.

67.	Practically it is not feasible to design an engine which closely follows the \Cannot cycle’ for the following reasons:1) Transfer of heat energy at constant temperature is very difficult to achieve2) Isentropic processes are very fast processes3) It makes use of smaller pressure ratios4) Thermal efficiency is not a function of source and sink temperaturesWhich of the above reasons is correct?
A.	1 and 2
B.	2 and 3
C.	3 and 4
D.	4 and 1
Answer» B. 2 and 3

68.	A water heating heat pump abstracting 10 kW of heat from the atmosphere requires 2 kW of power input. The COP of the heat pump is:
A.	4
B.	7
C.	5
D.	6
Answer» E.

70.	A solar collector receiving solar radiation at the rate of 0.6 kW/m2 transforms it to the internal energy of a fluid at an overall efficiency of 50% The fluid heated to 350 K is used to run a heat engine which rejects heat at 313 K. if the heat engine is to deliver 2.5 kW power, the minimum area of the solar collector required would be, nearly:
A.	8 m2
B.	17 m2
C.	39 m2
D.	79 m2
Answer» E.

64.	In a reversible process, the entropy of a system _________.
A.	first increases and then decreases
B.	increases
C.	remains the same
D.	decreases
Answer» D. decreases

65.	An engine operates between temperature limits of 900 K and T. Another heat engine operates between T and 400 K. For both to be equally efficient, the values of T will be
A.	700 K
B.	600 K
C.	750 K
D.	650 K
Answer» C. 750 K

69.	Change in entropy (in kJ/kg.K) in a reversible adiabatic process is:
A.	0
B.	1
C.	1.5
D.	2
Answer» B. 1

71.	A solar energy-based heat engine that receives 80 kJ of heat at 100°C and rejects 70 kJ of heat to the ambient at 30°C is to be designed. The thermal efficiency of the heat engine is
A.	70%
B.	1.88%
C.	12.5%
D.	None of the above
Answer» D. None of the above

72.	A Carnot heat engine receives 600 kJ of heat per cycle from a source at 627°C and rejects heat to a sink at 27°C. The amount of heat rejected to the sink per cycle (rounded off to the nearest integer) in kJ is
A.	26
B.	200
C.	400
D.	574
Answer» C. 400

74.	A system undergo a state change from 1 to 2, according to second law of thermodynamics for the process to be feasible, the entropy change S2 – S1 of the system
A.	Is positive or zero
B.	Is negative zero
C.	Is zero
D.	Can be positive, negative or zero
Answer» E.

75.	'Absolute zero' refers to ______.
A.	minus 273 °C
B.	minus 295 °C
C.	minus 300 °C
D.	minus 255 °C
Answer» B. minus 295 °C

76.	One kg of air in a closed system undergoes an irreversible process from an initial state of p1 = 1 bar (absolute) and T1 = 27°C, to a final state of p2 = 3 bar (absolute) and T2 = 127°C. If the gas constant of air is 287 J/kg.K and the ratio of the specific heats γ = 1.4, then the change in the specific entropy (in J/kg.K) of the air in the process is
A.	-26.3
B.	28.4
C.	172
D.	Indeterminate, as the process is irreversible
Answer» B. 28.4

77.	A heat engine is supplied heat at the rate of 1700 kJ/min and gives an output of 9 kW. Thermal efficiency and heat rejection in kW of the heat engine is
A.	34.0 %, 11.0
B.	28.3 %, 10.0
C.	31.76 %, 19.33
D.	32.3 %, 9.83
Answer» D. 32.3 %, 9.83

78.	A Carnot engine receiving heat at 400 K has an efficiency of 50 %. What is the COP of a Carnot refrigerator working between the same temperature limits?
A.	4
B.	1
C.	2
D.	3
Answer» C. 2

Explore topic-wise MCQs in Thermodynamics.

A Carnot engine rejects 50% of heat absorbed from a source to a sink at 27°C. What is the source temperature?

Ninety kilograms of ice at 0°C is completely melted. Find the entropy change, in kJ/K, if T2 = 0°C. (Latent heat of fusion is 318.5 kJ/kg)

A liquid of heat capacity 5 J/K in an insulated container is heated electrically from 300 K to 600 K. If, In 2 = 0.693, entropy generation of the universe would be

A Carnot engine operates between the temperatures of 300 K and 600 K. If engine produces 600 KJ of work, what is the entropy change during heat addition in KJ/K?

A Carnot engine receives 100 kJ of heat at 600 K. Heat is rejected at 300 K. the displacement volume is 0.2 m3. The mean effective pressure is

Efficiency of Carnot cycle is the function of

Choose Kelvin-Plank statement among the following

If the COP of Carnot refrigerator is 4, then the thermal efficiency of the Carnot engine would be ________.

If the air has to flow from station P to station Q, the maximum possible value of pressure in kPa at station Q is close to

For a heat engine operating on a Carnot cycle, the work output is 1/4th of the heat rejected to the sink. The thermal efficiency of the engine would be

According to Clausius statement

A reversible heat engine receives 2 kJ of heat from a reservoir at 1000 K and a certain amount of heat from a reservoir at 800 K. It rejects 1 kJ of heat to a reservoir at 400 K. The net work output (in kJ) of the cycle is

In a reversible process, the entropy of a system _________.

An engine operates between temperature limits of 900 K and T. Another heat engine operates between T and 400 K. For both to be equally efficient, the values of T will be

Kelvin-plank law deals with

A water heating heat pump abstracting 10 kW of heat from the atmosphere requires 2 kW of power input. The COP of the heat pump is:

Change in entropy (in kJ/kg.K) in a reversible adiabatic process is:

A solar energy-based heat engine that receives 80 kJ of heat at 100°C and rejects 70 kJ of heat to the ambient at 30°C is to be designed. The thermal efficiency of the heat engine is

A Carnot heat engine receives 600 kJ of heat per cycle from a source at 627°C and rejects heat to a sink at 27°C. The amount of heat rejected to the sink per cycle (rounded off to the nearest integer) in kJ is

According to Carnot's theorem _________.

A system undergo a state change from 1 to 2, according to second law of thermodynamics for the process to be feasible, the entropy change S2 – S1 of the system

'Absolute zero' refers to ______.

A heat engine is supplied heat at the rate of 1700 kJ/min and gives an output of 9 kW. Thermal efficiency and heat rejection in kW of the heat engine is

A Carnot engine receiving heat at 400 K has an efficiency of 50 %. What is the COP of a Carnot refrigerator working between the same temperature limits?

A Carnot heat pump is used to maintain a room at a temperature of 27°C, the initial temperature of the room was -4°C. The heat loss from the room in 20 kW. What is the power requirement of the pump?

PMM1 is closely related with

Heat of 1000 kJ is supplied to a heat engine from a reservoir at 1000 K, and it rejects waste heat to a river at 300 K. The engine’s work output is 400 kJ. Its efficiency is:

An engine works on Carnot cycle. Initially it had efficiency of 40 percent. Keeping lower temperature fixed, higher temperature is raised by 10 percent. New efficiency will be

A reversible heat engine operates between 300 K and 600 K. If heat output is 200 kJ, the heat input is

A heat engine is supplying heat at the rate of 30,000 J/s and gives an output of 9 kW. The thermal efficiency of the engine will be

A system of 100 kg mass undergoes a process in which its specific entropy increases from 0.3 kJ/kgK to 0.4 kJ/kgK. At the same time, the entropy of the surroundings decreases from 80 kJ/K to 75 kJ/K.The process is:

Efficiency of Carnot cycle depends on

On T-S diagram, constant pressure line slope is expressed as:

Entropy is:

A frictionless heat engine can be 100 percent efficient only if its exhaust temperature is

Kelvin Planck’s law deals with:

An isentropic flow is one which is

\(\oint \frac{{dQ}}{T}\), with usual notation represents:

Consider the following statements:1. Free expansion of a gas2. Slow heating of oil from a constant temperature source3. Evaporation of water at its saturation temperature by a source at the same temperature4. Isentropic compression of an ideal gasWhich of these processes are irreversible?

One reversible heat engine operates between 1000 K and T2 K and another reversible heat engine operates between T2 K and 400 K. If both the engines have the same heat input and output, then the temperature T2 must be equal to:

A heat engine is supplied with 450 kJ/s of heat at a constant fixed temperature of 227°C. The heat is rejected at 27°C. What will be the amount of heat rejected if the cycle is reversible?

An ideal engine absorbs heat at 127°C and rejects at 77°C. The efficiency is

A heat engine receives heat at the rate of 2500 kJ/min from source and gives a power output of 12.4 kW. What will be the % thermal efficiency of heat engine, nearly:

A heat engine operates between a cold reservoir at temperature T2 = 300 K and a hot reservoir at Temperature T1. It takes 200 J of heat from the hot reservoir and deliver 120 J of heat to the cold reservoir in a cycle. What will be the efficiency of the engine?

Efficiency of Carnot engine is given as 80%. If the cycle direction is reversed, what will be the value of COP of reversed Carnot refrigerator

79.	A Carnot heat pump is used to maintain a room at a temperature of 27°C, the initial temperature of the room was -4°C. The heat loss from the room in 20 kW. What is the power requirement of the pump?
A.	1
B.	2
C.	3
D.	4
Answer» C. 3

80.	PMM1 is closely related with
A.	First law of thermodynamics
B.	Second law of thermodynamics
C.	Third law of thermodynamics
D.	Zeroth law of thermodynamics
Answer» B. Second law of thermodynamics

81.	A diatomic gas is enclosed in a piston-cylinder arrangement at a pressure of 3 bar and 300 K. The cylinder has a volume of 1.5 m3. The process undergoes isothermal expansion to 3 m3. If the gas has a gas-constant as 1.486 KJ/Kg. using, In2 = 0.693, entropy change during the above process in kJ/kg is:
A.	1.03
B.	1.2
C.	1.65
D.	1.15
Answer» B. 1.2

82.	Heat of 1000 kJ is supplied to a heat engine from a reservoir at 1000 K, and it rejects waste heat to a river at 300 K. The engine’s work output is 400 kJ. Its efficiency is:
A.	57.14%
B.	65%
C.	0.30%
D.	40%
Answer» E.

83.	An engine works on Carnot cycle. Initially it had efficiency of 40 percent. Keeping lower temperature fixed, higher temperature is raised by 10 percent. New efficiency will be
A.	40 percent
B.	45.45 percent
C.	5.35 percent
D.	30 percent
Answer» C. 5.35 percent

84.	A reversible heat engine operates between 300 K and 600 K. If heat output is 200 kJ, the heat input is
A.	100 kJ
B.	300 kJ
C.	600 kJ
D.	400 kJ
Answer» E.

85.	A heat engine is supplying heat at the rate of 30,000 J/s and gives an output of 9 kW. The thermal efficiency of the engine will be
A.	30%
B.	33%
C.	40%
D.	50%
Answer» B. 33%

86.	A system of 100 kg mass undergoes a process in which its specific entropy increases from 0.3 kJ/kgK to 0.4 kJ/kgK. At the same time, the entropy of the surroundings decreases from 80 kJ/K to 75 kJ/K.The process is:
A.	Reversible and isothermal
B.	Irreversible
C.	Reversible
D.	Impossible
Answer» C. Reversible

87.	Efficiency of Carnot cycle depends on
A.	Engine design
B.	Working medium
C.	Source and sink temperature
D.	Engine size
Answer» D. Engine size

88.	On T-S diagram, constant pressure line slope is expressed as:
A.	Cp/γT
B.	T/cp
C.	T/S
D.	S/T
Answer» C. T/S