500+ Engineering Thermodynamics Solved MCQs

Engineering thermodynamics is a branch of engineering that deals with the study of energy, heat, and their relationship to work and the transfer of energy from one place to another.

It is a fundamental subject that forms the basis of many other branches of engineering, including mechanical, chemical, and electrical engineering. The principles of thermodynamics are used to design engines, power plants, refrigeration systems, and a wide variety of other devices and systems that are essential to modern society. Some of the key concepts in engineering thermodynamics include the laws of thermodynamics, entropy, and the concept of equilibrium.

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301.	Efficiency of a reversible heat engine is given by
A.	1-(t1/t2)
B.	1-(t2/t1)
C.	(t1/t2)-1
D.	(t2/t1)-1
Answer» B. 1-(t2/t1)

302.	For a reversible refrigerator, Coefficient of Performance is given by
A.	t2/(t1-t2)
B.	t1/(t1-t2)
C.	t2/(t2-t1)
D.	t1/(t2-t1)
Answer» A. t2/(t1-t2)

303.	Entropy principle is the quantitative statement of the second law of thermodynamics.
A.	true
B.	false
Answer» A. true

304.	Which of the following can be considered as an application of entropy principle?
A.	transfer of heat through a finite temperature difference
B.	mixing of two fluids
C.	maximum temperature obtainable from two finite bodies
D.	all of the mentioned
Answer» D. all of the mentioned

305.	The final temperatures of two bodies, initially at T1 and T2 can range from
A.	(t1-t2)/2 to sqrt(t1*t2)
B.	(t1+t2)/2 to sqrt(t1*t2)
C.	(t1+t2)/2 to (t1*t2)
D.	(t1-t2)/2 to (t1*t2)
Answer» B. (t1+t2)/2 to sqrt(t1*t2)

306.	Which of the following processes exhibit external mechanical irreversibility?
A.	isothermal dissipation of work
B.	adiabatic dissipation of work
C.	both of the mentioned
D.	none of the mentioned
Answer» C. both of the mentioned

307.	Which of the following is an example of low grade energy?
A.	heat or thermal energy
B.	heat from nuclear fission or fusion
C.	heat from combustion of fossil fuel
D.	all of the mentioned
Answer» D. all of the mentioned

308.	Which of the following is an example of high grade energy?
A.	mechanical work
B.	electrical energy
C.	water power and wind power
D.	all of the mentioned
Answer» D. all of the mentioned

309.	The unavailable energy is the product of the lowest temperature of heat rejection and the change of entropy of system during the process of supplying heat.
A.	true
B.	false
Answer» A. true

310.	The lowest practicable temperature of heat rejected is the
A.	given temperature
B.	0k
C.	temperature of surroundings
D.	273k
Answer» C. temperature of surroundings

311.	Exergy is lost due to
A.	irreversible heat transfer
B.	through finite temperature difference
C.	during the process of heat addition
D.	all of the mentioned
Answer» D. all of the mentioned

314.	Energy is said to be degraded each time it flows through a finite temperature difference.
A.	true
B.	false
Answer» A. true

315.	When considering a finite energy source, its working fluid expands,
A.	reversibly
B.	adiabatically
C.	reversibly and adiabatically
D.	none of the mentioned
Answer» C. reversibly and adiabatically

319.	Lost work is given by
A.	pdv-dw
B.	pdv+dw
C.	-pdv-dw
D.	pdv*dw
Answer» A. pdv-dw

320.	Which of the following statement is false?
A.	for a reversible process, entropy generation is zero
B.	the entropy generation does not depend on the path the system follows
C.	for an irreversible process, entropy generation is greater than zero
D.	none of the mentioned
Answer» B. the entropy generation does not depend on the path the system follows

312.	Which of the following is a type of energy?
A.	high grade energy
B.	low grade energy
C.	both of the mentioned
D.	none of the mentioned
Answer» C. both of the mentioned

313.	The complete conversion of heat into shaft- work is impossible.
A.	true
B.	false
Answer» A. true

316.	The entropy of any closed system can increase in which if the following way?
A.	by heat interaction in which there is entropy transfer
B.	dissipative effects or internal irreversibilities
C.	both of the mentioned
D.	none of the mentioned
Answer» C. both of the mentioned

317.	The entropy increase due to internal irreversibility is also called entropy production or entropy generation.
A.	true
B.	false
Answer» A. true

318.	Which of the following statement is true?
A.	if the isentropic process is reversible, it must be adiabatic
B.	if the isentropic process is adiabatic, it cannot but be reversible
C.	if the process is adiabatic and reversible, it must be isentropic
D.	all of the mentioned
Answer» D. all of the mentioned

321.	Mass and energy are conserved quantities, but entropy is generally not conserved.
A.	true
B.	false
Answer» A. true

322.	A chip dissipates 2 kJ of electric work and rejects it as heat transfer from its surface which is at 50°C to 25°C air. How much entropy is generated outside the chip?
A.	0.419 j/k
B.	0.519 j/k
C.	0.619 j/k
D.	0.719 j/k
Answer» B. 0.519 j/k

323.	Entropy increase dS of the system can be expressed as
A.	ds=ds(due to external heat interaction)- ds(due to internal irreversibility)
B.	ds=ds(due to external heat interaction)+ds(due to internal irreversibility)
C.	ds=-ds(due to external heat interaction)- ds(due to internal irreversibility)
D.	ds=-ds(due to external heat interaction)+ds(due to internal irreversibility)
Answer» B. ds=ds(due to external heat interaction)+ds(due to internal irreversibility)

324.	If the path A causes more entropy generation than path B, then
A.	path a is more irreversible than path b
B.	path a involves more lost work
C.	both of the mentioned
D.	none of the mentioned
Answer» C. both of the mentioned

325.	In an open system, there is a transfer of which of the following quantity?
A.	mass
B.	energy
C.	entropy
D.	all of the mentioned
Answer» D. all of the mentioned

500+ Engineering Thermodynamics Solved MCQs

Efficiency of a reversible heat engine is given by

For a reversible refrigerator, Coefficient of Performance is given by

Entropy principle is the quantitative statement of the second law of thermodynamics.

Which of the following can be considered as an application of entropy principle?

The final temperatures of two bodies, initially at T1 and T2 can range from

Which of the following processes exhibit external mechanical irreversibility?

Which of the following is an example of low grade energy?

Which of the following is an example of high grade energy?

The unavailable energy is the product of the lowest temperature of heat rejection and the change of entropy of system during the process of supplying heat.

The lowest practicable temperature of heat rejected is the

Exergy is lost due to

Which of the following is a type of energy?

The complete conversion of heat into shaft- work is impossible.

Energy is said to be degraded each time it flows through a finite temperature difference.

When considering a finite energy source, its working fluid expands,

The entropy of any closed system can increase in which if the following way?

The entropy increase due to internal irreversibility is also called entropy production or entropy generation.

Which of the following statement is true?

Lost work is given by

Which of the following statement is false?

Mass and energy are conserved quantities, but entropy is generally not conserved.

A chip dissipates 2 kJ of electric work and rejects it as heat transfer from its surface which is at 50°C to 25°C air. How much entropy is generated outside the chip?

Entropy increase dS of the system can be expressed as

If the path A causes more entropy generation than path B, then

In an open system, there is a transfer of which of the following quantity?

A chip dissipates 2 kJ of electric work and rejects it as heat transfer from its surface which is at 50°C to 25°C air. How much entropy is generated in the chip?

15 = 6.19 J/K.

Second law efficiency can also be given as

Second law efficiency is defined as

For a power plant, second law efficiency can be given by desired output(W) / available energy(Wmax).

In case of a heat pump, second law efficiency is given as

Both first law efficiency and second law efficiency indicate how effectively the input has been converted into the product.

Which of the following curves meet at triple point?

The slope of the fusion curve for water is

The equation which forms the basis of the Mollier diagram is

Which of the following statements is true?

Which of the following represents the latent heat of vaporization at a particular pressure.

At critical pressure, value of Hg-Hf is

In the Mollier diagram, the constant pressure lines diverge from one another.

Which of the following is a property of a pure substance?

For water, as temperature increases, volume always increases?

Which of the following exists in a p-V diagram for water?

The isotherm passing through the critical point is called the critical isotherm.

The properties of water are arranged in the steam tables as functions of

The internal energy of saturated water at the triple point is

The entropy of saturated water is chosen to be zero at triple point.

When a liquid and its vapour are in equilibrium at a certain pressure and temperature, then which of the following is required to identify the saturation state.

Saturated liquid or the saturated vapour has how many independent variables?

If data are required for intermediate temperatures or pressures, linear interpolation is normally accurate.

The superheat or degree of superheat is given by

When the temperature of a liquid is less than the saturation temperature at the given pressure, the liquid is called compressed liquid.

Which of the following statement is true?

Why is the steam not allowed to expand deep into the two phase region before it is taken to reheating?

Net Work output of the plant with reheat.

What is the effect of decrease of reheat pressure on the quality of steam at turbine exhaust?

The optimum reheat pressure for most of the power plants is how many times of the initial steam pressure?

What is the most preferable dryness

For pressure ratio = 1, efficiency = 0, then?

At critical point, value of Vg-Vf is

Above the critical point, the isotherms are continuous curves.

A piston –cylinder device contains 0.06m3 of saturated water vapour at 350 kPa pressure. Determine the temperature and mass of the vapour inside the cylinder.

A rigid tank contains 10 kg of water at 90°C. If 8 kg of the water is in the liquid form and the rest is in the vapour form, determine the pressure in the tank.

A rigid tank contains 10 kg of water at 90°C. If 8 kg of the water is in the liquid form and the rest is in the vapour form, determine the volume of the tank.

An 80 litre vessel contains 4 kg of R-134a at a pressure of 160 kPa. Determine the quality.

Determine the specific volume of R-134a at 1 MPa and 50°C, using ideal gas equation of state.

What is the unit of Heat rate?

Rankine cycle operating on low pressure limit of p1 and high pressure limit of p2

Rankine efficiency of a Steam Power Plant

Rankine cycle comprises of

In Rankine cycle, the work output from the turbine is given by

What is the actual turbine inlet temperature in Rankine cycle?

Rankine cycle efficiency of a good Steam Power Plant may be in the range of?

A simple Rankine cycle produces 40 MW of power, 50 MW of process heat and rejects 60 MW of heat to the surroundings. What is the utilization factor of this co generation cycle neglecting the pump work?

Why both reheating and regeneration is used together?

Which of the following statement is true?

Which of the following is true for an open heater?

Deaerator is a type of open heater.

Which of the following is true for a closed heater?

The efficiency gain follows the law of diminishing return with the increase in the number of heaters.

326.	A chip dissipates 2 kJ of electric work and rejects it as heat transfer from its surface which is at 50°C to 25°C air. How much entropy is generated in the chip?
A.	4.19 j/k
B.	5.19 j/k
C.	6.19 j/k
D.	7.19 j/k
Answer» C. 6.19 j/k

327.	15 = 6.19 J/K.
A.	0.419 j/k
B.	0.519 j/k
C.	0.619 j/k
D.	0.719 j/k
Answer» B. 0.519 j/k

328.	Second law efficiency can also be given as
A.	1 / ( first law efficiency * carnot efficiency)
B.	carnot efficiency * first law efficiency
C.	carnot efficiency / first law efficiency
D.	first law efficiency / carnot efficiency
Answer» D. first law efficiency / carnot efficiency

329.	Second law efficiency is defined as
A.	actual exergy intake / minimum exergy intake
B.	minimum exergy intake / actual exergy intake
C.	actual exergy intake / maximum exergy intake
D.	maximum exergy intake / minimum exergy intake
Answer» B. minimum exergy intake / actual exergy intake

330.	For a power plant, second law efficiency can be given by desired output(W) / available energy(Wmax).
A.	true
B.	false
Answer» A. true

331.	In case of a heat pump, second law efficiency is given as
A.	(first law efficiency)*(1-ta/to)
B.	(first law efficiency)*(1+to/ta)
C.	(first law efficiency)*(1-to/ta)
D.	none of the mentioned
Answer» C. (first law efficiency)*(1-to/ta)

332.	Both first law efficiency and second law efficiency indicate how effectively the input has been converted into the product.
A.	true
B.	false
Answer» A. true

333.	Which of the following curves meet at triple point?
A.	fusion curve and vaporization curve
B.	fusion curve and sublimation curve
C.	vaporization curve and sublimation curve
D.	fusion curve and vaporization curve and sublimation curve
Answer» D. fusion curve and vaporization curve and sublimation curve

334.	The slope of the fusion curve for water is
A.	negative
B.	positive
C.	zero
D.	none of the mentioned
Answer» A. negative

335.	The equation which forms the basis of the Mollier diagram is
A.	tds=-dh+vdp
B.	tds=dh+vdp
C.	tds=dh-vdp
D.	none of the mentioned
Answer» C. tds=dh-vdp