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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401.	For getting TdS equations, we assume entropy to be a function of T and V and also of T and p.
A.	true
B.	false
Answer» A. true

402.	During phase transitions like vaporization, melting and sublimation
A.	pressure and temperature remains constant
B.	volume and entropy changes
C.	both of the mentioned
D.	none of the mentioned
Answer» C. both of the mentioned

403.	Which of the following requirement is satisfied by a phase change of the first order?
A.	there are changes of volume and entropy
B.	the first-order derivative of the gibbs function changes discontinuously
C.	both of the mentioned
D.	none of the mentioned
Answer» C. both of the mentioned

404.	The vapour pressure p in kPa at
A.	p = 101.325 exp (88/r)(1+t/tb)
B.	p = 101.325 exp (88/r)(1+tb/t)
C.	p = 101.325 exp (88/r)(1-t/tb)
D.	p = 101.325 exp (88/r)(1-tb/t)
Answer» D. p = 101.325 exp (88/r)(1-tb/t)

405.	The vapour pressure curve is of the form ln(p) = A + B/T + C*lnT + DT.
A.	true
B.	false
Answer» A. true

406.	According to Trouton’s rule, the ratio of latent heat of vaporization to the boiling point at 1.013 bar is
A.	77 kj/kgmol k
B.	88 kj/kgmol k
C.	99 kj/kgmol k
D.	100 kj/kgmol k
Answer» B. 88 kj/kgmol k

407.	Estimate the freezing temperature of liquid water at a pressure of 30 MPa.
A.	-2.2°c
B.	0°c
C.	-0.2°c
D.	-1.2°c
Answer» A. -2.2°c

408.	The expression nRT/V is called the partial pressure of a gas.
A.	true
B.	false
Answer» A. true

409.	The gas constant of the mixture is the of the gas constants of the components.
A.	average
B.	weighted mean
C.	sum
D.	difference of the highest and the lowest
Answer» B. weighted mean

410.	A quantity called partial volume of a component of mixture is used.
A.	true
B.	false
Answer» A. true

411.	When gases which are at equal pressure and temperature are mixed adiabatically without work, then
A.	internal energy of the gaseous system remains constant
B.	heat transfer of the gaseous system remains constant
C.	entropy of the gaseous system remains constant
D.	all of the mentioned
Answer» A. internal energy of the gaseous system remains constant

415.	Cooling and dehumidification of air is done in summer air conditioning.
A.	true
B.	false
Answer» A. true

416.	Heating and humidification is done in
A.	summer air conditioning
B.	winter air conditioning
C.	both of the mentioned
D.	none of the mentioned
Answer» B. winter air conditioning

418.	When air passes through silica gel,
A.	it absorbs water vapour molecules
B.	latent heat of condensation is released
C.	dbt of air increases
D.	all of the mentioned
Answer» D. all of the mentioned

419.	In adiabatic evaporative cooling, heat transfer between chamber and surroundings is
A.	zero
B.	high
C.	low
D.	none of the mentioned
Answer» A. zero

412.	The fact that internal energy of a mixture is equal to the sum of the partial internal energies of the gases can also be applied to properties like H,Cv,Cp,S,F, and G.
A.	true
B.	false
Answer» A. true

413.	Which of the following statement is true?
A.	the chart is plotted for pressure equal to 760mm hg
B.	the constant wbt line represents adiabatic saturation process
C.	the constant wbt line coincides with constant enthalpy line
D.	all of the mentioned
Answer» D. all of the mentioned

414.	In sensible heating or cooling,
A.	work done remains constant
B.	dry bulb temperature or air remains constant
C.	both of the mentioned
D.	none of the mentioned
Answer» A. work done remains constant

417.	Which of the following is an absorbent?
A.	silica gel
B.	activated alumina
C.	both of the mentioned
D.	none of the mentioned
Answer» C. both of the mentioned

420.	The cooling tower uses the phenomenon of evaporative cooling to cool warm water above the dbt of air.
A.	true
B.	false
Answer» B. false

421.	Cooling towers are rated in terms of
A.	approach
B.	range
C.	both of the mentioned
D.	none of the mentioned
Answer» C. both of the mentioned

422.	Dry air consists of
A.	oxygen, nitrogen
B.	carbon dioxide
C.	hydrogen, argon
D.	all of the mentioned
Answer» D. all of the mentioned

423.	Complete dry air exists in nature.
A.	true
B.	false
Answer» B. false

424.	Which of the following is true?(here pa=partial pressure of dry air, pw=partial pressure of water vapour, p=atmospheric pressure)
A.	p=pw
B.	p=pa
C.	p=pw + pa
D.	all of the mentioned
Answer» C. p=pw + pa

425.	In a mixture of dry air and water vapour,
A.	mole fraction of dry air = pa/p
B.	mole fraction of water vapour = pw/p
C.	both of the mentioned
D.	none of the mentioned
Answer» C. both of the mentioned

500+ Engineering Thermodynamics Solved MCQs

For getting TdS equations, we assume entropy to be a function of T and V and also of T and p.

During phase transitions like vaporization, melting and sublimation

Which of the following requirement is satisfied by a phase change of the first order?

The vapour pressure p in kPa at

The vapour pressure curve is of the form ln(p) = A + B/T + C*lnT + DT.

According to Trouton’s rule, the ratio of latent heat of vaporization to the boiling point at 1.013 bar is

Estimate the freezing temperature of liquid water at a pressure of 30 MPa.

The expression nRT/V is called the partial pressure of a gas.

The gas constant of the mixture is the of the gas constants of the components.

A quantity called partial volume of a component of mixture is used.

When gases which are at equal pressure and temperature are mixed adiabatically without work, then

The fact that internal energy of a mixture is equal to the sum of the partial internal energies of the gases can also be applied to properties like H,Cv,Cp,S,F, and G.

Which of the following statement is true?

In sensible heating or cooling,

Cooling and dehumidification of air is done in summer air conditioning.

Heating and humidification is done in

Which of the following is an absorbent?

When air passes through silica gel,

In adiabatic evaporative cooling, heat transfer between chamber and surroundings is

The cooling tower uses the phenomenon of evaporative cooling to cool warm water above the dbt of air.

Cooling towers are rated in terms of

Dry air consists of

Complete dry air exists in nature.

Which of the following is true?(here pa=partial pressure of dry air, pw=partial pressure of water vapour, p=atmospheric pressure)

In a mixture of dry air and water vapour,

When pw is very small,

Relative humidity is defined as

For saturated air, relative humidity is 0%.

If water is injected into a container with has unsaturated air,

Humidity ratio is given by the ratio of

Which of the following statement is true?

The wet bulb temperature is the temperature recorded by moistened bulb.

Air can be cooled and dehumidified by

When two equilibrium states are infinitesimally near,

The greater the temperature, the is the vapour pressure.

It is necessary to have a temperature difference to obtain work of any cycle.

The absolute thermodynamic temperature scale is also known as

In defining the temperature scale, the standard reference point is taken as

When the heat transferred isothermally between the given decreases, the temperature

If a system undergoes a reversible isothermal process without transfer of heat, the temperature at which this process takes place is called

A definite zero point on the absolute temperature scale but this point be reached violation of the second law.

Which law is stated here, “It is impossible to reduce any system to the absolute zero of temperature in a finite number of operations.

The statement of third law is also called the Fowler-Guggenheim statement of the third law.

The Kelvin temperature is numerically equal to the and may be measured by means of a

During a fluid flow, the temperature is developed due to

The equation for the average kinetic energy is

Entropy occurs due to

Efficiency of a heat engine is defined as

A TER which transfers heat to system is called and one which receives heat is called

A reversible cycle has following processes.

2 STATEMENTS OF SECOND LAW AND ITS COROLLARIES. CARNOT CYCLE REVERSED CARNOT CYCLE, PERFORMANCE. CLAUSIUS INEQUALITY.

According to Carnot’s theorem, all heat engines operating between a given constant temperature source and sink, none has a higher efficiency than a reversible engine.

The efficiency of all reversible heat engines operating between the same heat reservoirs is

For a reversible heat pump, COP is given by

The entropy of an isolated system can never

According to entropy principle, the entropy of an isolated system can never decrease and remains constant only when the process is reversible.

Entropy may decrease locally at some region within the isolated system. How can this statement be justified?

The part of available for conversion is referred to

The obtainable from a certain heat input in a cyclic heat engine is called

4 APPLICATIONS OF II LAW. HIGH AND LOW GRADE ENERGY.

The available energy is known as and the unavailable energy is known as

Whenever heat is transferred through a finite temperature difference, there is always a decrease in the availability of energy so transferred.

Any thermodynamic process is accompanied by entropy generation.

The rate of entropy increase of the control volume or the net rate of entropy transfer to it.

The rate at which entropy is transferred out must the rate at which entropy enters the control volume.

The first law efficiency is defined as the ratio of the output energy to the input energy.

With the concept of exergy available, which of the following is possible?

If work is involved, Amin= and if heat is involved, Amin=

If solar energy Qr is available at a reservoir storage temperature of Tr and if quantity of heat Qa is transferred by the solar collector at temperature Ta, then which of the following is true?

For proper utilization of exergy, it is desirable to make first law efficiency and the source and use temperatures should

The slopes of sublimation and vaporization curves for all substances are

When does a vapour become superheated?

The properties of liquid with pressure.

What is the effect of reheat pressure on mean temperature of heat addition Tml?

Which of the following problems are posed by increasing the number of reheats?

What is the most preferable dryness fraction of the exhaust steam?

Which of the following represents the specific volume during phase transition.

An 80 litre vessel contains 4 kg of R-134a at a pressure of 160 kPa. Determine the volume occupied by the vapour phase.

Rankine cycle comprises of

426.	When pw is very small,
A.	saturation temperature of water vapour at pw is less than atmospheric temperature
B.	water vapour in air exists in superheated state
C.	air is said to be in unsaturated state
D.	all of the mentioned
Answer» D. all of the mentioned

427.	Relative humidity is defined as
A.	(saturation pressure of pure water) / pw
B.	pw / (saturation pressure of pure water)
C.	(saturation pressure of pure water) / p
D.	p / (saturation pressure of pure water)
Answer» B. pw / (saturation pressure of pure water)

428.	For saturated air, relative humidity is 0%.
A.	true
B.	false
Answer» B. false

429.	If water is injected into a container with has unsaturated air,
A.	water will evaporate
B.	moisture content of air will decrease
C.	pw will decrease
D.	all of the mentioned
Answer» A. water will evaporate

430.	Humidity ratio is given by the ratio of
A.	(mass of dry air per unit mass of water vapour)^2
B.	1/(mass of dry air * mass of water vapour)
C.	water vapour mass per unit mass of dry air
D.	mass of dry air per unit mass of water vapour
Answer» C. water vapour mass per unit mass of dry air

431.	Which of the following statement is true?
A.	dew point temperature is the temperature at which water vapour starts condensing
B.	dry bulb temperature is recorded by thermometer with dry bulb
C.	wet bulb temperature is recorded by thermometer when bulb is covered with a cotton wick which is saturated with water
D.	all of the mentioned
Answer» D. all of the mentioned

432.	The wet bulb temperature is the temperature recorded by moistened bulb.
A.	lowest
B.	highest
C.	atmospheric
D.	none of the mentioned
Answer» A. lowest

433.	Air can be cooled and dehumidified by
A.	circulating chilled water in tube across air flow
B.	placing evaporator coil across air flow
C.	spraying chilled water to air
D.	all of the mentioned
Answer» D. all of the mentioned

434.	When two equilibrium states are infinitesimally near,
A.	dq/t=ds
B.	dq/t>ds
C.	dq/t<ds
D.	none of the mentioned
Answer» A. dq/t=ds

435.	The greater the temperature, the is the vapour pressure.
A.	lower
B.	higher
C.	depends on the substance
D.	none of the mentioned
Answer» B. higher