Entropy in statistical thermodynamics isdefined as

d)measure of reversibilityof a system

In a steam power plant which cycle requires two or more feed pumps

idealized regenerative rankine cycle

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

(first law efficiency)*(1-ta/to)

(first law efficiency)*(1+to/ta)

(first law efficiency)*(1-to/ta)

For the ideal gas equation, what assumptions are made?

there is little or no attraction between the molecules of the gas

the volume occupied by the molecules is negligibly small compared to the volume of the gas

Which of the following is true for a closed heater?

it requires a single pump regardless of the number of heaters

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

difference of the highest and the lowest

The main cause of the irreversibility is

heat transfer with a finite temperature difference

In a regenerative Rankine cycle as compared to simple Rankine cycle

the addition of heat is smaller

the superheat is to lesser extent

the heat rejected in condenser is smaller

Which of the following statements regarding a perpetual motion machine is correct?

it is non-thermodynamic machine

it is hypothetic machine whose operation would violate the laws of thermodynamics

Boyle's law states that, when tempearture is constant, the volume of agiven mass of a perfect gas

varies as square of the absolute pressue

varies directly as the absolute pressure

varies inversely as the absolute pressure

varies as square of the absolute pressue

does not vary with the absolute pressure

The reversible engines are

having same efficiency asirreversible engines

Work done in a quasi-static process

independent of the path followed

depends only on the initial and final states

1092 + Mcqs in Engineering Thermodynamics Page 4 McqOptions

151.	A Rankine cycle has efficiency of 19.4%. The steam enters the turbine with enthalpy of 32.85 kJ/Kg while heat of water entering the boiler is 423.6 kJ/Kg.the work of the turbine is 560 kJ/ Kg. the pump work is
A.	3.5 kj/kg
B.	5 kj/kg
C.	6.5 kj/kg
D.	7 kj/kg
Answer» C. 6.5 kj/kg

Discussion

152.	SI unit of enthalpy is
A.	joule/kgk
B.	joule/k
C.	joule/kg
D.	k/kg
Answer» D. k/kg

Discussion

153.	The extension & compression of a helicalspring is an example of
A.	irreversible process
B.	reversible process
C.	isothermal process
D.	adiabatic process
Answer» C. isothermal process

Discussion

154.	The friction present in moving devices makes a process reversible.
A.	true
B.	false
Answer» C.

Discussion

155.	Entropy in statistical thermodynamics isdefined as
A.	a universal property
B.	reversible heat transfer
C.	degree of randomness
D.	d)measure of reversibilityof a system
Answer» D. d)measure of reversibilityof a system

Discussion

156.	In a Carnot cycle which of the followingprocessez must be carried out at extremely slow speed?
A.	isothermal compression
B.	adiabatic expansion
C.	adiabatic compression
D.	none of the above
Answer» B. adiabatic expansion

Discussion

157.	Entropy at absolute zero temperature iszero for a
A.	perfect gas
B.	perfect substance
C.	perfect crystal
D.	glass
Answer» D. glass

Discussion

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

Discussion

159.	In a steam power plant which cycle requires two or more feed pumps
A.	regenerative rankine cycle
B.	reheat rankine cycle
C.	simple rankine cycle
D.	idealized regenerative rankine cycle
Answer» B. reheat rankine cycle

Discussion

160.	The first law of thermodynamics doesn’t tell us whether a thermodynamic process is feasible or not.
A.	true
B.	false
Answer» B. false

Discussion

161.	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» D. none of the mentioned

Discussion

162.	In case of real gases, cp will be equal tocv
A.	at absolute zero
B.	at triple point
C.	at critical temperature
D.	above criticaltempeature
Answer» B. at triple point

Discussion

163.	Which statement is wrong for adiabaticexpansion
A.	h = 0
B.	w = 0
C.	ds = 0
D.	w+e = 0
Answer» E.

Discussion

164.	……….. Is the unit of entropy
A.	j/kg
B.	j/kg k
C.	j/k
D.	j/kgs
Answer» C. j/k

Discussion

165.	On which of the following factors does air standard efficiency of a diesel cycledepend?
A.	adiabatic compression ratio
B.	ratio of specific heats
C.	cut-off ratio
D.	all of the above
Answer» E.

Discussion

166.	An inventor claims that a new heat cycle will develop 0.4 kW for a heat addition of32.5 kJ/mm. The temperature of heat source is 1990 K & that of sink is 850K. Is his claim true?
A.	true
B.	false
C.	either of the above
D.	unpredictable
Answer» C. either of the above

Discussion

167.	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» B. t1/(t1-t2)

Discussion

168.	The latent enthalpy of vapourisation at criticalpoint is
A.	zero
B.	minimum
C.	maximum
D.	none of the above
Answer» B. minimum

Discussion

169.	Temperature of a gas is produced due towhich of the following?
A.	attraction of molecules
B.	repulsion of molecules
C.	kinetic energy of molecules
D.	all of the above
Answer» D. all of the above

Discussion

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

Discussion

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

Discussion

172.	For the ideal gas equation, what assumptions are made?
A.	there is little or no attraction between the molecules of the gas
B.	the volume occupied by the molecules is negligibly small compared to the volume of the gas
C.	both of the mentioned
D.	none of the mentioned
Answer» D. none of the mentioned

Discussion

173.	The equation for the average kinetic energy is
A.	0.5 kt
B.	1.5 kt
C.	2.5 kt
D.	3.5 kt
Answer» C. 2.5 kt

Discussion

174.	5 P-V DIAGRAM.
A.	saturated solid line
B.	saturated liquid lines
C.	saturated vapour line
D.	all of the mentioned
Answer» E.

Discussion

175.	Which of the following is true for a closed heater?
A.	it requires a single pump regardless of the number of heaters
B.	it is costly
C.	both of the mentioned
D.	none of the mentioned
Answer» D. none of the mentioned

Discussion

176.	A mixture of gases expands from 0.03 m³ to 0.06 m³ at a constant pressure of 1 Mpa & absorbs 84 kJ of heat during the process. The change in internal energy ofthe mixture is
A.	30 kj
B.	54 kj
C.	84 kj
D.	114 kj
Answer» C. 84 kj

Discussion

177.	The value of one bar (in SI units) is equalto
A.	100 n/m??
B.	1000 n/m??
C.	1??10⁴ n/m??
D.	1??10⁵ n/m??
Answer» E.

Discussion

178.	Maxwell’s equations consists of equations.
A.	four
B.	three
C.	two
D.	one
Answer» B. three

Discussion

179.	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» C. sum

Discussion

180.	The basis for measuring thermodynamic property of temperature is given by ……. Law of thermodynamics
A.	zeroth
B.	first
C.	second
D.	third
Answer» B. first

Discussion

181.	……….. Is an intensive property
A.	specific volume
B.	total volume
C.	total mass
D.	total energy of a system
Answer» B. total volume

Discussion

182.	A series of operations, which take place in a certain order & restore the initialcondition is known as
A.	reversible cycle
B.	irreversible cycle
C.	thermodynamic cycle
D.	none of the above
Answer» D. none of the above

Discussion

183.	The main cause of the irreversibility is
A.	mechanical & fluid friction
B.	unrestricted expansion
C.	heat transfer with a finite temperature difference
D.	all of the above
Answer» E.

Discussion

184.	Under which of the following conditionsall gases behave ideally?
A.	high pressure conditions
B.	law pressure conditions
C.	vaccum conditions
D.	all of the aboveconditions
Answer» C. vaccum conditions

Discussion

185.	In a regenerative Rankine cycle as compared to simple Rankine cycle
A.	the pump work is smaller
B.	the addition of heat is smaller
C.	the superheat is to lesser extent
D.	the heat rejected in condenser is smaller
Answer» E.

Discussion

186.	At critical pressure, value of Hg-Hf is
A.	two
B.	one
C.	zero
D.	infinity
Answer» D. infinity

Discussion

187.	In polytropic process pv?=C the value ofexponent n=±? is indicative of
A.	isobaric process
B.	isentropic process
C.	isochoric process
D.	throttling process
Answer» D. throttling process

Discussion

188.	Which of the following is not a propertyof the system
A.	temperature
B.	pressure
C.	specific volume
D.	heat
Answer» E.

Discussion

189.	Variations of pressure & volume atconstant temperature are correlated through
A.	charle\s law
B.	boyle\s law
C.	gas law
D.	gay lussac\s law
Answer» C. gas law

Discussion

190.	………. Is one in which neither any heatenters nor leaves the system
A.	isochoric process
B.	isobaric process
C.	isentropic process
D.	isothermal process
Answer» D. isothermal process

Discussion

191.	Which of the following statements regarding a perpetual motion machine is correct?
A.	it is an in efficient machine
B.	it is non-thermodynamic machine
C.	it is thermodynamic machine
D.	it is hypothetic machine whose operation would violate the laws of thermodynamics
Answer» E.

Discussion

192.	Which of the following is an intensive property of a thermodynamic system
A.	volume
B.	temperature
C.	mass
D.	energy
Answer» C. mass

Discussion

193.	The universal gas constant will be equal to difference between specific heats at constant pressure & constant volume for
A.	1 kg mass of gas
B.	1 molecule of gas
C.	1 kg molecule of gas
D.	any mass of gas
Answer» D. any mass of gas

Discussion

194.	Boyle's law states that, when tempearture is constant, the volume of agiven mass of a perfect gas
A.	varies directly as the absolute pressure
B.	varies inversely as the absolute pressure
C.	varies as square of the absolute pressue
D.	does not vary with the absolute pressure
Answer» C. varies as square of the absolute pressue

Discussion

195.	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» D. none of the mentioned

Discussion

196.	The reversible engines are
A.	least efficient
B.	most efficient
C.	having same efficiency asirreversible engines
D.	none of the above
Answer» C. having same efficiency asirreversible engines

Discussion

197.	During a constant pressure expansion of a gas 33.3 % heat is converted into work while the temperature rises by 20K. The specific heat of gas at constant pressureis
A.	10% w
B.	12 % w
C.	15% w
D.	20% w
Answer» D. 20% w

Discussion

198.	Kelvin-Plank's law deals with
A.	conservation of energy
B.	conservation of heat
C.	conservation of mass
D.	conversion of heat intowork
Answer» E.

Discussion

199.	Work done in a quasi-static process
A.	depends on the path followed
B.	independent of the path followed
C.	depends only on the initial and final states
D.	none of the mentioned
Answer» B. independent of the path followed

Discussion

200.	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.
A.	1.73 m3
B.	2.73 m3
C.	3.73 m3
D.	4.73 m3
Answer» E.

Discussion

Explore topic-wise MCQs in Mechanical Engineering.

A Rankine cycle has efficiency of 19.4%. The steam enters the turbine with enthalpy of 32.85 kJ/Kg while heat of water entering the boiler is 423.6 kJ/Kg.the work of the turbine is 560 kJ/ Kg. the pump work is

SI unit of enthalpy is

The extension & compression of a helicalspring is an example of

The friction present in moving devices makes a process reversible.

Entropy in statistical thermodynamics isdefined as

In a Carnot cycle which of the followingprocessez must be carried out at extremely slow speed?

Entropy at absolute zero temperature iszero for a

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

In a steam power plant which cycle requires two or more feed pumps

The first law of thermodynamics doesn’t tell us whether a thermodynamic process is feasible or not.

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

In case of real gases, cp will be equal tocv

Which statement is wrong for adiabaticexpansion

……….. Is the unit of entropy

On which of the following factors does air standard efficiency of a diesel cycledepend?

An inventor claims that a new heat cycle will develop 0.4 kW for a heat addition of32.5 kJ/mm. The temperature of heat source is 1990 K & that of sink is 850K. Is his claim true?

For a reversible refrigerator, Coefficient of Performance is given by

The latent enthalpy of vapourisation at criticalpoint is

Temperature of a gas is produced due towhich of the following?

Cooling towers are rated in terms of

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

For the ideal gas equation, what assumptions are made?

The equation for the average kinetic energy is

5 P-V DIAGRAM.

Which of the following is true for a closed heater?

A mixture of gases expands from 0.03 m³ to 0.06 m³ at a constant pressure of 1 Mpa & absorbs 84 kJ of heat during the process. The change in internal energy ofthe mixture is

The value of one bar (in SI units) is equalto

Maxwell’s equations consists of equations.

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

The basis for measuring thermodynamic property of temperature is given by ……. Law of thermodynamics

……….. Is an intensive property

A series of operations, which take place in a certain order & restore the initialcondition is known as

The main cause of the irreversibility is

Under which of the following conditionsall gases behave ideally?

In a regenerative Rankine cycle as compared to simple Rankine cycle

At critical pressure, value of Hg-Hf is

In polytropic process pv?=C the value ofexponent n=±? is indicative of

Which of the following is not a propertyof the system

Variations of pressure & volume atconstant temperature are correlated through

………. Is one in which neither any heatenters nor leaves the system

Which of the following statements regarding a perpetual motion machine is correct?

Which of the following is an intensive property of a thermodynamic system

The universal gas constant will be equal to difference between specific heats at constant pressure & constant volume for

Boyle's law states that, when tempearture is constant, the volume of agiven mass of a perfect gas

Which of the following processes exhibit external mechanical irreversibility?

The reversible engines are

During a constant pressure expansion of a gas 33.3 % heat is converted into work while the temperature rises by 20K. The specific heat of gas at constant pressureis

Kelvin-Plank's law deals with

Work done in a quasi-static process

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.