Explore topic-wise MCQs in Mechanical Engineering Questions.

This section includes 475 Mcqs, each offering curated multiple-choice questions to sharpen your Mechanical Engineering Questions knowledge and support exam preparation. Choose a topic below to get started.

101.

The temperature of air recorded by thermometer when the bulb is covered by a cotton wick saturated by water is called as
A. dry bulb temperature
B. wet bulb temperature
C. stream temperature
D. psychrometric temperature
Answer» C. stream temperature
Discussion
102.

Which of the following is NOT a path function?
A. Internal energy
B. Heat energy
C. Work energy
D. none of the above
Answer» B. Heat energy
Discussion
103.

All spontaneous processes are
A. reversible
B. irreversible
C. quasi-static
D. none of the above
Answer» C. quasi-static
Discussion
104.

If pressure ratio in Brayton cycle increases
A. the efficiency of the cycle increases
B. the efficiency of the cycle decreases
C. there is no any effect on the efficiency of the cycle
D. cannot say
Answer» B. the efficiency of the cycle decreases
Discussion
105.

The irreversibility of a process occurs due to
A. lack of equilibrium during the process
B. involvement of dissipative effects
C. either a. or b. or both
D. none of the above
Answer» D. none of the above
Discussion
106.

As the temperature difference between system and surroundings decreases the quality of the energy which is being transferred
A. increases
B. decreases
C. remains same
D. none of the above
Answer» C. remains same
Discussion
107.

How are the entropy increase of the universe during the irreversible process and its irreversibility related?
A. higher the entropy increase of the universe, lower will be the irreversibility
B. higher the entropy increase of the universe, higher will be the irreversibility
C. change in entropy increase of the universe does not change the irreversibili
D. none of the above
Answer» C. change in entropy increase of the universe does not change the irreversibili
Discussion
108.

If temperature difference between two bodies in which heat transfer takes place increases, the irreversibility of the process
A. increases
B. decreases
C. does not change
D. approaches toward reversibility
Answer» B. decreases
Discussion
109.

Which concept provides the useful measure of quality of energy?
A. entropy
B. exergy
C. energy
D. none of the above
Answer» C. energy
Discussion
110.

When heat is transferred from body A which is at temperature T1 to body B which at temperature T2 and there is no heat loss to the surrounding, what will be the change in entropy (dS) of the universe? (Given T1 > T2)
A. dS will remain constant
B. dS will be positive
C. dS will be negative
D. dS will either positive or negative
Answer» C. dS will be negative
Discussion
111.

Consider the same heat loss to the surrounding at temperature T0 is occurring from the systems A and B at different temperatures T1 and T2 respectively. If T1 is greater than T2, what is the loss of exergy in both the systems?
A. loss of exergy is more in system A than system B
B. loss of exergy is more in system B than system A
C. loss of exergy is same is both systems A and B
D. cannot say
Answer» B. loss of exergy is more in system B than system A
Discussion
112.

When the pressure at which heat is added in Rankine cycle increases, the moisture content at the turbine exhaust
A. increases
B. decreases
C. remains same
D. cannot say
Answer» B. decreases
Discussion
113.

What is the effect of superheated steam on efficiency of Rankine cycle?
A. efficiency of Rankine cycle decreases with increase in superheat of the steam
B. efficiency of Rankine cycle increases with increase in superheat of the steam
C. efficiency of Rankine cycle is not affected by change in superheat of the steam
D. none of the above
Answer» C. efficiency of Rankine cycle is not affected by change in superheat of the steam
Discussion
114.

What is the effect of increase in pressure at which heat is added on the pump work in the Rankine cycle?
A. the pump work increases with increase in pressure of heat addition
B. the pump work decreases with increase in pressure of heat addition
C. the pump work does not change with increase in pressure of heat addition
D. the pump work either increases or decreases with increase in pressure of heat addition
Answer» B. the pump work decreases with increase in pressure of heat addition
Discussion
115.

What is the maximum content of moisture allowed at the turbine exhaust in the steam power plant?
A. 50 %
B. 60 %
C. 30 %
D. 15 %
Answer» E.
Discussion
116.

What is the condition for increase the chances of corrosion of blades of turbine?
A. decrease in the pressure difference between which the Rankine cycle operates
B. increase in the pressure difference between which the Rankine cycle operates
C. both a. and b.
D. none of the above
Answer» C. both a. and b.
Discussion
117.

What is the difference between the Brayton cycle and the Rankine cycle?
A. Brayton cycle has two reversible isobars whereas Rankine cycle has two isotherms
B. The working fluid of Brayton cycle always remains in gaseous phase whereas in Rankine cycle the working fluid undergoes phase change
C. Brayton cycle operates between higher pressure ratio than the Rankine cycle for same capacity
D. all of the above
Answer» C. Brayton cycle operates between higher pressure ratio than the Rankine cycle for same capacity
Discussion
118.

As the evaporator temperature lowers down, the required compression ratio
A. becomes lower for a given condensation temperature
B. becomes higher for a given condensation temperature
C. becomes steady for a given condensation temperature
D. cannot say
Answer» C. becomes steady for a given condensation temperature
Discussion
119.

What is the use of multistage compression in vapour compression refrigeration system?
A. to increase volumetric efficiency of compressor
B. to allow the system to operate between higher pressures
C. to reduce risk of damage to refrigerant
D. all of the above
Answer» E.
Discussion
120.

The Brayton cycle is the air standard cycle for
A. gas turbine power plant
B. SI engine
C. CI engine
D. none of the above
Answer» B. SI engine
Discussion
121.

What is used as an intercooler in multistage compression of vapour compression refrigeration system?
A. water
B. air
C. refrigerant itself
D. none of the above
Answer» D. none of the above
Discussion
122.

The perfect example of an ideal gas is
A. air
B. hydrogen
C. water vapour
D. none of the above
Answer» E.
Discussion
123.

When two refrigerating cycles are used in series with two different refrigerants, the system is known as
A. dual refrigeration system
B. cascade refrigeration system
C. vapour absorption refrigeration system
D. none of the above
Answer» C. vapour absorption refrigeration system
Discussion
124.

Macroscopic thermodynamics ______
A. is concerned with the effects of action of many molecules in matter
B. results can be derived from microscopic study of matter
C. is not concerned with the events occurring at the molecular level
D. all of the above
Answer» E.
Discussion
125.

How is the natural draught produced for exhaust gases?
A. by using fan
B. by using chimney
C. by using gravity
D. none of the above
Answer» C. by using gravity
Discussion
126.

Which of the following is/are mode/s of storage of internal energy in a system?
A. Macroscopic energy mode
B. Microscopic energy mode
C. both a. and b.
D. none of the above
Answer» D. none of the above
Discussion
127.

Carnot cycle is
A. a reversible cycle
B. an irreversible cycle
C. practical cycle
D. none of the above
Answer» B. an irreversible cycle
Discussion
128.

A process of application of breaks in a vehicle is
A. a reversible process
B. an irreversible process
C. a quasi-static process
D. none of the above
Answer» C. a quasi-static process
Discussion
129.

Which of the following is a reversed heat engine?
A. Heat pump
B. Refrigerator
C. both a. and b.
D. none of the above
Answer» D. none of the above
Discussion
130.

A process becomes reversible when
A. it undergoes in the absence of any dissipative effect
B. all the points through the path are at thermodynamic equilibrium
C. it undergoes as a very slow quasi-static process
D. all of the above
Answer» E.
Discussion
131.

According to the Carnot's theorem, the efficiency of a reversible heat engine operating between a same given constant temperature source and a given constant temperature sink is
A. higher than any other irreversible heat engine
B. less than any other irreversible heat engine
C. equal to any other irreversible heat engine
D. none of the above
Answer» B. less than any other irreversible heat engine
Discussion
132.

If a reversible heat engine A is operating between the temperature levels T1 and T2 and another reversible heat engine B of different capacity is also operating between the same temperature difference T1 and T2, then the efficiency of reversible heat engine B is
A. greater than efficiency of the reversible heat engine A
B. less than the efficiency of the reversible heat engine A
C. equal to the efficiency of the reversible heat engine A
D. cannot say
Answer» D. cannot say
Discussion
133.

When dry bulb temperature (DBT) and wet bulb temperature (WBT) are measured, greater the difference between DBT and WBT,
A. greater the amount of water vapour held in the mixture
B. smaller the amount of water vapour held in the mixture
C. same the amount of water vapour held in the mixture
D. none of the above
Answer» C. same the amount of water vapour held in the mixture
Discussion
134.

If a gas is heated against a pressure, keeping the volume constant, then work done will be equal to__________________?
A. + v
B. – ve
C. zero
D. pressure x volume
E. any where between zero and infinity
Answer» D. pressure x volume
Discussion
135.

When the humidity ratio of air increases the air is said to be
A. dehumidified
B. humidified
C. heated
D. cooled
Answer» C. heated
Discussion
136.

What is sensible cooling of air?
A. the cooling in which sensible heat of air is removed in order to reduce temperature
B. the cooling in which temperature of air is reduced without changing in its moisture content
C. both a. and b.
D. none of the above
Answer» D. none of the above
Discussion
137.

Which processes do occur in the Brayton cycle?
A. two reversible adiabatic processes and two reversible isochoric processes
B. two reversible adiabatic processes and two reversible isobaric processes
C. two reversible adiabatic processes and two reversible isothermal processes
D. two reversible adiabatic processes and two reversible isentropic processes
Answer» C. two reversible adiabatic processes and two reversible isothermal processes
Discussion
138.

What is the purpose of reheat cycle?
A. to limit the pump work
B. to decrease heat input in the Rankine cycle
C. to limit the quality of steam to 0.85 at the turbine exhaust
D. none of the above
Answer» D. none of the above
Discussion
139.

The Brayton cycle used in gas-cooled nuclear reactor plant is
A. a closed cycle
B. an open cycle
C. either closed or open cycle
D. cannot say
Answer» B. an open cycle
Discussion
140.

For the same compression ratio, how is the efficiency of the Brayton cycle compared with the efficiency of Otto cycle?
A. Efficiency of the Brayton cycle is higher than the efficiency of the Otto cycle, for the same compression ratio
B. Efficiency of the Brayton cycle is lower than the efficiency of the Otto cycle, for the same compression ratio
C. Efficiency of the Brayton cycle is same as that of the Otto cycle, for the same compression ratio
D. cannot say
Answer» D. cannot say
Discussion
141.

What is an ideal gas?
A. which obeys the law pv = RT
B. which obeys the law p = vR / T
C. which obeys the law pv = R / T
D. none of the above
Answer» B. which obeys the law p = vR / T
Discussion
142.

What must be the initial temperature of gas for achieving cooling effect in Joule-Kelvin expansion?
A. the initial temperature must be above the maximum inversion temperature
B. the initial temperature must be below the maximum inversion temperature
C. the initial temperature must be equal to the maximum inversion temperature
D. the maximum inversion temperature has nothing to do with cooling effect in Joule-Kelvin expansion
Answer» C. the initial temperature must be equal to the maximum inversion temperature
Discussion
143.

Free expansion of gas within a system is
A. a reversible process
B. an irreversible process
C. a quasi-static process
D. none of the above
Answer» C. a quasi-static process
Discussion
144.

A process in which work is done without producing an equivalent increase in the kinetic or potential energy of any system is
A. a reversible process
B. an irreversible process
C. a quasi-static process
D. none of the above
Answer» C. a quasi-static process
Discussion
145.

What is a measure of extent of irreversibility of a process undergone by a system?
A. The entropy increase of an isolated system
B. The entropy decrease of an isolated system
C. both a. and b.
D. none of the above
Answer» B. The entropy decrease of an isolated system
Discussion
146.

The total energy of the universe
A. is always increasing
B. is always decreasing
C. either increases or decreases
D. is always constant
Answer» E.
Discussion
147.

At the equilibrium state of any system
A. entropy of the system becomes maximum
B. entropy of the system becomes minimum
C. entropy of the system becomes equal to entropy of the surrounding
D. none of the above
Answer» B. entropy of the system becomes minimum
Discussion
148.

Which temperature can be measured by an instrument called psychrometer?
A. dry bulb temperature
B. wet bulb temperature
C. both a. and b.
D. none of the above
Answer» D. none of the above
Discussion
149.

What is the purpose of using economizer in the boiler?
A. to heat feedwater by utilizing heat from exhaust gases
B. to heat feedwater by utilizing some heat from superheated steam
C. to superheat steam
D. none of the above
Answer» B. to heat feedwater by utilizing some heat from superheated steam
Discussion
150.

Which of the following is chosen as a standard thermometric substance?
A. Gas
B. Thermocouple
C. Electric resistance
D. Mercury
Answer» B. Thermocouple
Discussion