Explore topic-wise MCQs in Mechanical Engineering Questions.

This section includes 347 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.

1.

Axial flow compressor resembles____________________ ?
A. centrifugal pump
B. reciprocating pump
C. turbine
D. sliding vane compressor
E. none of the above
Answer» D. sliding vane compressor
Discussion
2.

Pick up the wrong statement about advantages of multistage compression____________________?
A. better lubrication is possible advantages of multistage
B. more loss of air due to leakage past the cylinder
C. mechanical balance is better
D. air can be cooled perfectly in between
E. more uniform torque, light cylinder and saving in work
Answer» C. mechanical balance is better
Discussion
3.

A closed gas turbine in which fuel is burnt directly in the air is not possible because of__________________?
A. high pressure ratio
B. increasing gas temperature
C. high specific volume
D. high friction losses
E. paucity of 02
Answer» F.
Discussion
4.

Atmospheric pressure is 1.03 kg/cm and vapour pressure is 0.03 kg/cm . The air pressure will be_____________________ ?
A. 1.03 kg/cm2
B. 1.06 kg/cm2
C. 1.00 kg/cm2
D. 0.53 kg/cm2
E. 0.5 kg/cm2
Answer» D. 0.53 kg/cm2
Discussion
5.

Volumetric efficiency of a compressor without clearance volume________________?
A. increases with increase in compression ratio
B. decreases with increase in compression ratio
C. is not dependent upon compressin ratio
D. may increase/decrease depending on compressor capacity
E. unpredictable
Answer» D. may increase/decrease depending on compressor capacity
Discussion
6.

Clearance volume in actual reciprocating compressors is essential __________________?
A. to accommedate Valves in the cylinder head
B. to provide cushioning effect
C. to attain high volumetric efficiency
D. to avoid mechanical bang of piston with cylinder head
E. to provide cushioning effect and also to avoid mechanical bang of piston with cylinder head
Answer» F.
Discussion
7.

The work done per unit mass of air in compression will’be least when n is equal to______________?
A. 1
B. 1.2
C. 1.3
D. 1.4
E. 1.5
Answer» B. 1.2
Discussion
8.

Inter cooling in compressors__________________?
A. cools the delivered air
B. results in saving of power in compressing a given volume to given pressure
C. is the standard practice for big compressors
D. enables compression in two stages
E. prevents compressor jacket running very hot
Answer» C. is the standard practice for big compressors
Discussion
9.

The compressor capacity with decrease in suction temperature_________________?
A. increases
B. decreases
C. remains unaffected
D. may increase or decrease depending on compressor capacity
E. increases upto certain limit and then decreases
Answer» B. decreases
Discussion
10.

An air compressor may be controlled by____________________?
A. throttle control B. clearance control
B. blow-off control
C. any one of the above
D. none of the above
Answer» D. none of the above
Discussion
11.

The- most efficient method of compressing air is to compress it_________________?
A. isothermally
B. adiabatically
C. isentropically
D. isochronically
E. as per law pV
Answer» B. adiabatically
Discussion
12.

Maximum work is done in compressing air when the compression is_________________?
A. isothermal
B. adiabatic
C. polytropic
D. any one of the above
E. none of the above
Answer» C. polytropic
Discussion
13.

Adiabatic compression is one in which___________________?
A. temperature during compression remains constant
B. no heat leaves or enters the compressor cylinder during cornpression
C. temperature rise follows a linear relationship
D. work done is maximum
E. entropy decreases
Answer» C. temperature rise follows a linear relationship
Discussion
14.

Isothermal compression efficiency, even when running at high speed, can be approached by using A. multi-stage compression B. cold water spray C. both A. and B. above D. fully insulating the cylinder E. high stroke_________________?
Isothermal compression efficiency, even when running at high speed, can be approached by using
A. multi-stage compression
B. cold water spray
C. both A. and B. above
D. fully insulating the cylinder
E. high stroke
Answer» D. fully insulating the cylinder
Discussion
15.

Isothermal compression effeicency can be attained by running the compressor__________________?
A. at very high speed
B. at very slow speed
C. at average speed
D. at zero speed
E. isothermally
Answer» C. at average speed
Discussion
16.

Free air is the air at________________?
A. atmospheric conditions at any specific location
B. 20°C and 1 kg/cm2 and relative humidity of 36%
C. 0°C and standard atmospheric conditions
D. 15°C and 1 kg/cm2
E. 25°C, 1 kg/cm2 and relative humidity of 50%
Answer» B. 20°C and 1 kg/cm2 and relative humidity of 36%
Discussion
17.

The overall isothermal eiffciency of compressor is defined as the ratio of_______________?
A. isothermal h.p. to the BHP of motor
B. isothermal h.p. to adiabatic h.p.
C. power to drive compressor to isothermal h.p.
D. work to compress air isothermally to work for actual compression
E. isothermal work to ideal work
Answer» B. isothermal h.p. to adiabatic h.p.
Discussion
18.

The capacity of a compressor is 5 m /mih. 5 m /min refers to_______________?
A. standard air
B. free air
C. compressed air
D. compressed air at delivery pressure
E. air sucked
Answer» C. compressed air
Discussion
19.

1 m of air at atmospheric condition weighs approximately__________________?
A. 0.5 kg
B. 1.0 kg
C. 1.3 kg
D. 2.2 kg
E. 3.2 kg
Answer» D. 2.2 kg
Discussion
20.

Separators in compressor installations are located_____________________?
A. before intercooler
B. after intercooler
C. after receiver
D. between after-cooler and air receiver
E. before suction
Answer» E. before suction
Discussion
21.

Mining industry usually employs following motive power___________________?
A. A.C. electric motor
B. compressed air
C. petrol engine
D. diesel engine
E. D.C. electric motor
Answer» C. petrol engine
Discussion
22.

During peak load periods, the best method of controlling compressors is___________________?
A. start-stop motor
B. constant speed unloader
C. relief valve
D. variable speed
E. none of the above
Answer» C. relief valve
Discussion
23.

Standard air is the air at_____________________?
A. atmospheric conditions at any specific location
B. 20°C and 1 kg/cm2 and relative humidity 36%
C. 0°C and standard atmospheric conditions
D. 15°C and 1 kg/cm2
E. 25°C, 1 kg/cm2 and RH of 60%.
Answer» C. 0°C and standard atmospheric conditions
Discussion
24.

A compressor at high altitude will draw________________?
A. more power
B. less power
C. same power
D. more/less power depending on other factors
E. none of the above
Answer» C. same power
Discussion
25.

The compressor performance at higher altitude compared to sea level will be _______________?
A. same
B. higher
C. lower
D. dependent on other factors
E. none of the above
Answer» D. dependent on other factors
Discussion
26.

After-cooler is used to__________________?
A. cool the air
B. decrease the delivery temperature for ease in handling
C. cause moisture and oil vapour to drop out
D. reduce volume
E. increase pressure
Answer» D. reduce volume
Discussion
27.

A centrifugal compressor works on the principle of__________________?
A. conversion of pressure energy into kinetic energy
B. conversion of kinetic energy into pres¬sure energy
C. centripetal action
D. generating pressure directly
E. combination of A. and D.
Answer» C. centripetal action
Discussion
28.

Which is false statement about multistage compression ?
A. Power consumption per unit of air delivered is low
B. Volumetric efficiency is high
C. It is best suited for compression ratios around 7:1
D. The moisture in air is condensed in the intercooler
E. Outlet temperature is reduced
Answer» C. It is best suited for compression ratios around 7:1
Discussion
29.

The thrust on the rotor in a centrifugal compressor is produced by________________?
A. radial component
B. axial component
C. tangential component
D. resultant component
Answer» C. tangential component
Discussion
30.

Which is false statement about air receivers ___________________?
A. These are used to dampen pulsations
B. These act as reservoir to- take care of sudden demands
C. These increase compressor efficiency
D. These knock out some oil and moisture
E. These reduce frequent on/off operation of compressors
Answer» D. These knock out some oil and moisture
Discussion
31.

Ratio of indicated h.p. to shaft h.p. in known as__________________?
A. compressor efficiency
B. isothermal efficiency
C. volumetric efficiency
D. mechanical efficiency
E. adiabatic efficiency
Answer» E. adiabatic efficiency
Discussion
32.

Rotary compressor is best suited for_____________________?
A. large quantity of air at high pressure
B. small quantity of air at high pressure
C. small quantity of air at low pressure
D. large quantity of air at low pressure
E. any one of the above
Answer» C. small quantity of air at low pressure
Discussion
33.

Euler’s equation is applicable for__________________?
A. centrifugal compressor
B. axial compressor
C. pumps
D. all of the above
E. none of the above
Answer» E. none of the above
Discussion
34.

The working fluid in ai turbine is___________________?
A. in two phases
B. in three phases
C. in a single phase
D. in the form of air and water mixture
E. gas and no air
Answer» D. in the form of air and water mixture
Discussion
35.

The clearance volume of the air compressor is kept minimum because____________________?
A. it allows maximum compression to be achieved
B. it greatly affects volumetric efficiency
C. it results in minimum work
D. it permits isothermal compression
E. none of the above
Answer» C. it results in minimum work
Discussion
36.

Reciprocating air compressor is best suited for___________________?
A. large quantity of air at high pressure
B. small quantity of air at high pressure
C. small quantity of air at low pressure
D. large quantity of air at low pressure
E. any one of the above
Answer» B. small quantity of air at high pressure
Discussion
37.

The compression ratio in a gas turbine is of the roder of____________________?
A. 3.5 : 1
B. 5 : 1
C. 8 : 1
D. 12 : 1
E. 20 : 1
Answer» D. 12 : 1
Discussion
38.

Cylinder clearance in a compressor should be _________________?
A. as large as possible
B. as small as possible
C. about 50% of swept volume
D. about 100% of swept volume
E. none of the above
Answer» C. about 50% of swept volume
Discussion
39.

If V, U and Vr represent the absolute velocity of fluid, velocity of blade, and relative velocity of fluid, and suffix i and o stand for entry and exit conditions, then in a rotary machine whose degree of reaction is unity______________?
A. Vi=V0B
B. Vt>V0
C. U,
Answer» B. Vt>V0
Discussion
40.

The ratio of work doen per cycle to the swept volume in case of compressor is called ______________?
A. compression index
B. compression ratio
C. compressor efficiency
D. mean effective pressure
E. compressor effectiveness
Answer» E. compressor effectiveness
Discussion
41.

In jet engines the products of combustion after passing through the gas lurbine are discharged into_______________?
A. atmosphere
B. back to the compressor
C. discharge nozzle
D. vacuum
E. none of the above
Answer» D. vacuum
Discussion
42.

Ratio of compression is the ratio of__________________?
A. gauge discharge pressure to the gauge intake pressure
B. absolute discharge pressure to the ab-solute intake pressure
C. pressures at discharge and suction cor-responding to same temperature
D. stroke volume and clearance volume
E. none of the above
Answer» C. pressures at discharge and suction cor-responding to same temperature
Discussion
43.

Volumetric efficiency of air compressors is of the order of________________?
A. 20-30%
B. 40-50%
C. 60-70%
D. 70-90%
E. 90-100%
Answer» E. 90-100%
Discussion
44.

What will be the volume of air at 327°C if its volume at 27°C is 1.5 m3/mt ?
A. 3 m3/mt
B. 1.5 m3/mt
C. 18 m3/mt
D. 6 m3/mt
E. 0.75 m3/mt
Answer» B. 1.5 m3/mt
Discussion
45.

Volumetric efficiency is_____________________?
A. the ratio of stroke volume to clearance volume
B. the ratio of the air actually delivered to the amount of piston displacement
C. reciprocal of compression ratio
D. index of compressor performance
E. proportional to compression ratio
Answer» C. reciprocal of compression ratio
Discussion
46.

The net work input required for compressor with increase in clearance volume_____________________?
A. increases
B. decreases
C. remains same
D. increases/decreases depending on com-pressor capacity
E. unpredictable
Answer» D. increases/decreases depending on com-pressor capacity
Discussion
47.

Isothermal compression though most efficient, but is not -practicable because_________________?
A. ityrequires very big cylinder
B. it does not increase pressure much
C. it is impossible in practice
D. compressor has to run at very slow speed to achieve it
E. it requires cylinder to be placed in water
Answer» E. it requires cylinder to be placed in water
Discussion
48.

An ideal air compressor cycle with clearance on p-v diagram can be represented by following processes_______________?
A. one adiabatic, two isobaric, and one constant volume
B. two adiabatic and two isobaric
C. two adiabatic, one isobaric and one constant volume
D. one adiabatic, one isobaric and two constant volume
E. two isobaric, two adiabatic and one constant volume
Answer» C. two adiabatic, one isobaric and one constant volume
Discussion
49.

Compression efficiency is compared against_____________________?
A. ideal compression
B. adiabatic compression
C. botii isothermal and adiabatic compression
D. isentropic compression
E. isothermal compression
Answer» F.
Discussion
50.

For an irreversible gas turbine cycle, the efficiency and work ratio both depend on___________________?
A. pressure ratio alone
B. maximum cycle temperature alone
C. minimum cycle temperature alone
D. both pressure ratio and maximum cycle temperature
E. none of the above
Answer» E. none of the above
Discussion