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Multiple choice question for engineering

Set 1

1. ________ produced can be varied by varying fuel flow.
a) Exhaust gases
b) Thrust
c) Exhaust gases & Thrust
d) None of the mentioned

View Answer

Answer: c [Reason:] Thrust produced can be varied by varying fuel flow. If more amount of fuel is made to flow inside more mount of energy is produced and more amount of exhaust gases are released.

2. Thrust produced also depends upon rotor _________
a) blade surface
b) blade pitch
c) blade angle
d) none of the mentioned

View Answer

Answer: b [Reason:] In helicopters thrust produced is varied by varying rotor blade pitch. If the pitch of the rotor blade is increased more thrust is produced.

3. Extra fuel supply causes compressor to _______
a) stall
b) surge
c) surge & stall
d) none of the mentioned

View Answer

Answer: a [Reason:] When extra fuel is supplied limiting temperature is crossed and causes compressor stall. Compressor stall is disruption of the air flow in the compressor.

4. _______ is caused when extra fuel is supplied.
a) Surge
b) Stall
c) Surge & Stall
d) None of the mentioned

View Answer

Answer: c [Reason:] Surge is caused when extra fuel is supplied. Stall is also caused when extra fuel is supplied. Surge is operational limit of compressor at which minimum limits are reached.

5. When fuel flow is _______ it causes surge.
a) fuel flow is not related to surge
b) decreased
c) increased
d) none of the mentioned

View Answer

Answer: c [Reason:] When fuel flow is increased it causes surge. Surge is the operational limit of compressor at which minimum levels are reached.

6. Fuel control is present in turbofan engines.
a) True
b) False

View Answer

Answer: a [Reason:] Fuel control is present in turbofan engines.

7. _______ control is present in turbojets.
a) Fuel
b) Thrust
c) Fuel & Thrust
d) None of the mentioned

View Answer

Answer: d [Reason:] Fuel control is present in turbojets. If the fuel is controlled it indirectly controls the thrust produced.

8. Turboprops have ________ control unit.
a) thrust
b) fuel
c) surge
d) none of the mentioned

View Answer

Answer: b [Reason:] Fuel control unit is present in turboprop. By using fuel control unit amount of thrust produced can be regulated.

9. _________ control unit is present in turboshaft engines.
a) exhaust
b) fuel
c) thrust
d) none of the mentioned

View Answer

Answer:b [Reason:] Fuel control unit is present in turboshaft engines. Thrust is varied by using fuel control unit in turboshaft engines.

10. Variable displacement pump is present in fuel control units.
a) True
b) False

View Answer

Answer: a [Reason:] Variable displacement pumps have variable displacements which was used to meet the fuel requirements.

Set 2

1. In cryogenic rocket engines use oxidizer as fuel.
a) True
b) False

View Answer

Answer: a [Reason:] In cryogenic rocket engines use oxidizer as fuel.

2. Cryogenic fuels are stored under _______ temperatures.
a) high
b) low
c) medium
d) none of the mentioned

View Answer

Answer: b [Reason:] Cryogenic rocket fuels are stored under low temperatures. Cryogenics works under minus degree Celsius and hence they are stored in low temperatures.

3. Rocket engines require _______ mass flow rate.
a) high
b) low
c) medium
d) none of the mentioned

View Answer

Answer: a [Reason:] Rocket engines require high mass flow rate. Rocket engines requires high thrust and for producing high thrust high mass flow rate is required.

4. Rocket fuels has ________ molecular weight.
a) medium
b) high
c) low
d) none of the mentioned

View Answer

Answer: c [Reason:] Rocket fuels has low molecular weight.

5. Cryogenic fuels are in _________ state at room temperature and pressure.
a) gaseous
b) liquid
c) solid
d) none of the mentioned

View Answer

Answer: a [Reason:] Cryogenic fuels are in a gaseous state at room temperature and pressure. Cryogenics work under low temperatures and when temperature is changed to room temperature then phase transfer takes place.

6. Cryogenic rocket engines are also called as hybrid rocket engines.
a) True
b) False

View Answer

Answer: a [Reason:] Cryogenic rocket engines are also called as hybrid rocket engines.

7. Hybrid rocket engines are also called as ________ propellant rocket engines.
a) solid
b) liquid
c) solid & liquid
d) none of the mentioned

View Answer

Answer: b [Reason:] Hybrid rocket engines are also called as liquid propellant rocket engines. Because fuels used in hybrid engines are in liquid state.

8. ____________ is used as cryogenic fuel.
a) Liquid oxygen
b) Liquid hydrogen
c) Combination of liquid oxygen and liquid hydrogen
d) None of the mentioned

View Answer

Answer: a [Reason:] Combination of both liquid oxygen and liquid hydrogen are used as cryogenic fuel. Mixture of this liquid oxygen and liquid hydrogen results in low temperature which is a main property of cryogenic fuels.

9. Liquid hydrogen and oxygen mixture produces thrust upto ________
a) 5 Km/s
b) 4 Km/s
c) 4.5 Km/s
d) none of the mentioned

View Answer

Answer: c [Reason:] Liquid hydrogen and oxygen mixture produces thrust upto 4.5 Km/s. Cryogenic fuels produce high thrust force.

10. _________ initiators are used in cryogenic rocket engines.
a) Pyrotechnic
b) Centrifugal
c) Pyrotechnic & Centrifugal
d) None of the mentioned

View Answer

Answer: a [Reason:] Pyrotechnic initiators are used in cryogenic rocket engines.

Set 3

1. Jet engines are classified into _______ types.
a) 5
b) 4
c) 3
d) 2

View Answer

Answer: a [Reason:] Jet engines are classified into five types. They are Turboshafts Turbo jets Turbo props Turbofans Propfan.

2. Jet engines works on ______ cycle.
a) brayton
b) dual
c) dual
d) otto

View Answer

Answer: d [Reason:] Jet engines works on brayton cycle. Gasoline engines works on otto cycle.

3. __________ bypass turbo fan engines are used in sub sonic flights.
a) Medium
b) Low
c) High
d) None of the mentioned

View Answer

Answer: c [Reason:] High bypass turbo fan engines are used in sub sonic flights. High bypass turbo fan engines produce more power output.

4. Jet engines works from newton’s law of motion.
a) True
b) False

View Answer

Answer: a [Reason:] Jet engines works from newton’s law of motion.

5. Turbofans gives more efficiency when the speed is ______ than the mach speed.
a) greater
b) less
c) equal
d) none of the mentioned

View Answer

Answer: b [Reason:] Turbofans efficiency decreases when the speed exceeds the mach number.

6. _________ compressors are used in turbojets.
a) Axial
b) Radial
c) Both
d) None of the mentioned

View Answer

Answer: a [Reason:] Turbojets use axial or centrifugal compressors. Centrifugal compressors pressurizes the working fluid by centrifugal principle.

7. ____________ compressors can be used in turbojets.
a) Radial
b) Centrifugal
c) Radial & Centrifugal
d) None of the mentioned

View Answer

Answer: b [Reason:] Both centrifugal or axial compressors can be used in turbo jets.

8. Internal energy in the fuel is converted into __________ of the exhaust in turbojets.
a) kinetic energy
b) pressure energy
c) kinetic & pressure energy
d) none of the mentioned

View Answer

Answer: a [Reason:] Internal energy in the fuel is converted into kinetic energy of the exhaust in turbojets. Compressors convert internal energy of the fluid into velocity and hence kinetic energy is increased.

9. Gas generator core is used in turbo fans.
a) True
b) False

View Answer

Answer: a [Reason:] Gas generator cores are used to convert internal energy of the gas to kinetic energy of the exhaust.

10. Jet engines have ________ shafts.
a) single
b) multiple
c) single or multiple
d) none of the mentioned

View Answer

Answer: c [Reason:] Jet engines may have multiple shafts depending on their energy requirements.

Set 4

1. Capacity of rotary screw compressor is _______ by using unloader.
a) constant
b) varied
c) unloader is not used for compressing
d) none of the mentioned

View Answer

Answer: a [Reason:] Capacity of rotary screw compressor can be varied by using unloader. When unloader is completely opened its capacity get decreased to the minimum.

2. Amount of air that can be sucked in by compressor is regulated by using ___________
a) check valve
b) feed valve
c) unloader
d) none of the mentioned

View Answer

Answer: c [Reason:] Amount of air that can be sucked in can be regulated using unloader. When unloader is completely opened compressor totally minimizes the air entering the compressor.

3. Unloader is also called as intake valve.
a) True
b) False

View Answer

Answer: b [Reason:] Intake valve is used to regulate the flow capacity where as unloader is used to vary the load.

4. Unloader closes 100% of the air intake.
a) True
b) False

View Answer

Answer: b [Reason:] Unloader closes the intake to the maximum extent but 100% cannot be closed.

5. When unloader is closed it uses _________ work.
a) 30%
b) 50%
c) 20%
d) none of the mentioned

View Answer

Answer: a [Reason:] When unloader is closed it used 30% work. For unloader to close it needs to apply some pressure which is applied in the form of work.

6. ___________ unloader are used in stationary compressors.
a) Continuous
b) Variable
c) Continuous & Variable
d) None of the mentioned

View Answer

Answer: a [Reason:] Stationary compressors use continuous unloader. In stationary compressors inlet air should be frequently controlled for proper working and hence continuous unloaders are used.

7. Continuous unloader is used in _________ engine compressor.
a) diesel
b) gasoline
c) dual
d) none of the mentioned

View Answer

Answer: a [Reason:] Continuous unloader is used in diesel engine compressor. In diesel engine the amount of fuel intake is to be controlled regularly.

8. When choke points are joined in graph representing speeds it is called as ________
a) temperature line
b) choke line
c) critical line
d) none of the mentioned

View Answer

Answer: b [Reason:] When choke points are joined in graph representing speeds it is called as choke lines. Choke points are the points at which the turbine starts choking at that particular speed and fuel intake.

9. When compressor operates at ________ choking takes place.
a) high mass
b) low mass
c) high temperature
d) none of the mentioned

View Answer

Answer: a [Reason:] When compressor operates at high mass choking takes place. When mass increases its inlet quantity increases and hence turbine starts to choke.

10. Choking occurs when mach number reaches ________
a) 3
b) 2
c) 1
d) 4

View Answer

Answer: c [Reason:] When mach number reaches unity no more mass can be reached and hence choking takes place. When mach number reaches unity its speed is heavily increased and hence mass flow is also increased to a great extent.

Set 5

1. High power density is the advantage obtained from_______
a) solar Gas turbines
b) steam Turbines
c) cryogenic Gas turbines
d) none of the mentioned

View Answer

Answer: a [Reason:] Gas turbines have higher power density than steam turbines and in the case of cryogenic gas turbines those could not be operated on solar power.

2. High power to weight ratio is the advantage of _______
a) Turboprop
b) Turbofan
c) Turbojet
d) All of the mentioned

View Answer

Answer: d [Reason:] All the turboprop,Turbofan,Turbojet have high power to weight ratio when compared to internal combustion engines. That is the reason behind using those gas turbines in place of internal combustion engines in aircrafts.

3. Gas turbine powered engines are smaller than reciprocating engines.
a) True
b) False

View Answer

Answer: a [Reason:] In gas turbines high power to weight ratio is obtained when compared to reciprocating engines which indicates that for producing equal power in both gas turbine engine and reciprocating engine weight of gas turbine engine should be less which indicates that gas turbine engines are smaller when compared to reciprocating engine.

4. Gas turbine engines moves only in _______ direction.
a) multi
b) two
c) one
d) none

View Answer

Answer: c [Reason:] In gas turbines turbine rotates due to combusted gases. Combusted gases flow only in one direction, so gas turbine engine moves in one direction only.

5. Gas turbine engines have ______ vibrations when compared to reciprocating engines.
a) less
b) more
c) equal
d) none

View Answer

Answer: a [Reason:] Gas turbine engines have less rotating parts when compared to reciprocating engines and so gas turbine engines have less vibrations when compared to reciprocating engines.

6. Gas turbine engines have low operating pressures when compared to reciprocating engines.
a) True
b) False

View Answer

Answer: a [Reason:] In gas turbine engines hot gases from combustors rotate the turbine which means there is separate combustor available in gas turbines where combustion takes place and high temperatures are obtained but turbine does not have high pressure but in the case of reciprocating engines combustion chamber and piston is in the same cylinder, so high pressure is obtained.

7. High operating speeds are obtained in _______
a) Reciprocating turbines
b) Gas turbines
c) Stirling engine
d) None of the mentioned

View Answer

Answer: b [Reason:] In gas turbines high rpm and low torques are obtained.

8. Consumption of lubricating oil is _______ in gas turbines.
a) low
b) high
c) medium
d) none

View Answer

Answer: a [Reason:] In reciprocating engines pistons are used but not in the case of gas turbines. Hence low lubrication oil is required.

9. At idle conditions gas turbine engines are ________ efficient than reciprocating engines.
a) more
b) less
c) moderately
d) none

View Answer

Answer: b [Reason:] In gas turbines two thirds of total energy produced is used in by compressor where as reciprocating engines have no compressor. So gas turbines use more power than reciprocating engines at idle conditions.

10. Reciprocating engines require __________ startups than Gas turbines.
a) longer
b) moderate
c) shorter
d) none

View Answer

Answer: c [Reason:] Initially for reciprocating engines to start only combustion process need to be started but in the case of Gas turbines both compressor and combustor need to start. So Gas turbines take longer startups when compared to reciprocating engines.