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Multiple choice question for engineering

Set 1

1. ____________ is a chemical reaction in which certain elements of the fuel like hydrogen and carbon combine with oxygen liberating heat energy and causing an increase in temperature of the gases.
a) Compression
b) Expansion
c) Combustion
d) None of the mentioned

View Answer

Answer: c [Reason:] Combustion is a chemical reaction in which certain elements of the fuel like hydrogen and carbon combine with oxygen liberating heat energy and causing an increase in temperature of the gases, while expansion and compression are not reactions, in fact they are processes in a fuel cycle.

2. The conditions necessary for combustion are the presence of combustible mixture and some means of initiating the process.
a) True
b) False

View Answer

Answer: a

3. The process of combustion in engines generally takes place either in a homogeneous or a heterogeneous fuel vapour air mixture depending on the type of engine.
a) True
b) False

View Answer

Answer: a

4. In spark ignition engines a nearly ____________ mixture of air and fuel is formed in the carburettor.
a) heterogeneous
b) homogeneous
c) solid
d) none of the mentioned

View Answer

Answer: b [Reason:] In spark ignition engines a nearly homogeneous mixture of air and fuel is formed in the carburettor and solid and heterogeneous mixture is never used.

5. Homogeneous mixture is formed inside the engine cylinder and the combustion is initiated inside the cylinder at a particular instant towards the end of the compression stroke.
a) True
b) False

View Answer

Answer: b [Reason:] In fact, homogeneous mixture is formed outside the engine cylinder and the combustion is initiated inside the cylinder at a particular instant towards the end of the compression stroke.

6. In a homogeneous gas mixture the fuel and oxygen molecules are more or less, uniformly distributed.
a) True
b) False

View Answer

Answer: a [Reason:] Yes, homogeneous means equally distributed and in a homogeneous gas mixture the fuel and oxygen molecules are more or less, uniformly distributed.

7. The complete combustion of ____________ mixture, and droplet combustion result in the smoke and odour.
a) heterogeneous
b) homogeneous
c) solid
d) none of the mentioned

View Answer

Answer: b [Reason:] Not, but the incomplete combustion of heterogeneous mixture, and droplet combustion result in the smoke and odour.

8. The ____________ rate is the result of a purely chemical combination process in which the flame eats it way into the unburned charge.
a) transposition
b) reaction
c) burning
d) none of the mentioned

View Answer

Answer: b [Reason:] The reaction rate is the result of a purely chemical combination process in which the flame eats it way into the unburned charge while the transposition rate is due to the physical movement of the flame front relative to the cylinder wall and also the result of the pressure differential between the burning gases and the unburnt gases in the combustion chamber.

9. The ____________ rate is due to the physical movement of the flame front relative to the cylinder wall and also the result of the pressure differential between the burning gases and the unburnt gases in the combustion chamber.
a) transposition
b) reaction
c) burning
d) none of the mentioned

View Answer

Answer: a [Reason:] The transposition rate is due to the physical movement of the flame front relative to the cylinder wall and also the result of the pressure differential between the burning gases and the unburnt gases in the combustion chamber while the reaction rate is the result of a purely chemical combination process in which the flame eats it way into the unburned charge.

10. A pre-combustion chamber gives shorter delay compared to an open type of combustion chamber.
a) True
b) False

View Answer

Answer: a

Set 2

1. Diesel as compared to petrol is
a) highly ignitable
b) more difficult to ignite
c) less difficult to ignite
d) none of the mentioned

View Answer

Answer: b

2. If the temperature of intake air in internal combustion engine increases, then its efficiency will
a) remain same
b) decrease
c) increase
d) none of the mentioned

View Answer

Answer: b

3. If petrol is used in a diesel engine, then
a) low power will be produced
b) efficiency will be low
c) higher knocking will occur
d) black smoke will be produced

View Answer

Answer: c [Reason:] Petrol is not used in diesel engine because if petrol is used in a diesel engine, then higher knocking will occur.

4. A petrol engine, during suction stroke draws
a) air only
b) petrol only
c) a mixture of petrol and air
d) none of the mentioned

View Answer

Answer: c

5. In order to mix air and petrol in the required proportion and to supply it to the engine during suction stroke, then ____________ is employed.
a) fuel pump
b) injector
c) carburetor
d) none of the mentioned

View Answer

Answer: c [Reason:] Carburetor is employed in order to mix air and petrol in the required proportion and to supply it to the engine during suction stroke.

6. A diesel engine, during suction stroke draws
a) air only
b) diesel only
c) a mixture of petrol and air
d) none of the mentioned

View Answer

Answer: a [Reason:] In a diesel engine, during suction stroke only air is drawn.

7. The colour of exhaust from diesel engine is generally
a) white
b) bluish
c) black
d) violet

View Answer

Answer: c

8. The pressure at the end of compression, in petrol engines, is approximately
a) 10 bar
b) 20 bar
c) 25 bar
d) 35 bar

View Answer

Answer: a

9. A petrol engine has compression ratio from
a) 6 to 10
b) 10 to 15
c) 15 to 25
d) 25 to 40

View Answer

Answer: a

10. The running cost of a petrol engine is ____________ that of a diesel engine.
a) higher than
b) lower than
c) equal to
d) none of the mentioned

View Answer

Answer: a

Set 3

1. ___________ is the time immediately following injection of the fuel during which the ignition process is being initiated and the pressure does not rise beyond the value it would have due to compression of air.
a) Knocking
b) Delay period
c) Startability
d) None of the mentioned

View Answer

Answer: b [Reason:] Delay period is defined as the time immediately following injection of the fuel during which the ignition process is being initiated and the pressure does not rise beyond the value it would have due to compression of air.

2. The ___________ extends for about 13º, movement of the crank.
a) knocking
b) delay period
c) startability
d) none of the mentioned

View Answer

Answer: b

3. The time for which delay period occurs decreases with ___________ in engine speed.
a) increases
b) decreases
c) unpredictable
d) none of the mentioned

View Answer

Answer: a

4. Delay period serves a useful purpose in that it allows the fuel jet to penetrate well into the combustion space.
a) True
b) False

View Answer

Answer: a

5. If the delay is too short the amount of fuel available for simultaneous explosion is too great and the resulting pressure rise is too rapid.
a) True
b) False

View Answer

Answer: b [Reason:] No, in fact, if the delay is too long the amount of fuel available for simultaneous explosion is too great and the resulting pressure rise is too rapid.

6. The delay period depends upon temperature and pressure in the cylinder at the time of injection.
a) True
b) False

View Answer

Answer: a

7. The delay period ___________ with load.
a) increases
b) decreases
c) unpredictable
d) none of the mentioned

View Answer

Answer: a [Reason:] Delay period is directly proportional to load, so the delay period increases with load.

8. The delay period depends upon nature of the fuel mixture strength.
a) True
b) False

View Answer

Answer: a

9. Higher cetane number means a ___________ delay period and smoother engine operation.
a) higher
b) lower
c) normal
d) none of the mentioned

View Answer

Answer: a

10. Increase in compression ratio ___________ delay period.
a) increases
b) reduces
c) unpredictable
d) none of the mentioned

View Answer

Answer: b [Reason:] Compression ratio is indirectly proportional to delay period, so increase in compression ratio reduces delay period.

11. At constant speed, delay period is proportional to the delay angle.
a) True
b) False

View Answer

Answer: a

12. A pre-combustion chamber gives shorter delay compared to an open type of combustion chamber.
a) True
b) False

View Answer

Answer: a

Set 4

1. The fuel air cycle efficiency _______________ with the compression ratio.
a) increases
b) decreases
c) remains same
d) none of the mentioned

View Answer

Answer: a [Reason:] As the compression ratio is increased the efficiency of fuel air cycle also increases as there is more scope of expansion work.

2. Fuel ratio is defined as the ratio of actual fuel air ratio to chemically correct fuel air ratio on mass basis.
a) True
b) False

View Answer

Answer: b [Reason:] Actually, equivalence ratio is defined as the ratio of actual fuel air ratio to chemically correct fuel air ratio on mass basis.

3. The maximum pressure and maximum temperature ____________ with compression ratio.
a) increases
b) decreases
c) remains same
d) none of the mentioned

View Answer

Answer: a [Reason:] Since, the temperature and pressure at the end of compression are higher, so, as a result the maximum pressure and maximum temperature increases with compression ratio.

4. As the mixture is made lean the temperature rise due to combustion will be lowered.
a) True
b) False

View Answer

Answer: a [Reason:] When the mixture is made lean the temperature rise due to combustion will be lowered as a result of reduced energy input per unit mass of mixture.

5. Fuel air ratio affects maximum power output of the engine due to
a) higher specific heats
b) chemical equilibrium losses
c) all of the mentioned
d) none of the mentioned

View Answer

Answer: c [Reason:] Due to both higher specific heats and chemical equilibrium losses, the fuel air ratio affects the maximum power output of the engine.

6. Mean effective pressure at a given compression ratio is maximum when the air fuel ratio is
a) higher than stoichiometric
b) lower than stoichiometric
c) equal to stoichiometric
d) none of the mentioned

View Answer

Answer: b [Reason:] When the air fuel ratio is lower than stoichiometric then only the mean effective pressure at a given compression ratio is maximum.

7. For a compression process with variable specific heat the peak temperature and pressure are _____________ as compared to constant specific heat.
a) lower
b) higher
c) no effect
d) none of the mentioned

View Answer

Answer: a [Reason:] The peak temperature and pressure are lower for a compression process with variable specific heat as compared to constant specific heat.

8. Cycles with lean to very lean mixture tend towards
a) practice cycles
b) fuel air cycles
c) air standard cycles
d) none of the mentioned

View Answer

Answer: d [Reason:] All the cycles mentioned above operates only on high mixtures.

9. When the mixture is lean
a) efficiency is less
b) power output is less
c) maximum temperature and pressure are higher
d) all of the mentioned

View Answer

Answer: b [Reason:] Power output is directly proportional to mixture, so when the mixture is lean, the power output is less and vice-versa.

10. For a given compression ratio, as the mixture is made progressively rich from lean the mean effective pressure
a) increases
b) decreases
c) initially increases and then decreases
d) remains more or less same

View Answer

Answer: c [Reason:] To get a stable condition, for a given compression ratio, as the mixture is made progressively rich from lean the mean effective pressure.

Set 5

1. The gasoline engine requires much ____________ air than a diesel engine.
a) less
b) more
c) equal
d) none of the mentioned

View Answer

Answer: b [Reason:] As gasoline engine works on the mixture of air and gasoline, therefore the gasoline engine requires much more air than a diesel engine.

2. The turbocharged diesel engine requires ____________ cooling air than naturally aspired diesel engines.
a) less
b) more
c) equal
d) none of the mentioned

View Answer

Answer: a [Reason:] As the turbocharged engine produce less heat so, the turbocharged diesel engine requires less cooling air than naturally aspired diesel engines.

3. The heat flow to water jackets, on an average, is about ____________ for large engines.
a) 500 kJ/kW-h
b) 4200 kJ/kW-h
c) 5700 kJ/kW-h
d) none of the mentioned

View Answer

Answer: b [Reason:] The heat flow to water jackets, on an average, is about 4200 kJ/kW-h for large engines and it is about 500-5700 kJ/kW-h for small engines.

4. The heat flow to water jackets, on an average, is about ____________ for small engines.
a) 500-6200 kJ/kW-h
b) 400-4200 kJ/kW-h
c) 500-5700 kJ/kW-h
d) none of the mentioned

View Answer

Answer: c [Reason:] The heat flow to water jackets, on an average, is about 500-5700 kJ/kW-h for small engines and is about 4200 kJ/kW-h for large engines.

5. The outlet cooling water temperature for large engines is
a) about 50ºC
b) 60 to 65ºC
c) 80ºC
d) none of the mentioned

View Answer

Answer: a [Reason:] The outlet cooling water temperature for large engines is about 50ºC and the outlet cooling water temperature for medium engines is 60 to 65ºC.

6. The outlet cooling water temperature for medium engines is
a) about 50ºC
b) 60 to 65ºC
c) 80ºC
d) none of the mentioned

View Answer

Answer: b [Reason:] The outlet cooling water temperature for medium engines is 60 to 65ºC and the outlet cooling water temperature for small engines is 80ºC.

7. The outlet cooling water temperature for small engines is
a) about 50ºC
b) 60 to 65ºC
c) 80ºC
d) none of the mentioned

View Answer

Answer: c [Reason:] The outlet cooling water temperature for small engines is 80ºC while the outlet cooling water temperature for medium engines is 60 to 65ºC and the outlet cooling water temperature for small engines is 80ºC.

8. In thermo-syphon system, the radiator should be kept well above the engine, to provide a height for natural circulation.
a) True
b) False

View Answer

Answer: a

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