I.C Engines Objective Questions with Answers – Set 05

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Q1. The thermal efficiency of diesel engines on weak mixtures is

(A) Unaffected
(B) Lower
(C) Higher
(D) Dependent on other factors

Answer: (C) Higher


Q2. The expansion of fuel in a four stroke cycle diesel engine

(A) Starts at 15° before top dead center and ends at 30° after top dead center
(B) Starts at top dead center and ends at 30° after top dead center
(C) Starts at 15° after top dead center and ends at 30° before bottom dead center
(D) May start and end anywhere

Answer: (C) Starts at 15° after top dead center and ends at 30° before bottom dead center


Q3. The scavenging efficiency of a four stroke cycle diesel engine is

(A) Below 50%
(B) Between 50 and 85%
(C) Between 85 and 95%
(D) Between 95 and 100%

Answer: (D) Between 95 and 100%


Q4. The thermal efficiency of a petrol engine is _ as compared to diesel engine.

(A) Same
(B) Less
(C) More
(D) None of these

Answer: (B) Less


Q5. If the compression ratio in I.C. engine increases, then its thermal efficiency will

(A) Decrease
(B) Increase
(C) Remain same
(D) None of these

Answer: (B) Increase


Q6. Number of working strokes per min. for a four stroke cycle engine are _ the speed of the engine in r.p.m.

(A) Equal to
(B) One-half
(C) Twice
(D) Four-times

Answer: (B) One-half


Q7. Pour point of fuel oil is the

(A) Minimum temperature to which oil is heated in order to give off inflammable vapours in sufficient quantity to ignite momentarily when brought in contact with a flame
(B) Temperature at which it solidifies or congeals
(C) It catches fire without external aid
(D) Indicated by 90% distillation temperature i.e., when 90% of sample oil has distilled off

Answer: (B) Temperature at which it solidifies or congeals


Q8. Which of the following medium is compressed in a Diesel engine cylinder?

(A) Air alone
(B) Air and fuel
(C) Air and lub oil
(D) Fuel alone

Answer: (A) Air alone


Q9. The spark ignition engines are governed by

(A) Hit and miss governing
(B) Qualitative governing
(C) Quantitative governing
(D) Combination of (B) and (C)

Answer: (C) Quantitative governing


Q10. The process of breaking up or a liquid into fine droplets by spraying is called

(A) Vaporisation
(B) Carburetion
(C) Ionization
(D) Atomization

Answer: (D) Atomization


Q11. The ratio of the indicated thermal efficiency to the air standard efficiency is known as

(A) Mechanical efficiency
(B) Overall efficiency
(C) Volumetric efficiency
(D) Relative efficiency

Answer: (D) Relative efficiency


Q12. The specific fuel consumption per BH hour for a petrol engine is approximately

(A) 0.15 kg
(B) 0.2 kg
(C) 0.25 kg
(D) 0.3 kg

Answer: (C) 0.25 kg


Q13. Which one of the following event would reduce volumetric efficiency of a vertical compression ignition engine?

(A) Inlet valve closing after bottom dead center
(B) Inlet valve closing before bottom dead center
(C) Inlet valve opening before top dead center
(D) Exhaust valve closing after top dead center

Answer: (B) Inlet valve closing before bottom dead center


Q14. Which of the following statements is correct?

(A) All the irreversible engines have same efficiency
(B) All the reversible engines have same efficiency
(C) Both Rankine and Carnot cycles have same efficiency between same temperature limits
(D) All reversible engines working between same temperature limits have same efficiency

Answer:(D) All reversible engines working between same temperature limits have same efficiency


Q15. The basic requirement of a good combustion chamber is

(A) Minimum turbulence
(B) Low compression ratio
(C) High thermal efficiency and power output
(D) Low volumetric efficiency

Answer: (C) High thermal efficiency and power output


Q16. In a cycle, the spark lasts roughly for

(A) 1 sec
(B) 0.1 sec
(C) 0.01 sec
(D) 0.001 sec

Answer: (D) 0.001 sec


Q17. The higher combustion chamber wall temperature in compression ignition engines will _ knocking tendency.

(A) Increase
(B) Reduce
(C) Not effect
(D) None of these

Answer: (B) Reduce


Q18. Combustion in compression ignition engines is

(A) Homogeneous
(B) Heterogeneous
(C) Both (A) and (B)
(D) Laminar

Answer: (B) Heterogeneous


Q19. In a diesel engine, the duration between the time of injection and ignition, is known as

(A) Pre-ignition period
(B) Delay period
(C) Period of ignition
(D) Burning period

Answer: (B) Delay period


Q20. If the speed of the engine is increased, the indicated power will

(A) Increase
(B) Decrease
(C) Remain same
(D) None of these

Answer: (A) Increase


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