I.C Engines Objective Questions with Answers – Set 08

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Q1. In order to prevent knocking in spark ignition engines, the charge away from the spark plug should have

(A) Low density
(B) Low temperature
(C) Long ignition delay
(D) All of these

Answer: (D) All of these

Q2. If one cylinder of a diesel engine receives more fuel than the others, then for that cylinder the

(A) Exhaust will be smoky
(B) Piston rings would stick into piston grooves
(C) Engine starts overheating
(D) Scavenging occurs

Answer: (D) Scavenging occurs

Q3. As compared to air standard cycle, in actual working, the effect of variation in specific heats is to

(A) Increase maximum pressure and maximum temperature
(B) Reduce maximum pressure and maximum temperature
(C) Increase maximum pressure and decrease maximum temperature
(D) Decrease maximum pressure and increase maximum temperature

Answer: (B) Reduce maximum pressure and maximum temperature

Q4. Compression loss in I.C engines occurs due to

(A) Leaking piston rings
(B) Use of thick head gasket
(C) Clogged air inlet slots
(D) All of the above

Answer: (D) All of the above

Q5. The thermal efficiency of petrol and gas engines is about

(A) 15%
(B) 30%
(C) 50%
(D) 70%

Answer: (B) 30%

Q6. Which of the following is false statement? Some of the methods used to reduce diesel smoke are as follows

(A) Using additives in the fuel
(B) Increasing the compression ratio
(C) Adherence to proper fuel specification
(D) Avoidance of overloading

Answer: (B) Increasing the compression ratio

Q7. The advancing of spark timing in spark ignition engines will _ knocking tendency.

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

Answer: (A) Increase

Q8. A heat engine utilizes the

(A) Calorific value of oil
(B) Low heat value of
(C) High heat value of oil
(D) Mean heat value of oil

Answer: (C) High heat value of oil

Q9. In a four stroke cycle petrol engine, the charge is ignited at

(A) 30° before top dead center
(B) 30° after top dead center
(C) 30° before bottom dead center
(D) 30° after bottom dead center

Answer: (A) 30° before top dead center

Q10. The pressure inside the cylinder is _ the atmospheric pressure during the exhaust stroke.

(A) Equal to
(B) Below
(C) Above
(D) None of these

Answer: (A) 30° before top dead center

Q11. A fuel of cetane number 40 has the same ignition quality as a mixture of

(A) 40% cetane and 60% alpha methyl naphthalene
(B) 40% alpha methyl naphthalene and 60% cetane
(C) 40% petrol and 60% diesel
(D) 40% diesel and 60% petrol

Answer: (A) 40% cetane and 60% alpha methyl naphthalene

Q12. In a coil ignition system of petrol engines, a condenser is connected across the contact breaker in order to

(A) Prevent sparking across the gap between the points
(B) Cause more rapid break of the primary current, giving a higher voltage in the secondary circuit
(C) Both (A) and (B)
(D) None of the above

Answer: (C) Both (A) and (B)

Q13. The increase of cooling water temperature in petrol engine will _ the knocking tendency.

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

Answer: (C) Increase

Q14. The ignition of the charge by some hot surface within the engine before the passage of spark is called

(A) Pre-ignition
(B) Detonation
(C) Ignition delay
(D) Auto-ignition

Answer: (A) Pre-ignition

Q15. Supercharging is the process of

(A) Supplying the intake of an engine with air at a density greater than the density of the surrounding atmosphere
(B) Providing forced cooling air
(C) Injecting excess fuel for raising more loads
(D) Supplying compressed air to remove combustion products fully

Answer: (A) Supplying the intake of an engine with air at a density greater than the density of the surrounding atmosphere

Q16. Pick up the false statement

(A) Thermal efficiency of diesel engine is about 34%
(B) Theoretically correct mixture of air and petrol is approximately 15:1
(C) High speed compression engines operate on dual combustion cycle
(D) S.I. engines are quality governed engines

Answer: (D) S.I. engines are quality governed engines

Q17. The brake power (B.P.) of the engine is given by (where W = Brake load or dead load in newtons, l = Length of arm in meters, N = Speed of engine in r.p.m., S = Spring balance reading in newtons, D = Dia. of brake drum in meters, and d = Dia. of rope in meters)

(A) B.P = (Wl × 2πN)/60 watts
(B) B.P = [(W – S) πDN]/60 watts
(C) B.P = [(W – S) π (D + d) N]/60 watts
(D) All of these

Answer: (D) All of these

Q18. The actual volume of fresh charge admitted in 4-stroke petrol engine is

(A) Equal to stroke volume
(B) Equal to stroke volume and clearance volume
(C) Less than stroke volume
(D) More than stroke volume

Answer: (C) Less than stroke volume

Q19. Pre-ignition is caused by the spontaneous combustion of the mixture before the end of the compression stroke, and is due to

(A) Cylinder walls being too hot
(B) Overheated spark plug points
(C) Red hot carbon deposits on cylinder walls
(D) Any one of these

Answer: (D) Any one of these

Q20. Fuel consumption of diesel engines is not guaranteed at one quarter load because at such low loads

(A) The friction is high
(B) The friction is unpredictable
(C) The small difference in cooling water temperature or in internal friction has a disproportionate effect
(D) The engine is rarely operated

Answer: (C) The small difference in cooling water temperature or in internal friction has a disproportionate effect

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