MCQOPTIONS
Saved Bookmarks
MCQOPTIONS
This section includes 261 Mcqs, each offering curated multiple-choice questions to sharpen your GATE (Mechanical Engineering) knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
In a four stroke cycle petrol engine, the compression |
| A. | Starts at 40° after bottom dead centre and ends at 30° before top dead centre |
| B. | Starts at 40° before bottom dead centre and ends at 30° after bottom dead centre |
| C. | Starts at bottom dead centre and ends at top dead centre |
| D. | May start and end anywhere |
| Answer» B. Starts at 40° before bottom dead centre and ends at 30° after bottom dead centre | |
| 2. |
In a four stroke cycle diesel engine, the compression |
| A. | Starts at 40° after bottom dead center and ends at 10° before top dead center |
| B. | Starts at 40° before top dead center and ends at 40° after top dead center |
| C. | Starts at top dead center and ends at 40° before bottom dead center |
| D. | May start and end anywhere |
| Answer» B. Starts at 40° before top dead center and ends at 40° after top dead center | |
| 3. |
In compression ignition engines, swirl denotes a |
| A. | Haphazard motion of the gases in the chamber |
| B. | Rotary motion of the gases in the chamber |
| C. | Radial motion of the gases in the chamber |
| D. | None of the above |
| Answer» C. Radial motion of the gases in the chamber | |
| 4. |
The thermal efficiency of diesel engines on weak mixtures is |
| A. | Unaffected |
| B. | Lower |
| C. | Higher |
| D. | Dependent on other factors |
| Answer» D. Dependent on other factors | |
| 5. |
Fuel oil consumption guarantees for I .C. engine are usually based on |
| A. | Low heat value of oil |
| B. | High heat value of oil |
| C. | Net calorific value of oil |
| D. | Calorific value of fuel |
| Answer» C. Net calorific value of oil | |
| 6. |
The turbine of the turboprop engine is __________ that of the turbojet engine. |
| A. | Same as |
| B. | Smaller than |
| C. | Bigger than |
| D. | None of these |
| Answer» D. None of these | |
| 7. |
The inlet valve of a four stroke cycle internal combustion engine remains open for |
| A. | 130° |
| B. | 180° |
| C. | 230° |
| D. | 270° |
| Answer» D. 270° | |
| 8. |
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» E. | |
| 9. |
The ratio of the volume of charge admitted at N.T.P. to the swept volume of the piston is called |
| A. | Mechanical efficiency |
| B. | Overall efficiency |
| C. | Volumetric efficiency |
| D. | Relative efficiency |
| Answer» D. Relative efficiency | |
| 10. |
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» D. More than stroke volume | |
| 11. |
In a four stroke cycle engine, the sequence of operations is |
| A. | Suction, compression, expansion and exhaust |
| B. | Suction, expansion, compression and exhaust |
| C. | Expansion, compression, suction and exhaust |
| D. | Compression, expansion, suction and exhaust |
| Answer» B. Suction, expansion, compression and exhaust | |
| 12. |
Iso-octane (C₈H₁₈) has octane number of |
| A. | 0 |
| B. | 50 |
| C. | 100 |
| D. | 120 |
| Answer» D. 120 | |
| 13. |
The _________ engines can work on very lean mixture of fuel. |
| A. | Spark ignition |
| B. | Compression ignition |
| C. | Both (A) and (B) |
| D. | None of these |
| Answer» C. Both (A) and (B) | |
| 14. |
The air-fuel ratio in petrol engines is controlled by |
| A. | Controlling valve opening/closing |
| B. | Governing |
| C. | Injection |
| D. | Carburetion |
| Answer» E. | |
| 15. |
The air-fuel ratio of the petrol engine is controlled by |
| A. | Fuel pump |
| B. | Governor |
| C. | Injector |
| D. | Carburettor |
| Answer» E. | |
| 16. |
The method of determination of indicated power of a multi cylinder spark ignition engine is by the use of |
| A. | Morse test |
| B. | Prony brake test |
| C. | Motoring test |
| D. | Heat balance test |
| Answer» B. Prony brake test | |
| 17. |
The maximum propulsive efficiency of a turbojet engine is at a speed of |
| A. | 1000 km/h |
| B. | 2000 km/h |
| C. | 2400 km/h |
| D. | 3000 km/h |
| Answer» D. 3000 km/h | |
| 18. |
The knocking in diesel engines may be prevented by |
| A. | Reducing the delay period |
| B. | Raising the compression ratio |
| C. | Increasing the inlet pressure of air |
| D. | All of these |
| Answer» E. | |
| 19. |
The knocking tendency in spark ignition engines may be decreased by |
| A. | Controlling the air-fuel mixture |
| B. | Controlling the ignition timing |
| C. | Controlling the exhaust temperature |
| D. | Reducing the compression ratio |
| Answer» E. | |
| 20. |
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» D. 0.3 kg | |
| 21. |
The pressure at the end of compression, in petrol engines, is approximately |
| A. | 10 bar |
| B. | 20 bar |
| C. | 25 bar |
| D. | 35 bar |
| Answer» B. 20 bar | |
| 22. |
The pressure at the end of compression, in diesel engines, is approximately |
| A. | 10 bar |
| B. | 20 bar |
| C. | 25 bar |
| D. | 35 bar |
| Answer» E. | |
| 23. |
A gas engine has a swept volume of 300 cm3 and clearance volume of 25 cm3. Its volumetric efficiency is 0.88 and mechanical efficiency is 0.90. The volume of the mixture taken in per stroke is |
| A. | 248 cm3 |
| B. | 252 cm3 |
| C. | 264 cm3 |
| D. | 286 cm3 |
| Answer» D. 286 cm3 | |
| 24. |
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» B. 40% alpha methyl naphthalene and 60% cetane | |
| 25. |
A fuel of an octane number rating of 75 matches in knocking intensity as a mixture of |
| A. | 75% iso-octane and 25% normal heptane |
| B. | 75% normal heptane and 25% iso-octane |
| C. | 75% petrol and 25% diesel |
| D. | 75% diesel and 25% petrol |
| Answer» B. 75% normal heptane and 25% iso-octane | |
| 26. |
The sensing element in the control system of nuclear reactors measures the _________ of the neutron flux in the reactor. |
| A. | Temperature |
| B. | Volume |
| C. | Density |
| D. | None of these |
| Answer» D. None of these | |
| 27. |
Which of the following fuel has little tendency towards detonation? |
| A. | Benzene |
| B. | Iso-octane |
| C. | Normal heptane |
| D. | Alcohol |
| Answer» C. Normal heptane | |
| 28. |
The reflectivity depends upon |
| A. | Geometry of the reflector |
| B. | Energy of neutrons |
| C. | Properties of the reflector |
| D. | All of these |
| Answer» E. | |
| 29. |
Which is more viscous lube oil? |
| A. | SEA 30 |
| B. | SAE 50 |
| C. | SAE 70 |
| D. | SAE 80 |
| Answer» E. | |
| 30. |
The thermal efficiency of a diesel cycle having fixed compression ratio, with increase in cut-off ratio will |
| A. | Increase |
| B. | Decrease |
| C. | Be independent |
| D. | May increase or decrease depending on other factors |
| Answer» C. Be independent | |
| 31. |
Crankcase explosion in I.C. engines usually occurs as |
| A. | First a mild explosion followed by a bi explosion |
| B. | First a big explosion followed by a mil explosion |
| C. | Both mild and big explosions occurs simultaneously |
| D. | Never occurs |
| Answer» B. First a big explosion followed by a mil explosion | |
| 32. |
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» D. Low volumetric efficiency | |
| 33. |
Which of the following is false statement?Excess quantities of sulphur in diesel fuel are Objectionable because it may cause the following |
| A. | Piston ring and cylinder wear |
| B. | Formation of hard coating on piston skirts |
| C. | Oil sludge in the engine crank case |
| D. | Detonation |
| Answer» E. | |
| 34. |
If V₁ is the jet velocity and V₀ is the vehicle velocity, then propulsive efficiency of a turbojet engine is |
| A. | V₁ / (V₀ + V₁) |
| B. | V₀ / (V₀ + V₁) |
| C. | 2V₀ / (V₀ + V₁) |
| D. | 2V₁ / (V₀ + V₁) |
| Answer» D. 2V₁ / (V₀ + V₁) | |
| 35. |
The accumulation of carbon in a cylinder results in increase of |
| A. | Clearance volume |
| B. | Volumetric efficiency |
| C. | Ignition time |
| D. | Effective compression ratio |
| Answer» E. | |
| 36. |
The thermal efficiency of a petrol engine is _________ as compared to diesel engine. |
| A. | Same |
| B. | Less |
| C. | More |
| D. | None of these |
| Answer» C. More | |
| 37. |
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» C. Period of ignition | |
| 38. |
A petrol engine, during suction stroke draws |
| A. | Air only |
| B. | Petrol only |
| C. | A mixture of petrol and air |
| D. | None of these |
| Answer» D. None of these | |
| 39. |
In a four stroke cycle diesel engine, the exhaust valve |
| A. | Opens at 30° before bottom dead centre and closes at 10° after top dead centre |
| B. | Opens at 30° after bottom dead centre and closes at 10° before top dead centre |
| C. | Opens at bottom dead centre and closes at top dead centre |
| D. | May open and close anywhere |
| Answer» B. Opens at 30° after bottom dead centre and closes at 10° before top dead centre | |
| 40. |
By higher octane number of spark ignition fuel, it is meant that the fuel has |
| A. | Higher heating value |
| B. | Higher flash point |
| C. | Lower volatility |
| D. | Longer ignition delay |
| Answer» E. | |
| 41. |
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» E. | |
| 42. |
The rating of a diesel engine, with increase in air inlet temperature, will |
| A. | Increase linearly |
| B. | Decrease linearly |
| C. | Increase parabolically |
| D. | Decrease parabolically |
| Answer» C. Increase parabolically | |
| 43. |
Gaseous fuel guarantees are based on |
| A. | Calorific value of oil |
| B. | Low heat value of oil |
| C. | High heat value of oil |
| D. | Mean heat value of oil |
| Answer» C. High heat value of oil | |
| 44. |
In a petrol engine, the mixture has the lowest pressure at the |
| A. | Beginning of suction stroke |
| B. | End of suction stroke |
| C. | End of compression stroke |
| D. | None of these |
| Answer» C. End of compression stroke | |
| 45. |
The injector nozzle of a compression ignition engine is required to inject fuel at a sufficiently high pressure in order to |
| A. | Inject fuel in a chamber of high pressure at the end of compression stroke |
| B. | Inject fuel at a high velocity to facilitate atomization |
| C. | Ensure that penetration is not high |
| D. | All of the above |
| Answer» E. | |
| 46. |
In a four stroke cycle petrol engine, the pressure inside the engine cylinder during the suction stroke is __________ the atmospheric pressure. |
| A. | Equal to |
| B. | Below |
| C. | Above |
| D. | None of these |
| Answer» C. Above | |
| 47. |
A higher compression ratio causes |
| A. | Pre-ignition |
| B. | Increase in detonation |
| C. | Acceleration in the rate of combustion |
| D. | Any one of these |
| Answer» E. | |
| 48. |
As a result of detonation in an I.C. engine, following parameter attains very high value |
| A. | Peak pressure |
| B. | Rate of rise of pressure |
| C. | Rate of rise of temperature |
| D. | Peak temperature |
| Answer» C. Rate of rise of temperature | |
| 49. |
In petrol engines, the delay period is of the order of |
| A. | 0.001 second |
| B. | 0.002 second |
| C. | 0.003 second |
| D. | 0.004 second |
| Answer» C. 0.003 second | |
| 50. |
For maximum power generation, the air fuel ratio for a petrol engine for vehicles, is of the order of |
| A. | 9 : 1 |
| B. | 12 : 1 |
| C. | 15 : 1 |
| D. | 18 : 1 |
| Answer» C. 15 : 1 | |