MCQOPTIONS
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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.
| 151. |
The effective inhibitor of pre-ignition is |
| A. | Alcohol |
| B. | Water |
| C. | Lead |
| D. | None of these |
| Answer» C. Lead | |
| 152. |
Compression ratio of I.C. Engines is |
| A. | The ratio of volumes of air in cylinder before compression stroke and after compression stroke |
| B. | Volume displaced by piston per stroke and clearance volume in cylinder |
| C. | Ratio of pressure after compression and before compression |
| D. | Swept volume/cylinder volume |
| Answer» B. Volume displaced by piston per stroke and clearance volume in cylinder | |
| 153. |
The function of a distributor in a coil ignition system of I.C. engines is |
| A. | To distribute spark |
| B. | To distribute power |
| C. | To distribute current |
| D. | To time the spark |
| Answer» E. | |
| 154. |
Which of the following fuel detonates readily? |
| A. | Benzene |
| B. | Iso-octane |
| C. | Normal heptane |
| D. | Alcohol |
| Answer» D. Alcohol | |
| 155. |
The air requirement of a petrol engine during starting compared to theoretical air required for complete combustion is |
| A. | More |
| B. | Less |
| C. | Same |
| D. | May be more or less depending on engine capacity |
| Answer» C. Same | |
| 156. |
Number of working strokes per min. for a two stroke cycle engine is _________ the speed of the engine in r.p.m. |
| A. | Equal to |
| B. | One-half |
| C. | Twice |
| D. | Four-times |
| Answer» B. One-half | |
| 157. |
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» C. Twice | |
| 158. |
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» B. Air and fuel | |
| 159. |
Scavenging is usually done to increase |
| A. | Thermal efficiency |
| B. | Speed |
| C. | Power output |
| D. | Fuel consumption |
| Answer» D. Fuel consumption | |
| 160. |
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» E. | |
| 161. |
A petrol engine has compression ratio from |
| A. | 6 to 10 |
| B. | 10 to 15 |
| C. | 15 to 25 |
| D. | 25 to 40 |
| Answer» B. 10 to 15 | |
| 162. |
A diesel engine has compression ratio from |
| A. | 6 to 10 |
| B. | 10 to 15 |
| C. | 15 to 25 |
| D. | 25 to 40 |
| Answer» D. 25 to 40 | |
| 163. |
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 |
| Answer» D. Black smoke will be produced | |
| 164. |
Scavenging air in diesel engine means |
| A. | Air used for combustion sent under pressure |
| B. | Forced air for cooling cylinder |
| C. | Burnt air containing products of combustion |
| D. | Air used for forcing burnt gases out of engine's cylinder during the exhaust period |
| Answer» E. | |
| 165. |
The air standard efficiency of an I.C. engine depends on |
| A. | Fuel used |
| B. | Speed of engine |
| C. | Compression ratio |
| D. | None of these |
| Answer» D. None of these | |
| 166. |
The self ignition temperature of petrol is _________ as compared to diesel oil. |
| A. | Same |
| B. | Lower |
| C. | Higher |
| D. | None of these |
| Answer» D. None of these | |
| 167. |
The fuel in diesel engine is normally injected at pressure of |
| A. | 5-10 kg/cm² |
| B. | 20-25 kg/cm² |
| C. | 60-80 kg/cm² |
| D. | 90-130 kg/cm² |
| Answer» E. | |
| 168. |
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» D. None of the above | |
| 169. |
Which one of the following engines will have heavier flywheel than the remaining ones? |
| A. | 30 kW four-stroke petrol engine running at 1500 r.p.m. |
| B. | 30 kW two-stroke petrol engine running at 1500 r.p.m. |
| C. | 30 kW two-stroke diesel engine running at 750 r.p.m. |
| D. | 30 kW four-stroke diesel engine running at 750 r.p.m. |
| Answer» B. 30 kW two-stroke petrol engine running at 1500 r.p.m. | |
| 170. |
The brake power is the power available |
| A. | In the engine cylinder |
| B. | At the crank shaft |
| C. | At the crank pin |
| D. | None of these |
| Answer» C. At the crank pin | |
| 171. |
The pressure and temperature at the end of compression stroke in a petrol engine are of the order of |
| A. | 4-6 kg/cm² and 200-250°C |
| B. | 6-12 kg/cm² and 250-350°C |
| C. | 12-20 kg/cm² and 350-450°C |
| D. | 20-30 kg/cm² and 450-500°C |
| Answer» C. 12-20 kg/cm² and 350-450°C | |
| 172. |
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» D. None of these | |
| 173. |
A diesel engine has |
| A. | 1 valve |
| B. | 2 valves |
| C. | 3 valves |
| D. | 4 valves |
| Answer» D. 4 valves | |
| 174. |
In a four stroke cycle, the minimum temperature inside the engine cylinder occurs at the |
| A. | Beginning of suction stroke |
| B. | End of suction stroke |
| C. | Beginning of exhaust stroke |
| D. | End of exhaust stroke |
| Answer» B. End of suction stroke | |
| 175. |
The fuel valve in a four stroke cycle diesel engine |
| A. | Opens at 15° after top dead center and closes at 20° before bottom dead center |
| B. | Opens at 15° before top dead center and closes at 20° after top dead center |
| C. | Opens at top dead center and closes at bottom dead center |
| D. | May open and close anywhere |
| Answer» C. Opens at top dead center and closes at bottom dead center | |
| 176. |
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» D. May start and end anywhere | |
| 177. |
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» C. Increase maximum pressure and decrease maximum temperature | |
| 178. |
The two reference fuels used for cetane rating are |
| A. | Cetane and iso-octane |
| B. | Cetane and alpha-methyl naphthalene |
| C. | Cetane and normal heptane |
| D. | Cetane and tetra ethyl lead |
| Answer» C. Cetane and normal heptane | |
| 179. |
The ratio of the brake power to the indicated power is called |
| A. | Mechanical efficiency |
| B. | Overall efficiency |
| C. | Indicated thermal efficiency |
| D. | Volumetric efficiency |
| Answer» B. Overall efficiency | |
| 180. |
For the same compression ratio |
| A. | Otto cycle is more efficient than the Diesel |
| B. | Diesel cycle is more efficient than Otto |
| C. | Both Otto and Diesel cycles are, equally efficient |
| D. | Compression ratio has nothing to do with efficiency |
| Answer» B. Diesel cycle is more efficient than Otto | |
| 181. |
The exhaust valve in a four stroke cycle petrol engine |
| A. | Opens at 50° before bottom dead center and closes at 15° after top dead center |
| B. | Opens at bottom dead center and closes at top dead center |
| C. | Opens at 50° after bottom dead center and closes at 15° before top dead center |
| D. | May open and close anywhere |
| Answer» B. Opens at bottom dead center and closes at top dead center | |
| 182. |
The knocking in spark ignition engines can be reduced by |
| A. | Retarding the spark |
| B. | Increasing the engine speed |
| C. | Both (A) and (B) |
| D. | None of these |
| Answer» D. None of these | |
| 183. |
The purpose of testing an internal combustion engine is |
| A. | To determine the information, which cannot be obtained by calculations |
| B. | To conform the data used in design, the validity of which may be doubtful |
| C. | To satisfy the customer regarding the performance of the engine |
| D. | All of the above |
| Answer» E. | |
| 184. |
The magneto in an automobile is basically |
| A. | Transformer |
| B. | D.C. generator |
| C. | Capacitor |
| D. | Magnetic circuit |
| Answer» C. Capacitor | |
| 185. |
The fuel air ratio in a petrol engine fitted with suction carburettor, operating with dirty air filter as compared to clean filter will be |
| A. | Higher |
| B. | Lower |
| C. | Remain unaffected |
| D. | None of the above |
| Answer» B. Lower | |
| 186. |
A two stroke cycle engine gives ________ the number of power strokes as compared to the four stroke cycle engine, at the same engine speed. |
| A. | Half |
| B. | Same |
| C. | Double |
| D. | Four times |
| Answer» D. Four times | |
| 187. |
An hmh flame speed is obtained in diesel engine when air fuel ratio is |
| A. | Uniform throughout the mixture |
| B. | Chemically correct mixture |
| C. | About 35% of rich mixture |
| D. | About 10% of rich mixture |
| Answer» E. | |
| 188. |
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» D. The engine is rarely operated | |
| 189. |
Diesel as compared to petrol is |
| A. | Highly ignitable |
| B. | More difficult to ignite |
| C. | Less difficult to ignite |
| D. | None of these |
| Answer» C. Less difficult to ignite | |
| 190. |
Diesel engine can work on very lean air fuel ratio of the order of 30: 1. A petrol engine can also work on such a lean ratio provided |
| A. | It is properly designed |
| B. | Best quality fuel is used |
| C. | Cannot work as it is impossible |
| D. | Flywheel size is proper |
| Answer» D. Flywheel size is proper | |
| 191. |
The theoretically correct mixture of air and petrol is |
| A. | 10 : 1 |
| B. | 15 : 1 |
| C. | 20 : 1 |
| D. | 25 : 1 |
| Answer» C. 20 : 1 | |
| 192. |
Polymerization is a chemical process in which molecules of a compound become |
| A. | Larger |
| B. | Slowed down |
| C. | Smaller |
| D. | Liquid |
| Answer» B. Slowed down | |
| 193. |
The cam shaft of a four stroke I.C. engine running at 1500 rpm will run at |
| A. | 1500 rpm |
| B. | 750 rpm |
| C. | 3000 rpm |
| D. | Any value independent of engine speed |
| Answer» C. 3000 rpm | |
| 194. |
During idling, a petrol engine requires _________ mixture. |
| A. | Lean |
| B. | Rich |
| C. | Chemically correct |
| D. | None of these |
| Answer» C. Chemically correct | |
| 195. |
The increase in intake temperature of internal combustion engines will _________ efficiency. |
| A. | Have no effect on |
| B. | Increase |
| C. | Decrease |
| D. | None of these |
| Answer» D. None of these | |
| 196. |
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. | Carburettor |
| D. | None of these |
| Answer» D. None of these | |
| 197. |
The normal heptane (C₇H₁₆) is given a rating of ________ octane number. |
| A. | 0 |
| B. | 50 |
| C. | 100 |
| D. | 120 |
| Answer» B. 50 | |
| 198. |
In order to eliminate knocking in compression ignition engines, there should be |
| A. | Short delay period |
| B. | Late auto-ignition |
| C. | Low compression ratio |
| D. | High self ignition temperature of fuel |
| Answer» B. Late auto-ignition | |
| 199. |
In a four stroke cycle petrol engine, the inlet valve |
| A. | Opens at top dead center and closes at bottom dead center |
| B. | Opens at 20° before top dead center and closes at 40° after bottom dead center |
| C. | Opens at 20° after top dead center and closes at 20° before bottom dead center |
| D. | May open or close anywhere |
| Answer» C. Opens at 20° after top dead center and closes at 20° before bottom dead center | |
| 200. |
In a four stroke cycle diesel engine, the inlet valve |
| A. | Opens at 20° before top dead center and closes at 40° after bottom dead center |
| B. | Opens at 20° after top dead center and closes at 20° before bottom dead center |
| C. | Opens at top dead center and closes at bottom dead center |
| D. | May open and close anywhere |
| Answer» B. Opens at 20° after top dead center and closes at 20° before bottom dead center | |