McqMate
These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Mechanical Engineering .
Chapters
| 151. |
Ignition timing is adjusted by |
| A. | tachometer |
| B. | stroboscopic light |
| C. | stop watch |
| D. | accurate clock |
| Answer» B. stroboscopic light | |
| 152. |
Vacuum advance mechanism shifts the ignition point under |
| A. | no load operation |
| B. | full load operation |
| C. | part load operation |
| D. | under sudden acceleration |
| Answer» C. part load operation | |
| 153. |
Which of the following statement is wrong? |
| A. | retarded timing causes exhaust gas temperature to be higher |
| B. | retarded timing improves fuel economy |
| C. | retarded timing requires slightly longer throttle opening |
| D. | retarded timing causes burning of the hydrocarbons in the exhaust |
| Answer» D. retarded timing causes burning of the hydrocarbons in the exhaust | |
| 154. |
Choose the correct statement from the following |
| A. | maintenance problem in magneto-ignition system is more |
| B. | magneto ignition system occupies more space |
| C. | magneto ignition system is used in larger four wheelers |
| D. | magneto ignition system has poor quality of spark during starting |
| Answer» D. magneto ignition system has poor quality of spark during starting | |
| 155. |
Battery ignition system |
| A. | occupies more space |
| B. | has more maintenance problem |
| C. | is commonly employed in four wheelers |
| D. | all of the above |
| Answer» D. all of the above | |
| 156. |
Method of governing used in petrol engine is |
| A. | hit and miss governing. |
| B. | quality governing |
| C. | quantity governing |
| D. | none of above |
| Answer» C. quantity governing | |
| 157. |
Pick up the false statement |
| A. | Thermal efficiency of diesel engine i about 34% |
| B. | Theoretically correct mixture of air am 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. | |
| 158. |
The centrifugal type supercharger is preferable only for |
| A. | low speeds |
| B. | high speeds |
| C. | high pressures |
| D. | none of the above |
| Answer» A. low speeds | |
| 159. |
The advantage of Root's supercharger is |
| A. | big pressure |
| B. | minimum maintenance |
| C. | consumes less power |
| D. | occupies less space |
| Answer» B. minimum maintenance | |
| 160. |
Supercharging air compressor is driven by |
| A. | exhaust gas turbine |
| B. | engine itself |
| C. | separate electrical motor |
| D. | none of the above |
| Answer» B. engine itself | |
| 161. |
If turbochargers compressor is driven by |
| A. | exhaust gas turbine |
| B. | engine itself |
| C. | separate electrical motor |
| D. | none of the above |
| Answer» A. exhaust gas turbine | |
| 162. |
Cooling after compression is necessary to |
| A. | increase the density of air |
| B. | reduce engine operating temperatures |
| C. | both (a) and (b) |
| D. | increase exhaust temperature |
| Answer» C. both (a) and (b) | |
| 163. |
Volumetric efficiency of supercharged engine is |
| A. | between 100 - 110% |
| B. | between 90 - 100% |
| C. | between 80 - 90% |
| D. | between 70 - 80% |
| Answer» A. between 100 - 110% | |
| 164. |
Supercharging is normally done in |
| A. | racing cars |
| B. | marine engines |
| C. | automotive diesel engines |
| D. | none of the above |
| Answer» D. none of the above | |
| 165. |
Compared to engine driven supercharger the exhaust driven super charger is |
| A. | easy to handle |
| B. | supplies more air |
| C. | utilizes the exhaust energy of the engine |
| D. | matching with engine is easy |
| Answer» C. utilizes the exhaust energy of the engine | |
| 166. |
Types of supercharger are |
| A. | reciprocating type |
| B. | gear type |
| C. | centrifugal type |
| D. | none of the above |
| Answer» C. centrifugal type | |
| 167. |
The operation of forcing additional air under pressure in the engine cylinder is known as |
| A. | scavenging |
| B. | turbulence |
| C. | supercharging |
| D. | pre-ignition |
| Answer» C. supercharging | |
| 168. |
Supercharging is essential in |
| A. | diesel engines |
| B. | gas turbines |
| C. | petrol engines |
| D. | aircraft engines. |
| Answer» D. aircraft engines. | |
| 169. |
The output of a diesel engine can be increased without increasing the engine revolution or size in following way |
| A. | feeding more fuel |
| B. | increasing flywheel size |
| C. | heating incoming air |
| D. | supercharging. |
| Answer» D. supercharging. | |
| 170. |
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 load |
| 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 | |
| 171. |
Pick up the wrong statement about supercharging |
| A. | supercharging reduces knocking in diesel engines |
| B. | there can be limited supercharging in petrol engines because of detonation |
| C. | supercharging at high altitudes is essential |
| D. | supercharging results in fuel economy |
| Answer» D. supercharging results in fuel economy | |
| 172. |
The reason for supercharging in any engine is to |
| A. | increase efficiency |
| B. | increase power |
| C. | reduce weight and bulk for a given out-put |
| D. | effect fuel economy |
| Answer» C. reduce weight and bulk for a given out-put | |
| 173. |
For the same power developed in I.C. engines, the cheaper system is |
| A. | naturally aspirated |
| B. | supercharged |
| C. | centrifugal pump |
| D. | turbo charger |
| Answer» B. supercharged | |
| 174. |
In SI engines maximum flame speed is obtained when the equivalent ratio is between |
| A. | 1.1 and 1.2 |
| B. | 1.0 and 1.1 |
| C. | 1.2 and 1.3 |
| D. | less than 1 |
| Answer» A. 1.1 and 1.2 | |
| 175. |
In SI engines flame speed increases |
| A. | with turbulence |
| B. | with fuel-air ratio |
| C. | both (a) and (b) |
| D. | none of the above |
| Answer» C. both (a) and (b) | |
| 176. |
with increase in compression ratio flame speed |
| A. | increases |
| B. | decreases |
| C. | remains the same |
| D. | none of the above |
| Answer» A. increases | |
| 177. |
With increase in speed the crank angle required for fame propagation |
| A. | increases |
| B. | decreases |
| C. | not affected |
| D. | none of the above |
| Answer» C. not affected | |
| 178. |
Increasing the compression ratio in SI engines the knocking tendency |
| A. | decreases |
| B. | increases |
| C. | not affected |
| D. | none of the above |
| Answer» B. increases | |
| 179. |
Decreasing the cooling water temperature in SI engines the knocking tendency |
| A. | increases |
| B. | decreases |
| C. | not affected |
| D. | none of the above |
| Answer» B. decreases | |
| 180. |
Detonation in SI engines occur due to |
| A. | pre ignition of the charge before the spark |
| B. | sudden ignition of the charge before the spark |
| C. | autoignition of the charge after the spark in struck |
| D. | none of the above |
| Answer» C. autoignition of the charge after the spark in struck | |
| 181. |
Desirable characteristics of the combustion chamber for SI engines to avoid knock is |
| A. | small bore |
| B. | short ratio of fame path to bore |
| C. | absence of hot surfaces in the last region of the charge |
| D. | all of the above |
| Answer» D. all of the above | |
| 182. |
In CI engines with increase in compression ratio the delay period |
| A. | increases |
| B. | decreases |
| C. | first increases and then decreases |
| D. | not affected |
| Answer» C. first increases and then decreases | |
| 183. |
Knocking takes place in CI engines |
| A. | at the start of combustion |
| B. | at the end of combustion |
| C. | during combustion |
| D. | none of the above |
| Answer» A. at the start of combustion | |
| 184. |
In CI engines knocking tendency increases with |
| A. | increase in compression ratio |
| B. | increasing inlet temperature of air |
| C. | decrease in compression ratio |
| D. | increasing coolant water temperature |
| Answer» C. decrease in compression ratio | |
| 185. |
In CI engines by increasing inlet air pressure the knocking tendency |
| A. | increases |
| B. | decreases |
| C. | not affected |
| D. | first decreases and then increases |
| Answer» B. decreases | |
| 186. |
Open combustion chambers in CI engines require |
| A. | high injection pressures |
| B. | accurate metering of fuel by the injection system |
| C. | both (a) and (b) |
| D. | none of the above |
| Answer» C. both (a) and (b) | |
| 187. |
The advantages of the indirect injection combustion chambers are |
| A. | low injection pressure |
| B. | direction of spray is not critical |
| C. | both (a) and (b) |
| D. | good cold starting performance |
| Answer» C. both (a) and (b) | |
| 188. |
In CI engines the delay period is affected by |
| A. | compression ratio |
| B. | engine speed |
| C. | output |
| D. | all of the above |
| Answer» D. all of the above | |
| 189. |
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 occi simultaneously |
| D. | never occurs |
| Answer» A. first a mild explosion followed by a bi explosion | |
| 190. |
Compression loss in I.C engines occurs duto |
| 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. | |
| 191. |
It the temperature of intake air in IC engines is lowered, then its efficiency will |
| A. | increase |
| B. | decrease |
| C. | remain same |
| D. | increase upto certain limit and then decrease |
| Answer» A. increase | |
| 192. |
The precess of breaking up or a liquid into fine droplets by spraying is called |
| A. | vaporisation |
| B. | carburetion |
| C. | ionisation |
| D. | atomisation. |
| Answer» D. atomisation. | |
| 193. |
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» B. rate of rise of pressure | |
| 194. |
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 Caront 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 | |
| 195. |
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» D. effective compression ratio | |
| 196. |
In diesel engine the diesel fuel injected intc cylinder would burn instantly at about compressed air temperature of |
| A. | 250°C |
| B. | 500°C |
| C. | 1000°C |
| D. | 150CPC |
| Answer» C. 1000°C | |
| 197. |
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 | |
| 198. |
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» D. detonation | |
| 199. |
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. | engine derating i.e. reducing the maxi-mum flow of fuel |
| C. | increasing the compression ratio |
| D. | adherence to proper fuel specification |
| Answer» C. increasing the compression ratio | |
| 200. |
A high flame speed is obtained in diesel engine when air fuel ratio is |
| A. | uniform throughout the mixture |
| B. | chemically correct mixture |
| C. | about 3-5% rich mixture |
| D. | about 10% rich mixture |
| Answer» D. about 10% rich mixture | |
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