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.
| 101. |
A supercharged engine as compared to an ordinary engine |
| A. | Requires smaller foundation |
| B. | Is lighter |
| C. | Consumes less lubricating oil |
| D. | All of these |
| Answer» E. | |
| 102. |
The brake power of a diesel engine, keeping other parameters constant, can be increased by |
| A. | Decreasing the density of intake air |
| B. | Increasing the temperature of intake air |
| C. | Increasing the pressure of intake air |
| D. | Decreasing the pressure of intake air |
| Answer» D. Decreasing the pressure of intake air | |
| 103. |
The ratio of the work obtained at the crankshaft in a given time to the energy supplied during the same time is called |
| A. | Mechanical efficiency |
| B. | Overall efficiency |
| C. | Indicated thermal efficiency |
| D. | Volumetric efficiency |
| Answer» C. Indicated thermal efficiency | |
| 104. |
The cetane number of diesel oil, generally available, is |
| A. | 20 to 25 |
| B. | 25 to 30 |
| C. | 30 to 40 |
| D. | 40 to 55 |
| Answer» E. | |
| 105. |
The octane number of petrol, generally available, is |
| A. | 20 to 40 |
| B. | 40 to 60 |
| C. | 60 to 80 |
| D. | 80 to 100 |
| Answer» E. | |
| 106. |
In a typical medium speed 4-stroke cycle diesel engines |
| A. | Exhaust valve opens at 35° before bottom dead center and closes at 20° after top dead center |
| B. | Exhaust valve opens at bottom dead center and closes at top dead center |
| C. | Exhaust valve opens just after bottom dead center and closes just before top dead center |
| D. | May open and close anywhere |
| Answer» B. Exhaust valve opens at bottom dead center and closes at top dead center | |
| 107. |
The ignition quality of diesel oil is expressed by |
| A. | Cetane number |
| B. | Octane number |
| C. | Calorific value |
| D. | None of these |
| Answer» B. Octane number | |
| 108. |
The ignition quality of petrol is expressed by |
| A. | Cetane number |
| B. | Octane number |
| C. | Calorific value |
| D. | All of these |
| Answer» C. Calorific value | |
| 109. |
The specific fuel consumption per B.P. hour for a diesel engine is about |
| A. | 0.2 kg |
| B. | 0.25 kg |
| C. | 0.3 kg |
| D. | 0.35 kg |
| Answer» B. 0.25 kg | |
| 110. |
The specific fuel consumption per B.P. hour for a petrol engine is about |
| A. | 0.2 kg |
| B. | 0.25 kg |
| C. | 0.3 kg |
| D. | 0.35 kg |
| Answer» C. 0.3 kg | |
| 111. |
The injection pressure in a diesel engine is about |
| A. | 10 bar |
| B. | 100 bar |
| C. | 150 bar |
| D. | 500 bar |
| Answer» C. 150 bar | |
| 112. |
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» C. Remain same | |
| 113. |
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» E. | |
| 114. |
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» C. Adherence to proper fuel specification | |
| 115. |
The knocking tendency in compression ignition engines for a given fuel will be |
| A. | Enhanced by decreasing compression ratio |
| B. | Enhanced by increasing compression ratio |
| C. | Dependent on other factors |
| D. | None of the above |
| Answer» B. Enhanced by increasing compression ratio | |
| 116. |
The fuels in order of decreasing knock tendency for spark ignition engines are |
| A. | Paraffin, aromatic, napthene |
| B. | Paraffin, napthene, aromatic |
| C. | Napthene, aromatics, paraffin |
| D. | Napthene, paraffin, aromatic |
| Answer» C. Napthene, aromatics, paraffin | |
| 117. |
A carburettor is used to supply |
| A. | Petrol, air and lubricating oil |
| B. | Air and diesel |
| C. | Petrol and lubricating oil |
| D. | Petrol and air |
| Answer» E. | |
| 118. |
A spark plug gap is kept from |
| A. | 0.3 to 0.7 mm |
| B. | 0.2 to 0.8 mm |
| C. | 0.4 to 0.9 mm |
| D. | 0.6 to 1.0 mm |
| Answer» B. 0.2 to 0.8 mm | |
| 119. |
The size of inlet valve of an engine in comparison to exhaust valve is |
| A. | More |
| B. | Less |
| C. | Same |
| D. | More/less depending on capacity of engine |
| Answer» B. Less | |
| 120. |
The thermal efficiency of diesel engines is about |
| A. | 15% |
| B. | 30% |
| C. | 50% |
| D. | 70% |
| Answer» E. | |
| 121. |
The thermal efficiency of petrol and gas engines is about |
| A. | 15% |
| B. | 30% |
| C. | 50% |
| D. | 70% |
| Answer» C. 50% | |
| 122. |
The thermodynamic cycle on which the petrol engine works, is |
| A. | Otto cycle |
| B. | Joule cycle |
| C. | Rankine cycle |
| D. | Stirling cycle |
| Answer» B. Joule cycle | |
| 123. |
Solid fuel fabricated into various small shapes, which are assembled to form fuel elements, is in the form of |
| A. | Plates |
| B. | Pallets |
| C. | Pins |
| D. | All of these |
| Answer» E. | |
| 124. |
In a petrol engine, the fuel supplied to the engine cylinder is mixed with required quantity of air and the mixture is ignited with a |
| A. | Fuel pump |
| B. | Fuel injector |
| C. | Spark plug |
| D. | None of these |
| Answer» D. None of these | |
| 125. |
Detonation is harmful due to |
| A. | Increase in the rate of heat transfer, there is a reduction in the power output and efficiency of the engine |
| B. | Excessive turbulence which removes most of the insulating gas boundary layer from the cylinder walls |
| C. | High intensity of knock causes crankshaft vibration and the engine runs rough |
| D. | None of the above |
| Answer» E. | |
| 126. |
In diesel engine the diesel fuel injected into cylinder would burn instantly at about compressed air temperature of |
| A. | 250°C |
| B. | 500°C |
| C. | 1000°C |
| D. | 2000°C |
| Answer» D. 2000°C | |
| 127. |
A diesel engine, during suction stroke, draws |
| A. | Air only |
| B. | Diesel only |
| C. | A mixture of diesel and air |
| D. | None of these |
| Answer» B. Diesel only | |
| 128. |
The object of providing masked inlet valve in the air passage of compression ignition engines is to |
| A. | Enhance flow rate |
| B. | Control air flow |
| C. | Induce primary swirl |
| D. | Induce secondary turbulence |
| Answer» D. Induce secondary turbulence | |
| 129. |
Stoichiometric ratio is |
| A. | Chemically correct air-fuel ratio by weight |
| B. | Chemically correct air-fuel ratio by volume |
| C. | Actual air-fuel ratio for maximum efficiency |
| D. | None of the above |
| Answer» C. Actual air-fuel ratio for maximum efficiency | |
| 130. |
The thermal efficiency of a standard Otto cycle for a compression ratio of 5.5 will be |
| A. | 25% |
| B. | 50% |
| C. | 70% |
| D. | 100% |
| Answer» C. 70% | |
| 131. |
The object of supercharging the engine is |
| A. | To reduce mass of the engine per brake power |
| B. | To reduce space occupied by the engine |
| C. | To increase the power output of an engine when greater power is required |
| D. | All of the above |
| Answer» E. | |
| 132. |
The delay period in compression ignition engines depends upon |
| A. | Temperature and pressure in the cylinder at the time of injection |
| B. | Nature of the fuel mixture strength |
| C. | Relative velocity between the fuel injection and air turbulence pressure of residual gases |
| D. | All of the above |
| Answer» E. | |
| 133. |
Morse test is used to determine the I.P. of a |
| A. | Single cylinder petrol engine |
| B. | Four stroke engine |
| C. | Single cylinder diesel engine |
| D. | Multi cylinder engine |
| Answer» E. | |
| 134. |
An engine indicator is used to determine the following |
| A. | Speed |
| B. | Temperature |
| C. | Volume of cylinder |
| D. | m.e.p. and I.H.P. |
| Answer» E. | |
| 135. |
In an internal combustion engine, the process of removing the burnt gases from the combustion chamber of the engine cylinder is known as |
| A. | Scavenging |
| B. | Detonation |
| C. | Supercharging |
| D. | Polymerisation |
| Answer» B. Detonation | |
| 136. |
The operation of forcing additional air under pressure into the engine cylinder is known as |
| A. | Supercharging |
| B. | Carburetion |
| C. | Turbulence |
| D. | Delay period |
| Answer» B. Carburetion | |
| 137. |
Installation of supercharger on a four cycle diesel engine can result in the following percentage increase in power |
| A. | Up to 35% |
| B. | Up to 50% |
| C. | Up to 75% |
| D. | Up to 100% |
| Answer» E. | |
| 138. |
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» E. | |
| 139. |
If the speed of the engine is increased, the indicated power will |
| A. | Increase |
| B. | Decrease |
| C. | Remain same |
| D. | None of these |
| Answer» B. Decrease | |
| 140. |
A mixture containing 65% of iso-octane and 35% of normal heptane will have |
| A. | Cetane number 65 |
| B. | Octane number 65 |
| C. | Cetane number 35 |
| D. | Octane number 35 |
| Answer» C. Cetane number 35 | |
| 141. |
In the opposed piston diesel engine, the combustion chamber is located |
| A. | Above the piston |
| B. | Below the piston |
| C. | Between the pistons |
| D. | There is no such criterion |
| Answer» D. There is no such criterion | |
| 142. |
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» D. Mean heat value of oil | |
| 143. |
The colour of exhaust from diesel engine is generally |
| A. | White |
| B. | Bluish |
| C. | Black |
| D. | Violet |
| Answer» D. Violet | |
| 144. |
The firing order in an I.C. engine depends upon |
| A. | Arrangement of the cylinders |
| B. | Design of crankshaft |
| C. | Number of cylinders |
| D. | All of these |
| Answer» E. | |
| 145. |
Which of the following statement is correct regarding petrol engines? |
| A. | A fine fuel spray mixed with air is ignited by the heat of compression which is at a high pressure |
| B. | The fuel supplied to the engine cylinder is mixed with necessary amount of air and the mixture in ignited with the help of a spark plug |
| C. | The fuel is first evaporated after passing through a carburettor and is mixed with air before ignition |
| D. | All of the above |
| Answer» C. The fuel is first evaporated after passing through a carburettor and is mixed with air before ignition | |
| 146. |
If the compression ratio of an engine working on Otto cycle is increased from 5 to 7, the percentage increase in efficiency will be |
| A. | 2% |
| B. | 4% |
| C. | 8% |
| D. | 14% |
| Answer» E. | |
| 147. |
The frictional power (F.P.) is given by |
| A. | F.P. = B.P. - I.P. |
| B. | F.P. = I.P. - B.P. |
| C. | F.P. = B.P./I.P. |
| D. | F.P. = I.P./B.P. |
| Answer» C. F.P. = B.P./I.P. | |
| 148. |
The air standard efficiency of an I.C. engine is given by (where r = Compression ratio, and γ = Ratio of specific heats) |
| A. | 1 - rγ - 1 |
| B. | 1 + rγ - 1 |
| C. | 1 - (1/rγ - 1) |
| D. | None of these |
| Answer» D. None of these | |
| 149. |
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» B. Detonation | |
| 150. |
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» E. | |