RRB JE Mechanical-IC ENGINE Questionbank 3

Mechanical-Engineering

The thermal efficiency of the theoretical Otto cycle increases with an increase in —-? (RRB JE (Shift-2), 29.8.2015)

• Compression ratio
• Compression ratio
• Specific heat ratio
• None of these

Explanation:

• The thermal efficiency of the theoretical Otto cycle increases with an increase in compression ratio.

By higher octane number of SI fuel, it is meant that the fuel has —-? (RRB JE (Shift-2), 29.8.2015)

• Higher heating value
• Higher flash point
• Lower volatility
• Longer ignition delay

Explanation:

• Higher octane number indicates longer ignition delay which prevents knocking. Higher octane is desirable for petrol engines.

Petrol is used in which cycle? (RRB JE (Shift-1), 28.08.2015)

• Otto cycle
• Diesel cycle
• Rankine cycle
• Carnot cycle

Explanation:

• Petrol is used in Otto cycle. Processes: 1-2 Isentropic compression, 2-3 Constant volume heat addition, 3-4 Isentropic expansion, 4-1 Constant volume heat rejection.

The float in the carburetor of a petrol engine controls —-? (RRB JE Bhopal Paper-1 (Shift-I), 28.08.2015)

• Flow rate of air
• Flow rate of fuel
• Flow rate of air-fuel mixture
• Level of the petrol in the float chamber

Explanation:

• The float in a carburetor controls the level of fuel in the float chamber. Carburation is influenced by engine speed, incoming air temperature, and fuel vaporization characteristics.

In a variable speed SI engine, the maximum torque occurs at the maximum —-? (RRB SSE (Shift-I), 03.09.2015)

• volumetric efficiency
• brake power
• indicated power
• speed

Explanation:

• In a variable speed SI engine, maximum torque occurs at maximum brake power. BP = 2πNT/60, so when BP is maximum, torque is also maximum.

Which type of engine is used in heavy commercial vehicle? (RRB SSE (Shift-III), 03.09.2015)

• diesel
• petrol
• compressed air
• LPG

Explanation:

• Diesel engines are used in heavy commercial vehicles due to greater compression resistance, higher compression ratio, and bigger flywheel generating maximum torque.

The given P-V diagram indicates the following cycle —-? (RRB JE (Shift-III), 26.08.2015) (RRB JE Chandigarh 2014)

• Carnot cycle
• Otto cycle
• Diesel cycle
• Dual cycle

Explanation:

• The P-V diagram represents Otto cycle. Processes: 1-2 Isentropic compression, 2-3 Constant volume heat addition, 3-4 Isentropic expansion, 4-1 Constant volume heat rejection.

In Spark ignition engine, fuel used is —-? (RRB JE (Shift-III), 27.08.2015)

• Diesel
• Petrol
• Kerosene
• Both Diesel and kerosene

Explanation:

• In SI engines, petrol is used with ignition by spark plug. In CI engines, diesel is used with ignition by compressed air.

In some carburettors, meter rod and economiser device are used for —-? (RRB JE (Shift-III), 29.8.2015)

• Cold starting
• Idling
• Power enrichment
• Acceleration

Explanation:

• Economiser regulates additional fuel supply at full throttle. It is best for power enrichment system.

In spark ignition engines knocking can be reduced by —-? (RRB JE (Shift-III), 16.09.2015)

• Increasing the compression ratio
• Increasing the cooling water temperature
• Retarding the spark advance
• Increasing the inlet air temperature

Explanation:

• Retarding the spark advance reduces knocking. The burning gas is impressed by the rising piston, increasing temperature and pressure, so end charge is not externally ignited because flame quickly reaches end charge.

In a petrol engine, the tendency for detonation increases with —-? (RRB JE (Shift-III), 30.08.2015)

• Retarded spark timing
• Running the engine at high speed
• Supercharging
• Increasing the cooling rate

Explanation:

• Supercharging increases pressure 1.5-2 times the entry air pressure. As pressure increases, temperature also increases, causing knocking.

A four stroke, four cylinder SI engine has a swept volume of 450 cc and compression ratio is 8. The clearance volume of each cylinder is equal to —-? (RRB JE (Shift-I), 27.08.2015)

• 48 cc
• 55 cc
• 65 cc
• 70 cc

Explanation:

• r_c = (V_c + V_s)/V_c, 8 = (V_c + 450)/V_c, V_c = 450/7 = 64.29 ≈ 65 cc.

The thermal efficiency of Otto cycle is a function of —-? (RRB SSE (Shift-III), 01.09.2015)

• Compression ratio only
• Specific heats ratio only
• Compression ratio and specific heat ratio
• Clearance volume only

Explanation:

• η = 1 – 1/r_c^(γ-1). It is a function of compression ratio and specific heat ratio.

Which of the following characteristic does not belong to SI engine? (RRB SSE (Shift-II), 01.09.2015)

• It works on Otto cycle
• It has a carburetor
• The maximum obtainable value of thermal efficiency is high
• Its compression ratio lower

Explanation:

• Since compression ratio is lower for SI engines, the obtainable value of thermal efficiency is low.

Diesel used in automobile engines is mainly composed of Carbon and —-? (RRB SSE (Shift-III), 02.09.2015) RRB Chandigarh Section Eng. Mech. 15.03.2009

• Nitrogen
• Oxygen
• Hydrogen
• Water molecules

Explanation:

• Diesel and gasoline fuel contain approximately 86 wt% carbon and 14 wt% hydrogen.

Which of the following is an SI Engine? (RRB SSE Secunderabad Red Paper, 21.12.2014)

• Diesel Engine
• Petrol Engine
• Gas Engine
• None of these

Explanation:

• Petrol engine is an SI engine. Diesel engine is a CI engine.

IC engines are classified into carburetor engine and air injection engine based on the —-? RRB JE (Re-Exam) 04.06.2025

• speed of the engine
• cooling system used
• number of cylinders
• method of fuel injection

Explanation:

• IC engines are classified into carburetor engine and air injection engine based on the method of fuel injection.

In a four-stroke cycle diesel engine, the intake valve starts to open at —-? RRB JE Stage 2 (22.04.2025 9:00 AM-11:00 AM)

• 10° – 25° before TDC
• 25° – 40° before BDC
• 25° – 40° after BDC
• 10° – 15° after TDC

Explanation:

• In four-stroke diesel engine, the intake valve begins to open 10°-25° before TDC on exhaust stroke to ensure valve is fully open when intake stroke begins.

In a battery or coil ignition system, what is the role of the ignition coil? RRB JE Stage 2 (22.04.2025 9:00 AM-11:00 AM)

• To transform the low battery voltage into a high voltage required for spark generation
• To regulate the fuel injection timing
• To compress the air entering the combustion chamber
• To control the engine’s exhaust temperature

Explanation:

• The ignition coil transforms low battery voltage into high voltage required for spark generation in internal combustion engines.

In most of the SI engines, the intake valve opens a few degrees before the TDC on the exhaust stroke to —-? RRB JE Stage 2 (22.04.2025 9:00 AM-11:00 AM)

• ensure complete combustion of the fuel-air mixture
• ensure that the intake valve is fully open when the piston reaches the TDC
• allow for better scavenging of exhaust gases
• increase the engine’s compression ratio

Explanation:

• Intake valve opens a few degrees before TDC on exhaust stroke to improve scavenging and maximize fresh air-fuel charge drawn into the cylinder.

The intake valve closes at ____ for a low-speed engine and ____ for high-speed four-stroke petrol engines. RRB JE Stage 2 (22.04.2025 2:30-4:30 PM)

• 60 deg before BDC; 10 deg before BDC
• 60 deg after BDC; 10 deg after BDC
• 10 deg before BDC; 60 deg before BDC
• 10 deg after BDC; 60 deg after BDC

Explanation:

• Intake valve closes at 10° after BDC for low-speed engines and 60° after BDC for high-speed four-stroke petrol engines.

In an ideal four-stroke petrol engine, the assumption made about the burning process during the power stroke is —-? RRB JE Stage 2 (22.04.2025 2:30-4:30 PM)

• It is a gradual process that starts before the piston reaches top dead centre
• It occurs instantaneously when the piston is at the top dead centre
• It takes a significant amount of time
• It starts at the bottom dead centre and continues as the piston moves up

Explanation:

• Instantaneous combustion at TDC is assumed to ensure combustion occurs at constant volume, as the piston momentarily stops at TDC.

The reason for supercharging in any engine is to —-? (RRB Gorakhpur Design SSE 09.09.2012)

• increase efficiency
• increase power reduce weight and bulk for a given output
• effect fuel economy
• None of these

Explanation:

• Supercharging increases density, therefore mass of air inducted increases, increasing power output and reducing weight for the same output.

The thermostat valve is used in —-? (RRB Bhopal SSE 09.09.2012)

• Fuel supply system of engine
• cooling system of engine
• ignition system of engine
• lubrication system of engine

Explanation:

• The thermostat valve is used in the cooling system. It isolates the engine from the radiator until minimum temperature is reached.

In MPFI system, the fuel is injected into the —-? (RRB Jammu SSE 09.09.2012)

• Carburetor
• Intake manifold
• Cylinder
• Before air cleaner

Explanation:

• In MPFI system, fuel is injected into the intake manifold to evenly distribute combustion mixture to each cylinder.

Which of the following medium is compressed in a supercharger? (RRB Jammu JE 25.10.2009)

• Air
• Gasoline
• Fuel oil
• All options are correct

Explanation:

• Air is compressed in a supercharger.

The thermostat valve of engine cooling system of vehicle —-? (RRB Allahabad SSE 19.12.2010)

• remains closed while starting the engine from cold condition
• opens as soon as the engine is started from cold condition
• opens as soon as the engine is started and then closed after some time
• remains closed when the engine is not running and always remains open when the engine is running

Explanation:

• The thermostat remains closed while starting the engine from cold condition to bring the engine to operating temperature quickly. It opens after reaching minimum temperature.

Where does mixing of fuel and air take place in case of diesel engine? (RRB JE (Shift-II), 29.8.2015)

• Injection pump
• Injector
• Engine cylinder
• Inlet manifold

Explanation:

• In diesel engine, mixing of fuel and air takes place in the engine cylinder. Air temperature and pressure are above fuel’s ignition point, causing spontaneous ignition after delay period.

The Silencer of an Internal Combustion Engine —-? (RRB Bhubneshwar JE-II 19.12.2010)

• Increases brake specific fuel consumption (BSFC)
• It has no effect on its efficiency
• reduces noise
• decreases BSFC

Explanation:

• The silencer reduces noise. Flow obstruction causes back pressure, reducing efficiency and power.

Which part is not common between the petrol and diesel engines? (JMRC JE 10.06.2017)

• Air cleaner
• Exhaust silencer
• Battery
• Fuel injector

Explanation:

• Fuel injector is used in diesel engines while carburetor is used in petrol engines.

The atmosphere pressure with rise in altitude decreases —-? (RRB Kolkata SSE 09.09.2012)

• linearly
• first slowly and then steeply
• first steeply and then gradually
• unpredictable

Explanation:

• Atmospheric pressure with rise in altitude decreases first slowly and then steeply.

Air cooling of engines is preferred because —-? (RRB Jammu SSE 09.09.2012)

• It is compact
• It is more efficient
• Cooling rate can be controlled
• None of the above

Explanation:

• Air cooling is preferred because it is compact. Weight is less than water-cooled engine, power-to-weight ratio is improved, and installation is easier.

Which one of the following configuration has the highest fin effectiveness? (RRB Chandigarh SSE 09.09.2012)

• Thin, close spaced
• Thin, widely spaced
• Thick, widely spaced
• Thick, close spaced

Explanation:

• Thin, close-spaced fins have the highest effectiveness as P increases and A must be small.

Engine temperature indicated is actually the measurement of —-? (RRB JE BHOPAL 2014)

• jacket cooling water
• engine cylinder
• exhaust gases
• lubricating oil

Explanation:

• Engine temperature indicated is actually the measurement of jacket cooling water temperature.

Which of the following processes is commonly used to manufacture powder coated steel central heating radiators? (RRB Bhopal SSE 09.09.2012)

• Sand Casting
• Presswork
• Bending
• Shaping

Explanation:

• Presswork is commonly used to manufacture powder coated steel central heating radiators.

Radiator tubes are generally made of —-? (RRB Patna JE 25.10.2009)

• Steel
• Cast-iron
• Plastic
• Brass

Explanation:

• Radiator tubes are generally made of brass, an alloy of copper and zinc.

In vehicles, the prime exhaust pollutants other than hydrocarbon, are —-? (RRB Bhopal TM SSE 25.10.2009)

• CO and CO₂
• CO and NO
• CO₂ and H₂O
• CO and NOx

Explanation:

• The prime exhaust pollutants are CO and NOx.

Diesel engines used in power plants are usually —-? (RRB Bhopal SSE 09.09.2012)

• Air cooled
• Supercharged
• Horizontal
• High speed

Explanation:

• Diesel engines used in power plants are usually supercharged to increase density of air.

Fins are made as thin as possible to —-? (RRB JE (Shift-II), 19.09.2015)

• Reduce the total weight
• Accommodate more number of fins
• Increase the width for the same profile area
• Improve flow of coolant around the fin

Explanation:

• Fins are made thin to accommodate more number of fins, resulting in more heat exchange.

Function of turbocharger is —-? (RRB SSE (Shift-III), 03.09.2015)

• to increase the power
• to decrease the thermal efficiency
• to reduce the noise
• to reduce fuel consumption

Explanation:

• A turbocharger increases inlet air density, increasing power output and efficiency.

What does mean effective pressure (MEP) indicate in engine performance analysis? RRB JE (Re-Exam) 04.06.2025

• The pressure of the fuel injected into the cylinder
• The average pressure acting on the piston during the complete engine cycle that would produce the measured work output
• The maximum pressure reached in the combustion chamber
• The difference between intake and exhaust pressures

Explanation:

• MEP indicates the average pressure acting on the piston during the complete engine cycle that would produce the measured work output. MEP = Work done per cycle/Swept volume.

How does indicated power differ from brake power in an internal combustion engine? RRB JE (Re-Exam) 04.06.2025

• Indicated power is measured at the engine’s output shaft, while brake power is measured in the cylinders
• Indicated power is derived from combustion chamber pressures, whereas brake power is the net output at the crankshaft after mechanical losses
• Both indicated and brake power represent the same value under ideal conditions
• Indicated power accounts for frictional losses, whereas brake power does not

Explanation:

• Indicated power is measured inside the engine cylinder, while brake power is measured at the crankshaft. FP = IP – BP.

It is important for the piston to fit ‘snugly’ into the cylinder to —-? RRB JE Stage 2 (22.04.2025 9:00 AM-11:00 AM)

• both, allow for easy movement and provide a gas-tight space
• allow for easy movement alone
• provide a gas-tight space alone
• neither allow for easy movement nor provide a gas-tight space

Explanation:

• A “snug” piston fit facilitates both smooth movement and a gas-tight seal, which are essential for engine performance.

In a dry sump lubrication system, how is oil returned to the storage tank? RRB JE Stage 2 (22.04.2025 9:00 AM-11:00 AM)

• Gravity drains oil directly to the crankcase
• Centrifugal force separates oil from air
• A scavenge pump actively pumps oil back
• Oil remains in the engine block indefinitely

Explanation:

• In a dry sump lubrication system, a scavenge pump actively pumps oil from the crankcase back to the external oil reservoir.

How is thermal efficiency defined in the context of internal combustion engines? RRB JE Stage 2 (22.04.2025 9:00 AM-11:00 AM)

• The ratio of the engine displacement to the fuel mass used
• The ratio of useful work output to the total chemical energy input from fuel
• The ratio of exhaust gas temperature to the intake air temperature
• The ratio of indicated power to frictional power losses

Explanation:

• Thermal efficiency = Useful work output / Total chemical energy input from fuel.

What does specific fuel consumption (SFC) measure in an internal combustion engine? RRB JE Stage 2 (22.04.2025 2:30-4:30 PM)

• The total mass of the fuel used during engine operation
• The fuel efficiency expressed as the amount of fuel consumed per unit of power produced
• The ratio of air intake to fuel delivered per combustion cycle
• The efficiency of the engine’s exhaust system

Explanation:

• SFC measures fuel efficiency as amount of fuel consumed per unit of power produced.

In which type of engine is a mist lubricating system most commonly used? RRB JE Stage 2 (22.04.2025 2:30-4:30 PM)

• Four-stroke diesel engines
• Two-stroke petrol engines
• Gas turbine engines
• Rotary engines

Explanation:

• Mist lubrication is most commonly used in two-stroke petrol engines because oil is mixed with fuel and enters the crankcase.

Frictional power in an engine is calculated as —-? RRB JE Stage 2 (22.04.2025 2:30-4:30 PM)

• Brake power / Mechanical efficiency
• Indicated power + Brake power
• Indicated power – Brake power
• Indicated power × Mechanical efficiency

Explanation:

• Frictional power = Indicated power – Brake power.

Which statement best compares battery and magneto ignition systems in internal combustion engines? RRB JE Stage 2 (22.04.2025 2:30-4:30 PM)

• Both systems depend on an external battery for operation
• Magneto systems require more frequent maintenance than battery systems
• Battery ignition systems are independent of engine speed, unlike magneto systems
• Battery ignition systems rely on stored electrical energy, whereas magneto systems generate power on-demand via electromagnetic induction

Explanation:

• Battery ignition uses stored electrical energy from battery. Magneto systems generate power on-demand via electromagnetic induction.

The air standard efficiency of an Otto cycle compared to diesel cycle for the given compression ratio is —-? (RRB Allahabad SSE 19.12.2010)

• the same
• more or less depending on power rating
• more
• less

Explanation:

• For same compression ratio and heat addition: η_otto > η_dual > η_diesel.

Calorific value of a fuel is based on —-? (RRB Mumbai JE 05.10.2008)

• 1 kg of fuel
• 1 kg/m³ of fuel
• 1 m³ of fuel
• Any one of these

Explanation:

• Calorific value is determined per kg or per m³ of fuel. Unit is kJ/kg.

Which of the following is the lightest and most volatile liquid fuel? (RRB Mumbai SSE 05.10.2008)

• 6:1
• 9:1
• 12:1
• 15:1

Explanation:

• Gasoline is the lightest and most volatile liquid fuel. Increasing order of volatility: Diesel < Kerosene < Gasoline.

An engine indicator is used to determine the following —-? (RRB Mumbai JE 19.12.2010)

• speed
• temperature
• volume of cylinder
• none of these

Explanation:

• An engine indicator is used to determine mean effective pressure and indicated power.

Diesel fuel, compared to petrol is —-? (RRB Mumbai SSE 19.12.2010)

• less difficult to ignite
• just about the same difficult to ignite
• more difficult to ignite
• highly ignitable

Explanation:

• Self-ignition temperature of diesel (210°C) is lower than petrol (247°C-280°C). Diesel is more difficult to ignite compared to petrol.

The self ignition temperature of diesel is ____ as compared to that of petrol. (DMRC JE 2013)

• is higher
• is lower
• is same
• Cannot be determined

Explanation:

• Self-ignition temperature of diesel is lower as compared to petrol.

Ethyl fuel is used —-? (DMRC JE 20.04.2018)

• to increase the octane rating of the fuel
• to increase the cetane rating of the fuel
• as a defrosting agent
• as a superior type of fluid compared to others

Explanation:

• Ethanol has a higher octane number than gasoline, providing more thermal efficiency.

Which of the following represents the CORRECT graph for relation between efficiency (η) and compression ratio (r_c)? (RRB Allahabad JE 09.09.2012)

• Efficiency increases linearly with compression ratio
• Efficiency decreases with compression ratio
• Efficiency remains constant
• Efficiency increases with compression ratio but flattens after a certain limit

Explanation:

• Efficiency of both Otto and Diesel cycles increases with increasing compression ratio but flattens after a certain limit.

Alcohol, which is a liquid fuel is obtained from —-? (Konkan Railway TA 2017)

• the distillation of crude oil
• vegetable matters by the fermentation process
• destructive distillation of coal
• None of these

Explanation:

• Alcohol is obtained from vegetable matters by the fermentation process.

The diesel oil is obtained during distillation process between the temperature limits —-? (Konkan Railway SSE 2015)

• 100°C to 200°C
• 200°C to 300°C
• 360°C to 475°C
• 500°C to 675°C

Explanation:

• Diesel oil is obtained during distillation between 200°C to 300°C.

Select the correct option for increasing order of the following efficiencies of an engine: (I) Brake thermal efficiency (II) Air standard efficiency (III) Indicated thermal efficiency (RRB Kolkata Diesel JE 25.10.2009)

• (I), (II), (III)
• (I), (III), (II)
• (II), (III), (I)
• (III), (I), (II)

Explanation:

• Increasing order: Brake thermal efficiency < Indicated thermal efficiency < Air standard efficiency.

If η_bt = Brake thermal efficiency, η_it = Indicated thermal efficiency, and η_m = Mechanical efficiency, which one of the following is the correct relation? (RRB Chandigarh SSE 25.10.2009)

• η_bt = η_it × η_m
• η_bt = η_it × η_m
• η_bt = η_it × η_m
• η_bt = η_it / η_m

Explanation:

• η_bt = η_it × η_m. Mechanical efficiency = BP/IP = η_bt/η_it.

In individual pump fuel injection system of diesel engine, what is the function of fuel feed pump? (RRB Mumbai C&G JE 25.10.2009)

• To supply correct quantity of diesel to the injector
• To produce high pressure for the injection of diesel
• To supply diesel from tank to injection pump
• To supply diesel to the injector at correct time

Explanation:

• Feed pump supplies diesel from the fuel tank to the injection pump, driven by the camshaft.

Efficiency of a Diesel cycle will approach to Otto cycle when —-? (RRB Gorakhpur RDSO SSE 25.10.2009)

• Diesel engine will operate at high speed
• Cut-off period of diesel cycle is reduced to zero
• Diesel fuel is balanced with petrol
• None of these

Explanation:

• When cut-off ratio ρ = 1, η_diesel = η_Otto. As ρ approaches 1 (cut-off reduced), diesel cycle efficiency approaches Otto cycle efficiency.

If area of actual indicator diagram is 20 cm² and base width is 10 cm and spring value is 5 N/m²/cm, then mean effective pressure will be —-? (RRB Jammu JE 25.10.2009)

• 30 N/m²
• 20 N/m²
• 10 N/m²
• 50 N/m²

Explanation:

• P_m = (a/l) × k = (20/10) × 5 = 10 N/m².

The power to operate oil pump is obtained from —-? (RRB Malda SSE 25.10.2009)

• Camshaft
• Alternator
• Thermostat
• Crankshaft

Explanation:

• The oil pump is directly driven by the crankshaft.

The part of ignition system that stores energy in the form of magnetism and delivers it to distributor via HT lead is —-? (RRB Allahabad JE 25.10.2009)

• Contact breakers
• Ballast resistor
• Ignition coil
• Ignition switch

Explanation:

• The ignition coil is a transformer that transforms battery voltage into many thousand volts and stores energy in magnetic field.

A two stroke IC engine has stroke length 120 mm and cylinder diameter 80 mm. Mean effective pressure is 4×10⁵ N/m² and crankshaft speed is 1500 rpm. What is its indicated power (in kW)? (RRB Mumbai C&G SSE 25.10.2009)

• 1.92
• 24.12
• 60.3
• None of these

Explanation:

• IP = P_m × L × A × n / 60000 for 2-stroke. n = N = 1500. IP = 4×10⁵ × 0.12 × π/4 × 0.08² × 1500 / 60000 = 60.3 kW.

Which test can be considered only for multi-cylinder engine? (DMRC 18.02.2017, 8.30 a.m)

• Frictional power test
• Brake rate test
• Motoring test
• Morse test

Explanation:

• Morse test is conducted to determine the power developed in each cylinder in a multi-cylinder IC engine.

Which dynamometer will be used for measuring BHP of an automobile engine? (DMRC 18.02.2017, 8.30 a.m)

• Hydraulic
• Electrical generator type
• Electrical resistance type
• Prony brake

Explanation:

• Hydraulic dynamometers are used to measure force, torque, and power produced by engines.

Useful power available at crankshaft is known as —-? (DMRC 18.02.2017, 8.30 a.m) (RRB JE BHOPAL 2014)

• Brake power
• Friction power
• Thermal power
• Indicated power

Explanation:

• Brake power/shaft power is the power available at the engine crankshaft.

Orsat apparatus is used to find the —-? (RRB Bhopal SSE 09.09.2012)

• Indicated horse power of I.C. engine
• Composition of exhaust of I.C. engine
• Thermal efficiency of the I.C. engine
• Dryness fraction of steam

Explanation:

• Orsat apparatus is used for volumetric analysis of dry products of combustion (oxygen, CO, CO₂ content).

Morse test is used to find the —-? (RRB Jammu SSE 09.09.2012)

• indicated thermal efficiency of single cylinder
• indicated horse power of multi cylinder engine
• brake thermal efficiency of multi cylinder engine
• mechanical efficiency of multi cylinder engine

Explanation:

• Morse test determines the power developed in each cylinder in a multi-cylinder IC engine.

Which of the following thermodynamic cycle is most efficient for same compression ratio and same heat input? (RRB Bhubneshwar JE II 29.11.2008)

• Diesel cycle
• Dual cycle
• Otto cycle
• None of the above

Explanation:

• For same compression ratio and heat addition: η_otto > η_dual > η_diesel.

Iso-Octane content in a fuel for S.I. Engines —-? (RRB Mumbai C&G SSE 25.10.2009)

• retards auto-ignition
• accelerates auto-ignition
• does not affect auto ignition
• none of the above

Explanation:

• Iso-Octane is a very good antiknock fuel with octane number 100. It retards auto-ignition.

Willan’s law gives a straight line graph between the rate of steam consumption and —-? (RRB Chandigarh SSE 25.10.2009)

• pressure of steam
• temperature of steam
• volume of steam
• indicated horse power

Explanation:

• Willan’s law gives a straight line graph between rate of steam consumption and indicated horse power.

The specific fuel consumption of a diesel engine as compared to that for petrol engine is —-? (Konkan Railway TA 2017)

• lower
• higher
• same for same output
• none of the above

Explanation:

• Specific fuel consumption of CI engine is lower than SI engine because diesel contains more energy by volume.

The cetane number of automotive diesel fuel used in India lies in which of the following ranges? (RRB Mumbai SSE 19.12.2010)

• 30-40
• 41-50
• 51-60
• 61-70

Explanation:

• In India, cetane number lies between 40 to 60.

Morse test is used for multi-cylinder spark ignition engine to determine —-? (RRB Bhubneshwar JE-II 19.12.2010)

• Thermal efficiency
• Mechanical efficiency
• Volumetric efficiency
• Relative efficiency

Explanation:

• Morse test is used to determine mechanical efficiency of multi-cylinder SI engines.

Actual power generated in engine cylinder is known as —-? (RRB Allahabad JE 25.10.2009)

• brake horse power
• indicated horse power
• one boiler horse power
• fractional horse power

Explanation:

• Indicated power is the actual power developed inside the engine cylinder.

Morse test is conducted on —-? (RRB Allahabad SSE 09.09.2012)

• vertical engines
• horizontal engines
• single cylinder engines
• multi cylinder engines

Explanation:

• Morse test is conducted on multi-cylinder engines to determine power developed in each cylinder.

Octane number of iso-octane is —-? (RRB Kolkata SSE 09.09.2012)

• 50
• 70
• 0
• 100

Explanation:

• Iso-octane has octane number of 100 (resists knocking). Heptane has octane number of 0 (causes knocking).

The commercially available petrol in India has an octane rating of —-? (RRB Bhopal SSE 09.09.2012)

• 40-50
• 60-75
• 85-90
• 30-36

Explanation:

• In India, passenger cars use petrol with octane rating 80-85. High speed racing cars use 95-100.

Which of the following fuel having maximum resistance to detonation? (RRB Jammu SSE 09.09.2012)

• toluene
• iso-octane
• n-heptane
• benzene

Explanation:

• Iso-octane has maximum resistance to detonation with octane number 100.

The indicator on engine is used to determine —-? (RRB Bhubneshwar JE II 29.11.2008)

• Speed
• Temperature
• IHP and MEP
• BHP

Explanation:

• Engine indicator is used to determine indicated horse power (IHP) and mean effective pressure (MEP).

For complete burning of 1 kg of carbon, the air required will be about —-? (RRB Gorakhpur RDSO SSE 25.10.2009)

• 3.67 kg
• 13.7 kg
• 11.6 kg
• 14.5 kg

Explanation:

• For complete combustion of 1 kg carbon, air required = (32/12) × (100/23) = 11.6 kg.

Morse test is conducted on multicylinder engine to find the engine’s —-? (Konkan Railway TA 2017)

• stroke length
• emission performance
• compression ratio
• indicated power

Explanation:

• Morse test is conducted on multicylinder engine to find the engine’s indicated power.

Sulphur content in diesel fuel should not be more than —-? (RRB Mumbai SSE 19.12.2010)

• 10%
• 5%
• 1%
• 0.01%

Explanation:

• Sulphur content in diesel fuel should not be more than 1%.

In a four stroke engine, the speed of the engine is N r.p.m. The speed of the cam shaft will be —-? (JMRC JE 10.06.2017)

• N/2 r.p.m
• N r.p.m
• 2N r.p.m
• 4N r.p.m

Explanation:

• In a 4-stroke engine, camshaft speed = N/2 rpm. In 2-stroke engine, camshaft speed = N rpm.

In motor-cycles fitted with four-stroke engines, ____ mechanism is used to operate the valves. (BMRCL JE 24 Feb.2019)

• Chain drive
• Gear drive
• Belt drive
• Push rod

Explanation:

• In motorcycles with four-stroke engines, chain mechanism is used to operate the valves. Push rod is generally used in CI engines.

By which one of the following actions, diesel knock can not be prevented? (RRB Allahabad SSE 19.12.2010)

• by keeping the compression ratio high
• by increasing the intake air pressure
• by decreasing the temperature of the combustion chamber
• by increasing the injection pressure of diesel

Explanation:

• Decreasing combustion chamber temperature cannot prevent diesel knock. Low temperature causes improper burning, smoky exhaust, and reduced power.

The components of secondary ignition circuit of battery ignition system are —-? (RRB Mumbai JE 05.10.2008)

• Battery, contact breaker, distributor
• Contact breaker, condenser, distributor
• Secondary winding, contact breaker, condenser
• Secondary winding, distributor, spark plug

Explanation:

• Secondary ignition circuit includes secondary winding, distributor, and spark plug.

The components of primary ignition circuit of battery ignition system are —-? (RRB Mumbai SSE 05.10.2008)

• Contact breaker, Condenser, Distributor cap
• Contact breaker, Ignition coil, Spark plug
• Contact breaker, Ignition switch, Condenser
• Contact breaker, Ignition switch, Rotor

Explanation:

• Primary ignition circuit includes contact breaker, ignition switch, and condenser.

The primary winding of ignition coil consists of —-? (RRB Mumbai JE 19.12.2010)

• few turns of thin wire
• many turns of thin wire
• few turns of thick wire
• many turns of thick wire

Explanation:

• Primary coil consists of few turns (150) of heavy wire. Secondary coil consists of many turns (18000) of fine wire.

The parameter to be kept constant during Morse test is —-? (RRB Mumbai SSE 19.12.2010)

• Load on the engine
• Speed of the engine
• Brake power of the engine
• Temperature of exhaust gases

Explanation:

• Morse test involves running the engine at a particular speed, cutting out firing of each cylinder, and maintaining speed constant.

If p_m = mean effective pressure, L = Length of stroke, N = engine speed (revolutions per second), A = Bore area, the indicated power of four stroke engine will be —-? (DMRC JE 2013)

• p_m L A N
• p_m L A N
• p_m L A N
• p_m L A N/2

Explanation:

• For four-stroke engine, IP = p_m × L × A × N/2 (since N/2 power strokes per second).