Quick recall · 253 cards
Short MCQ-style retrieval prompts. Tap a card to reveal the answer.
PYQ
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Compression ratio for diesel engine may have a range of:
B · 16 to 20
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A compression ignition engine is a:
B · Internal combustion engine
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A fuel has the following ultimate analysis: C = 75%, H = 6.0%, N = 1.3%, W = 3.4%, and ash = 14.3%. Calculate the theoretical weight of air required for combustion in kg air/kg fuel.
B · 11.45
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For the balanced combustion equation: C₄H₁₀ + 6.5(O₂ + 3.76N₂) → 4CO₂ + 5H₂O + 24.44N₂, what is the air-to-fuel ratio by mass?
D · 15.4
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What are the main products of incomplete combustion of a hydrocarbon fuel?
B · Carbon monoxide, carbon, unburned hydrocarbons, and water
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Which instrument is used for adjusting the ignition timing?
B · Stroboscope
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The dwell meter is used for setting ________
B · Contact breaker gap
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In comparison with the conventional ignition system, the magneto ignition system.
D · Is independent of battery
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Consider two mating spur gears, A and B. Gear A has a pitch diameter of 5 inches and gear B has a pitch diameter of 8 inches. If gear A is rotating at 300 RPM, how fast is gear B rotating?
B · 188 RPM
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What is fatigue stress concentration factor, \( K_f \), for a material with a notch sensitivity, \( q \), of 0.8 and a theoretical stress concentration factor, \( K_t \), of 2.2?
B · 1.96
PYQ
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Which of the following is a manual layout planning method commonly used in manufacturing facilities?
B · B. Systematic Layout Planning (SLP)
PYQ · 2022
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In manual drafting for mechanical components, which type of line represents the visible edges of an object in an orthographic projection?
C · C. Continuous thick line
PYQ · 2014
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I. Mating spur gear teeth is an example of higher pair
II. A revolute joint is an example of lower pair
Indicate the correct answer using the codes given below.
C · I is false and II is true
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Gears are classified based on their peripheral velocity. What is the peripheral velocity range for medium velocity gears?
B · 3-15 m/s
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With increase in pinion to gear speed ratio, the minimum number of teeth on the pinion _________
A · increases
PYQ
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In India, what is the rated frequency of generated electric power?
A) 60 Hz
B) 50 Hz
C) 55 Hz
D) 53 Hz
B · 50 Hz
PYQ
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Ohm's Law states that:
A · V = IR
PYQ
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System reliability in electrical power supply and distribution describes and quantifies:
B · The ability of a system to consistently provide uninterrupted power
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A compressor has a pressure ratio of 10. Air enters the compressor at 70°F. If the air leaves at a temperature of 600°F, what is the isentropic efficiency of the compressor?
C · C) 0.86
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Which energy losses of turbomachines are related to efficiencies? (Choose all that apply)
A · A) Disc or hydraulic friction energy loss
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In a disc brake, which component provides the pad-to-disc adjustment?
B · Piston
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What is the basic principle of operation of a braking system during normal braking?
A · Conversion of kinetic energy into heat energy
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Brake fade is primarily caused by:
A · Reduction in the coefficient of friction due to overheating
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Which of the following is NOT a type of gear?
A. Spur Gear
B. Helical Gear
C. Bevel Gear
D. V-Belt Gear
D · V-Belt Gear
Spur, helical, and bevel gears are toothed mechanical elements for power transmission. V-belt gear does not exist; V-belts use sheaves/pulleys with friction drive, not teeth. Option D is correct.
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The main function of Actuator is _____.
A · To produce motion
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What is the primary goal of a safety engineer?
B · B) Minimize workplace hazards and risks
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Which of the following is NOT a common machine safeguard?
C · C. Safety glasses
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What is the condition called when the vehicle tends to steer more than required to keep it on the right path due to greater slip angles of front wheels compared to rear wheels?
A · Understeer
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The main advantage of rack and pinion steering over recirculating ball steering is:
C · C. More precise steering feel and fewer components
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Steering wheel return to center is controlled primarily by:
A · A. Caster angle
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Which steering geometry provides directional stability?
C · C. Positive caster
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Toe is the:
C · C. Tilt of the tires inward or outward
PYQ · 2023
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In a unity feedback control system, the open-loop transfer function is \( G(s) = \frac{K}{s(s+1)(s+2)} \). The value of K that results in a 30° phase margin is:
B · 30
PYQ
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What are the common methods used for pump alignment?
B · B. Straight edge, filler gauge, and dial indicator method
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In the turning process, which of the following statements is correct?
A · True
PYQ
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Which of the following best describes the purpose of cutting speed in turning operations?
B · B) The surface velocity of the workpiece at the point of cutting contact
PYQ
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What is the primary goal of a safety engineer?
B · Minimize workplace hazards and risks
PYQ
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Which of the following is NOT a common machine safeguard?
C · Safety glasses
PYQ
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What does OSHA require as the minimum distance from the edge of an excavation for workers to maintain as a buffer zone?
B · 2 feet
PYQ
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What are the two basic types of production systems?
B · Intermittent and non-intermittent process
PYQ · 2023
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Which of the following is a seven basic quality control tool used for identifying the most significant causes of a problem?
C · Pareto Chart
PYQ
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What is the primary goal of a safety engineer?
B · B) Minimize workplace hazards and risks
PYQ
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Which of the following is NOT a common machine safeguard?
C · C) Safety glasses
PYQ
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Which is the incorrect statement about results of hot working? (A) Porosity in the metal is largely eliminated. (B) Grain refinement is possible. (C) Close tolerances can be obtained. (D) Surface has good finish.
C · (C) Close tolerances can be obtained.
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What type of coupling should you use to connect shafts that are misaligned?
C · C. Single-cardanic universal joint
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Which of the following is a common method used for non-destructive testing (NDT) in mechanical inspection to detect surface and near-surface defects in metallic components?
B · B. Magnetic particle testing
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In inspection of welded joints, which NDT method is most suitable for detecting volumetric defects like porosity and lack of fusion in thick-walled pressure vessels?
B · B. Ultrasonic testing
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Which hardness testing method is most appropriate for inspecting the surface hardness of large, heavy mechanical components like gears and shafts without causing significant damage?
C · C. Rebound (Scleroscope)
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Which of the following is NOT a common classification of engines based on the working fluid cycle?
C · Rankine cycle engine
Rankine cycle is a thermodynamic cycle used mainly in steam power plants, not typical for internal combustion engines.
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A two-stroke engine completes a power cycle in how many piston strokes?
B · Two strokes
In two-stroke engines, the complete engine cycle is completed in two strokes of the piston — one upward and one downward stroke.
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Which of the following best classifies a diesel engine?
C · Compression ignition engine
Diesel engines ignite fuel-air mixture by compressing air to raise its temperature enough to ignite the fuel, hence compression ignition.
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Which of the following best explains the working principle of a four-stroke petrol engine?
B · Combustion occurs once every four strokes involving intake, compression, power, and exhaust strokes
A four-stroke petrol engine completes its cycle in four strokes: intake, compression, combustion (power), and exhaust.
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In a spark ignition engine, the air-fuel mixture is ignited by:
C · Electrical spark from a spark plug
Spark ignition engines use an electrical spark from the spark plug to ignite the air-fuel mixture.
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Refer to the diagram below showing the P-V diagram of an ideal Otto cycle engine. What happens during the process 2→3 in the diagram?
C · Constant volume heat addition
In the Otto cycle, process 2→3 is the constant volume heat addition where combustion occurs rapidly increasing pressure.
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Compared to a two-stroke engine, a four-stroke engine generally has which of the following advantages?
C · Better fuel efficiency and emission control
Four-stroke engines generally provide better fuel efficiency and cleaner emissions due to more complete combustion and separate strokes for exhaust.
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Which one of the following components is responsible for converting the reciprocating motion of the piston into rotary motion?
B · Crankshaft
The crankshaft converts the reciprocating motion of the piston into rotary motion which is then transmitted to the drivetrain.
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Refer to the schematic diagram below of a typical four-stroke engine. Which numbered part represents the camshaft controlling valve timing?
C · 3
In the typical engine schematic, the camshaft (3) controls the opening and closing of intake and exhaust valves.
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The compression ratio of an engine is defined as the ratio of:
A · Volume of combustion chamber when piston is at bottom dead center to volume when piston is at top dead center
Compression ratio is the ratio of volume when piston is at bottom dead center (largest volume) to volume at top dead center (smallest volume).
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Which of the following statements about thermal efficiency \( \eta_{th} \) of an ideal Otto cycle engine is TRUE?
C · \( \eta_{th} \) increases with increasing compression ratio
Thermal efficiency of an ideal Otto cycle increases with increasing compression ratio because more work is extracted from the fuel energy.
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Which type of ignition method is used in compression ignition engines?
B · Compression ignition
Compression ignition engines ignite fuel by the high temperature caused by compressing the air, leading to auto-ignition without a spark.
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Which of the following statements correctly distinguishes Spark Ignition (SI) and Compression Ignition (CI) engines?
B · SI engines mix fuel and air externally before intake; CI engines inject fuel directly into compressed hot air
SI engines use externally premixed fuel-air mixture ignited by spark; CI engines compress air only and inject fuel directly which ignites by hot compressed air.
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Which performance parameter is primarily a measure of how completely the fuel's chemical energy is converted into work output in an engine?
C · Thermal efficiency
Thermal efficiency measures how effectively the engine converts chemical energy of fuel into mechanical work output.
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Refer to the flow diagram below illustrating the diesel engine cycle. Which step involves the injection of fuel and auto-ignition due to high air temperature?
C · Fuel injection and auto-ignition
In the diesel cycle, after air is compressed, fuel is injected causing immediate ignition due to the high temperature of compressed air.
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Which of the following best describes the characteristic feature of the Dual cycle in internal combustion engines?
C · Heat addition partly at constant volume and partly at constant pressure
The Dual cycle (also called the mixed cycle) features heat addition partly at constant volume and partly at constant pressure, combining Otto and Diesel cycle features.
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Which of the following correctly classifies an engine by its working cycle?
A · Two-stroke and four-stroke engines
Engines are commonly classified based on their working cycle as two-stroke or four-stroke, which relates to the number of piston strokes per cycle.
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Which engine type is primarily classified based on the ignition method used?
A · Compression ignition and spark ignition engines
Engines can be classified based on ignition as spark ignition (SI) engines and compression ignition (CI) engines.
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Which of the following is a correct classification of engines based on working medium?
A · Air-breathing and non-air-breathing engines
Engines are sometimes classified based on working medium like air-breathing (e.g., piston engines) and non-air-breathing (e.g., rocket engines).
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In a four-stroke petrol engine, which stroke is responsible for the combustion of the air-fuel mixture?
A · Power stroke
In a four-stroke engine, the power stroke is the third stroke where combustion of the air-fuel mixture releases energy to push the piston down.
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Refer to the diagram below of a four-stroke engine cycle. During which stroke does the piston move upwards with both valves closed, compressing the air-fuel mixture?
A · Compression stroke
The compression stroke involves the piston moving upward with both valves closed compressing the air-fuel mixture in the cylinder.
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Which process in an engine cycle results in the conversion of chemical energy of fuel into mechanical energy?
A · Combustion during the power stroke
The combustion process during the power stroke converts chemical energy into mechanical energy pushing the piston.
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Which of the following engine parts controls the opening and closing of intake and exhaust valves?
A · Camshaft
The camshaft is responsible for the timing and actuation of the intake and exhaust valves in an engine.
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Which component in an internal combustion engine converts the reciprocating motion of the piston into rotary motion?
A · Crankshaft
The crankshaft converts the piston's reciprocating motion into rotary motion used to drive the vehicle's wheels.
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Refer to the piston and cylinder arrangement diagram below. Which labeled part allows the piston to move smoothly by reducing friction?
A · Piston rings
Piston rings reduce friction between the piston and cylinder liner and provide a seal for compression.
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What is the expression for thermal efficiency \( \eta_{th} \) of an ideal Otto cycle engine in terms of compression ratio \( r \) and specific heat ratio \( \gamma \)?
A · \( \eta_{th} = 1 - \frac{1}{r^{\gamma-1}} \)
The thermal efficiency of an ideal Otto cycle is \( \eta_{th} = 1 - \frac{1}{r^{\gamma-1}} \), where \( r \) is compression ratio and \( \gamma \) is ratio of specific heats.
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Which parameter directly affects the indicated mean effective pressure (IMEP) of an engine, assuming other factors constant?
A · Compression ratio
Increasing the compression ratio increases peak pressure leading to higher IMEP, improving engine performance.
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Refer to the P-V diagram of an ideal Diesel cycle below. Which process represents the constant pressure heat addition phase?
A · Process 2-3
In the Diesel cycle, heat is added at constant pressure during process 2-3 on the P-V diagram.
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Which component in a fuel system regulates the amount of fuel delivered to the engine based on load and speed?
A · Fuel injection pump
The fuel injection pump meters and supplies the precise fuel quantity to the engine according to load and speed.
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What is the main effect of increasing the air-fuel ratio in a petrol engine combustion process?
A · Lean mixture, lower power output, and reduced emissions
Increasing air-fuel ratio means lean mixture, which decreases power output but can reduce exhaust emissions like CO and unburnt hydrocarbons.
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Which combustion phenomenon can cause engine knocking and potential damage in petrol engines?
A · Auto-ignition of air-fuel mixture ahead of flame front
Knocking is caused by auto-ignition of the unburnt air-fuel mixture before the flame reaches it, leading to pressure spikes and engine damage.
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What is the primary function of the lubrication system in an internal combustion engine?
A · Reduce friction and wear between moving parts
The lubrication system reduces friction, prevents wear, and helps remove contaminants from moving engine parts.
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Which cooling system is commonly used in modern vehicle engines to maintain optimal operating temperature?
A · Liquid cooling system using coolant and radiator
Most modern engines use a liquid cooling system with circulating coolant and radiator to effectively dissipate heat.
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Which emission component is primarily responsible for the formation of smog and acid rain from vehicle exhaust gases?
A · Nitrogen oxides (NOx)
Nitrogen oxides (NOx) react in the atmosphere to form smog and acid rain, making them a key pollutant from engine emissions.
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Which emission control device converts harmful gases like CO, HC, and NOx into less harmful substances in a petrol engine exhaust system?
A · Three-way catalytic converter
The three-way catalytic converter simultaneously reduces CO, HC, and NOx emissions by catalyzing chemical reactions.
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Which of the following is NOT a primary classification of vehicle systems?
C · Optical system
Optical system is not a main vehicle system classification. Powertrain, suspension, and fuel systems are key vehicle systems.
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Which vehicle system primarily manages the energy transmission from the engine to the drive wheels?
A · Transmission system
The transmission system transfers power from the engine to the wheels, controlling speed and torque.
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Which of the following best describes the main difference between a petrol and a diesel engine?
A · Petrol engines use spark ignition; diesel engines use compression ignition
Petrol engines ignite the air-fuel mixture with a spark plug, while diesel engines ignite fuel by compression heating.
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In a 4-stroke IC engine, which of the following is the correct order of strokes?
A · Intake, Compression, Power, Exhaust
The 4-stroke cycle follows Intake, Compression, Power (combustion), and Exhaust strokes sequentially.
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Refer to the diagram below showing a typical Manual Transmission layout. Which component is responsible for changing gear ratios?
A · Gearbox
The gearbox contains sets of gears that are selected to provide different gear ratios in a manual transmission system.
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Which type of transmission system continuously varies gear ratios without discrete steps?
A · Continuously Variable Transmission (CVT)
CVT allows seamless changes of gear ratios providing smooth acceleration without discrete gear steps.
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Which of the following suspension types uses a spring and a damper system to absorb shocks and control vehicle stability?
A · MacPherson strut suspension
MacPherson strut combines a spring and damper in one assembly, providing good shock absorption and handling control.
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Which braking system component converts kinetic energy into heat energy to slow down a vehicle?
A · Brake pads and discs
Brake pads press against discs (or drums) to convert kinetic energy into heat through friction.
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Which type of fuel system component is responsible for mixing air and fuel in precise proportions before combustion in gasoline engines?
A · Carburetor
In gasoline engines, the carburetor mixes air and fuel in a controlled ratio before it enters the engine cylinders.
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Two-stroke engines differ from four-stroke engines primarily in which way?
A · Complete power cycle in two strokes instead of four
Two-stroke engines complete the power cycle in two strokes (up and down movements), while four-stroke engines need four strokes.
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Which of the following is a correct classification of vehicle systems?
A · Powertrain, Electrical, Chassis, and Safety systems
Vehicle systems are typically classified into Powertrain (engine and transmission), Electrical, Chassis (suspension, steering), and Safety systems for functional grouping.
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Which component is primarily responsible for converting fuel energy into mechanical energy in a vehicle system?
B · Engine
The engine converts the chemical energy of fuel into mechanical energy to move the vehicle.
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Among vehicle systems, which system is responsible for controlling speed and torque delivered to the wheels?
B · Transmission system
The transmission system controls the speed and torque transfer from the engine to the drive wheels through various gear ratios.
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In a spark ignition (SI) engine, the ignition of the air-fuel mixture happens due to:
B · Spark plug
An SI engine uses a spark plug to ignite the compressed air-fuel mixture, whereas compression ignition engines rely on compression heating.
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Which of the following correctly differentiates compression ignition (CI) and spark ignition (SI) engines?
B · CI engines compress air only and ignite by heat; SI engines mix air-fuel and ignite by spark
CI engines compress only air leading to high temperature for ignition, while SI engines mix air and fuel and ignite with a spark plug.
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Which engine type is most suitable for heavy-duty vehicles due to its fuel efficiency and torque characteristics?
C · Compression ignition engine
Compression ignition (diesel) engines provide better fuel efficiency and higher torque at low RPM, making them suitable for heavy-duty vehicles.
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In a fuel injection system compared to a carburetor, the primary advantage is:
C · Improved fuel atomization and control
Fuel injection systems provide better atomization and precise control over the air-fuel mixture, improving efficiency over carburetors.
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Which feature distinguishes a direct fuel injection system from an indirect fuel injection system in vehicles?
B · Fuel is injected directly into the combustion chamber
Direct injection delivers fuel directly into the combustion chamber, increasing efficiency and power, whereas indirect injects into the intake manifold.
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Which of the following is a major disadvantage of carburetors compared to modern fuel injection systems?
B · Inability to adjust fuel mixture under varying operating conditions
Carburetors have limited ability to adjust fuel-air mixture dynamically leading to less efficient combustion compared to fuel injection systems.
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Which transmission system allows the driver to change gear ratios manually using a clutch?
C · Manual transmission
Manual transmission uses the driver-operated clutch and gear lever to select gear ratios manually.
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Which of the following best describes the working principle of a continuously variable transmission (CVT)?
B · Uses belts and pulleys to provide stepless variable gear ratios
CVT employs a system of belts and variable diameter pulleys to provide an infinite number of gear ratios providing smooth acceleration.
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Which is a key advantage of automatic transmission over manual transmission?
B · Driver convenience with no clutch operation
Automatic transmissions provide easier driving experience by eliminating the need to manually operate clutch and shift gears.
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Which type of braking system uses calipers and rotors to stop the vehicle wheels?
B · Disc brakes
Disc brakes use calipers that squeeze the rotor discs attached to the wheels to provide stopping force.
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What is an advantage of disc brakes compared to drum brakes in vehicle braking systems?
A · Better heat dissipation and performance under repeated use
Disc brakes dissipate heat more effectively, reducing brake fade under heavy or repeated braking compared to drum brakes.
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Which of the following statements best describes the primary purpose of combustion in an internal combustion engine?
A · To convert chemical energy in fuel into mechanical work
Combustion converts the chemical energy stored in fuel into thermal energy, which is then transformed into mechanical work by the engine.
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Which gas is primarily produced in large quantities during complete combustion of hydrocarbon fuels?
C · Carbon dioxide (CO₂)
Complete combustion of hydrocarbons produces mainly carbon dioxide (CO₂) and water vapor (H₂O).
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In combustion, which condition generally leads to incomplete combustion in vehicle engines?
C · Insufficient oxygen supply
Insufficient oxygen leads to incomplete combustion, producing CO and unburnt hydrocarbons.
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Which of the following is a characteristic of a two-stroke combustion engine compared to a four-stroke engine?
C · Completes power cycle in only one crankshaft revolution
A two-stroke engine completes the combustion cycle within one crankshaft revolution, unlike the four-stroke which takes two revolutions.
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What is the primary difference between a spark ignition (SI) engine and a compression ignition (CI) engine?
C · SI engine ignites fuel-air mixture by spark; CI engine ignites fuel by compression heating
SI engines use spark plugs to ignite the fuel-air mixture, whereas CI engines ignite fuel by the heat of compressed air.
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Refer to the diagram below showing the combustion chamber cross-section of a typical SI engine.
Which labeled feature in the diagram primarily assists in creating turbulence for better fuel-air mixing?
B · Feature B: Squish area
The squish area forces the air-fuel mixture toward the center causing turbulence and improving mixing and combustion.
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Which phase of the combustion process in an engine is characterized by rapid pressure rise after ignition?
B · Flame propagation period
During the flame propagation period, the combustion front moves rapidly causing a steep pressure rise inside the cylinder.
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In the Otto cycle diagram shown below, what does the area enclosed by the cycle represent?
B · Work done by the cycle
The enclosed area in the pressure-volume (P-V) diagram of the Otto cycle represents the net work output by the engine during one cycle.
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Which of the following correctly represents the order of events in the combustion process inside a CI engine?
A · Fuel injection, ignition delay, combustion, expansion
Fuel is first injected, then ignition delay occurs before actual combustion starts, followed by expansion stroke.
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Considering combustion heat release, peak pressure in an engine cylinder occurs during which process phase?
B · Rapid combustion phase
Peak pressure is reached during the rapid combustion phase when most fuel burns quickly, releasing maximum energy.
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Which of the following fuels has the highest octane number, making it suitable for spark ignition engines?
C · Gasoline
Gasoline typically has higher octane numbers, indicating resistance to knocking in SI engines.
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Which property of fuel primarily affects the ignition delay in compression ignition engines?
B · Cetane number
The cetane number indicates ignition quality; higher cetane fuels have shorter ignition delay in CI engines.
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Refer to the fuel-air mixture flow diagram below.
Which process is primarily indicated by the arrow labeled 'C' directing into the intake manifold?
B · Air intake from the atmosphere
Arrow 'C' shows fresh air intake entering the intake manifold before mixing with fuel.
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In an engine, the brake thermal efficiency \( \eta_{bth} \) is defined as the ratio of:
C · Brake power to energy input from fuel
Brake thermal efficiency measures how effectively the chemical energy in fuel is converted into useful brake power output.
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Which combustion parameter does NOT directly impact the engine's torque output?
D · Exhaust emission levels
Exhaust emissions relate to pollutant formation and environmental impact but do not directly affect torque production.
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Refer to the engine cycle diagram below.
If the indicated mean effective pressure (IMEP) increases while other parameters remain constant, which of the following engine performance aspects will most likely improve?
B · Increased thermal efficiency
Higher IMEP means higher work output per cycle, improving thermal efficiency if fuel consumption is unchanged.
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Which pollutant produced during combustion is the main cause of photochemical smog in urban areas?
B · Nitrogen oxides (NOₓ)
Nitrogen oxides (NOₓ) react with sunlight and volatile organic compounds to form photochemical smog.
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Which emission control technique primarily reduces nitrogen oxide emissions in combustion engines?
B · EGR (Exhaust Gas Recirculation)
EGR reduces the peak combustion temperature, thereby suppressing NOₓ formation.
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Refer to the fuel/air mixture flow diagram below.
Which component in the diagram is responsible for reducing harmful particulate emissions by trapping carbon particles?
B · Component B: Particulate filter
The particulate filter traps soot and carbon particles, reducing particulate emissions from diesel engines.
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Which of the following best defines the combustion process in an internal combustion engine?
A · A chemical reaction between fuel and oxygen releasing heat and producing combustion products
Combustion is a chemical reaction where fuel reacts with oxygen to release heat energy and combustion products such as CO₂ and H₂O.
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The primary purpose of combustion in vehicle engines is to:
A · Generate mechanical work by releasing energy stored in fuel
The combustion process converts the chemical energy in fuel into heat, which then converts into mechanical work driving the piston.
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Refer to the diagram below showing the steps in a combustion process inside an engine cylinder. What stage directly follows the ignition phase?
A · Flame propagation
After ignition, the flame front propagates throughout the air-fuel mixture causing combustion heat release.
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Which type of combustion engine typically uses both spark ignition and air-fuel mixture compression in its operation?
D · Homogeneous Charge Compression Ignition (HCCI) Engine
HCCI engines use both high compression and controlled ignition without a spark plug, combining features of spark ignition and compression ignition.
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Which type of engine operates by compressing only air before fuel injection and ignition occurs by compression?
A · Diesel engine
Diesel engines compress air to high pressure and temperature, and fuel is injected and ignites due to compression heat.
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In a spark ignition engine, which combustion engine type is most commonly used?
A · Four-stroke petrol engine
Most spark ignition engines are four-stroke petrol engines that use spark plugs to ignite the air-fuel mixture.
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The compression ratio of an ideal gasoline engine is generally limited by:
A · Knock or pre-ignition occurring at high compression ratios
High compression ratios increase temperature and pressure, risking spark knock and engine damage in gasoline engines.
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If \( V_c \) is clearance volume and \( V_d \) is displacement volume, how is the compression ratio (CR) defined?
A · \( \frac{V_c + V_d}{V_c} \)
Compression ratio is the total cylinder volume (clearance + displacement) divided by the clearance volume.
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How does increasing the compression ratio of a petrol engine affect its thermal efficiency, assuming all other factors remain constant?
A · Thermal efficiency increases due to higher pressure and temperature
Higher compression ratios increase thermal efficiency by enabling better combustion and higher pressure during expansion.
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A stoichiometric air-fuel mixture refers to:
A · The exact amount of air needed to completely burn the given fuel
The stoichiometric ratio is the chemically correct amount of air to fully burn the fuel without excess air or fuel.
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Ignition delay in diesel engines primarily depends on which of the following factors?
A · Fuel properties and temperature of compressed air
Ignition delay is sensitive to fuel cetane number and temperature of compressed air before ignition occurs.
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Refer to the combustion chamber layout in the diagram. Which ignition method is used in the design shown where a spark plug is embedded centrally?
A · Spark Ignition
Spark plugs are the ignition source in spark ignition engines, where the air-fuel mixture ignites electrically.
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Which of the following is a key difference between two-stroke and four-stroke engines relating to their combustion cycle?
A · Two-stroke engines complete a power cycle in two piston strokes whereas four-stroke engines take four strokes
Two-stroke engines combine intake, compression, power, and exhaust in two strokes; four-stroke engines separate these into four strokes.
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Compared to four-stroke engines, two-stroke engines typically:
A · Have a higher power-to-weight ratio but poorer fuel efficiency
Two-stroke engines produce a power stroke every revolution increasing power density but often at the cost of efficiency and emissions.
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Refer to the PV diagram below of an ideal Otto cycle. Which curve represents the adiabatic compression phase?
A · From bottom right to top left curve
Adiabatic compression occurs as volume decreases and pressure rises without heat transfer, moving from bottom right to top left in Otto cycle PV diagrams.
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Which thermodynamic process in an ideal Otto cycle corresponds to constant volume heat addition?
A · Combustion phase
In the Otto cycle, heat addition (combustion) occurs at constant volume between the compression and expansion strokes.
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Thermal efficiency of an ideal Otto cycle is primarily dependent on:
A · Compression ratio
The Otto cycle efficiency increases with higher compression ratio according to the formula \( \eta = 1 - \frac{1}{r^{\gamma-1}} \).
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Which parameter is commonly used to measure knocking tendency in spark ignition engines?
A · Octane number
Octane number indicates fuel resistance to knock, affecting ignition delay and combustion stability in petrol engines.
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Brake Thermal Efficiency (BTE) is defined as:
A · Ratio of brake power output to fuel energy input
BTE measures how efficiently the engine converts fuel energy into useful mechanical power delivered at the output shaft.
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Which of the following is a commonly used gaseous fuel in vehicle systems?
C · CNG
CNG (Compressed Natural Gas) is a commonly used gaseous fuel in vehicle systems due to its clean-burning properties.
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Which fuel type is primarily used in compression ignition engines?
A · Diesel
Diesel is commonly used in compression ignition engines due to its ignition characteristics under high compression.
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Which of the following is NOT a biofuel used in vehicle systems?
C · CNG
CNG is a fossil-fuel-based gaseous fuel, not a biofuel, unlike biodiesel, ethanol, and methanol which are derived from biological sources.
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Which property of fuel primarily affects its ignition quality in engines?
B · Octane number
Octane number is a key property indicating fuel's resistance to knocking and hence its ignition quality, especially in petrol engines.
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Which of these fuel properties is critical to determine the ease of cold starting in diesel engines?
A · Cetane number
Cetane number indicates the ignition delay of diesel fuel; higher cetane number improves cold start performance.
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Compared to petrol, diesel typically has which of the following properties?
C · Higher cetane number and higher energy density
Diesel fuel generally has a higher cetane number and higher energy density compared to petrol, making it suitable for compression ignition engines.
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In a typical four-stroke petrol engine, fuel combustion takes place during which stroke?
C · Power stroke
Fuel combustion occurs during the power stroke, pushing the piston down to produce mechanical work.
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Which of the following best describes the mixing process in a carburetor used in petrol engines?
A · Fuel is atomized and mixed with air before entering the combustion chamber
A carburetor atomizes the fuel and mixes it with incoming air to form a combustible mixture before entering the cylinder.
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Which fuel injection method improves fuel atomization and reduces emissions in modern diesel engines?
C · Common rail direct injection
Common rail direct injection allows precise control of fuel delivery and pressure, improving atomization and reducing emissions.
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Which of the following statements about combustion in SI (spark ignition) engines is correct?
B · Combustion occurs due to spark ignition with a homogeneous air-fuel mixture
In SI engines, a homogeneous air-fuel mixture is ignited by a spark plug causing combustion.
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Which of the following fuel properties primarily influences the thermal efficiency of an engine?
A · Calorific value
Calorific value indicates the amount of energy released during combustion, directly affecting thermal efficiency.
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Which measure is most effective in reducing NOx emissions from a diesel engine without compromising performance significantly?
B · Exhaust gas recirculation (EGR)
Exhaust gas recirculation (EGR) reduces combustion temperature, thus lowering NOx emissions, and is widely used without major performance loss.
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Which of the following fuel delivery systems provides the most precise and timely fuel metering for improved fuel efficiency in petrol engines?
D · Direct fuel injection
Direct fuel injection sprays fuel directly into the combustion chamber allowing precise control for better fuel efficiency and emissions control.
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Which of the following is a common gaseous fuel used in vehicles?
C · Compressed Natural Gas (CNG)
Compressed Natural Gas (CNG) is a common gaseous fuel used in vehicles due to its cleaner-burning properties compared to liquid fuels like petrol or diesel.
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Which of the following biofuels is derived primarily from sugarcane or corn?
B · Ethanol
Ethanol is commonly produced from sugarcane or corn through fermentation and is used as a biofuel in vehicles.
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Among the following, which fuel type has the highest energy content per unit volume?
B · Diesel
Diesel fuel has a higher energy content per unit volume compared to gaseous or alcohol-based fuels, making it more energy dense.
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Which property of vehicle fuel directly influences the knocking tendency in spark ignition engines?
B · Octane number
The octane number of fuel indicates its resistance to knocking or premature ignition in spark ignition engines.
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Which of the following fuel properties is critical for cold starting performance in diesel engines?
A · Cetane number
Cetane number measures the ignition quality of diesel fuel and influences the ease of cold starting of diesel engines.
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A fuel has a flash point of 25°C, a density of 0.75 g/cm³, and a viscosity of 2 cSt. Which problem might arise if this fuel is used in a vehicle during winter?
B · Fuel may gel or thicken, causing poor flow
Low temperature conditions during winter may cause fuel with inadequate low-temperature viscosity to gel or thicken, leading to poor fuel flow.
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In a typical gasoline fuel supply system, what is the main role of the fuel pump?
B · To pressurize and deliver fuel to the carburetor or fuel injectors
The fuel pump pressurizes and delivers the fuel from the tank to the carburetor or injectors at the required pressure.
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Which of the following correctly describes the function of a fuel injector in a modern fuel supply system?
B · Convert liquid fuel into a fine mist for better combustion
Fuel injectors atomize the liquid fuel into fine droplets to ensure better mixing with air and more efficient combustion.
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In a carbureted fuel supply system, what effect does an increase in altitude have on the air-fuel mixture, and how is it compensated?
A · Mixture becomes richer; compensated by decreasing fuel flow
With increasing altitude, the air density decreases making the mixture leaner; this is compensated by increasing fuel flow to maintain proper mixture ratio.
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During the combustion process in a diesel engine, what primarily initiates combustion?
B · Compression heating of air raising temperature above ignition point
In diesel engines, combustion initiates due to compression heating of air which raises the temperature enough to ignite the injected fuel without spark plugs.
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Which stage of the combustion process in SI engines is associated with the highest rate of pressure rise inside the cylinder?
B · Flame propagation
During flame propagation in SI engines, the combustion happens rapidly, causing the highest rate of pressure rise inside the cylinder.
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Which of the following factors directly increases NOx emissions in vehicle engines during combustion?
B · Higher combustion temperature
Higher combustion temperatures promote the formation of nitrogen oxides (NOx) due to nitrogen and oxygen reaction in air.
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Which of the following fuel characteristics leads to higher thermal efficiency in an internal combustion engine?
C · Higher octane or cetane number
Higher octane (in SI engines) or cetane number (in CI engines) fuels allow for optimized combustion timing, improving thermal efficiency.
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Which of the following methods is commonly used to reduce unburned hydrocarbon emissions in gasoline engines?
B · Using catalytic converters in the exhaust system
Catalytic converters convert unburned hydrocarbons and other pollutants into less harmful substances before exhaust is released.
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Consider a vehicle engine running on a lean air-fuel mixture. What is the likely effect on fuel efficiency and NOx emissions?
C · Higher fuel efficiency; higher NOx emissions
Lean mixtures improve fuel efficiency but tend to raise combustion temperature, which increases NOx emissions.
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What is the primary function of the ignition system in an internal combustion engine?
A · To ignite the air-fuel mixture in the combustion chamber
The ignition system's main role is to ignite the air-fuel mixture inside the combustion chamber at the correct time to initiate combustion.
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Which of the following is NOT a characteristic of an ignition system?
C · Controlling fuel injection timing
Controlling fuel injection timing is the function of the fuel delivery system, not the ignition system.
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Which type of ignition system uses a battery, an ignition coil, and breaker points to generate sparks?
C · Conventional (Contact Breaker) Ignition
The Conventional ignition system relies on battery, ignition coil, and mechanical breaker points to interrupt current and produce high voltage spark.
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Which of the following is a key advantage of Capacitor Discharge Ignition (CDI) systems over conventional ignition systems?
C · Faster spark buildup and better high-speed performance
CDI systems charge a capacitor and discharge it rapidly, producing a high voltage spark that improves performance at higher engine speeds.
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In a petrol engine ignition system, the spark is produced by converting low voltage supplied by the battery into high voltage using which component?
B · Ignition Coil
The ignition coil acts as a step-up transformer that converts low voltage from the battery into the high voltage needed to produce a spark at the spark plug.
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Refer to the diagram below of a basic ignition circuit.
Which component is responsible for interrupting the current flow to the ignition coil to generate a high voltage pulse?
C · Contact Breaker
The contact breaker opens and closes the circuit to the ignition coil primary winding, causing rapid current interruption and producing the high voltage pulse.
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Which component in an ignition system is responsible for distributing high voltage to the correct cylinder in multi-cylinder engines?
A · Distributor Rotor
The distributor rotor directs the high voltage produced by the ignition coil to the correct spark plug terminal, ensuring proper firing sequence.
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Identify from the options the component that stores electrical charge in the ignition system to prevent arcing across contact breaker points.
C · Condenser (Capacitor)
The condenser stores charge to absorb voltage spikes and prevents arcing at the contact breaker points.
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Refer to the timing chart below showing ignition timing advance.
What happens to the ignition timing as engine speed increases to maintain optimal combustion?
C · Ignition timing is advanced (spark fires earlier)
At higher engine speeds, ignition timing needs to be advanced so the spark occurs earlier to complete combustion in time for the piston’s power stroke.
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Which method is commonly used to advance ignition timing with increasing engine speed?
B · Mechanical centrifugal advance weights
Mechanical centrifugal advance uses rotating weights in the distributor that move outward with engine speed to advance the ignition timing automatically.
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At what condition will ignition timing be most likely retarded intentionally to prevent engine knocking?
C · When engine is overheating
Retarding ignition timing reduces peak combustion temperatures, helping to prevent knocking and engine damage when overheating occurs.
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Which of the following is a common ignition system fault characterized by misfires and weak spark due to worn contact breaker points?
C · Contact point pitting and erosion
Wear and erosion of contact breaker points increase contact resistance, causing weak or intermittent spark and resulting in engine misfires.
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Which diagnostic method would best help identify an ignition coil failure causing no spark in the ignition system?
B · Measuring coil resistance and spark test using a spark tester
Measuring coil resistance with a multimeter and performing a spark test helps identify if the ignition coil is generating sufficient voltage to produce spark.
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Which of the following is NOT a common type of ignition system used in vehicles?
D · Hydraulic Ignition System
Hydraulic ignition system is not a type of ignition system. The common types include battery, magneto, and capacitor discharge ignition systems.
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Which ignition system type is most suitable for small engines without external power sources?
B · Magneto Ignition System
Magneto ignition systems are self-contained and generate electricity without a battery, making them suitable for small engines without external power.
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Which of these ignition systems uses a capacitor to store and release energy rapidly to the ignition coil?
C · Capacitor Discharge Ignition System
Capacitor Discharge Ignition (CDI) systems store energy in a capacitor and release it quickly to the ignition coil to produce high voltage sparks.
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Refer to the diagram below of a basic ignition system circuit. What is the function of component labeled 'C' (capacitor)?
B · Suppress sparking at contact breaker points
The capacitor connected across the contact breaker points prevents sparking when the points open, thus protecting the points and ensuring the coil can generate a high voltage spark.
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Identify the component responsible for generating high voltage needed to create the spark in a conventional ignition system.
B · Ignition Coil
The ignition coil transforms the low battery voltage into the high voltage necessary for spark plug operation.
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Which of the following components controls the timing of the spark by mechanically opening and closing the circuit in older ignition systems?
B · Contact Breaker Points
Contact breaker points open and close to interrupt current flow, triggering the coil to produce a spark at the correct timing.
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Refer to the timing chart below for a 4-stroke petrol engine ignition system. At what crank angle (degrees before top dead center) should the spark ideally occur for optimal combustion efficiency?
B · 15° Before TDC
Ignition is commonly advanced to about 15° before top dead center to allow sufficient time for combustion to reach peak pressure just after TDC.
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What is the primary effect of advancing the spark timing in a petrol engine ignition system?
B · Improved fuel economy and increased engine knock risk
Advancing spark timing helps improve fuel economy and power by igniting the mixture earlier but can cause engine knock if advanced excessively.
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Which of the following methods is commonly used for automatic spark timing control in modern ignition systems?
A · Vacuum advance mechanism
Vacuum advance uses engine manifold vacuum to adjust spark timing automatically based on engine load, improving performance and efficiency.
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Refer to the diagnostic flowchart below for ignition system faults. If the spark plug is fouled and the ignition coil tests good, which component is the most probable cause?
B · Defective contact breaker points
Fouled spark plugs with good coil performance often indicate ineffective sparking due to defective contact breaker points not triggering coil properly.
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Which fault is most likely if an engine experiences intermittent misfires and the ignition coil shows secondary winding failure upon testing?
B · Open circuit in coil secondary winding
An open circuit in the coil’s secondary winding causes weak or no spark resulting in intermittent misfire.
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What is the recommended first step in diagnosing a no-spark condition in a conventional ignition system?
B · Verify battery voltage and connections
The initial step is always to check battery voltage and wiring to ensure the ignition system has power before proceeding with other tests.
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Which of the following is NOT an engine performance parameter?
C · Fuel Octane Rating
Fuel Octane Rating refers to fuel quality and knocking resistance, not an engine performance parameter.
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The brake thermal efficiency of an engine is defined as the ratio of:
A · Brake power to the heat supplied by fuel
Brake thermal efficiency measures how efficiently the engine converts fuel energy into brake power output.
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For a given engine, the brake specific fuel consumption (BSFC) is minimum at which of the following operating conditions?
B · Maximum torque RPM
BSFC is typically minimum at the RPM where the engine produces maximum torque efficiently.
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If an engine has an indicated power of 100 kW and a brake power of 85 kW, what is the mechanical efficiency of the engine?
A · 85%
Mechanical efficiency = (Brake Power / Indicated Power) × 100 = (85 / 100) × 100 = 85%
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Refer to the diagram below showing the power and torque curves of an engine. At which engine speed does the engine produce maximum torque?
B · 3000 RPM
The torque curve peaks at 3000 RPM as shown in the diagram where torque reaches its highest value.
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Which expression correctly relates power \( P \) (in watts), torque \( T \) (in newton-meters), and angular speed \( \omega \) (in radians per second)?
A · \( P = T \times \omega \)
Power is the product of torque and angular speed: \( P = T \times \omega \).
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At a particular engine speed, if torque increases while power remains constant, what must happen to the engine speed?
B · Engine speed decreases
Since power \( P = T \times \omega \) is constant, if torque increases, angular velocity (engine speed) must decrease.
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Which one of the following statements about torque and power characteristics of a vehicle engine is TRUE?
B · Power continues to increase even after torque starts to fall with increasing RPM
Power can increase with RPM even if torque decreases because power depends on both torque and engine speed.
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An engine has a maximum brake power of 120 kW at 5000 RPM and maximum torque of 230 Nm at 3500 RPM. What is the approximate brake power at 3500 RPM? (Use \( P = \frac{2\pi NT}{60} \))
A · 85 kW
At 3500 RPM: \( P = \frac{2\pi \times 3500 \times 230}{60} = \) approx 85 kW.
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Refer to the diagram below illustrating the schematic of a dynamometer used for performance testing. What is the primary purpose of the load application unit?
B · To apply controlled load to the engine
Load application unit applies and controls torque/load to measure engine output under various conditions.
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Which of the following is commonly used to measure brake power during performance testing of engines?
A · Dynamometer
Dynamometers are devices used to measure brake power by applying load and measuring torque and speed.
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What is the primary reason for conducting transient performance tests on vehicles instead of only steady-state tests?
A · To evaluate acceleration and response under varying load
Transient tests assess vehicle response to changing conditions such as acceleration and deceleration, closer to real driving.
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If a vehicle accelerates uniformly from 0 to 30 m/s in 10 seconds, what is its acceleration?
A · 3 m/s²
Acceleration \( a = \frac{\Delta v}{\Delta t} = \frac{30 - 0}{10} = 3 \; m/s^2 \).
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Refer to the graph below representing vehicle speed and acceleration versus time. At what time interval is the acceleration zero?
A · Between 5s and 10s
Acceleration is zero when speed is constant; the graph shows constant speed between 5s and 10s.
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Which factor does NOT directly affect the fuel consumption of a vehicle?
C · Radiator color
Radiator color has no significant impact on fuel consumption; other options directly influence fuel use.
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Which measure expresses the amount of fuel consumed per unit power output over time?
A · Brake specific fuel consumption (BSFC)
BSFC indicates fuel efficiency relative to power output over time.
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If the calorific value of fuel is 42 MJ/kg and an engine consumes 0.5 kg/hr producing 20 kW brake power, what is the brake thermal efficiency? (\( \eta_b = \frac{BP}{mf \times CV} \))
B · 36%
Calculate fuel energy/hr = 0.5 × 42 = 21 MJ/hr = 21,000 kJ/hr, power output = 20 kW = 20 kJ/s = 72,000 kJ/hr; Brake thermal efficiency = (72,000 / 21,000) × 100 = 36%.
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Which of the following improves fuel efficiency in a typical gasoline engine?
A · Lean air-fuel mixture
A lean air-fuel mixture improves fuel efficiency by reducing fuel consumption per air volume.
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During a performance test, if the vehicle speed doubles and the power requirement increases eightfold, what type of resistance mainly dominates vehicle motion?
A · Aerodynamic resistance
Aerodynamic drag increases roughly with the square of speed causing power requirement to increase with the cube of speed.
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Refer to the diagram below showing a vehicle speed vs time and acceleration vs time graph. At what time does the acceleration peak occur?
A · At 2 seconds
The acceleration curve reaches its maximum value at 2 seconds as shown in the diagram.
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Which of the following is NOT a type of transmission system commonly used in vehicles?
D · Vacuum Transmission
Vacuum transmission is not a recognized type of transmission system in vehicles. Manual, Hydraulic, and CVT are common types.
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Which transmission system allows infinite variability in gear ratios within a specified range?
C · Continuously Variable Transmission (CVT)
Continuously Variable Transmission (CVT) allows seamless changes in gear ratio for smoother acceleration and better fuel efficiency.
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Select the main advantage of a manual transmission over an automatic transmission.
A · Higher fuel efficiency due to direct driver control
Manual transmissions allow the driver to optimize gear selection, generally offering better fuel efficiency than automatic transmissions.
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The gear ratio is defined as the ratio of the number of teeth on the driven gear to the number of teeth on the driving gear. If a driving gear has 20 teeth and the driven gear has 60 teeth, what is the gear ratio?
B · 3:1
Gear ratio = Number of teeth on driven gear / Number of teeth on driving gear = 60/20 = 3:1, often expressed as 1:3 indicating speed reduction.
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Which of the following gear systems is typically used in automotive transmissions to achieve multiple gear ratios within a compact space?
B · Epicyclic (Planetary) Gear Train
Epicyclic or planetary gear trains provide multiple gear ratios in a compact design widely used in automatic transmissions.
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What is the primary function of a clutch in a vehicle transmission system?
B · To connect and disconnect the engine from the transmission
The clutch allows the driver to disconnect the engine power from the transmission so gears can be changed without damage.
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Which type of clutch operates by frictional contact and is most commonly used in manual transmissions?
C · Single Plate Friction Clutch
Single plate friction clutches use friction plates to engage and disengage the engine from the gearbox, commonly used in cars.
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Which of the following is a significant advantage of automatic transmission compared to manual transmission?
C · Ease of use due to no clutch operation
Automatic transmissions eliminate the need for driver-operated clutches, providing ease of operation especially in traffic.
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Which component in a manual transmission system is responsible for engaging different gear sets to provide various speed ratios?
A · Synchronizer
Synchronizers engage gears smoothly by matching speeds, enabling smooth gear changes in manual transmissions.
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Which transmission component is primarily responsible for transmitting torque from the engine to the transmission while allowing for slippage in automatic vehicles?
B · Torque Converter
The torque converter in automatic transmissions transmits and multiplies torque while allowing for controlled slippage.
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Which factor has the greatest impact on the efficiency of a vehicle transmission system?
A · Gear tooth profile and lubrication
The gear tooth geometry and lubrication reduce friction losses, directly influencing transmission efficiency.
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Improving the transmission efficiency reduces power losses. Which one of these best describes a common method to improve transmission efficiency?
C · Employing high-quality synthetic lubricants to reduce friction
High-quality lubricants reduce friction and wear, resulting in improved transmission efficiency and performance.
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Which of the following gear types is commonly used in manual vehicle gearboxes due to its high strength and smooth operation?
B · Helical gear
Helical gears are used commonly in manual vehicle gearboxes because their angled teeth engage gradually, resulting in smoother operation and higher load capacity compared to spur gears.
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What type of gear arrangement allows the direction of the output shaft to be perpendicular to the input shaft in a gearbox?
C · Bevel gear
Bevel gears are used when the input and output shafts have to be at an angle, usually 90 degrees, allowing change in shaft direction.
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Refer to the diagram below showing different gear tooth profiles in a manual gearbox. Which gear type is best suited for transmitting high torque smoothly at high speeds?
C · Helical gear
Helical gears, due to their angled teeth, provide gradual engagement leading to smooth transmission of high torque at high speeds.
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In a standard manual gearbox, what is the primary function of the idler gear?
B · Reverse the direction of rotation
The idler gear is used primarily to reverse the direction of the output shaft without changing the gear ratio.
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Which of the following gear types inside a manual transmission would produce the highest noise levels during operation if not properly lubricated?
B · Spur gear
Spur gears have straight teeth and make a sudden contact causing higher noise and vibration compared to helical or bevel gears.
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What is the main purpose of a clutch in a manual transmission system?
B · To connect and disconnect the engine from the transmission
The clutch enables the driver to temporarily disconnect the engine from the transmission to enable gear changes and smooth vehicle starts.
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Identify the component in a typical clutch assembly that engages the engine flywheel directly to transmit torque.
B · Clutch disc
The clutch disc is sandwiched between the flywheel and pressure plate and transmits torque from the engine to the transmission when engaged.
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Refer to the diagram below showing a cross-section of a clutch assembly. Which part is responsible for disengaging the clutch when the pedal is pressed?
C · Throw-out bearing
The throw-out bearing presses against the pressure plate levers to release the pressure on the clutch disc, thereby disengaging the clutch.
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Which of the following clutch types is most commonly used in manual transmission vehicles for its smooth engagement and ease of control?
C · Single plate dry clutch
The single plate dry clutch is widely used in manual transmissions due to its simplicity, smooth operation, and reliable torque transmission.
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What could be a likely cause of clutch slipping in a manual transmission vehicle under load conditions?
A · Worn clutch lining
A worn clutch lining reduces friction causing the clutch to slip and fail to transmit full torque, particularly noticeable under load.
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Refer to the transmission system flow diagram below. Which component transfers torque from the clutch to the gearbox input shaft?
B · Clutch disc
The clutch disc is connected to the input shaft and transfers torque from the clutch assembly into the gearbox.
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What is the primary purpose of the gearbox layout in a manual transmission vehicle?
B · To change gear ratios for speed and torque control
The gearbox's main purpose is to provide different gear ratios to control the vehicle’s speed and torque output effectively.
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In a typical manual transmission layout, which shaft connects the gear selector mechanism to the gears inside the gearbox?
D · Selector shaft
The selector shaft is connected to the gear lever and moves the sliding collars to engage different gears.
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Refer to the schematic diagram of a manual transmission system below. If the input shaft rotates at 3000 rpm and the selected gear ratio is 3:1, what will be the speed of the output shaft?
A · 1000 rpm
Output shaft speed = Input speed / Gear ratio = 3000 rpm / 3 = 1000 rpm.
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Which part in a manual transmission facilitates smooth mesh and engagement of gears of different speeds during shifting?
B · Synchromesh ring
The synchromesh ring synchronizes the speeds of gears before engagement ensuring smooth shifting.
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Refer to the synchromesh ring illustration below. What happens when the brass ring engages with the hub sleeve during gear shifting?
B · The gear and shaft speeds are synchronized before engagement
The brass synchromesh ring uses friction to equalize gear and shaft speeds allowing gears to engage smoothly without grinding.
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Which of the following problems is commonly caused by a faulty synchromesh mechanism in a manual transmission?
B · Difficulty in engaging certain gears
A faulty synchromesh ring or mechanism causes difficulty or grinding noise when shifting gears because gear speeds are not synchronized.
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What is the recommended technique to avoid gear clash while shifting gears in a manual transmission vehicle?
B · Depress clutch fully before shifting and match engine speed
Proper clutch operation combined with speed matching (rev matching) helps prevent gear clash and damage to the gearbox.
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Which of the following is NOT a common issue related to poor shifting techniques in manual transmissions?
D · Reduced brake efficiency
Poor shifting techniques cause gear clash, clutch wear, and synchronizer damage but do not directly affect brake efficiency.
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During downshifting in a manual transmission, a driver experiences engine braking and jerks. Which adjustment in shifting technique can reduce this issue?
B · Apply throttle to increase engine speed before clutch release (rev matching)
Rev matching by increasing engine speed before releasing the clutch during downshift reduces engine braking jerks and makes the transition smoother.
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Which path correctly describes power flow in a manual transmission system starting from the engine to the wheels?
A · Engine → Clutch → Input shaft → Gearbox → Driveshaft → Wheels
In manual transmissions, power flows from the engine to the clutch, then input shaft into the gearbox, followed by the driveshaft and ultimately to the wheels.
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Refer to the schematic power flow diagram below of a manual transmission system. Which component is responsible for transmitting power directly to the differential and wheels after gear selection?
C · Output shaft
The output shaft delivers power from the gearbox to the driveshaft and differential, finally turning the wheels.
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Which of the following best explains the advantage of using a manual transmission system power flow over an automatic transmission?
B · Allows driver control over gear ratio resulting in better fuel efficiency
Manual transmissions allow the driver to control gear changes directly, offering better fuel efficiency especially under varying driving conditions.
