Internal Combustion Engines (I.C. Engines) MCQ

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These 25 MCQs cover a range of topics within Internal Combustion Engines, including engine components, operations, and emissions control. They are designed to test knowledge in both theoretical and practical contexts in the field of Mechanical Engineering.

1. What is the primary purpose of an internal combustion engine?

a) To convert chemical energy of fuel into thermal energy
b) To convert thermal energy into mechanical energy
c) To reduce fuel consumption
d) To increase the speed of the vehicle

Answer:

b) To convert thermal energy into mechanical energy

Explanation:

An internal combustion engine converts the thermal energy produced by the burning of fuel into mechanical energy, which is used to power vehicles or machinery.

2. What distinguishes a diesel engine from a gasoline engine?

a) Type of fuel used
b) Method of igniting the fuel-air mixture
c) Engine speed
d) Both a and b

Answer:

d) Both a and b

Explanation:

Diesel engines use diesel fuel and rely on compression ignition, where the air is compressed to a high temperature, igniting the fuel. Gasoline engines use gasoline and spark plugs for ignition.

3. What is the four-stroke cycle in an I.C. engine?

a) Intake, compression, power, exhaust
b) Intake, power, exhaust, compression
c) Compression, intake, power, exhaust
d) Power, intake, compression, exhaust

Answer:

a) Intake, compression, power, exhaust

Explanation:

The four-stroke cycle consists of four distinct strokes: intake (air and fuel enter the engine), compression (compression of the mixture), power (ignition and combustion), and exhaust (expulsion of combustion gases).

4. In an I.C. engine, what is the role of the piston?

a) To open and close the intake and exhaust valves
b) To convert linear motion into rotational motion
c) To create a vacuum for fuel intake
d) To compress the air-fuel mixture

Answer:

b) To convert linear motion into rotational motion

Explanation:

The piston in an I.C. engine moves up and down in the cylinder due to combustion. This linear motion is converted into rotational motion by the connecting rod and crankshaft, driving the vehicle's wheels.

5. What is knocking in an I.C. engine?

a) A loud noise from the exhaust system
b) Premature combustion of the air-fuel mixture
c) A problem with the engine's cooling system
d) Leakage of fuel from the injector

Answer:

b) Premature combustion of the air-fuel mixture

Explanation:

Knocking, or detonation, occurs when the air-fuel mixture in the cylinder ignites prematurely, causing a high-pressure wave that creates a pinging or knocking sound and can damage the engine.

6. What is the function of a carburetor in a gasoline engine?

a) To ignite the fuel
b) To filter the air
c) To mix air with fuel in the correct ratio
d) To cool the engine

Answer:

c) To mix air with fuel in the correct ratio

Explanation:

The carburetor in a gasoline engine mixes air and fuel in the correct ratio for efficient combustion. It ensures the right amount of fuel is combined with air before it enters the combustion chamber.

7. What is the purpose of a turbocharger in an I.C. engine?

a) To cool the engine
b) To filter the engine oil
c) To increase engine power by forcing more air into the combustion chamber
d) To reduce fuel consumption

Answer:

c) To increase engine power by forcing more air into the combustion chamber

Explanation:

A turbocharger increases engine power by using exhaust gases to drive a turbine, which compresses air and forces it into the combustion chamber, allowing more fuel to be burned.

8. What is the primary advantage of fuel injection over carburetion in I.C. engines?

a) Lower fuel costs
b) More precise fuel delivery
c) Simpler design
d) Longer engine life

Answer:

b) More precise fuel delivery

Explanation:

Fuel injection systems offer more precise control over the quantity and timing of fuel delivery to the engine, leading to better fuel efficiency, lower emissions, and improved engine performance.

9. What is a common symptom of a faulty spark plug in a gasoline engine?

a) Excessive fuel consumption
b) Reduced engine power
c) Oil leakage
d) Both a and b

Answer:

d) Both a and b

Explanation:

Faulty spark plugs can lead to misfires, resulting in excessive fuel consumption and reduced engine power. They are crucial for the proper ignition of the air-fuel mixture in gasoline engines.

10. What is the primary purpose of a camshaft in an I.C. engine?

a) To control the opening and closing of the valves
b) To convert linear motion to rotary motion
c) To increase air intake
d) To drive the fuel pump

Answer:

a) To control the opening and closing of the valves

Explanation:

The camshaft in an I.C. engine is designed to control the timing of the opening and closing of the intake and exhaust valves, ensuring that they operate in sync with the piston movement.

11. What is the main advantage of using a multi-cylinder engine over a single-cylinder engine?

a) Simpler construction
b) Higher power output
c) Lower manufacturing cost
d) Easier maintenance

Answer:

b) Higher power output

Explanation:

Multi-cylinder engines provide higher power output and smoother operation compared to single-cylinder engines due to more balanced power strokes and reduced vibration.

12. In a diesel engine, what is the role of the glow plug?

a) To initiate the combustion process
b) To heat the air-fuel mixture
c) To assist in cold starts by heating the combustion chamber
d) To regulate fuel injection

Answer:

c) To assist in cold starts by heating the combustion chamber

Explanation:

Glow plugs in diesel engines help in cold starts by heating the air in the combustion chamber, facilitating the compression and ignition of the diesel fuel in low-temperature conditions.

13. What is the function of the flywheel in an I.C. engine?

a) To store and release energy for smoothing out power delivery
b) To control engine speed
c) To cool the engine
d) To increase fuel efficiency

Answer:

a) To store and release energy for smoothing out power delivery

Explanation:

The flywheel in an I.C. engine stores rotational energy and releases it, helping to smooth out the power delivery over each engine cycle and maintain a consistent engine speed.

14. What is the purpose of valve timing in an I.C. engine?

a) To control the engine's exhaust emissions
b) To regulate the engine's cooling system
c) To determine the precise opening and closing of the intake and exhaust valves
d) To adjust the engine's idle speed

Answer:

c) To determine the precise opening and closing of the intake and exhaust valves

Explanation:

Valve timing in an I.C. engine is crucial for optimal engine performance. It involves setting the precise timing for the opening and closing of the intake and exhaust valves relative to the position of the pistons.

15. What is the primary cause of engine overheating?

a) Low oil level
b) Faulty spark plugs
c) Malfunctioning cooling system
d) Improper valve timing

Answer:

c) Malfunctioning cooling system

Explanation:

The most common cause of engine overheating is a malfunctioning cooling system, which fails to remove sufficient heat from the engine, leading to excessive temperatures that can damage engine components.

16. What is the role of the crankshaft in an I.C. engine?

a) To open and close the valves
b) To initiate the ignition process
c) To convert the reciprocating motion of the pistons into rotational motion
d) To mix air and fuel

Answer:

c) To convert the reciprocating motion of the pistons into rotational motion

Explanation:

The crankshaft in an I.C. engine converts the up-and-down (reciprocating) motion of the pistons into rotational motion, which is then transmitted to the wheels of the vehicle.

17. What does the term 'stoichiometric mixture' refer to in an I.C. engine?

a) A mixture with excess air
b) A mixture with excess fuel
c) The ideal ratio of air to fuel for complete combustion
d) A lean mixture used for emission control

Answer:

c) The ideal ratio of air to fuel for complete combustion

Explanation:

The stoichiometric mixture in an I.C. engine is the ideal ratio of air to fuel that allows for complete combustion of the fuel with no excess air or fuel remaining.

18. What is a common symptom of an inefficient combustion process in an I.C. engine?

a) High fuel consumption
b) Reduced engine noise
c) Increased engine cooling
d) Decreased exhaust emissions

Answer:

a) High fuel consumption

Explanation:

Inefficient combustion in an I.C. engine often leads to high fuel consumption, as the engine requires more fuel to produce the same amount of power. It can also cause increased emissions and reduced performance.

19. What is the main advantage of variable valve timing (VVT) in an I.C. engine?

a) Reduced fuel consumption
b) Improved engine performance at different speeds
c) Lower exhaust emissions
d) Both b and c

Answer:

d) Both b and c

Explanation:

Variable valve timing allows for optimized engine performance at different speeds and load conditions, improving overall efficiency, power output, and reducing exhaust emissions.

20. What is the main purpose of an oil filter in an I.C. engine?

a) To cool the engine oil
b) To regulate oil pressure
c) To remove contaminants from the engine oil
d) To increase oil flow

Answer:

c) To remove contaminants from the engine oil

Explanation:

The oil filter in an I.C. engine is designed to remove contaminants such as dirt, metal particles, and carbon deposits from the engine oil, ensuring that the oil remains clean to lubricate and protect the engine effectively.

21. What is the function of a muffler in an I.C. engine's exhaust system?

a) To reduce harmful emissions
b) To cool the exhaust gases
c) To reduce the noise produced by the exhaust
d) To increase engine efficiency

Answer:

c) To reduce the noise produced by the exhaust

Explanation:

The muffler in an I.C. engine's exhaust system is designed to reduce the noise produced by the exhaust gases as they exit the engine. It does this by dissipating the sound energy and reducing the sound pressure.

22. What is the primary purpose of a timing belt in an I.C. engine?

a) To drive the water pump
b) To ensure synchronized operation of the engine's valves and pistons
c) To regulate the fuel injection timing
d) To control the engine's cooling system

Answer:

b) To ensure synchronized operation of the engine's valves and pistons

Explanation:

The timing belt in an I.C. engine ensures the synchronized operation of the engine's camshaft and crankshaft. This synchronization is crucial for the proper timing of the valves' opening and closing in relation to the pistons' movement.

23. What causes 'pre-ignition' in a gasoline engine?

a) Faulty fuel injectors
b) Spark plug igniting the fuel-air mixture too early
c) Hot spots in the combustion chamber igniting the fuel-air mixture before the spark
d) Insufficient air supply

Answer:

c) Hot spots in the combustion chamber igniting the fuel-air mixture before the spark

Explanation:

Pre-ignition in a gasoline engine occurs when the fuel-air mixture ignites prematurely, before the spark plug fires. This premature ignition is usually caused by hot spots in the combustion chamber, such as overheated valves or carbon deposits.

24. In an I.C. engine, what is the function of the alternator?

a) To charge the battery
b) To start the engine
c) To power the ignition system
d) To provide lighting for the vehicle

Answer:

a) To charge the battery

Explanation:

The alternator in an I.C. engine is responsible for charging the battery while the engine is running. It converts mechanical energy into electrical energy, providing power to the vehicle's electrical systems and recharging the battery.

25. What is the purpose of a catalytic converter in an I.C. engine?

a) To increase fuel efficiency
b) To enhance engine performance
c) To reduce harmful exhaust emissions
d) To filter particulates from the exhaust

Answer:

c) To reduce harmful exhaust emissions

Explanation:

A catalytic converter in an I.C. engine reduces harmful exhaust emissions by converting pollutants like carbon monoxide, nitrogen oxides, and hydrocarbons into less harmful substances such as carbon dioxide, nitrogen, and water vapor.

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