Past Questions — 2025

Daily vehicle maintenance (often called a 'pre-trip inspection') focuses on safety-critical items and fluids that fluctuate or deplete quickly. 1. **Check coolant (Option a):** Essential for daily checks to prevent engine overheating, especially in varying weather conditions. 2. **Check cleanliness of mirror (Option b):** A critical safety requirement for visibility and road safety, performed every time a vehicle is started. 3. **Check Tyre Pressure (Option c):** While some modern vehicles have TPMS, a visual or gauge check of tyre pressure is a standard daily/regular safety practice to ensure traction and fuel efficiency. 4. **Check Gear oil (Option d):** Gear oil is a long-term lubricant. Unlike engine oil or coolant, gear oil levels do not fluctuate daily and are typically checked during scheduled periodic maintenance (e.g., every 10,000 to 50,000 km) or when a leak is suspected. It is not part of a standard daily checklist.

BS-VI stands for 'Bharat Stage VI'. It is an emission standard instituted by the Government of India to regulate the output of air pollutants (such as nitrogen oxides, particulate matter, and carbon monoxide) from internal combustion engines. These standards are based on the European (Euro) emission standards. - Option (a) 'Bharat State' is incorrect as it refers to a political entity, not a technical standard. - Option (b) 'Bharat Standard' is a common misconception, but the official terminology used by the Ministry of Road Transport and Highways (MoRTH) is 'Stage'. - Option (d) 'Bureau of Standard' is incorrect; while the Bureau of Indian Standards (BIS) exists, the specific automotive emission nomenclature is 'Bharat Stage'.

A Vehicle History Sheet (also known as a vehicle maintenance log or service record) is a formal document used by fleet managers and engineers to track the lifecycle, maintenance, and repair history of a specific vehicle. 1. **Dates of Services (Option a):** Essential for tracking maintenance intervals and ensuring the vehicle is serviced according to the manufacturer's schedule. 2. **Types of repair done (Option b):** Critical for identifying recurring faults, tracking part replacements, and assessing the overall mechanical health of the vehicle. 3. **Name of workshop (Option d):** Necessary for accountability, warranty claims, and verifying that the work was performed by an authorized or qualified service provider. **Why Option c is correct:** 'Road condition during trips' is operational data typically recorded in a **Trip Sheet** or a **Driver's Log Book**, not a Vehicle History Sheet. The history sheet focuses on the physical state and maintenance of the machine itself, whereas road conditions are external environmental factors related to specific journeys.

In a two-stroke internal combustion engine, the functions of intake, compression, power, and exhaust are completed in just two strokes of the piston. Unlike a four-stroke engine, which has dedicated strokes for intake and exhaust, a two-stroke engine performs these actions simultaneously. 'Scavenging' is the specific process where the fresh air-fuel mixture (or just air in diesel engines) enters the cylinder and pushes out the burnt exhaust gases from the previous combustion cycle. This ensures the cylinder is cleared of waste gases and filled with a fresh charge for the next cycle. Analysis of other options: - Option (a) refers to 'Compression', which is a separate phase of the cycle. - Option (b) refers to 'Ignition' or 'Combustion'. - Option (d) refers to 'Lubrication', which is a maintenance process to reduce friction, not a cycle phase.

Step-by-step reasoning: 1. Definition of Arc Welding: Arc welding is a process that uses an electric arc to create intense heat to melt the base metals and usually a filler material to join two pieces of metal together. 2. Classification of Welding: Welding processes are broadly categorized based on whether the base metal is melted or not. - Fusion Welding: Processes where the base metal is melted to form a pool of molten metal that solidifies to create a joint. Examples include Arc welding, Gas welding, and Laser beam welding. - Solid-state Welding: Processes where joining occurs without melting the base metal, typically using pressure and heat below the melting point. Examples include Friction welding and Forge welding. 3. Evaluating Options: - Option (a) Solid-state Welding: Incorrect, as arc welding involves melting the metal. - Option (b) Fusion Welding: Correct, as the electric arc melts the metal to create a fusion joint. - Option (c) Resistance Welding: While resistance welding uses electricity, it is a specific sub-category that relies on electrical resistance and pressure; arc welding relies on an open electric arc. - Option (d) Pressure Welding: Incorrect, as arc welding relies on heat/melting rather than primary mechanical pressure to achieve the bond.

The air filter is a critical component of the engine intake system. Its primary function is to act as a barrier that traps airborne contaminants—such as dust, dirt, pollen, and other debris—before the air enters the combustion chamber. If these particles were allowed to enter the engine, they would act as abrasives, causing premature wear and tear on the cylinder walls, piston rings, and valves, eventually leading to engine failure. Analysis of other options: - Option (a): While a clean air filter helps maintain optimal performance, the 'primary purpose' is protection, not performance enhancement itself. - Option (c): Cooling the engine is the primary purpose of the radiator and cooling system, not the air filter. - Option (d): The air filter is typically located inside the engine bay or a housing and is not a cosmetic feature designed to make the car look nicer.

In gas welding (such as Oxy-Acetylene welding), the flow of gases from the cylinders to the torch and finally to the tip is controlled by valves. Specifically, the torch contains control valves (needle valves) that allow the operator to precisely adjust the flow rate of oxygen and fuel gas to achieve the desired flame type (neutral, oxidizing, or carburizing). Why other options are incorrect: - a. Mixture: This refers to the combination of gases, not a mechanical component that controls flow. - c. Tip: The tip (or nozzle) determines the size and shape of the flame and the exit point of the gas, but it does not 'control' the flow rate; that is done upstream by the valves. - d. Regulator: While a regulator controls the pressure of the gas leaving the cylinder, the specific component on the torch used to control the flow into the flame is the valve.

In a petrol engine (which operates on the Spark Ignition or SI cycle), the air-fuel mixture is compressed within the cylinder. Unlike a diesel engine, which uses compression heat to ignite the fuel, a petrol engine requires an external source of ignition. The spark plug is an electrical device that delivers a high-voltage electric spark across a small gap at the end of the plug, which initiates the combustion of the compressed air-fuel mixture, driving the piston downward. Analysis of other options: - Option (a) is incorrect because the mixing of air and fuel is performed by the carburetor or fuel injectors. - Option (c) is incorrect because engine temperature is measured by a temperature sensor or thermocouple. - Option (d) is incorrect because the opening and closing of valves are controlled by the camshaft and valve train mechanism.

TIG (Tungsten Inert Gas) welding, also known as Gas Tungsten Arc Welding (GTAW), uses a non-consumable electrode made of tungsten. The purpose of the electrode in TIG welding is solely to create the electric arc that melts the base metal; it does not melt into the weld pool. If filler metal is required, it is added separately by the welder. Analysis of other options: - (a) Consumable: This describes electrodes used in MIG (Metal Inert Gas) or SMAW (Shielded Metal Arc Welding), where the electrode melts to become part of the joint. - (b) Coated: This refers to electrodes used in SMAW (Stick welding), where a flux coating provides shielding gas and slag. - (d) Made of copper: Copper is too conductive and has a melting point too low for the arc temperatures required in TIG welding; tungsten is used because of its extremely high melting point.

To determine which option is not a type of welding, we analyze each process: 1. **TIG Welding (Tungsten Inert Gas Welding):** This is a legitimate arc welding process that uses a non-consumable tungsten electrode to produce the weld. It is widely used for high-quality welds on stainless steel and aluminum. 2. **MIG Welding (Metal Inert Gas Welding):** This is a legitimate arc welding process where a consumable wire electrode is fed through a welding gun. It is known for its speed and efficiency in industrial applications. 3. **Gas Welding:** This is a legitimate welding process (such as Oxy-Acetylene welding) that uses the combustion of fuel gases and oxygen to create a flame that melts the base metal and filler rod. 4. **Lathe Welding:** A lathe is a machine tool used for machining (turning, facing, threading) by rotating a workpiece against a cutting tool. While welding can be performed on a part that is held in a lathe (for symmetry), 'Lathe Welding' is not a recognized category or process of welding in mechanical engineering. Therefore, option (d) is the correct answer as it describes a machine tool rather than a welding process.

MPFI stands for Multi Point Fuel Injection. In this system, each cylinder has its own dedicated fuel injector located just before the intake valve. This allows for precise control of the fuel-air mixture for each individual cylinder, leading to better fuel efficiency, lower emissions, and improved engine performance compared to single-point injection or carburetors. Analysis of other options: - Option (a) 'Mechanical Petrol Fuel Injection' is incorrect as modern MPFI systems are electronically controlled (EFI). - Option (c) 'Manifold Pressure Fuel Injection' is incorrect; while manifold pressure is a sensor input (MAP sensor) used to calculate fuel delivery, it is not what MPFI stands for. - Option (d) 'Maximum Petrol Fuel Intake' is a nonsensical term in the context of fuel injection system nomenclature.

Step-by-step reasoning: 1. Gas welding typically involves a fuel gas and an oxidizing agent (oxygen). 2. Acetylene (C2H2) is the most common fuel gas used due to its high flame temperature. 3. Acetylene is chemically unstable and highly explosive when mixed with air or oxygen, especially at pressures above 15 psi (approx 1 bar), where it can decompose violently without an external ignition source. This is why it is stored dissolved in acetone within porous masses in cylinders. 4. Oxygen (Option a) is an oxidizer; it supports combustion but is not explosive on its own. 5. Hydrogen (Option b) is flammable and explosive, but in the context of standard gas welding (Oxy-Acetylene welding), Acetylene is the primary gas noted for its extreme instability and specific handling requirements (like flash-back arrestors). 6. Nitrogen (Option c) is an inert gas and is not explosive.

Step-by-step reasoning: 1. **Function of a Pressure Relief Valve (PRV):** In a lubrication system, the oil pump delivers oil at a rate that may exceed the system's requirements or the capacity of the bearings/galleries to absorb it, especially at high engine speeds. A pressure relief valve is a safety mechanism designed to open when the system pressure reaches a predetermined maximum limit. 2. **Mechanism:** When the pressure exceeds the spring tension of the valve, the valve opens and diverts the excess oil back to the oil sump or the pump inlet, thereby capping the maximum pressure. 3. **Why Option 'b' is correct:** Its primary purpose is to protect the system components (such as oil filters, seals, and gaskets) from bursting or leaking due to excessive pressure. 4. **Why other options are incorrect:** - Option 'a' (Regulate flow): While it affects flow, 'regulation' usually implies maintaining a specific flow rate for operation, whereas a relief valve is specifically for over-pressure protection. - Option 'c' (Cool the oil): Oil cooling is handled by an oil cooler (heat exchanger) or the oil sump. - Option 'd' (Filter the oil): Oil filtration is performed by the oil filter or strainer.

A Spark Ignition (S.I.) engine is an internal combustion engine where the fuel-air mixture is ignited by an electric spark produced by a spark plug. Petrol (gasoline) is the primary fuel used in these engines because of its volatility and ability to mix with air to form a combustible mixture. Analysis of options: - Option (a) Diesel Engine: These are Compression Ignition (C.I.) engines, where fuel is ignited by the heat of highly compressed air, not by a spark. - Option (b) Petrol Engine: Correct. These utilize spark plugs for ignition. - Option (c) Steam Engine: This is an External Combustion engine where steam is generated in a boiler outside the cylinder. - Option (d) Electric Engine: This is an electrical machine (motor) that converts electrical energy into mechanical energy; it is not an internal combustion engine.

Step-by-step reasoning: 1. The objective is to identify the tool used to measure the outer diameter of a cylindrical object. 2. Analysis of options: - (a) Vernier Height Gauge: Used primarily for measuring the height of objects or marking off heights from a reference surface. - (b) Micrometer (specifically the Outside Micrometer): Designed specifically to measure external dimensions, such as the outer diameter of a cylinder or the thickness of a plate, with very high precision (typically up to 0.01mm or 0.001mm). - (c) Dial Gauge: Used for checking the roundness (ovality) of a cylinder, flatness of a surface, or comparing dimensions against a standard; it does not measure the absolute diameter directly. - (d) Bevel Protractor: Used for measuring or marking angles. 3. Conclusion: The Micrometer is the standard instrument for measuring the outer diameter of cylindrical objects.

A vehicle survey report is a formal technical document used to document the current state of a vehicle. Its primary purposes include: 1. Condition Assessment: Determining if the vehicle is roadworthy or requires maintenance. 2. Damage Evaluation: In the event of an accident, a survey is conducted to quantify the extent of damage for insurance claims or repair estimates. 3. Valuation: Establishing the current market or book value of the asset for accounting, disposal, or insurance purposes. Why other options are incorrect: - Option (a): While a survey report may be used as a supporting document during a sale, the report's purpose is the evaluation itself, not the act of selling. - Option (b): Vehicle taxes are typically assessed based on engine capacity, fuel type, weight, or age (registration details), not through a physical survey report. - Option (d): Fuel efficiency is improved through mechanical tuning, aerodynamic changes, or driving habits, not by preparing a documentation report.

Step-by-step reasoning: 1. **Analysis of Option (a):** Diesel engines operate at higher compression ratios compared to petrol engines. According to the laws of thermodynamics, a higher compression ratio leads to higher thermal efficiency. Additionally, diesel fuel has a higher energy density per gallon/liter than gasoline, resulting in higher fuel efficiency (better mileage). 2. **Analysis of Option (b):** This is incorrect. Diesel engines are known for providing *higher* torque at lower RPMs due to their high compression ratios and the nature of the diesel combustion process, making them ideal for heavy-duty hauling. 3. **Analysis of Option (c):** This is not an 'advantage'. While diesel engines may produce lower CO2 per kilometer due to efficiency, they typically produce higher NOx and particulate matter (soot). Regardless, higher emissions are never considered an advantage. 4. **Analysis of Option (d):** This is incorrect. Diesel engines are *more* robust (sturdier) than petrol engines because they must be built to withstand the much higher cylinder pressures associated with compression ignition. Conclusion: The only positive attribute listed that correctly describes a Diesel engine relative to a Petrol engine is its higher fuel efficiency.

A vehicle repair estimate is a document that outlines the projected costs required to restore a vehicle to working condition or to perform scheduled maintenance. 1. **Labor Charges (Option a):** These are essential as they cover the technician's time and expertise required to perform the repair. 2. **Spare parts Cost (Option b):** This is a primary component of any estimate, covering the cost of replacing worn-out or damaged components (e.g., brake pads, filters, belts). 3. **Paint and Material Cost (Option d):** In the case of bodywork or surface restoration, the cost of paint, primers, and consumables is standard in a repair estimate. 4. **Fuel Charges (Option c):** Fuel is an operational expense (running cost), not a repair cost. While a small amount of fuel might be used for testing a vehicle after repair, it is not listed as a line item in a standard repair estimate. Fuel is consumed during the usage of the vehicle, whereas repair estimates focus on the restoration of the asset.

Step-by-step reasoning: 1. The question asks for the term describing a fluid's resistance to flow. 2. Viscosity is defined as the internal friction of a fluid that opposes the relative motion between its layers (shear stress). A fluid with high viscosity (like honey) resists flow more than a fluid with low viscosity (like water). 3. Evaluating other options: (a) Density is the mass per unit volume of a substance, not its resistance to flow. (b) Flash point is the lowest temperature at which a liquid gives off enough vapor to ignite in air. (d) Pour point is the lowest temperature at which a liquid (usually oil) remains fluid and can still be poured. Therefore, option 'c' is the only correct technical term for resistance to flow.

TIG welding, which stands for Tungsten Inert Gas welding (also known as Gas Tungsten Arc Welding or GTAW), is an arc welding process. In this process, heat is generated by creating an electric arc between a non-consumable tungsten electrode and the workpiece (workspace). An inert gas, such as Argon or Helium, is used to shield the weld area from atmospheric contamination. Analysis of other options: - Option (a) Friction: This is the heat source for Friction Stir Welding (FSW), not TIG. - Option (b) Gas Combustion: This is the heat source for Oxy-Fuel welding (Gas welding). - Option (d) Laser Beam: This is the heat source for Laser Beam Welding (LBW).

To understand why a worn shock absorber causes excessive bouncing, it is essential to distinguish between the roles of the spring and the damper (shock absorber) in a suspension system: 1. **The Role of the Spring (Coil Spring):** The spring's primary job is to support the vehicle's weight and absorb the energy from a bump. When a car hits a bump, the spring compresses and then releases that stored energy. Without a damping mechanism, the spring would continue to oscillate (bounce) up and down for a long time. 2. **The Role of the Shock Absorber (Damper):** The shock absorber is designed to 'dampen' or control the oscillations of the spring. It converts the kinetic energy of the bouncing spring into thermal energy (heat) via hydraulic fluid. If the shock absorber is worn or leaking, it can no longer resist the spring's motion, leading to 'excessive bouncing' after a bump. **Analysis of other options:** - **b. Worn coil spring:** A worn or sagging spring usually results in a lower ride height or a 'harsh' ride because the spring cannot support the load, but it does not typically cause the car to bounce repeatedly; rather, it may bottom out. - **c. A broken sway bar:** The sway bar (anti-roll bar) controls body roll during cornering. A broken sway bar would cause the car to lean excessively in turns, but it would not cause vertical bouncing after hitting a bump. - **d. Low tyre pressure:** While low tyre pressure affects ride quality and handling, the primary control of vertical oscillation (bouncing) is handled by the shock absorbers, not the tyres.

Arc welding is a fusion welding process that uses an electric arc to create heat to melt and join metals. An electric arc is formed between an electrode and the base material; the high current flowing through this ionized gas gap generates intense heat (typically between 3,000°C to 20,000°C), which melts the metals to form a weld pool. Why other options are incorrect: - a. Friction: This is the heat source for Friction Welding, where mechanical rubbing generates heat. - b. Resistance Heating: This is the heat source for Resistance Welding (e.g., Spot Welding), where heat is generated by the electrical resistance of the materials to the current flow. - c. Chemical Reaction: This is the heat source for Thermite Welding, where an exothermic chemical reaction between aluminum powder and metal oxide is used.

In arc welding, flux is a chemical cleaning agent, flowing agent, or shielding agent. Its primary functions are: 1. To prevent the molten weld pool from reacting with atmospheric oxygen and nitrogen (shielding), which prevents porosity and oxidation. 2. To react with and remove impurities and oxides from the surface of the base metal, forming a liquid slag that floats to the top of the weld pool. While flux can contribute to arc stability (option a), its 'main' or fundamental metallurgical function is the removal of impurities and the protection of the weld pool from oxidation. Option c is incorrect because flux is not used for electrical insulation, and option d is incorrect because flux coating does not increase the functional diameter of the electrode core.

To determine the advantage of a petrol engine (Spark Ignition - SI) over a diesel engine (Compression Ignition - CI), we must compare their design and operational characteristics: 1. **Initial Cost (Option c):** Petrol engines operate at lower compression ratios compared to diesel engines. Because they do not need to withstand the extreme pressures associated with high compression ratios, the engine components (cylinder block, piston, connecting rods) can be made of lighter, less expensive materials. Additionally, they do not require the heavy-duty high-pressure fuel injection pumps found in diesel engines. Therefore, the initial manufacturing cost of a petrol engine is lower. This is the correct answer. 2. **Performance (Option a):** 'Performance' is subjective. While petrol engines offer better acceleration and higher RPMs (power-to-weight ratio), diesel engines provide superior torque and efficiency. Thus, it is not a definitive universal advantage. 3. **Cost of Fuel (Option b):** Historically and generally, diesel fuel is often priced similarly to or lower than petrol in various markets, but more importantly, diesel engines are more thermally efficient, meaning they use less fuel for the same amount of work. Petrol is not cheaper in terms of energy output per unit cost. 4. **Running Cost (Option d):** Diesel engines have higher thermal efficiency and better fuel economy, leading to lower running costs per kilometer/hour compared to petrol engines. Therefore, lower running cost is an advantage of the diesel engine, not the petrol engine.

A feeler gauge is a precision measurement tool consisting of a series of thin steel strips (blades) of varying, calibrated thicknesses. It is specifically designed to measure the width of small gaps, clearances, or the distance between two mating parts (such as the gap between spark plug electrodes or valve clearances in an engine). Why other options are incorrect: - b. Diameter: Measured using tools like Vernier calipers, micrometers, or bore gauges. - c. Height: Measured using height gauges or calipers. - d. Radius: Measured using radius gauges or a spherometer.