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Class 9 Automotive Service Technician Chapter 3 Major Systems and Components of an Automobile
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Major Systems and Components of an Automobile
Chapter: 3
Session – 1: Chassis and Auto Body
Check Your Progress
A. Fill in the blanks:
1. A chassis is almost a complete _________ mounting body.
Ans: Vehicle.
2. The shape of the chassis depends upon the ultimate use of the _________.
Ans: Vehicle.
3. Major part of a chassis is the __________frame.
Ans: Steel.
4. In commercial vehicles like trucks and buses the body is not a _________ of the chassis.
Ans: Part.
5. In most of the cases, it is an open body, whereas for liquid material like water, milk and fuel a __________ is mounted on the chassis.
Ans: Tank.
B. Multiple choice questions:
1. Chassis is a French term and was initially used to denote ___________.
(a) Main structure of a vehicle.
(b) Fixing the automobile body.
(c) Transmission system, front and rear axle.
(d) Carrying the bolt.
Ans: (a) Main structure of a vehicle.
2. What are the functions of the chassis frame?
(a) To carry the weight of the vehicle and its passengers.
(b) To withstand the engine and transmission torque.
(c) To withstand the centrifugal force while cornering.
(d) All of the above.
Ans: (d) All of the above.
3. Automobile body is made of ________________.
(a) Sheet metal or fiberglass.
(b) Iron.
(c) Copper.
(d) Gun metal.
Ans: (a) Sheet metal or fiberglass.
4. The body is fixed to the chassis with the help of ________.
(a) I or U bolts.
(b) Rivet.
(c) Welding.
(d) Threaded bolt.
Ans: (a) I or U bolts.
5. Automobile body should fulfill which of the following requirements?
(a) The body should be light.
(b) It should have a long fatigue life.
(c) Both (a) and (b).
(d) None of the above.
Ans: (c) Both (a) and (b).
C. Short answer questions:
1. Differentiate between chassis frame and automobile body.
Ans: The differences between chassis frame and automobile body are:
| Chassis frame | Automobile body |
| Chassis is a French term and was initially used to denote the frame or main structure of a vehicle. | The body or superstructure is made after receiving the chassis from the manufacturer (in conventional chassis construction). |
| It includes a steel frame which is a major part. | The body of a car is made of a sheet of metal or fiberglass. |
| The chassis contains all the major units necessary to propel the vehicle, guide its motion, stop it, and allow it to run smoothly over uneven surfaces. | The body provides space for passengers and cargo, protects from dust and rain, and makes the journey comfortable with cushioned seats and glass panes. |
| Supports vehicle weight, absorbs shocks, and provides stability. | Protects occupants, provides comfort, and enhances aesthetics. |
| Strength, durability, and stability. | Aerodynamics, styling, and functionality. |
2. Explain the use of the chassis frame.
Ans: The chassis frame is used to provide structural support to the vehicle, and its functions include:
(i) Carrying the weight of the vehicle and its passengers.
(ii) Withstanding the engine and transmission torque and thrust stresses, as well as accelerating and braking torque.
(iii) Withstanding the centrifugal force while taking a turn.
(iv) Withstanding the bending load and twisting due to the rise and fall of the front and rear axles.
3. How does auto body help in transport?
Ans: Automobile Body or Superstructure: In case of integral or frameless construction, the body is an integral part of the chassis. But, in case of the conventional chassis, the body or superstructure is made after receiving the chassis from the manufacturer. The shape of the body depends upon the ultimate use for which the vehicle is meant. The body of a car is made of a sheet of metal or fiberglass, so that passengers can sit in it. To make the journey comfortable, cushioned seats are provided. The body is provided on all sides with glass panes fixed to protect the passengers from dust and rain.
| Session – 2: Engine and Its Components |
| Check Your Progress |
A.Fill in the blanks:
1. Engine is the __________ of an automobile. Its role is very important.
Ans: Heart.
2. Engine converts the Chemical Energy (heat energy) to ___________ Energy.
Ans: Mechanical.
3. Major parts of engine are ___________, ____________, _________ and ___________.
Ans: Crankshaft, connecting rod, piston, cylinder.
4. The function of the carburettor is to supply uniform ___________ to the cylinder of a _______ through the intake manifold.
Ans: Air-fuel, petrol engine.
5. Sparkplug is used to ____________.
Ans: Ignite the mixture.
B. Multiple choice questions:
1. The compression-ignition engine air is compressed so that its temperature goes up to ____________.
(a) 538 °C (1000 °F) or higher.
(b) 348 °C.
(c) 2480 °C.
(d) None of the above.
Ans: (a) 538 °C (1000 °F) or higher.
2. The cylinder of an IC engine is generally made of _____________.
(a) Cast iron.
(b) Copper.
(c) Iron.
(d) Fibre.
Ans: (a) Cast iron.
3. The charge (fuel and air mixture for SI engine and only air for CI engine) enters through the _____________.
(a) Inlet valve.
(b) Spark plug.
(c) Outlet valve.
(d) Piston.
Ans: (a) Inlet valve.
4. The heart of the engine is the _____________.
(a) Piston.
(b) Cylinder head.
(c) Connecting rod.
(d) All of the above.
Ans: (a) Piston.
C. Short answer questions:
1. Explain the role of engine and its components.
Ans: An engine is a complex unit in which different components are assembled together, and fuel is burned to produce power or energy. The engine converts chemical energy (heat energy) into mechanical energy, which is then utilized for vehicular movement. There are different processes of fuel combustion. When the fuel is burned within the engine, it is called an Internal Combustion (IC) engine, and when it is burned externally and the produced steam is used for the mechanical movement, it is called an External Combustion (EC) engine.
2. Explain the difference between compression ignition engine and spark ignition engine?
Ans: The spark ignition engine uses a highly volatile fuel, such as gasoline, which turns into vapor easily. The fuel is mixed with air before it enters the combustion chamber and forms a combustible air-fuel mixture. This mixture then enters the cylinder and gets compressed with the help of a piston. An electric spark is produced by the ignition system which ignites the combustible air-fuel mixture. The combustible gases burn and expand, which forces the piston downwards for generating power.
Whereas, In the compression ignition engine or diesel engine, only fresh air enters the cylinder, which is compressed to a very high pressure and temperature, which could go up to 1000°F (538°C). The diesel is then injected or sprayed into the engine combustion chamber. This spray contains very fine and tiny particles of diesel in an atomized form. The hot air or heat of compression ignites the fuel and generates the power stroke.
| Session – 3: Lubrication System |
| Check Your Progress |
A. Fill in the blanks:
1. Dry or solid friction is produced in _____________.
Ans: Two metallic surfaces.
2. Dry friction creates lot of ______________.
Ans: Heat.
3. The objective of lubrication is to reduce __________.
Ans: Friction.
4. Lubrication provides ________ and ______ effect.
Ans: Cushioning, cooling.
B. Multiple choice questions:
1. Viscosity is measured using a _____________.
(a) Barometer.
(b) Thermometer.
(c) Viscometer.
(d) Fathometer.
Ans: (c) Viscometer.
2. Lubricating oil is used for ______________.
(a) Minimising wear in moving parts.
(b) Help in keeping parts cool.
(c) Both (a) and (b).
(d) None of the above.
Ans: (a) Minimising wear in moving parts.
3. Which type of lubrication system is used in a two-stroke engine?
(a) Petrol system.
(b) Wet sump system.
(c) Dry sump system.
(d) All of the above.
Ans:(d) All of the above.
4. Viscosity index is a measure for the change of viscosity with change in ______________.
(a) Pressure.
(b) Temperature.
(c) Volume.
(d) Mass.
Ans: (b) Temperature.
C. Short answer questions:
1. Explain the importance of lubrication in engine.
Ans: The importance of lubrication are:
(i) To reduce friction between moving parts to its minimum value so that power loss is minimized.
(ii) To reduce wear and tear of the moving parts as much as possible.
Apart from these objectives, lubrication also serves other important purposes, which may be called secondary. These are as follows:
(a) To provide cooling effect: The lubricating oil takes heat from the hot moving parts during its circulation and delivers it to the surrounding air through the crank case.
(b) To provide cushioning effect: The lubricating oil also serves as a good cushion against the shocks experienced by the engine. For example, instant combustion of the fuel in the combustion chamber produces a sudden rise of pressure in the cylinder and the shock goes to the bearings through the piston, gudgeon pin and the connecting rod. This shock is then absorbed by the layer of oil present in the main bearings.
(c) To provide cleaning action: The lubricating oil serves another useful purpose of providing a cleaning action. During its circulation, it carries away many impurities, such as carbon particles, etc.
(d) To provide a sealing action: The lubricating oil also helps the piston rings in maintaining an effective seal against the high-pressure gases in the cylinder thus preventing leakage towards the crankcase.”
2. List the properties of lubricant.
Ans: A good lubricant should possess the following properties:
(i) Viscosity: It should have sufficient viscosity to form a lubricating film between moving parts.
(ii) Viscosity Index: The viscosity of the lubricant should not change much with the change in temperature.
(iii) Oiliness: The lubricant should possess adequate oiliness to adhere to the surfaces.
(iv) Pour Point: It should have a low pour point to remain fluid at low temperatures.
(v) Corrosion Resistance: A good lubricant should protect metallic surfaces from corrosion, which can occur due to chemical reactions.
(vi) Thermal Stability: The lubricant should be able to withstand high temperatures without breaking down or forming harmful deposits, says Petro Online.
| Session – 4: Cooling System |
| Check Your Progress |
A. Fill in the blanks:
1. The cooling system removes excess __________ from the engine.
Ans: Heat.
2. Cooling_____________a constant engine operating temperature.
Ans: Maintains.
3. The objective of cooling is to reduce_____________.
Ans: Temperature.
4. Liquid cooling is employed in most ___________engines.
Ans: IC.
B. Multiple choice question:
1. Which of the following type of cooling system is used in a motorcycle?
(a) Air cooling system.
(b) Water cooling system.
(c) Both (a) and (b).
(d) None of the above.
Ans: (b) Water cooling system.
2. The cooling fan is _______________.
(a) Driven by belt and pulleys.
(b) Fitted between the engine and the radiator.
(c) Driven from the camshaft.
(d) All of the above.
Ans: (a) Driven by belt and pulleys.
3. In water cooling, the water in the jacket obtains heat from the cylinder due to _______________.
(a) Conduction.
(b) Convection.
(c) Radiation.
(d) All of the above.
Ans: (a) Conduction.
C. Short answer questions:
1. How does a cooling system work?
Ans: The cylinders of internal combustion engines require cooling because the engine cannot convert all the heat energy released by combustion into useful work. Liquid cooling is employed in most of the IC engines, whether they are used in automobiles or elsewhere. The water (coolant) is circulated around the cylinders to pick up heat and then dissipate it through a radiator. As the temperature increases from 71 to 82 degrees centigrade, the thermostat valve opens and sends water to the radiator to radiate the heat. When the temperature rises above 82 degrees, the thermostat switch operates the cooling fan to support the cooling process in the radiator.
2. What is the role of coolants?
Ans: The role of coolants in an engine is to regulate temperature and prevent overheating. Coolants are specially formulated liquids that circulate through the engine to absorb excess heat and maintain optimal operating temperatures.
Roles of Coolants:
(i) Heat Absorption and Dissipation: Coolants absorb the heat generated by the engine during combustion and transfer it to the radiator, where it is released into the atmosphere. This prevents the engine from overheating.
(ii) Corrosion Protection: Coolants contain additives that prevent corrosion and rust in the engine’s cooling system components, such as the radiator, water pump, and engine block.
(ii) Freezing Prevention: Coolants contain antifreeze additives that lower the freezing point of the coolant, preventing it from turning to ice and potentially damaging the engine in cold weather.
(iv) Lubrication: Coolants help lubricate components like the water pump, reducing friction and wear.
| Session – 5: Fuel Supply System |
| Check Your Progress |
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