Automobile 2 and 11 marks unit v

Sri Ganesh College of Engineering and Technology
Department of Mechanical Engineering
MEE61-Automobile Engineering
2 MARK AND 11 MARK QUESTION AND ANSWERS
UNIT –V
PART A (2 MARKS)
1. List the types of battery and state its function.
Storage battery is the most important electrical system of a vehicle. It supplies the current for the
starting motor and various electrical components and accessories. It is the electro chemical apparatus
which supplies regular current due to chemical action inside. The types are
• Lead acid battery
• Alkaline battery
• Zinc air battery
2. What are the components of lead acid battery?
• Lead terminals
• Electrolyte
• Internal plates (positive and negative plates)
• Resilient Plastic container
3. What are the chemicals used in battery?
PbO2 – Positive plate
Pb – Negative plate
Electrolyte – Diluted Sulphuric acid
4. List the different method of charging.
a. Slow and quick rate of charging
Slow rate of charging of battery is preferable. A battery takes about 12 to 20 hours for
charging. It is a safe method.
Quick rate of charging of a battery which consumes a high charging current. After 80
percent charge is over, the current may be reduced.
b. Trickle charging
This charging is done during day time only. The self discharged batteries, because of
the batteries left in storage. Very low charging rate of about 5 percent of normal charging
current is employed for keeping proper condition.
c. Dry charged batteries
Dry charged batteries are available which do not contain electrolyte. The plates are in
it already charged. No moisture enters the battery, because the vent holes are closed. So, the
battery is stored without damage for 2 to 3 years. When the battery is intended for service,
open the vent holes and put the electrolyte to half, fill each cell. Allow it to stand for one or two
hours. Then pour more electrolytes to bring it up to proper level. Now the battery is ready for
use.
5. How will you distinguish a positive plate from a negative plate in a lead acid battery?
The positive plates are coated with PbO2 and chocolate brown in colour. The negative plates
are coated with spongy lead and grey in colour.
6. Name the different types test used for battery life.
Important tests conducted to know the conditions of the battery are

1.Specific gravity test- This is conducted with the help of a hydrometer containing a glass float.
2. Open volt test- Voltmeter is used to find the open circuit voltage of the battery cell.
3. High discharge test- The cranking motor at the time of starting draws a heavy current. So, it causes
the cell voltage to drop heavily, to test the condition of the cell, a cell voltage tester is used.
4. Cadmium test- This test is conducted to know the chemical conditions of positive and negative plates.
7. What are the types of battery rating?
Battery ratings are the ratings provided with a battery which defines the characteristics and quality of a
battery. Some of the popularly used battery ratings are:
1. Twenty hour rate (Ampere-hour capacity)
It indicates the power loss of a battery on small load. The rate of current delivers for 20Hrs continuously
by a battery. After which the cell voltage should not drop below 1.75. During the test the temperature of
the battery is 26°C.
2. Twenty minute rate
It is the rate of current delivering continuously for 20mts. The cell voltage should not drop below 1.5 at
26°C.
3. Cold rate (Zero test)
It represents the current in amperes which the battery can deliver continuously for 30 seconds without
the cell voltage drop below 1.2V. The temperature of the battery is kept -18°C. It indicates the ability of
battery during cold weather starting.
8. What are the different types of starter motor drives?
• Bendix drive
• Overrunning drive
9. What are the types of ignition system and state its purpose?
Purpose:
A battery of 12Volts is generally employed. To produce such a high voltage (of 25000 Volts), for igniting
the air fuel mixture a special ignition system has to be employed.
Types:
1. Battery coil ignition system
2. Magneto coil ignition system
3. Electronic coil ignition system
10. What is conventional ignition system?
The conventional ignition system gets its electrical voltage either from battery or dynamo, which
will be boosted to a very high voltage due to which spark is produced in the cylinder to combust the
mixture.
11. What is a rotary distributor?
The rotary distributor has a rotating element, which release a high intensity spark to the
individual spark plugs according to the engine firing order.
12. What is the function of a spark plug?
The spark plug is a device to produce electric spark to ignite the compressed air-fuel mixture
inside the cylinder.
13. What is an Electronic ignition system?
The ignition system, in which the mechanical contact points are replaced by electronic
triggering and switching devices, is known as electronic ignition system.

14. State the principle of working of an A.C. Generator.
The basic principle of ac generator is electromagnetic induction when a coil of a conductor
moves in a magnetic field the electrons in it starts moving because of attraction and repulsion of
magnetic field. Thus, an emf is induced in it.
15. What is the function of regulators in a charging system?
Current regulator – regulates the alternator/dynamo current for charging the battery (constant current
charging mode).
Voltage regulator – regulates the alternator/dynamo voltage for charging the battery (constant voltage
charging mode).
16. What is the function a cut out in a charging system?
The cut out permits the current flow from dynamo/alternator to battery for charging while it does not
permit the reverse flow of current.
UNIT-V
PART- B (11 Marks)
1. Discuss the construction, working and maintenance of lead acid battery.
Construction:
Invented by the French physician Gaston Planté in 1859, lead acid was the first rechargeable battery
for commercial use. Despite its advanced age, the lead chemistry continues to be in wide use today,
and there are good reasons for its popularity; lead acid is dependable and inexpensive on cost-per-watt
base. There are few other batteries that deliver bulk power as cheaply as lead acid, and this makes the
battery cost-effective for automobiles, golf cars, forklifts, marine and uninterruptible power supplies
(UPS). It consists of the following components.
1. Container
2. Plates
3. Separators
4. Cell covers
5. Electrolyte
1. Container: It is a single piece construction and is made of hard rubber or bituminous material. It is
divided into compartments by partitions for different cells.
2. Pates: The plates in the battery consist of perforated grids into which lead or lead peroxide has been
pressed. There are two types of plate groups in each cell positive plate group and negative pate group.
The plate group connected to the positive terminal of the cells consists of the grids filled with a paste of
Lead Peroxide. The negative plate group consists of Metallic lead.
3. Separators: Separators are placed between the negative and positive plates to keep them separate
with each other. These are usually made of special treated wood, hard rubber etc.
4 .Cell Cover: Each cell is covered by a cover of hard rubber through which the positive and negative
terminals project.
5 .Electrolyte: The electrolyte used in the lead acid battery is the solution of sulphuric acid. It consists
of 40% of sulphuric acid and 60% of AUTO TRANSMISSION SYSTEM distilled water. The level of
electrolyte should be about 10 mm over the tops of the plates.

Working:
The chemical reactions take place between the three chemicals in the battery. In the presence of
sulphuric acid, the electrons from one group of plates collect on the other group of plates. The following
chemical reactions take place while charging and discharging.
While charging:
At Anode (+ve Plate):
PBSO4 + 2H20 => PBO2 +2H2SO4
At Cathode (-ve Plate)
PBSO4 + H2 => PB + H2SO4
During Discharge: The acid H2SO4 attacks lead to form PBSO4 (Lead sulphate)
At Anode: PBO2 + H2SO4 => PBSO4 + 2H2O
At Cathode SO4 combines with it to form PBSO4.
PB+SO4=> PBSO4
So both at anode (+ve) and at Cathode (-ve) PBSO4 is formed. During this process water is also
formed which dilutes sulphuric acid and thereby decreases its specific gravity.
This battery converts electrical energy into chemical energy during charging and chemical energy into
electrical energy during discharging.
2. Explain constructional features and operation of series wound starting motor with neat
sketch.
STARTER MOTOR
Construction
It consist of a cylindrical housing, field coils, pole shoes, armature and brushes etc as
shown in fig . The steel pole shoes are securely attached to the inner surface of steel housing.
The number of pole shoes varies from two to six but mostly there are four pole shoes. These
pole shoes hold the field coils and become magnetized when the current flows through the
coils.

The armature consists of a slotted iron core, shaft, commutator and armature
windings. The windings are made of heavy flat copper strip for carrying heavy current. The
windings consist of number of coils. These coils are connected to the
commutator for flowing the current to all the coils at a time.
Working Principle
"Unlike magnetic fields attract each other and like magnetic fields repel each other".
When the starter motor switch is on, the current from the battery flows to the starting
motor. One half of the current flows through one pair of field coils and other half flows through
other pair of field coils to the other insulated brush. It sets up a strong circular magnetic field
around the armature coil. The reaction between the two magnetic fields exerts a force on the
armature coils causing it to rotate. When the current flowing through the armature is more, the
torque produced by the starting motor is also more.
3. Explain the different types of starting motor drives.
For starting the engine it is sufficient to rotate it at about 100RPM, if the motor speed
used is 1500RPM. Gear ratio between a pinion and flywheel teeth is of 15:1. So less torque is
required to start the engine. But when the engine starts, the pinion should reach to its original
position. Otherwise the pinion will mesh with the flywheel. The flywheel will rotate, it at a high
speed equal to 15 times the engine speed. The starting motor drive mechanism permits quick
disengagement of drive gear from flywheel ring gear.

The drive mechanism is of the following two types
i) Over running clutch drive.
ii) Bendix drive.
i) Over running clutch drive:
It consists of a shell and a pinion collar connected in such a way that when the shell is
rotating at a speed greater than that of the pinion collar, the former will drive the later.
Whenever the speed the collar becomes more than the speed of the shell, there is no
connection between the two. Such a connection is provided by the spring loaded rollers, the
shell is connected with the armature shaft through splines, where as the collar is attached to
the pinion.
A starting device employing the over running clutch is shown in fig.5.4. The shift lever
is attached to the starting pedal in case of mechanical starters or may be operated by means of
solenoid switches. When the starting pedal is pressed by the driver, the shift lever moves about
its pivot, thereby pushing the switch of starting motor and moving the over running clutch and
the pinion assembly through the spring simultaneously. This causes the pinion to get engaged
with the fly wheel teeth and also get the armature shaft and therefore the pinion to rotate, which
starts the engine. As soon as the engine starts, the driver leaves the starting pedal which
causes the shift lever to come back to its previous position.

ii) Bendix drive
Bendix drives are the- inertia drives. The starter motor pinion is made to engage or
disengage with the toothed ring of flywheel. There are two types called, out board and inboard
models. In the outboard type pinion moves away from the starter motor. In the inboard type the
pinion moves towards the starting motor,
There is a threaded sleeve on the armature shaft. The sleeve can slide or {urn freely
over the shaft. The shaft is keyed to the fixed drive head. The head is connected to the sleeve.
A coil spring is attached to the sleeve. On the sleeve there is a pinion. An unbalanced weight is
attached with the pinion. The purpose of weight is to prevent the rotation of the pinion on the
sleeve threads.
When the motor starts, the armature shaft rotates. Due to the unbalance weight, the
pinion cannot rotate and it moves axially towards the motor. The pinion is engaged with
flywheel. There is collar attached on the sleeve. Now the pinion is engaged and rotates the
flywheel of the engine and the engine starts. When the engine starts, the self starter switch is
off. Now the flywheel rotates the pinion faster than the armature. Result of that the pinion is
backed out of mesh with the flywheel.

In compression spring type Bendix drive, the threaded sleeve is mounted directly on
the splined armature shaft. When the motor is started, the sleeve starts rotating along with the
armature shaft. This causes the pinion towards the motor and engaged with the flywheel ring
gear. Now the flywheel rotates and starts the engine. When the engine starts, the flywheel
rotating at a faster speed causes the pinion to the backed out of meshing flywheel ring.
4. Explain the coil ignition system with neat diagram.
Coil Ignition System
This system includes a battery supplying current via the ignition switch to the ignition coil, low-tension
or primary winding. The current flow from primary winding terminal of the coil flows to an engine
operated the contact breaker thereby induced current in the high tension or secondary winding of the
coil due to electromagnetic action in the coil windings.
This current flowing to the sparking plug jumps the air gap. The circuit break to the coil through the
battery and low tension windings is completed. In order to prevent arcing causing the low tension
current flowing even when the contact breaker points open, a condenser is fitted in parallel with the
contact breaker points.
This also helps to increase the spark at the sparking-plug gap. The sparking plug gap and the pressure
in the cylinder affect the voltage required at the plug points.
This system consists of Battery, Ammeter, Ignition switch, Ignition coil, Condenser, contact breaker
points, Distributor and spark plugs.
The primary Ignition circuit starts at the battery and passes through the switch, Ammeter, primary
winding, contract Breaker points to the ground. A condenser is also connected in parallel to the contact
breaker points. One end of condenser is connected to the contact breaker arm and the other and is
grounded.
The secondary Ignition Circuit starts from the ground and passes through the secondary winding,
distributor, spark plug to the ground.
The Ignition coil steps up the voltage of 6 or 12 Volts received from the battery to the high tension
voltage of about 20000 to 24000 volts required to jump the spark at the spark plug gap which ignites
the combustible charge in the cylinder.
The rotor of distributor revolves and distributes the current to the segments which in turn send it to the
spark plugs as per the number of cylinders.

When the ignition switch is on, the current will flow from the battery through the primary winding. It
produces magnetic field in the coil. When the contact points open, the magnetic field collapses and the
movement of magnetic field induces current in the secondary winding coil in which many more turns of
fine wire will increase the voltage up to a maximum valve which is required for jumping of spark at the
spark plug gap. The distributor then directs this high voltage to the proper spark plug as per the firing
order arranged in the distributor rotor. This gives spark to the required spark plug.
5. Briefly explain the Magneto ignition system with neat sketch.
Magneto Ignition System:
In this system the Magneto produces and supplies current in the primary winding. The magneto
consists of a fixed armature having primary and secondary winding and rotating magnetic assembly
which is driven by the engine.
When the magnet rotates the current flows in the primary winding. The Secondary winding gives high
voltage current to the distributor which distributes it to the respective spark plugs according to the firing
order.
In a magneto, the magnetic field is produced by means of permanent magnets. The magneto may be
either rotating armature type or rotating magnet type. . It is less efficient in comparison to a transformer
except for certain characteristics making it suitable for a particular use. Generally two types of ignition
or induction coils are used in modern ignition systems: core type and metal clad or cane type ignition
coils.

6. Explain the electronic coil ignition system with a neat sketch.
In this system the contact breaker point is omitted. For that one magnetic pick up, electronic amplifying unit and a
control unit are placed.
One component is so called reluctor / armature in the distributor. The reluctor is a rotor that contains
tips of four numbers. A pick up coil and a permanent magnet are also in the distributor. The magnetic
flux formed in the magnet flows through reluctor. The tips pass over the pick-up coil each time. So, the
current made pulses after the flux is formed in the coil. The current runs the control unit. The unit
consists of diode and transistors. The unit controls the current flow in ignition coil. When the. Pulses of
current from pickup coil reaches the control unit, the current flow to ignition coil is stopped. So the-
magnetic field is collapsed in the ignition coil. Due to this a high voltage is induced current in the
secondary coil of ignition coil.

The high voltage jumped a current to the respective spark plug and made a spark in
the engine cylinder. While pass over of the reluctor tip from pickup coil, the pulse of current in
the coil is lost. Then the control unit connects the battery and the ignition coil circuit. Again the
magnetic field is formed in the primary circuit of coil. The cycle is repeated, h is mostly used in
high speed vehicles and racing cars.
6. Write short notes on Distributor and firing order in automobile.
Distributor:
In Multi cylinder engine, the high voltage current from ignition coil is distributed to the required spark
plug according to the firing order. The distributor consists of housing, driving shaft with breaker cam,
breaker plate with contact points, governor, condenser, rotor, advance mechanism and cap. A rotor is
mounted on the breaker can which is carried by the drive shaft.
The distributor opens and closes the circuit between the battery and the ignition coil. During closing of
circuit the current flows in the ignition coil and build up a magnetic field. While opening the magnetic
field collapses and high voltage current is produced by the coil. It distributes this high tension current to
the proper spark plug at correct time as per the firing older.
Firing order:
The order or sequence in which the firing takes places in different cylinders of a multi cylinder engine is
called firing order. The following are the most common firing orders in different engines.
4Cylinder Engine: 1-3-4-2 (Inline)
6Cylinder Engine: 1-5-3-6-2-4(Inline)
8Cylinder Engine: 1-6-2-5-8-3-7-4(Inline)

7. Briefly explain the working of DC Generator with neat sketch.
Working principle of D. C. Generator:
When a conductor is moved in a magnetic field, a current is produced in it. The direction of flow of
current is determined by fleming’s left hand rule. It gives relationship between the direction of lines of
force direction of conductor motion and direction of current flow.
Construction and working of D C Generator:
Mostly Commentator type D C Generators are used in Automobiles. It consists of pole pieces fitted in a
frame armature commutator and filed winding. The pole shoes are the laminated iron cores for the filed
winding that furnish the magnetic field for the generator. Most generators contain one pair of North-
South poles, shaped to allow the armature to rotate between them with little clearance.
The armature is made up of conductors of insulated wire around on a laminated iron core. The
conductor ends are soldered to copper tars, separated from each other by mica which makes the
commutator. A steel shaft running the armature and commutator is supported by means of bearing so
that the pulley and fan mounted on the front end can be turned by an engine driven belt.
Two carbon brushes are held in the brush holders, which make firm contact with commutator segments
in order to connect the coils of rotating armature with the outside circuit.
Working:
When the armature rotates, the current is induced and flows in the conductors through the load. Part of
the current flows through two field winding, assembles around two magnetic poles. The magnetic field
is strengthened. The Armature and commutator are designed to rotate together. They allow the
generator to produce a flow of direct current continues to flow in the same direction.
Cut-out:
The Cut-out relay (or Circuit breaks) is an automatic device between dynamic and the battery which
prevents the battery from discharging through the dynamo, when dynamo is not charging the battery. It
is a magnetic switch and consists of two windings shunt; winding and series winding. It closes the
circuit between the generator and the battery when the generator is producing current.
Voltage Regulator:
The Voltage regulator consists of a relay coil wound with many turns of fine wire on the Iron core. The
function of voltage regulator is to control the magnetic field circuit of dynamo. It consists of two windings
on a single core, a shunt winding of many turns of fine wire and series winding of a few turns of heavy
wire. The Shunt winding (Voltage winding) is connected at the input side of the cut-out and grounded to
the other end.

8. Explain the working principle of alternator.
The alternator or a.c generator is the generator which produces alternating current. However, as the automobile.
Electrical system requires direct current. So, the alternating current produced in the a.c generator is to be converted full into the
direct current with the help of diodes.
An electromagnet or rotor is mounted on a shaft. The battery supplies the current for rotor energisation. The slip
rings and brushes are at the rotor shaft. The rotor is turned by a belt and pulley by the engine. Two diodes are connected to
outside electric circuit with stator winding.

When the electromagnet is rotated the magnetic lines of force cut the stator loop to
produce an induced current. Every 1/2 revolution, the magnet reverses its polarities thus the
stator alternates the current produced in one revolution. To convert the alternating current into
the direct current, diodes are employed. So, the diodes allow the current to pass in only one
direction and are fed to the electrical circuit.
Construction details
a) Housing: This encloses the entire alternator assembly. It is made of
aluminum alloy casting in two pieces. Aluminum is light weight, non-magnetic and higher
thermal conductivity. The drive end has ball bearings and brush end housing contains a roller
bearing.
b) Rotor: It consists of an iron core around the rotor shaft. Many turns of copper
wire coated with varnish are wound over the core. On both sides of the rotor winding are thick
metal plates bent over the winding with triangular fingers called poles.
c) Slip rings and brushes: The current to the rotor winding is carried through
the copper slip rings and carbon brushes. These brushes carry the field current only. They
have a much longer life.
d) Stator: Between two halves of the alternator casing the stator is situated. The stator
consists of three sets of winding wounded over a laminated iron core. When the rotor rotates, its moving
magnetic field induces current in all the three stator windings.
e) Rectifier: Every Auto, Truck, Farm, Industrial, Marine Alternator has inside it what
is called a Bridge Rectifier. The Bridge Rectifier is the assembly in every alternator that
converts the AC (alternating current) that alternators make to DC (direct current) for use by the
vehicles battery & electrical system. The Bridge Rectifier converts AC to DC using diodes
which are semiconductors that are one way gates. Diodes allow current to flow in only one
direction making alternating current into direct current.
9. Write short notes on Automotive lighting in detail.
AUTOMOTIVE LIGHTING:

The Automobile lighting consists of Head lights, side lamps, tail lamps, reverse lamp. Apart from these
there are panel lights, direction indicator flash lights and the lights inside the body to light up the
passenger compartments.
In addition to lights some other instruments like wind screen wiper, meter lights etc are also being used
in Automobiles.
LIGHTING:
The lighting system includes Head lights, side lights, tail lamps etc.
MAIN BEAM HEADLIGHTS:
These are also known as Full Beam, or High Beam. They should be used on unlit roads at
night (for example, in the countryside.) They may also be used as a means of informing other road
users of your presence (for example, when approaching a hump back bridge.) You must dip the
headlights when there are other road users approaching you.
DIPPED HEADLIGHTS:
Dipped Headlights must be used at night, and when visibility is seriously reduced due to heavy
rain, fog, or snow. The level of dip should be adjusted according to the weight in the rear of the car.
Dipped headlights should not cause other road users to be dazzled. Use your dipped headlights if you
have the windscreen wipers on constantly.
FOG LIGHTS:
My car in only fitted with a rear fog light. Many cars also have front fog lights. They should not
be used if visibility is better than 100m (25 car lengths). Using rear fog lights in good conditions creates
dazzle for following drivers. On some models the fog lights can make the brake lights less conspicuous.
PATKING LIGHTS:
Parking Lights are fitted to most cars. They must be used when parking on a road where the
speed limit exceeds 30mph (even if you are parking all night!). This rule may seem strange, as leaving
lights on all night may drain the battery. However, it is quite unusual to park on a road where the speed
limit exceeds 30mph anyway. Normally you would park off-road.
HAZARD LIGHTS:
Hazard Lights should be used to alert other road users of a hazard in the road. For example, if you are
following a truck, and a box falls from the back of the truck, then you should use your hazard lights as a
warning to others. You may also use hazard lights when you have broken down, and need to warn
other road users of your presence.
BRAKE LIGHTS:
Brake lights are activated by the footbrake, NOT by the handbrake. Many cars now have three lights at
the back, so that it is more difficult to confuse them with tail-lights. Use the brake gently and early to
warn following traffic of your intentions.
INDICATORS/SIGNALS:
Use directional indicators to give a Clear message to other road users of your intentions, and to
eliminate confusion. If you think that another road user has not registered your signal, turn it off, and
then on again. On many cars the signal is automatically cancelled after turns. However, it may
automatically cancel too soon. You MUST repeat signals if they prematurely cancel.
SIDE LIGHTS:
Side Lights are not always on the side of the car. They are dim lights (with small bulbs) which
help other road users to see your car, but may not help you to see other road users. They should be

used for at least 1 hour after sunrise, and one hour before sunset. You may also use side lights when
visibility is poor, due to light rain for example. When your side lights are on, your tail lights are also on.

Automobile 2 and 11 marks unit v

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Automobile 2 and 11 marks unit v