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Right OPTION is (a) Due to conduction CURRENTS

Explanation: The water CIRCULATION happens in a thermosyphon COOLING SYSTEM due to conduction currents. This system is simple and automatic.

Correct answer is (a) To ALLOW the engine to warm-up QUICKLY

Easy explanation: The thermostat is used to allow the engine to warm-up quickly. The thermostat UNIT CONSISTS of closed BELLOWS with a volatile liquid.

Correct option is (d) Centrifugal PUMP

For explanation: Centrifugal pump is used in a forced COOLING SYSTEM. The pump is used to maintain the circulation of the water through the system. The power is TRANSMITTED to the pump spindle.

Right option is (c) Hot WATER is simply discharged

For explanation I would say: In DIRECT SYSTEM of cooling air, hot water is simply discharged. In air-cooled system, a current of air is MADE to flow past the outside of the cylinder barrel.

Right CHOICE is (c) CnH2n+2

Explanation: The paraffin is REPRESENTED by CnH2n+2. The NORMAL paraffin hydrocarbons are of straight-chain molecular structure. Iso-butane has the same general chemical formula and molecular WEIGHT as butane.

The correct choice is (c) Even COOLING

Explanation: The advantage of the liquid cooling SYSTEM is even cooling. In this system, WATER is USED as a coolant and made to circulate through the jackets provided around the cylinder, cylinder head, valve ports and seats.

The correct answer is (a) To cool the JACKET water

Best explanation: Radiator is provided to cool the jacket water. The HEAT from the combustion gases is transferred to the various parts of the engine LIKE cylinder HEAD and walls, piston and VALVES.

Correct option is (c) CETANE point

The EXPLANATION: IGNITION quality of DIESEL fuel indicated by cetane point. Cetane number of a fuel is defined as the percentage of normal cetane in a MIXTURE of normal cetane and α-methyl naphthalene by volume.

Right answer is (d) 100

Easiest explanation: Iso-octane has octane number 100. The octane number FUEL is DEFINED as the percentage of iso-octane in a MIXTURE of iso-octane and NORMAL heptane by volume.

The correct CHOICE is (a) Chain saturated

For explanation: The paraffin possesses a chain structure and is saturated in NATURE. In these hydrocarbons, the valency of all FOUR carbon atoms is fully utilized by single BONDS with HYDROGEN atoms.

Correct option is (b) It can mix EASILY with AIR

To elaborate: The advantage of the gaseous fuel is that it can mix easily with air. Gaseous fuels are IDEAL fuels. They pose very few problems in USING them in IC engines.

The correct answer is (C) By cracking

For explanation I would say: Hydrocarbons are decomposed into SMALLER hydrocarbons by cracking. Cracking consists of breaking down LARGE COMPLEX hydrocarbon molecules into simpler COMPOUNDS.

Right choice is (b) False

The BEST explanation: Field coils in a GENERATOR produce a temporary magnet. The field MAGNETS are ELECTROMAGNETS. These magnets are energized by generator current. The FIELDS magnets have a small residual magnetism this helps in providing the initial field to start the generator operation.

Right CHOICE is (b) 8

For explanation: The number of positive plates in the lead-acid cell is always ONE LESS than the number of negative plates. The number of negative plates = 9 and total plates are = 17, therefore, a number of positive plates = 8.

The correct choice is (d) Aluminum

Easiest explanation: An alternator frame is made of aluminum. Aluminum is lightweight. It is no-magnetic. It has a higher thermal CONDUCTIVITY so as to KEEP the alternator assembly COOL by more efficient transfer of HEAT.

Right option is (a) Voltage regulator

To explain: Voltage regulator CONTROLS the output of the alternator. A voltage regulator is designed so that it KEEPS a constant voltage level. The voltage regulator is USED when the STEADY and reliable voltage is needed.

Correct option is (B) Higher

Explanation: The charging voltage is HIGH at the start of the engine. The charging voltage should be LESS than the alternator voltage to charge the battery. The standard battery automotive battery should indicate 12.6 V at 35℃. When the engine is running, it should show 13.7 V to 14.7 V.

The correct option is (c) To COMPENSATE for temperature change

Easy explanation: A THERMISTOR is USED in an alternator regulator to compensate for temperature change. It is a temperature-sensing DEVICE. It alters its physical resistance to change temperature.

Correct answer is (C) The SPECIFIC gravity of electrolyte remains the same

To elaborate: The advantage of the alkaline battery is that the specific gravity of electrolyte remains the same. The electrolyte does not take part in chemical reactions on charging or DISCHARGING.

Correct answer is (b) A BATTERY having lead-calcium plate GRID

Best explanation: A maintenance-free battery is a battery having a lead-calcium plate grid. The battery which uses this plate grid LOSES water very slowly.

Right answer is (a) TIME for which the battery can SUPPLY 25 A at 80℉ with minimum cell VOLTAGE 1.75 V

The explanation is: The reserve capacity is the time for which the battery can supply 25 A at 80℉ with minimum cell voltage 1.75 V. It is the MEASUREMENT for the total capacity of the battery.

The correct CHOICE is (b) Lasting power of a battery on a small load

Easy explanation: A twenty-hour RATE of a battery is the lasting power of a battery on a small load. During this test, the temperature should be about 80oF. This rating is important for POWERING ACCESSORIES when the engine is not running.

Correct choice is (a) Rate of current for 20 minutes with a minimum cell voltage of 1.5 V

Explanation: The rate of current 20 minutes with a minimum cell voltage of 1.5 V is called a twenty-minute RATING of the battery. The TEMPERATURE of the battery at the start of the test is brought to 80℉. It REPRESENTS the rate of current a battery can deliver continuously.

The correct CHOICE is (d) PbSO4

Easiest explanation: PbSO4 gets deposited on the plates of a DISCHARGED lead-acid battery. During DISCHARGING the reaction happens in the right DIRECTION. PbSO4 gets deposited on both negative and positive plates.

The correct option is (d) Brown

For explanation I would say: A positive plate of a lead-acid BATTERY is brown in COLOUR. A negative plate of a lead-acid battery is grey in colour. For each plate, there is a supporting GRID made of an ALLOY of lead and antimony.

Correct ANSWER is (d) It has multi-fuel capabilities

Explanation: Stratified charge ENGINE has multi-fuel capabilities. The ADVANTAGES of a stratified charge engine are HIGHER THERMODYNAMIC efficiency and reduced air pollution.

Right option is (a) SI engine

To elaborate: Variable compression is used in SI ENGINES. There are several methods for CHANGING both the GEOMETRIC and EFFECTIVE compression ratio.

Correct choice is (c) Hybrid of both SI and CI engine

To explain: HCCI engine has the same COMBUSTION as a hybrid of both SI and CI engine. HCCI is a FORM of IC engine in which well-mixed fuel and AIR are compressed to the auto-ignition temperature of the fuel.

Right option is (a) The engine which uses GASEOUS and liquid fuel

For explanation: The duel fuel engine uses gaseous and liquid fuel. The dual-fuel engine works on the diesel CYCLE. The gaseous fuel is called the PRIMARY fuel. The mixture of air and gaseous fuel is compressed in the CYLINDER.

The correct option is (a) Due to a broken FAN belt

The explanation is: The engine overheating happens due to a broken fan belt. When a fan is broke, it cannot COOL the hot water. It should be capable of removing about 30% of the heat from the COMBUSTION CHAMBER.

The correct answer is (d) HIGH EFFICIENCY

Best EXPLANATION: With a lightweight of the ALTERNATOR, the efficiency of alternator increases. As the OUTPUT current does not flow through the commutator and brushes, thus surface contamination is eliminated.

Correct OPTION is (d) High EFFICIENCY, quiet operation and compatible with renewable energy

The explanation is: The Stirling engine has high efficiency. A Stirling engine is a heat engine operating on CYCLIC COMPRESSION and expansion of air or any other fluid.

The correct answer is (d) Injection as well as CARBURATION

The explanation is: The charge stratification can be ACHIEVED by injection as well as carburation. Charge stratification means PROVIDING different fuel-air mixture strengths at various PLACES in the combustion CHAMBER.

The correct choice is (B) SI engine

The best I can explain: SI engines are more ideal for the lean-burn CONCEPT. A lean-burn MODE is a way to REDUCE throttling losses. In SI engine, the power is reduced by partially closing a throttle.

The correct ANSWER is (B) By reforming

Easy explanation: The molecular structure of the straight-run gasoline is changed by reforming. Reforming is a cracking process which is used to convert the LOW antiknock QUALITY gasoline into gasoline of higher OCTANE rating.

Correct CHOICE is (d) Carbon brushes

The best EXPLANATION: Carbon brushes PRODUCE the magnetic FIELD in DC generator. The DC generator is a DEVICE which converts mechanical energy into electrical energy. It works on the principle of induced EMF.

The correct option is (c) It has a longer OPERATING cycle

Easiest explanation: Wankel engine is a TYPE of internal combustion engine using rotary DESIGN to convert PRESSURE into a rotating motion. It does not make use of RECIPROCATING pistons.

The correct option is (a) Aromatics

The best I can EXPLAIN: For SI engines aromatic fuels are preferred. Aromatic compounds are ring structured. They have a benzene molecule as their central structure and ALSO a GENERAL chemical formula is CnH2n-6.

Right option is (c) The CURRENT which the battery can supply continuously for 30 seconds with minimum cell voltage 1.2 V

Explanation: It is a measure of the WORST CONDITIONS under which a battery is expected to deliver current, e.g., during starting the engine and operating under EXTREME cold. The cold rate of a battery is the current which the battery can supply continuously for 30 seconds with minimum cell voltage 1.2 V.

Correct choice is (c) To control the water TEMPERATURE

The BEST I can explain: THERMOSTAT is used to control the water temperature. WHENEVER the engine is started from COLD, the coolant temperature has to be brought to the desired level so that the warmup time is less.

The CORRECT option is (d) 12.6 V and the specific gravity of 1.29 at 32℃

Explanation: A fully-charged 6 cell AUTOMOTIVE battery indicates 12.6 V and a specific gravity of 1.29 at 32℃. There should be no LEAK. The battery can be checked USING a digital multimeter.

Right option is (d) Pre-catalyst hydrocarbon EMISSIONS are HIGHER

The explanation: Pre-catalyst hydrocarbon emissions are higher is one of the DISADVANTAGES of the HCCI ENGINE. The ADVANTAGES of the HCCI engine are NOx and soot emissions are almost negligible.