# Applied Thermodynamics 5

Mechanical Engineering MCQ Question Papers: DRDO, ISRO, Interview

Subject: Applied Thermodynamics 5

Part 5: List for questions and answers of Applied Thermo dynamics

Q1. The air standard efficiency of an Otto cycle compared to diesel cycle for the given compression ratio is
a) Same
b) Less
c) More
d) More or less depending on power rating

Q2. In order to prevent knocking in spark ignition engines, the charge away from the spark plug should have
a) Low density
b) Low temperature
c) Long ignition delay
d) All of these

Q3. The actual volume of fresh charge admitted in 4-stroke petrol engine is
a) Equal to stroke volume
b) Equal to stroke volume and clearance volume
c) Less than stroke volume
d) More than stroke volume

Q4. The power actually developed by the engine cylinder of an I.C. engine is known as
a) Theoretical power
b) Actual power
c) Indicated power
d) None of these

Q5. In loop scavenging, the top of the piston is
a) Flat
b) Contoured
c) Slanted
d) Depressed

Q6. If the compression ratio of an engine working on Otto cycle is increased from 5 to 7, the percentage increase in efficiency will be
a) 2%
b) 4%
c) 8%
d) 14%

Q7. When crude oil is heated, then which of the following hydrocarbon is given off first?
a) Kerosene
b) Gasoline
c) Paraffin
d) Natural gas

Q8. Supercharging is the process of supplying the intake air to the engine cylinder at a density _________ the density of the surrounding atmosphere
a) Equal to
b) Less than
c) Greater than
d) None of these

Q9. In a petrol engine, the fuel supplied to the engine cylinder is mixed with required quantity of air and the mixture is ignited with a
a) Fuel pump
b) Fuel injector
c) Spark plug
d) None of these

Q10. For maximum po For maximum power generation, the air fuel ratio for a petrol engine for vehicles, is of the order of
a) 9 : 1
b) 12 : 1
c) 15 : 1
d) 18 : 1

Q11. The ratio of the indicated thermal efficiency to the air standard efficiency is known as
a) Mechanical efficiency
b) Overall efficiency
c) Volumetric efficiency
d) Relative efficiency

Q12. The knock in diesel engine occurs due to
a) Instantaneous and rapid burning of the first part of the charge
b) Instantaneous auto ignition of last part of charge
c) Delayed burning of the first part of the charge
d) Reduction of delay period

Q13. If one cylinder of a diesel engine receives more fuel than the others, then for thatcylinder the
a) Exhaust will be smoky
b) Piston rings would stick into piston grooves
c) Engine starts overheating
d) Scavenging occurs

Q14. Pre-ignition is caused by the spontaneous combustion of the mixture before the end of the compression stroke, and is due to
a) Cylinder walls being too hot
b) Overheated spark plug points
c) Red hot carbon deposits on cylinder walls
d) Any one of these

Q15. Scavenging air in diesel engine means
a) Air used for combustion sent under pressure
b) Forced air for cooling cylinder
c) Burnt air containing products of combustion
d) Air used for forcing burnt gases out of engine’s cylinder during the exhaust period

Q16. The reference fuels for knock rating of spark ignition engines would include
a) Iso-octane and alpha-methyl naphthalene
b) Normal octane and aniline
c) Iso-octane and normal hexane
d) Normal heptane and iso-octane

Q17. The brake power of a diesel engine, keeping other parameters constant, can be increased by
a) Decreasing the density of intake air
b) Increasing the temperature of intake air
c) Increasing the pressure of intake air
d) Decreasing the pressure of intake air

Q18. Engine pistons are usually made of aluminium alloy because it
a) Is lighter
b) Wear is less
c) Absorbs shocks
d) Is stronger

Q19. During idling, a petrol engine requires _________ mixture
a) Lean
b) Rich
c) Chemically correct
d) None of these

Q20. Mass of any substance per amount of substance is called
a) Relative Mass
b) Molar Mass
c) Atomic Mass
d) Total Mass

Part 5: List for questions and answers of Applied Thermo dynamics