21. The detonating tendency in petrol engines increases with increase of compression ratio.

A. True
B. False

22. Each fission of U₂₃₅ produces on the average __________ fast neutrons as a product of reaction.

A. 2.46
B. 24.6
C. 246
D. 2460

23. Reactors for propulsion applications are designed for

A. any form of uranium
B. natural uranium
C. enriched uranium
D. plutonium

24. The primary fuel used in nuclear power plants is

A. U₂₃₅
B. U₂₃₈
C. Pu₂₃₉
D. Pu₂₃₃

25. In petrol engine, using a fixed octane rating fuel and fixed compression ratio, supercharging will __________ the knocking tendency.

A. not effect
B. decrease
C. increase

26. Ordinary water is sometimes used as moderator when enriched uranium is used as a fuel in nuclear power plants.

A. Yes
B. No

27. The compensating jet in a carburetor supplies an almost constant amount of petrol at all speeds because of the

A. jet area is automatically varied depending on the suction
B. the flow from the main jet is diverted to the compensating jet with increase in speed
C. the diameter of the jet is constant and the discharge coefficient is invariant
D. flow is produced due to the static head in the float chamber

28. The effective inhibitor of pre-ignition is

A. alcohol
B. water
C. lead
D. none of these

29. The purpose of testing an internal combustion engine is

A. to determine the information, which can not be obtained by calculations
B. to conform the data used in design, the validity of which may be doubtful
C. to satisfy the customer regarding the performance of the engine
D. all of the above

30. The thermal efficiency of diesel engines is about

A. 15%
B. 30%
C. 50%
D. 70%