41. A moderator

A. absorbs neutrons
B. does not absorb neutrons
C. accelerates neutrons
D. none of these

42. In a four stroke cycle diesel engine, the exhaust valve

A. opens at 30° before bottom dead center and closes at 10° after top dead center
B. opens at 30° after bottom dead center and closes at 10° before top dead center
C. opens at bottom dead center and closes at top dead center
D. may open and close anywhere

43. The two stroke cycle engines have lighter flywheel.

A. Agree
B. Disagree

44. The thermodynamic cycle on which the petrol engine works, is

A. Otto cycle
B. Joule cycle
C. Rankine cycle
D. Stirling cycle

45. The inlet valve of a four stroke cycle internal combustion engine remains open for

A. 130°
B. 180°
C. 230°
D. 270°

46. The correct mixture strength (by weight) for petrol is about

A. 14.6:1
B. 18.5:1
C. 20.4:1
D. 22.6:1

47. The working pressure and temperature inside the cylinder of an internal combustion engine is __________ as compared to a steam engine.

A. low
B. very low
C. high
D. very high

48. The scavenging efficiency of a four stroke cycle diesel engine is

A. below 50%
B. between 50 and 85%
C. between 85 and 95%
D. between 95 and 100%

49. The voltage required to produce a spark across the gap, between the sparking points is

A. 2000 to 4000 volts
B. 4000 to 6000 volts
C. 6000 to 10 000 volts
D. 10 000 to 12 000 volts

50. The control rods in the control system of nuclear reactors are used to

A. absorb excess neutrons
B. control fuel consumption
C. control temperature
D. all of these