78) In order to mix air and petrol in the required proportion and to supply it to the engine during suction stroke, then __________ is employed.

79) The advancing of spark timing in spark ignition engines will __________ knocking tendency.

80) The knocking in spark ignition engines can be reduced by

81) An atom bomb utilises uncontrolled nuclear fission.

82) The ratio of the brake power to the indicated power is called