⚙️ Mechanical Eng Solved MCQs with Answers

Practice 934 approved ⚙️ Mechanical Eng questions with verified answers from the 🛠️ Engineering Essentials subject for Pakistan exams.

934 solved MCQs

The compensating jet in a carburettor supplies almost constant amount of petrol at all speeds because theAnswer: flow is produced due to the static head in the float chamber The effective inhibitor of pre-ignition isAnswer: water The purpose of testing an internal combustion engine isAnswer: all of the above The thermal efficiency of diesel engines is aboutAnswer: 70% A diesel engine hasAnswer: three valves The self ignition temperature of petrol is __________ as compared to diesel oil.Answer: higher The pressure inside the cylinder is __________ the atmospheric pressure during the exhaust stroke.Answer: above The increase of cooling water temperature in petrol engine will __________ the knocking tendency.Answer: increase A carburettor is used to supplyAnswer: petrol and air The actual volume of air delivered by a compressor, When reduced to the normal temperature and pressure conditions is called compressor capacity.Answer: No The compression ratio in a gas turbine isAnswer: 1 Intercooling in compressors results in saving of power in compressing given volume of air to a given pressure.Answer: Correct Only rocket engines can be propelled to space becauseAnswer: they are not air-breathing engines The maximum combustion pressure in gas turbine is __________ as compared to I.C. engine.Answer: less An aftercooler is used toAnswer: cause moisture and oil vapour to drop out High air-fuel ratio in gas turbinesAnswer: reduces exhaust temperature The ratio of the volume of free air delivery per stroke to the swept volume of the piston, is known asAnswer: volumetric efficiency The ratio of the indicated power to the shaft power or brake power of the motor or engine required to drive the compressor, is calledAnswer: mechanical efficiency The increase in pressure in a roots blower is entirely due to back flow of air.Answer: Agree The type of rotary compressor used in aeroplanes, is ofAnswer: axial flow type An axial compressor gives optimum performance at high speeds and large volume flows.Answer: Agree In a reciprocating air compressor, the compression work per kg of airAnswer: is independent of clearance volume The degree of reaction in an axial flow compressor is defined as the ratio of static enthalpy rise in theAnswer: rotor to static enthalpy rise in the stage Specify the sequence correctlyAnswer: Stress relief, recrystallisation, grain growth Thermoplastic materials are those materials whichAnswer: do not become hard with the application of heat and pressure and no chemical change occurs Which of the following material has maximum ductility?Answer: Mild steel An eutectoid steel consists ofAnswer: wholly pearlite Shock resisting steels should haveAnswer: toughness Cast iron is aAnswer: brittle material The hardness is the property of a material due to which itAnswer: can cut another metal