⚙️ 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

In a psychrometric process, the sensible heat added is 30 kJ/s and the latent heat added is 20 kJ/s. The sensible heat factor for the process will beAnswer: 0.6 The aim of a compound steam engine isAnswer: all of the above The amount of radiation mainly depends upon theAnswer: all of these The amount of radiation mainly depends upon theAnswer: all of these The average operating pressure of Benson boiler isAnswer: 250 bar For ammonia refrigerating systems, the tubes of a shell and tube condenser are made ofAnswer: steel The highest thermal diffusivity is ofAnswer: lead The diameter of Cornish boiler varies fromAnswer: 1 to 2 m While designing the refrigeration system of an aircraft, the prime consideration is that theAnswer: mass of the refrigeration equipment is low A single acting steam engine produces __________ power than that of double acting steam engine.Answer: half The heat transfer takes place according toAnswer: Second law of thermodynamics The pressure of steam in the engine cylinder at the beginning of the stroke is __________ the boiler pressure.Answer: less than An electrolux refrigerator is called a __________ absorption system.Answer: three fluids An electrolux refrigerator is called a __________ absorption system.Answer: three fluids The function of a flywheel isAnswer: to prevent fluctuation of speed The rate of steam produced in Benson boiler isAnswer: 135 tonnes/h In natural circulation steam boilers, the circulation of water is by convection currents which are set up during the heating of water.Answer: Correct The heat transfer by radiation __________ a medium.Answer: does not require Cut-off governing of steam engines is a method of controlling the engine output by varyingAnswer: volume of intake steam Thermal conductivity of water __________ with rise in temperature.Answer: may increase or decrease depending upon temperature In a boiler, feed water supplied per hour is 205 kg while coal fired per hour is 23 kg. The net enthalpy rise per kg of water is 145 kJ. If the calorific valve of the coal is 2050 kJ/kg, then the boiler efficiency will beAnswer: 63% A safety valve mainly used with locomotive and marine boilers isAnswer: spring loaded safety valve Which of the following boiler is best suited to meet the fluctuating demand of steam ?Answer: Locomotive boiler Which of the following statement is correct ?Answer: All of the above A nozzle is said to be a convergent nozzleAnswer: when the cross-section of the nozzle decreases continuously from entrance to exit A turbine is said to have an axial discharge when the steam leaves the blade tip at __________ to the direction of the blade motion.Answer: 90° The flow through a nozzle is regarded asAnswer: isentropic flow The ratio of total useful heat drop to the total isentropic heat drop, is calledAnswer: internal efficiency The pressure at which the steam leaves the nozzle is known as back pressure.Answer: Correct The discharge of steam in a convergent-divergent nozzle __________ after the throat (i.e. in the divergent portion of the nozzle)Answer: remains constant