Quiz:Mechanical Engineering 15 June 2020

Quiz: Mechanical Engineering
Exam: UPSSSC JE
Topic: Miscellaneous

Each question carries 1 mark
Negative marking: 1/4 mark
Time: 10 Minutes

Q1. In a reaction stage turbine, the velocity
(a) increases in stator and remains constant in rotor
(b) increases in stator and decreases in rotor
(c) decreases in stator and remains constant in rotor
(d) remains constant throughout

Q2. With Reheat Rankine cycle:
(a) Quality of exhaust steam is improved
(b) Network output of cycle increases
(c) Specific steam consumption decreases
(d) All of the above

Q3. The knocking sensitivity of S.I. engines could be reduced by:
(a) Compact combustion chamber geometry
(b) Central position of the spark plug
(c) Increased turbulence
(d) All of the above

Q4. Which device can be used to measure aromatic hydrocarbon in exhaust gas?
(a) Dispersion analyser
(b) Non-dispersive infrared analyser
(c) Flame ionization detector
(d) All of the above

Q5. Which of the following is not true for heat pump?
(a) Low temperature reservoir is environment
(b) Low temperature reservoir is conditioned space
(c) It is a cyclic device
(d) Work done is negative

Q6. Amongst the following options what remains constant during adiabatic saturation process on unsaturated air?
(a) Dew point temperature
(b) Relative humidity
(c) Wet bulb temperature
(d) Dry bulb temperature

Q7. A stone weighs 405 N in air and 206 N in water. Find the weight of water displaced.
(a) 206
(b) 199
(c) 200
(d) 405

Q8. Temperature stresses are set up in a material when
(a) It is free to expand or contract
(b) It is first heated then cooled
(c) It is first cooled and then heated
(d) Its expansion and contraction are restrained

Q9. A transmission shaft includes:
(a) Counter shaft
(b) Line shaft
(c) Over head shaft
(d) All of these

Q10. The unbalanced force due to reciprocating masses
(a) Varies in magnitude but constant in direction
(b) Varies in direction but constant in magnitude
(c) Varies in both magnitude and direction
(d) Constant in both direction and magnitude

Solutions

S1. Ans (b)
Sol. In a reaction stage turbine, the velocity increases in stator as it works as a nozzle and decreases in rotor.

S2. Ans (d)
Sol. With Reheat application in Rankine cycle,
1.Work output increases
2.Dryness fraction or quality of steam improves
3.Specific steam consumption i.e. Steam consumption per KWh decreases due to increases in work output

S3. Ans (d)
Sol. Knocking sensitivity in S.I. engine can be reduced by:
1.Compact construction of combustion chamber to reduce flame travel distance
2.Locating the spark plug centrally or near exhaust valve
3.Increasing turbulence

S4. Ans (d)
Sol. An aromatic hydrocarbon or arene (or sometimes aryl hydrocarbon) is a hydrocarbon with sigma bonds and delocalized pi electrons between carbon atoms forming a circle.
Dispersion analyser, Non-dispersive infrared analyser and flame-ionization detector all are used for measure aromatic hydrocarbon in exhaust gases.

S5. Ans (b)
Sol. Heat pump is a cyclic device, in which high temperature reservoir is a conditioned space maintained above the temperature of surrounding. Work done is negative for the heat pump.

S6. Ans (c)
Sol. Adiabatic saturation process is that process in which water converts into vapour and mixed with air till its saturation, adiabatically.
Wet bulb temperature remains constant during this process.

S7. Ans (b)
Sol. According to Archimedes principle,
Weight of displaced water = weight of stone in air-weight of stone in water
=405-206=199 N

S8. Ans (d)
Sol. When there is generation of thermal strain (tensile or compressive) in a body due to change in temperature and it is made restricted for this, then stresses (tensile or compressive depending upon the temperature decrease or increase) will be generated in it.

S9. Ans (d)
Sol. A power transmission can be done by using counter shaft, line shaft and overhead shaft etc.

S10. Ans (a)
Sol. The unbalanced force due to reciprocating masses has same direction irrespective of the magnitude but magnitude may change.

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