BPSC AE 2024: Assistant Engineer (Civil/Mechanical/Electrical) (Advt. 33/2024), Paper V Mechanical Engineering I
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Booklet Serial No.
22/AE/CM/M –2024-05
AAAAA Booklet Series Question Booklet
AAAAA
A
AAAAA MECHANICAL ENGINEERING – I
AAAAA Paper – V Candidate’s Roll Number
Time Allowed : 01 Hour Maximum Marks : 100
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1. The flash chamber in vapour compression 4. What assumption is made about
cycle (Single stage) is incorporated to frictional power in the Morse test ?
(A) Increase the compressor pressure (A) It decreases when a cylinder is
ratio cut off
(B) Decrease the refrigerating effect (B) It increases when a cylinder is
cut off
(C) Reduce the size of evaporator
(C) It varies with the speed of the
(D) Increase the refrigerating effect
engine
(D) It remains constant whether a
2. Which one of the following pairs of cylinder is working or not
materials is used as moderators in
nuclear reactors ? 5. The maximum efficiency of transmission
of power through a pipe is
(A) Cadmium and beryllium
(A) 33.3%
(B) Zirconium and beryllium
(B) 66.66%
(C) Beryllium and heavy water
(C) 50%
(D) Heavy water and zirconium (D) 25%
3. An ideal Brayton cycle, operating 6. In incompressible fluid flows over a flat
between the pressure limits of
plate with zero pressure gradient. The
1 bar and 6 bar, has minimum and
boundary layer thickness is 1 mm at a
maximum temperatures of 300 K
and 1500 K. The ratio of specific location where the Reynolds number is
heats of the working fluid is 1.4. The 1000. If the velocity of the fluid alone
approximate final temperatures in is increased by a factor of 4, then the
Kelvin at the end of the compression boundary layer thickness at the same
and expansion processes are location, in mm, will be
respectively
(A) 0.5
(A) 500 and 500
(B) 2
(B) 900 and 500
(C) 900 and 900 (C) 0.25
(D) 500 and 900 (D) 4
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7. Under ideal conditions, for a drop of 10. Gauge pressure is equal to
50 kJ/kg enthalpy, what will be the
(A) Patmospheric – Pabsolute
approximate velocity of steam at the
outlet of the nozzle if the inlet velocity (B) Pabsolute – Patmospheric
of the steam is 5 m/s ? (C) Patmospheric – Pvacuum
(A) 400 m/s (D) Pabsolute + Patmospheric
(B) 410 m/s
(C) 325 m/s 11. Interaction of unsaturated air with
water droplets in air washer can
(D) 317 m/s leads to
(A) Dehumidification
8. In order to achieve maximum heat (B) Humidification
dissipation, the fin should be designed
(C) Constant DPT line
in such a way that
(D) All of the above
(A) It should have maximum lateral
surface near the centre of the fin
(B) It should have maximum lateral 12. Consider the following statements,
High condenser pressure in a
surface towards the tip side of the
refrigeration system can occur because
fin
1. The water flow rate is lower than
(C) It should have minimum lateral the desired value.
surface near the centre of the fin
2. Non-condensable gases are present
(D) It should have maximum lateral in the system.
surface at the root side of the fin
3. Of accumulation of lubricating oil
in condenser.
9. The centrifugal compressor in vapour 4. Of low charge of refrigerant in the
compression refrigeration system is system.
very sensitive to Of these statements :
(A) evaporator temperature (A) 1, 2 and 4 are correct
(B) condenser temperature (B) 1, 2 and 3 are correct
(C) both (A) and (B) (C) 2, 3 and 4 are correct
(D) 1, 3 and 4 are correct
(D) none of the above
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13. A centrifugal pump gives the maximum 15. For burning of 2 kilograms of
efficiency when its blade are methane (CH4) completely, the
minimum number of kilograms
(A) Straight of oxygen needed is (take atomic
weight of H, C and O as 1, 12 and 16
(B) Bent backward
respectively)
(C) Wave shaped
(A) 6
(D) Bent forward
(B) 4
(C) 8
14. Given below are two statements, one is
(D) 2
labelled as Assertion (A) and other as
Reason (R). Choose the correct answer
from the options given below. 16. The fluid forces considered in the
Navier-Stokes equation are
Assertion (A) : Fire tube boilers do not
operate at high pressures while water (A) Pressure, viscous and turbulent
tube boilers operate at high pressures. (B) Gravity, pressure and turbulent
Reason (R) : Due to high temperature (C) Gravity, viscous and turbulent
of flue gases, fire tubes may fail due to
(D) Gravity, pressure and viscous
creep.
(A) (A) is true but (R) is false
17. If there is no change in the fluid
(B) Both (A) and (R) are individually true pressure between the inlet and outlet
of the rotor of an axial flow machine,
but (R) is not the correct explanation
then degree of reaction (R)
of (A)
(A) R > 0
(C) (A) is false but (R) is true
(B) R = 1
(D) Both (A) and (R) are individually
(C) R < 0
true and (R) is the correct explanation
of (A) (D) R = 0
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18. Consider the following statements : 21. It is proposed to build refrigeration
plant for a cold storage to be maintained
1. Pulverized fuel gives high and
controlled burning rate. at –3ºC. The ambient temperature is
27ºC. If 5 × 106 kJ/h of energy is to be
2. Insufficient air causes excessive
smoking of exhaust. continuously removed from the cold
storage, the minimum power required
3. Excess air is provided to control
to run the refrigerator will be
the flue gas temperature.
4. Effect of sulphur in fuel is to give (A) 154.3 kW
high heat transfer rate.
(B) 75.3 kW
Which of these statements are correct ?
(C) 245.3 kW
(A) 1 and 4
(B) 1, 2 and 3 (D) 14.3 kW
(C) 1 and 2
(D) 1 and 3 22. Surging is instability of operation
caused by mismatch between the
impeller and the diffuser at _______
19. Cooling tower in steam power station flow rates.
is a device
(A) medium
(A) Reducing the temperature of
superheated steam
(B) low
(B) Cooling the exhaust gases coming
out of the boiler (C) very high
(C) Reducing the temperature of cooling (D) high
water used in condenser
(D) Condensing the steam into water
23. The pressure in meters of oil (specific
gravity 0.85) equivalent to 42.5 m of
20. Which of the following is true about
the optimum effective temperature for water is
human comfort ?
(A) 52.5 m
(A) Lower in winter than in summer
(B) 50 m
(B) Not dependent on season
(C) 85 m
(C) Higher in winter than in summer
(D) Same in winter and summer (D) 42.5 m
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24. In a parallel flow heat exchanger, if the 27. In modern boilers, stacks alone can not
heat capacity ratio is 1, then what is create enough mechanical draught
the maximum value of effectiveness ? because
(A) 0.75 (A) The rate of air supply as well as the
rate of flue gas removal is high
(B) 2/3
(B) Various heat exchangers are used on
(C) 0.5
the way cause large pressure drop
(D) 1
(C) Both (A) and (B)
(D) Modern boilers operate at high
25. Frosting on the evaporator coils
pressure range
(A) causes increase in heat transfer
rate
28. Which one of the following statements
(B) is the sign of good cooling
is true to two-dimensional flow of ideal
(C) causes decrease in heat transfer fluids ?
rate
(A) Both potential function and stream
(D) is the sign of good compressor function must exist for every flow
(B) Stream function may or may not
26. Consider the following statements exist
pertaining to large heat transfer rate
using fins (C) Stream function will exist but
potential function may or may not
1. Fins should be used on the side exist
where heat transfer coefficient is
small. (D) Potential function exists if stream
function exists
2. Long and thick fins should be
used.
3. Short and thin fins should be 29. The hydrodynamic boundary layer
used. thickness is defined as the distance
from the surface where the
4. Thermal conductivity of fin
material should be large. (A) Momentum equals 99% of the
momentum of the free stream
Which of the above statements are
correct ? (B) Velocity equals the approach
velocity
(A) 2, 3 and 4
(B) 1, 2 and 4 (C) Velocity equals 99% of the local
external velocity
(C) 1, 3 and 4
(D) Velocity equals the local external
(D) 1, 2 and 3 velocity
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30. Which one of the following 33. The specific speed of a turbine is given
non-dimensional numbers is mostly by the equation
used for determining the transition (A) N P/(H)5/4
from laminar to turbulent flow in free
(B) N Q/(H)3/2
convection ?
(C) N Q/(H)5/4
(A) Peclet number
(D) N P/(H)3/2
(B) Grashof number
(C) Rayleigh number
34. If the capillary rise of water in a 2 mm
diameter tube is 1.5 cm, the height of
(D) Reynolds number
capillary rise in a 0.5 mm diameter
tube, in cm, will be
31. Which of the following water turbines (A) 6.0
does not require a draft tube ?
(B) 1.5
(A) Kaplan Turbine
(C) 24.0
(B) Pelton Turbine (D) 10.0
(C) Francis Turbine
(D) Propeller Turbine 35. In a gas cycle refrigeration, an expander
is used instead of a throttle valve for
pressure drop of the refrigerant, because
32. Which law states that for an adiabatic
(A) there is inadequate content of
and steady flow, the Mach number can temperature
not increase across a normal shock
(B) there can be even heating of the gas
wave ?
if the temperature before throttling
(A) First law of thermodynamics is not below the maximum inversion
temperature
(B) Rayleigh line
(C) there can be leakage of gas
(C) Second law of thermodynamics
(D) enough cooling or temperature drop
(D) Rankine-Hugoniot relation is not obtained by throttling
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36. COP of refrigerator based on reverse 38. The critical pressure ratio of a
Carnot cycle decreases on convergent nozzle is defined as
(A) increasing the higher temperature (A) The ratio of outlet pressure to inlet
pressure only when mass flow rate
and keeping the lower temperature
per unit area is the maximum
constant
(B) The ratio of inlet pressure to outlet
(B) keeping the higher temperature
pressure of nozzle
constant and increasing the lower
temperature (C) The ratio of outlet pressure to inlet
pressure only when mass flow rate
(C) increasing the higher temperature and per unit area is the minimum
decreasing the lower temperature
(D) The ratio of outlet pressure to inlet
(D) decreasing the difference in pressure of nozzle
operating temperatures
39. Match the following :
37. Which of the following can not be a. Lancashire 1. High pressure
caused by a hot spark plug ? water tube
1. Pre-ignition b. Cornish 2. Horizontal
double fire tube
2. Post-ignition
c. La Mont 3. Vertical multiple
3. Detonation fire tube
4. Run-on-ignition d. Cochran 4. Low pressure
inclined water
Select the correct answer using the
tube
code given below :
5. Horizontal single
Code : fire tube
(A) 2 and 3 (A) a – 3 b–2 c–1 d–4
(B) 2 only (B) a – 2 b–1 c–3 d–4
(C) 3 only (C) a – 5 b–2 c–4 d–3
(D) 1 and 4 (D) a – 2 b–5 c–1 d–3
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40. Steam enters a De Laval steam turbine 43. A steam turbine receives steam
with an inlet velocity of 30 m/s and steadily at 10 bar with an enthalpy
leaves with an outlet velocity of 10 m/s.
of 3000 kJ/kg and discharges at 1 bar
The work done by 1 kg of steam is
with an enthalpy of 2700 kJ/kg. The
(A) 600 N-m
work output is 250 kJ/kg. The changes
(B) 400 N-m in kinetic and potential energies are
(C) 800 N-m negligible. The heat transfer from the
(D) 200 N-m turbine casing to the surroundings is
equal to
41. If a hydraulic press has a ram of (A) 125 kJ
12.5 cm diameter and plunger of
1.25 cm diameter, what force would be (B) 75 kJ
required on the plunger to raise a
mass of 1 ton on the ram ? (C) 150 kJ
(A) 9.81 N (D) 50 kJ
(B) 98.1 N
(C) 0.98 N 44. A four stroke automobile engine operates
(D) 981 N at a fuel-air ratio of 0.05, volumetric
efficiency of 90% and indicated thermal
efficiency of 30%. Given that the calorific
42. The correct sequence of the given
hydraulic turbine in decreasing order value of the fuel is 45 MJ/kg and the
of their specific speeds is density of air at intake is 1 kg/m3, the
(A) Kaplan turbine, Pelton wheel and indicated mean effective pressure for
Francis turbine the engine is
(B) Propeller turbine, Francis turbine
(A) 60.75 bar
and Pelton wheel
(C) Francis turbine, Kaplan turbine and (B) 6.075 bar
Pelton wheel
(C) 4.35 bar
(D) Pelton wheel, Francis turbine and
Kaplan turbine (D) 12.15 bar
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45. A balloon containing an ideal gas is 48. The conservation of energy principles
initially kept in an evacuated and reduces to conserving mechanical
insulated room. The balloon ruptures energy alone in case of
and the gas fills up the entire room.
Which one of the following statements (A) Compressible fluid
is true at the end of above process ?
(B) Isothermal fluid
(A) Both internal energy and enthalpy
of the gas remains constant (C) Incompressible fluid
(B) The internal energy of the gas
(D) None of the above
increases from its initial value, but
the enthalpy remains constant
(C) Both internal energy and enthalpy 49. A tank contains 100 kg of liquid
of the gas increase
water and 5 kg of water vapour under
(D) The internal energy of the gas saturation conditions at 20ºC. If the
decreases from its initial value, but specific volume of saturated vapour at
the enthalpy remains constant that temperature is 57.8 m3/kg, what is
the approximate volume of the tank ?
46. The equivalent evaporation (kg/hr) of
(A) 320 m3
a boiler producing 2000 kg/hr of steam
with enthalpy content of 2426 kJ/kg (B) 290 m3
from feed water at temperature 40ºC
(liquid enthalpy at 40ºC = 168 kJ/kg, (C) 430 m3
enthalpy of vaporization of water at
100ºC = 2258 kJ/kg) will be (D) 250 m3
(A) 3262
(B) 2150 50. In steam turbine, what do you mean by
(C) 3248 diaphragm ?
(D) 2000 (A) Separating wall between rotors
carrying nozzles
47. If pump NPSH (Net Positive Suction (B) A partition between low and high
Head) requirements are not satisfied pressure sides
(A) Efficiency will be low
(C) The flange connecting the turbine
(B) It will be cavitated exit to the condenser
(C) No flow will take place (D) The ring of guide blades between
(D) It will not develop head rotors
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SPACE FOR ROUGH WORK 22/AE/CM/M– 2024-05/A 11 [ P.T.O.
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SPACE FOR ROUGH WORK
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Bihar Public Service Commission, Patna
Advt. No. 33/2024, Mechanical Engineering - I, Paper - V
Assistant Engineer, Mechanical Written (Objective)
Competitive Examination
Final Answer key (Set- A)
Question No. Ans. Key Question No. Ans. Key
1 C 26 C
2 C 27 C
3 D 28 C
4 D 29 C
5 B 30 C
6 A 31 B
7 D 32 D
8 D 33 A
9 C 34 A
10 B 35 Deleted
11 D 36 C
12 B 37 B
13 B 38 A
14 D 39 D
15 C 40 B
16 D 41 B
17 D 42 B
18 C 43 D
19 C 44 D
20 A 45 A
Text of page 2
Question No. Ans. Key Question No. Ans. Key
21 A 46 D
22 B 47 B
23 B 48 B
24 C 49 B
25 C 50 A
Text of page 3
(Set - B)
Question No. Ans. Key Question No. Ans. Key
1 B 26 C
2 C 27 B
3 B 28 C
4 B 29 A
5 A 30 A
6 B 31 A
7 D 32 B
8 A 33 D
9 A 34 D
10 D 35 C
11 C 36 B
12 C 37 C
13 Deleted 38 C
14 A 39 D
15 D 40 C
16 D 41 D
17 C 42 A
18 B 43 B
19 B 44 C
20 D 45 A
21 C 46 A
22 A 47 B
23 A 48 C
24 C 49 B
25 C 50 C
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(Set - C)
Question No. Ans. Key Question No. Ans. Key
1 D 26 B
2 C 27 D
3 D 28 C
4 A 29 B
5 A 30 D
6 C 31 B
7 A 32 A
8 C 33 D
9 A 34 C
10 C 35 A
11 B 36 C
12 D 37 D
13 B 38 A
14 D 39 C
15 B 40 C
16 C 41 A
17 C 42 C
18 B 43 C
19 A 44 B
20 A 45 A
21 B 46 D
22 B 47 A
23 B 48 C
24 B 49 Deleted
25 A 50 A
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(Set - D)
Question No. Ans. Key Question No. Ans. Key
1 B 26 A
2 C 27 A
3 C 28 D
4 B 29 B
5 A 30 D
6 B 31 A
7 B 32 A
8 D 33 D
9 D 34 D
10 C 35 A
11 B 36 C
12 B 37 C
13 B 38 D
14 D 39 A
15 A 40 C
16 A 41 B
17 C 42 B
18 D 43 C
19 C 44 A
20 D 45 A
21 C 46 D
22 A 47 C
23 B 48 D
24 D 49 D
25 B 50 Deleted
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Question sequence as per Set - A
Set-A Set-B Set-C Set-D
15 19 2 22
35 13 49 50
36 18 48 32
44 23 29 6
Reasons as per Set-A
Q. No. 15- No Change.
Reason :- CH4 + 2O2 => CO2 +2H2O
16 Kg 64 Kg
2Kg (64/16) x2 = 8Kg
For 2 Kg CH4 requires 8 kg of O2 for complete combustion.
Q. No. 35- Deleted
Option (B) and (D) both are correct. From isenthalpic curve and
inversion curve, Option (B) is correct. For liquification of gases
Reason :- under Joule-Kelvin expansion through throttle valve, Option 'D'
is correct. Ref. Thermal engineering by P.K.Nag, Six edition,
page no. 437 & 647.
Q. No. 36- No Change.
(COP ref.) rev. Carnot = T2/ (T1- T2) COP decreases with
increase in temperature difference (T1- T2),
i.e. higher temperature has to be increased and lower
Reason :- temperature has to be decreased.
Ref. Engineering thermodynamics by P.K.Nag, six edition, Page
no. 629
Q. No. 44- No Change.
Reason :- Indicated Thermal efficiency (.3) = Pm LAN/(2 mf.CV)
Volumetric efficiency = Va/ VS = 0.9, Va =0.9 Vs
mf =0.05 x 0.9 x Vs = 0.045 Vs
Indicated Thermal efficiency (.3)= Pm x Vs/(2 x 0.045 Vs x 45 x 106)
Pm = 12.15 bar
Ref. I.C. Engines by V.Ganesan, fourth edition, Page no. 25.Page 1 of 12
Source: Bihar Public Service Commission. Question paper published by Bihar Public Service Commission.