## NHPC JE Recruitment 2021

National Hydroelectric Power Corporation (NHPC) has released the recruitment notification for engagement of following posts such as Senior Medical Officer, Assistant Rajbhasha Officer, Junior Engineer & Sr. Accountant posts. NHPC expects application from High Performing, Dynamic & Achievement-Oriented Professionals candidates to fill up these 173 vacancies.

### NHPC-JE’21 ME: Daily Practices Quiz

NHPC-JE’21 ME: Daily Practices Quiz 12-Oct-2021

Quiz: Mechanical Engineering
Exam: NHPC
Topic: Miscellaneous

Each question carries 1 mark
Negative marking: 1/4 mark
Time: 6 Minutes

Q1. The minimum number of teeth on pinion in case of 20° full depth involute gear is used is
(a) 18
(b) 14
(c) 32
(d) 12

Q2. A thin plate has been placed parallel to flow direction. The relative magnitude of friction and pressure drags will be
(a) Negligible friction as well as pressure drag
(b) Negligible pressure drag and maximum friction drag
(c) Maximum pressure drag and negligible friction drag
(d) Pressure drag equals the friction drag

Q3. A turbine pump is basically a centrifugal pump equipped additionally with
(b) vaned diffusion casing

Q4. Which one of the following relationships defines the Helmholtz function F?
(a) F=H+ TS
(b) F=H– TS
(c) F=U – TS
(d) F= U+ TV

Q5. Detonation in the SI engine becomes severe during
(a) Low load and high speed
(b) High load and high speed
(c) Low load and low speed
(d) High load and low speed

Q6. Sialon ceramic is used as:
(a) Cutting tool material
(b) Creep resistant
(c) furnace linens
(d) High strength

### Solutions

S1. Ans. (a)
Sol.
System of gear Minimum number of teeth on pinion
20° full depth involute gear 18
20° Stub involute gear 14
〖14 1/2〗^°full depth involute gear 32
〖14 1/2〗^° composite gear 12

S2. Ans (b)
Sol. A thin plate has been placed parallel to flow direction. That body is known as streamlined body, and the relative magnitude of friction drag will be maximum and that of pressure drag will be minimum.

S3. Ans (b)
Sol. A turbine pump in basically a centrifugal pump equipped additionally with vaned diffusion casing.

S4. Ans (c)
Helmholtz function F
F=U – TS, it is applicable for closed system
Gibbs Function
G=H-TS, it is applicable for open system

S5. Ans (d)
Sol. Detonation in SI engine will become severe at high load and low speed because at higher loads, the temperature of cylinder and combustion chamber walls will be higher and hence temperature of the end charge will be more which increases knocking tendency in SI engine. And at lower engine speed, longer will be the absolute time for the flame to traverse the cylinder which increases the time available for pre flame reactions, hence the tendency to knock increases.

S6. Ans.(a)
Sol. Si Al ON: It is silicon nitride-based cutting tool materials with aluminium and oxygen additions. This tool material is tougher than alumina. Aerospace alloys and nickel-based gas turbine discs can be machined using sialon tool bit at a cutting speed of 200 -300 m/mt.

## PSPCL RECRUITMENT 2021

Punjab State Power Corporation Ltd. (PSPCL), a power generating and distributing company of the Government of Punjab state, has released the notification for recruitment to the post of Clerk, Revenue Accountant, Junior Engineer (Electrical), Assistant Lineman & Assistant Sub Station Attendant Posts .
A total of 75 vacancies have been announced for the recruitment process of JE ELECTRICAL Engineering.

Exam Dates: 10 N0V-21 to 17 Nov-21

## PSPCL-JE’21 EE: Daily Quiz

PSPCL-JE’21 EE: Daily Practices Quiz 11-Oct-2021

Each question carries 1 mark.
Negative marking: 1/4 mark
Total Questions: 06
Time: 06 min.

Q1. Which motor should not be used for centrifugal pumps?
(a) Series
(b) Shunt
(c) Cumulatively compound
(d) Differentially compound

Q2. DC series motors are very suitable for heavy duty applications such as electric railways, rolling mills because of
(a) Nearly constant speed
(b) Possibility of speed control
(c) High starting torque
(d) Low initial as well as maintenance cost

Q3. Which of the following loss in a transformer is zero at all operating conditions?
(a) Iron loss
(b) Eddy current loss
(c) Hysteresis loss
(d) Friction loss

Q4. A circuit is disconnected by isolators when:
(a) Line is on full load
(b) Line is energized
(c) There is no current in the line
(d) Circuit breaker is not open

Q5. A 3-phase, 6-pole, 50 Hz induction motor has a slip of 1 % at no load and 3 % at full load. The frequency of rotor current at standstill will be:
(a) 50 Hz
(b) 100 Hz
(c) 1.5 Hz
(d) Zero

Q6. Which of the following relation is correct for current carrying capacity of fuse element?
(a) I ∝ d
(b) I² ∝ d²
(c) I² ∝ d³
(d) I² ∝ d
Where d = diameter of fuse element

## SOLUTIONS

S1. Ans.(a)
Sol. Series motors is best suited for electric traction work because of its large starting torque characteristics.

S2. Ans.(c)
Sol. Series motors is best suited for electric traction work because of its large starting torque characteristics. It is not suited for centrifugal pumps as in case of centrifugal pumps the starting torque is usually less than the running torque.

S3. Ans.(d)
Sol. Transformer is a static device.
Friction losses are involved with rotating parts of a machine. Since in a transformer all parts are stationary, friction losses will always be equal to zero, irrespective of the loading condition.

S4. Ans.(c)
Sol. Isolators operation occurs, when there is no current in the line.

S5. Ans.(a)
Sol. f_r=sf
At standstill condition: slip(s)=1
So, frequency of rotor current at standstill=supply frequency=50 Hz.

S6. Ans.(c)
Sol. Heat produced per sec = Heat lost per sec (convection, conduction, radiation)
⇒ I²R = K × d × l
⇒ I²(ρl/A) = K × d × l
⇒ (I^2∝d^3 ) also called fuse law.

## GATE’22 CE:- Daily Practice Quiz 09-October-2021

Know your strengths and practice your concepts with this quiz on GATE Recruitment 2022. This quiz for GATE Recruitment 2022 is designed specially according to GATE Syllabus 2021.

Quiz: Civil Engineering
Exam: GATE
Topic: Miscellaneous

Each question carries 2 marks
Negative marking: 1/3 mark
Time: 20 Minutes

Q1. At a section of highway, the sight distance is 150m, height of driver’s eye is 1.5m, the height of obstacle is 15cm and the grade difference of the intersecting gradients is 0.08, the required length of parabolic summit curve is?
(a) 150m
(b) 350m
(c) 250m
(d) 270m

Q2. A simple supported beam of length 9 m. carries a concreted load W at its centre such that BM at centre of the beam is 9 KNm. If EI is the flexural rigidity of the beam then deflection at the centre is
(a) 54/EI
(b) 24/EI
(c) 64/EI
(d) 70/EI

Q3. The equilibrium discharge of an S-curve obtained by 4 – hr. unit hydrograph summation is ___________. When the catchment area is 40 km²
(a) 25 m³/sec
(b) 10 m³/sec
(c) 28 m³/sec
(d) 50 m³/sec

Q4. On a circular curve, the superelevation rate is e. While negotiating the curve, a vehicle comes to stop. It is seen radial direction. If the coefficient of lateral friction is f, then?
(a) e≥f
(b) e≥f
(c) f≤e≤2f
(d) e≤2f

Q5. The downhill end of a 50 m tape is held 100 cm too low. What is the horizonal distance measure
(a) 49.999 m
(b) 48.999 m
(c) 48 m
(d) 49 m

Q6. The speed delay study on a highway section is conducted by:
(a) Enoscope
(c) Moving car method
(d) Pneumatic tube

Q7. If one litre of sample settle in 30 minutes and the measuring cylinder showed a sludge vol. of 300 ml, then the sludge volume index would be nearly ________? If the MLSS concentration in the aeration tank of extended aeration activated sludge process is 5000 mg/lit.
(a) 200
(b) 150
(c) 100
(d) 60

Q8. The permissible speed on a horizontal curve of radius 875m on a BG track is 100 kmph. What should be the maximum permissible cant on this curve as per Indian Railway?
(a) 10cm
(b) 15.75cm
(c) 16.5 cm
(d) 7cm

Q9. If the stability number is 0.07, unit weight of soil is 30 kN/m³ concession is 20 kN/m², factor of safety is 2.5 then safe max. height of the slope is
(a) 5.0 m
(b) 2.0 m
(c) 3.81 m
(d) 4.50 m

Q10. Polar moment of inertia of a rectangular section having 3cm width and 6 cm depth is?
(a) 40cm^4
(b) 53.4cm^4
(c) 75cm^4
(d) 67.5cm^4

SOLUTION

S1. Ans.(b)
Sol. Let us assume that the length of summit curve is grater than the sight distance.
∴ Length of parabolic summit curve =(NS^2)/(√2H+√2h)^2
=(0.08×150^2)/(√(2×1.5)+√(2×0.15))^2
=346.33m/(>150m ▭ok)

S2. Ans.(c)
Sol.

BM at centre = 9 kN-m
∵WL/4=9
⇒(W×9)/4=9
⇒W=4 kN
∵ Deflection at centre = (WL^3)/48EI=(4×9^3)/48EI=61/EI

S3. Ans.(c)
Sol. Equilibrium discharge of S-curve = (Total discharge)/(Unit hr.duration)
=(40×10^6×0.01)/(4×3600)
= 28 m³/sec
S4. Ans.(b)
Sol.

For no sliding,
fN≥mgsinθ
⇒fmg wsθ≥mgsinθ
⇒f≥tanθ
⇒▭(f≥e)

S5. Ans.(a)
Sol. Correction of slope = h^2/2L=〖0.10〗^2/(2×50)=0.0001 m
∵ Horizontal distance
= 50 – 0.0001 = 49.999 m.
S6. Ans.(c)
Sol. Floating car method or riding cheek method or moving car method is used for speed and delay studies. Radar gun is used to measure spot speed. Enoscope and pneumatic tube are used for traffic counting.

S7. Ans.(d)
Sol. Sludge vol. index (S V I) = (Vob (ml\/l))/(X_ob (mg\/l) )×1000
=300/5000×1000
= 60 ml/gm
S8. Ans.(b)
Sol. e_max=e_th=(G V_max^2 )/127R
= (1.676×100^2)/(127×875)
=0.1575
=▁((15.75cm) ̅ )

S9. Ans.(c)
Sol. Stability number S_N=Cm/γ_H
Where, C_m=C/FOS=20/2.5=8 kN\/m^2
∵ Maximum safe height
H = 8/(30×0.07)=3.81 m.
S10. Ans.(d)
Sol. Ip=I_zz=I_xx+I_yy
= (bd^3)/12+(db^3)/12
=bd/12 (d^2+b^2 )
=(3×6)/12 (6^2+3^2 )
=(▁(67.5cm^4 )) ̅

## NHPC-JE’21 CE: Daily Practices Quiz. 11-Oct-2021

Know your strengths and practice your concepts with this quiz on NHPC JE Recruitment 2021. This quiz for NHPC JE Recruitment 2021 is designed specially according to NHPC Syllabus 2021.

Quiz: Civil Engineering
Exam: NHPC-JE
Topic: Miscellaneous

Each question carries 1 mark
Negative marking: 1/4 mark
Time: 8 Minutes

Q1. What shall be the pressure intensity inside a soap bubble of radius 4 cm? (Surface tension of water is 0.0736 N/m):
(a) 7.36 N/m^2
(b) 1.84 N/m^2
(c) 3.68 N/m^2
(d) None of these

Q2. Loam is
(a) A mixture of sand, silt and clay
(b) A mixture of gravel, sand and silt
(c) An impure form of limestone
(d) Is a wind blow deposit

Q3. The activity of batching in production of concrete refers to:
(a) Weighing of all ingredients within the acceptable tolerances for all batches
(b) Weighing of all ingredients
(c) Most accurate weighing of cement & water that influence strength of concrete
(d)Measuring the workability of concrete

Q4. A type of valve which provided at the corner of roads to control the flow of water at the cross section of the distribution system is called?
(a) Safety valve
(b) Scour valve
(c) Sluice valve
(d) check valve

Q5. Which one of the following is the largest scale?
(a) 1 : 500
(b) 1 : 1000
(c) 1 : 2500
(d) 1 : 50,000

Q6. Which of the following is the correct sequence of the parts of a canal system?
(a) Head works, distributary and minor
(b) Head works, main canal and minor
(c) Head works, main canal, branch canal, distributary and minor
(d) None of the above

Solutions

S1. Ans.(a)
Sol. Surface tension (σ)=0.0736 N/m
Pressure intensity inside soap bubble ⇒ 4σ/r
=(4×0.0736)/(4×10^(-2) )
=7.36 N\/m^2

S2. Ans.(a)
Sol. Loam is a mixture of sand, silt and clay.

S3. Ans.(a)
Sol. Batching→ It is the process of proper and accurate measurement of concrete ingredients. It is either done by mass or volume batching.

S4. Ans.(c)
Sol. Sluice value or gate value are provided at the corner of roads which control and regulate the flow of water at the cross-section of the distribution system.

S5. Ans.(a)
Sol. Arrangement of scale from largest to smallest.
▭(1∶500>1:1000>1∶2500>1∶50,000)
Hence, 1∶500 is the largest scale.

S6. Ans.(c)
Sol. Correct sequence of the parts of a canal system is
Head works → main canal → Branch canal → Distributary → Minor.

## Pressure Vessels

Pressure vessels are mainly of two type first one is thin shells and another is thick shells.

## Thin shells

If the ratio of thickness of the wall to the its diameter of the shell is less than 1/10 to 1/15, then shell is called thin shells.
i.e., t/D_i < 1/10 to 1/15

### Important Points

In case of thin shells, it is assumed that the normal stresses, which may be either tensile or compressive are uniformly distributed through the thickness of wall.

### Nature of stress in thin cylindrical shell subjected to internal pressure

(i) Hoop stress or circumferential stress will be tensile.
(ii) Longitudinal stress or axial stress will be tensile.
(iii) Radial stress will be compressive.

## Thick Shells

If the ratio of thickness of the wall of the shell to its diameter is greater than 1/10 to 1/15, then such type of shell is called thick shells.
i.e., t/D_i > 1/10 to 1/15

### Important Points

Radial compressive stress varies from a value at the inner surface equal to pressure ‘P’ to the atmospheric pressure at the outside surface.
If internal pressure in thin cylinders is low, the radial stress is negligible compared with axial stress and hoop stress. This radial stress is neglected.

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## GATE 2022

GATE 2022 Important Dates: Organizing Institute for GATE 2022 is the Indian Institute of Technology Kharagpur. For GATE 2022 Exam IIT Kharagpur has released the official notification and Important dates regarding the GATE 2022 Exam. Aspirants preparing for GATE 2022 must check the details regarding GATE 2022 Important Dates. Read the complete article below for the information related to GATE 2022 Important dates.

## GATE’22 EE: Daily Practices Quiz

GATE’22 EE: Daily Practices Quiz 09-Oct-2021

Each question carries 2 marks
Negative marking: 0.66 mark

Total Questions: 10
Total marks: 20
Time: 20 min.

Q1. A co-axial cable of inner radius a and outer radius b. The space between conductor is filled with dielectric of permittivity ∈ and length of cable 4m. what is the capacitance of the cable?
(a) (2π∈)/ln⁡(b/a)
(b) ln⁡(b/a)/(2π∈)
(c) (π∈)/(2 ln⁡(b/a) )
(d) (8π∈)/ln⁡(b/a)

Q2. In a two-unit insulator string, voltage across the unit near to line conductor is 18.5 kV and string efficiency is 75%. The voltage of line conductor will be:
(a) 37 kV
(b) 48.07 kV
(c) 27.75 kV
(d) 30 kV

Q3. A step-down chopper connected to a d.c. supply, supplies a separately excited d.c. motor at a duty ratio of α. The ripple factor in the terminal voltage of the motor assuming continuous current conduction is-
(a) α/(1-α)
(b) (1-α)/α
(c) √((1-α)/α)
(d) √(α/(1-α))

Q5. In a three-phase induction motor, the ratio power across air gap, rotor copper loss and gross mechanical power output is
(a) PG:sPG:(1-s) PG
(b) PG:sPG:(s-1) PG
(c) PG:(1-s) PG:sPG
(d) PG:sPG:(1+s) PG

Q7. Consider a network function H(s)= (2(s+3))/((s+2)(s+4)). What is the steady state response due to step input?
(a) ½
(b) ¾
(c) 2
(d) 1

Q8. Which of the following is a non-maskable interrupt of 8085 microprocessors?
(a) INTR
(b) TRAP
(c) RST 6.5
(d) RST 7.5

Q9. For a JFET I_DSS = 8 mA and peak voltage V_p = –8V, what will be the drain current for gate to source voltage of –2V?
(a) 4.5 mA
(b) 8 mA
(c) 16 mA
(d) 12 mA

Q10. Determine the deflection factor (in V/m) of a CRO, when the deflection sensitivity of the CRO is 5 m/V.
(a) 0.25
(b) 0.35
(c) 0.20
(d) 0.40

## SOLUTIONS

S5. Ans.(a)
Sol. In a three-phase induction motor, the ratio power across air gap, rotor copper loss and gross mechanical power output is-
P_G= Air gap power
sP_G = rotor copper loss
P_G (1-s) = gross mechanical power
So, ratio is-
P_G:sP_G ∶(1-s) P_G

S6. Ans.(c)
Sol. Peak current=I_0+(△i_c)/2=5+1.6/2=5.8 A

S7. Ans.(b)
Sol. steady state response=lim┬(s→0)⁡〖sC(s)=〗 lim┬(s→0)⁡= s×(2(s+3))/((s+2)(s+4))×1/s=3/4

S8. Ans.(b)
Sol. The hardware vectored interrupts are classified in to maskable and non-maskable interrupts.
RST 7.5, RST 6.5, RST 5.5 and INTR are maskable interrupt.

S9. Ans.(a)
Sol. I_D=I_DSS (1-V_GS/V_P )^2=8×10^(-3) (1-(-2)/(-8))^2=4.5 mA

S10. Ans.(c)
Sol. Deflection factor=1/(deflection sensitivity)=1/5=0.2 V/m.

## PSPCL RECRUITMENT 2021

Punjab State Power Corporation Ltd. (PSPCL), a power generating and distributing company of the Government of Punjab state, has released the notification for recruitment to the post of Clerk, Revenue Accountant, Junior Engineer (Electrical), Assistant Lineman & Assistant Sub Station Attendant Posts .
A total of 75 vacancies have been announced for the recruitment process of JE ELECTRICAL Engineering.

Exam Dates: 10 N0V-21 to 17 Nov-21

## PSPCL-JE’21 EE: Daily Quiz

PSPCL-JE’21 EE: Daily Practices Quiz 08-Oct-2021

Each question carries 1 mark.
Negative marking: 1/4 mark
Total Questions: 06
Time: 06 min.

Q1. Which of the following instruments has the same calibration in AC and DC?
(a) Moving iron type
(b) Moving coil type
(c) Induction type
(d) Electrodynamometer type

Q2. A slip test is conducted on synchronous generator to determine:
(a) Slip
(b) Direct and quadrature axis reactance
(c) Sub-transient reactance
(d) Positive and negative sequence reactance

Q3. Which of the following insulators is selected for HV application?
(a) Suspension type
(b) Strain type
(c) Disc type
(d) Pin type

Q4. In the salient pole of 3-phase synchronous machine the rotor will have
(a) Larger diameter, shorter axial length
(b) Smaller diameter, larger axial length
(c) Larger diameter, larger axial length
(d) Smaller diameter, shorter axial length

Q5. In a two-value capacitor motor, the capacitor used for running purposes is
(a) Air capacitor
(b) Paper spaced oil filled type
(c) Ceramic type
(d) A.c electrolyte type

Q6. A negative sequence relay is commonly used to protect
(a) An alternator
(b) A transformer
(c) A transmission-line
(d) A bus-bar

## SOLUTIONS

S1. Ans.(d)
Sol. Electrodynamometer type instruments has the same calibration in AC and DC.
NOTE: A transfer instrument is one that may be calibrated with a d.c. source and then used without modification to measure a.c This requires the transfer type instrument to have the same accuracy for both a.c and d.c., which have electrodynamometer instruments have.

S2. Ans.(b)
Sol. A slip test is conducted on synchronous generator to determine Direct and quadrature axis reactance.
From slip test: X_d=V_max/I_min &X_q=V_min/I_max

S3. Ans.(a)
Sol. In higher voltage, beyond 33KV, it becomes uneconomical to use pin insulator because size, weight of the insulator become more. Handling and replacing bigger size single unit insulator are quite difficult task. For overcoming these difficulties, suspension insulator is used for HV application.

S4. Ans.(a)
Sol. 3-phase synchronous machine rotor construction:
• Salient pole rotor: larger diameter, shorter axial length
• Cylindrical pole rotor: smaller diameter, larger axial length

S5. Ans.(b)
Sol. Two-value capacitor motor also known as capacitor start capacitor run induction motor.
In a two-value capacitor motor:
At the starting, the two capacitors are connected in parallel.
Starting capacitor is short time rated and is almost electrolytic.
The run capacitor is long time rated and is made of oil filled paper.

S6. Ans.(a)
Sol. A negative sequence relay is commonly used to protect an alternator.
A relay which protects the electrical system from negative sequence component is called a negative sequence relay or unbalance phase relay.
The negative sequence relay protects the generator(alternator) and motor from the unbalanced load which mainly occurs because of the phase-to-phase faults.

## NHPC JE Recruitment 2021

National Hydroelectric Power Corporation (NHPC) has released the recruitment notification for engagement of the following posts as Senior Medical Officer, Assistant Rajbhasha Officer, Junior Engineer & Sr. Accountant posts. NHPC expects applications from High Performing, Dynamic & Achievement-Oriented Professionals candidates to fill up these 173 vacancies.

## NHPC-JE’21 EE: Daily Practices Quiz

NHPC-JE’21 EE: Daily Practices Quiz 08-Oct-2021

Each question carries 1 mark.
Negative marking: 1/4 mark
Total Questions: 06
Time: 06 min.

Q1. Which part of DC machines converts the alternating current induced in armature conductors into unidirectional current in the external load circuit?
(a) Pole coils
(b) Commutator
(c) Armature windings
(d) Armature core

Q2. Power transformers are generally designed to have maximum efficiency around
(d) None of the above

Q3. Thin laminations are used in a machine in order to reduce
(a) Eddy current losses
(b) Hysteresis losses
(c) Both a and b
(d) None of the above

Q4. Which of the following theorems can be applied to any network linear or non-linear, active or passive, time-variant or time-invariant?
(a) Norton theorem
(b) Thevenin theorem
(c) Superposition theorem
(d) Tellegen theorem

Q5. The bandwidth of an AC series circuit consisting of R, L & C is
(a) L/RC
(b) RC/L
(c) R/L
(d) L/R

Q6. Which of the following statement is true?
(a) At higher voltage, cost of transmission is reduced
(b) At higher voltage, cost of transmission is increased
(c) Both a and b
(d) None of the above

## SOLUTIONS

S1. Ans.(b)
Sol. The commutator will convert AC to DC in DC generators and vice versa in DC motors.
In the generator, the main function of the commutator is to facilitate the collection of current from the armature conductors and to convert the alternating emf induced (AC) in the armature conductors to unidirectional emf (DC) in the external load circuit.
In the motor, the main function of the commutator is to supply current to armature from the external DC circuit and to convert this unidirectional emf (DC) of the external DC circuit to alternating emf in the armature.

S2. Ans.(c)
Sol. Power transformers are generally designed to have maximum efficiency near full load, whereas distribution transformers have maximum efficiency at 50% of full load.

S3. Ans.(a)
Sol. Thin laminations are used in order to reduce the eddy current losses only. Due to laminations the area of the eddy currents loops is minimized and the losses due to eddy current losses are minimized.

S4. Ans.(d)
Sol. Tellegen theorem can be applied to any network linear or non-linear, active or passive, time-variant or time-invariant.

S5. Ans.(c)
Sol. The bandwidth of an AC series circuit consisting of R, L & C: BW=R/L

S6. Ans.(a)
Sol. At higher voltage, the volume of the conductor is reduced. Area of conductor A ∝ 1/Vs² Where Vs = Supply voltage. So that material requirement is reduced and hence cost of the material and transmission is reduced.

## NHPC JE Recruitment 2021

National Hydroelectric Power Corporation (NHPC) has released the recruitment notification for engagement of following posts such as Senior Medical Officer, Assistant Rajbhasha Officer, Junior Engineer & Sr. Accountant posts. NHPC expects application from High Performing, Dynamic & Achievement-Oriented Professionals candidates to fill up these 173 vacancies.

### NHPC-JE’21 ME: Daily Practices Quiz

NHPC-JE’21 ME: Daily Practices Quiz 11-Oct-2021

Quiz: Mechanical Engineering
Exam: NHPC
Topic: Machine Design

Each question carries 1 mark
Negative marking: 1/4 mark
Time: 6 Minutes

Q1. The wet bulb temperature is a measure of which humidity?
(a) Relative
(b) Absolute
(c) Specific
(d) None of the above

Q2. The curved lines on Psychrometric chart indicate
(a) Specific humidity
(b) Relative humidity
(c) Dew point temperature
(d) Dry bulb temperature

Q3. When heat is transferred from one particle of hot body to another by actual motion of the heated
particle, it is referred to as heat transfer by
(a) conduction
(b) convection
(d) conduction and convection

Q4. An ideal gas at 27°C is heated at constant pressure till its volume becomes two times. The temperature of gas then will be
(a) 81°C
(b) 900°C
(c) 600°C
(d) 327°C

Q5. Which one of the following non-dimensional numbers is used for transition from laminar to turbulent flow in free convection?
(a) Reynolds number
(b) Grashoff number
(c) Peclet number
(d) Rayleigh number

Q6. The component of torque converter that allows torque multiplication is
(a) Turbine
(b) Impeller
(c) Stator
(d) Freewheel

### Solutions

S1. Ans. (b)
Sol. Absolute

S2. Ans. (b)
Sol. Relative humidity

S3. Ans. (a)

S4. Ans. (d)
Sol. At constant pressure. According to Charle’s law
V α T
V_1/V_2 =T_1/T_2
T_2=(V_2/V_1 ) T_1 [V_2=2V_1 ]
= 2T1 = 2(27 + 273)
T2 = 600 K = 327°C

S5. Ans (d)
Sol. Rayleigh number is used to determine whether the flow is laminar or turbulent in natural convection.
Ra<10^8 Laminar
10^8<Ra<10^10 Transaction
Ra>10^10 Turbulent

S6. Ans (c)
Sol. A hydraulic torque converter consists of series of fixed guide vanes which are provided between turbine runner and pump impeller. The liquid exerts a torque on the driven unit through these stationary guide vanes as it flows from pump to turbine runner.

## UPPSC Lec’21 ME: Daily Practices Quiz. 11-Oct-2021

Quiz: Mechanical Engineering
Exam: UPPSC Lecturer
Topic: Miscellaneous

Each question carries 1 mark
Negative marking: 1/4 mark
Time: 6 Minutes

Q1. The gas turbine which is used in an aircraft is
(a) Constant temperature turbine
(b) Open cycle turbine
(c) Closed cycle turbine
(d) None of these

Q2. The type of compressor which is used in vapour compression refrigeration system for more than 100 tonnes capacity is
(a) Reciprocating compressor
(b) Centrifugal compressor
(c) Rotary compressor
(d) Both (a) and (b)

Q3. The type of flow in convergent divergent nozzle in which the Mach number is 6
(a) Hypersonic
(b) Subsonic
(c) Supersonic
(d) Sonic

Q4. Critical activities
(a) Is longest path
(b) Is shortest path
(c) Has zero float
(d) Both (a) and (c)

Q5. Which of the following behaviour of the system defines under-damped harmonic oscillator?
(a) The system returns (exponentially decays) to equilibrium without oscillating
(b) The system returns to equilibrium as quickly as possible without oscillation.
(c) The system oscillates (at reduced frequency compared to the undamped case) with the amplitude gradually decreasing to zero.
(d) The system oscillates at its natural resonant frequency.

Q6. Force F in the given figure equals to

(a) √3 kN
(b) 2 kN
(c) – √3 kN
(d) 3√3 kN

### Solutions

S1. Ans. (b)
Sol. The gas turbine which is used in an aircraft is open cycle turbine.
In this cycle the gas is released from the turbine to the surroundings

S2. Ans. (b)
The type of compressor which is used in vapour compression refrigeration system for more than 100 tonnes capacity is Centrifugal compressor and the type of compressor which is used in vapour compression refrigeration system for less than 100 tonnes capacity is reciprocating compressor

S3. Ans. (a)
Sol.
Mach Number Type of Flow
Mach No. < 0.8 Sub-sonic
0.8 < Mach No. < 1.3 Trans-sonic
Mach No. = 1 Sonic
1.3 < Mach No. < 5 Super-sonic
Mach No. > 5 Hypersonic

S4. Ans (d)
Sol. Critical activities are those activities whose float is zero and has longest path.

S5. Ans.(d)
Sol. ς=c/(2mω_n )<1
This condition is known as under-damping, as under damping system does simple harmonic motion.
In underdamped system, amplitude of vibration decreases slowly in exponential manner.
Displacement at any instant of time for under damped system is given by ▭(x=Ae^(- ςω_n t) (sin⁡( ςω_n t)+ϕ) )

S6. Ans.(a)
Fig.

Sol. from lami’s theorem
1/sin⁡150 = F/sin⁡〖60°〗
F = sin⁡〖60°〗/sin⁡〖150°〗
F = √3 N