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Non-reactive loads of 10 kW, 8 kW and 5 kW are connected between the neutral and the red, yellow, and blue phases, respectively, of a 3- phase, 4-wire system. The line voltage is 400 V. Calculate the current IR.
34.6 A
43.3 A
18.9 A
21.6 A
Correct answer
34.6 A
Which method of electrical heating involves passing electrical energy through a heating element to generate heat, which is then transferred to the substance to be heated?
Induction heating
Direct arc heating
Power frequency heating
Resistance heating
Correct answer
Induction heating
Find the value of Load resistance(RL) for maximum power transfer in the following circuit.
11 Ω
22 Ω
33 Ω
9 Ω
Correct answer
11 Ω
In a parallel RC circuit, the phase difference between the applied voltage and the voltage across R and C in parallel will be _____.
45°
30°
0°
90°
Correct answer
45°
For a certain D-MOSFET, IDSS = 10 mA and VGS(off) = -8 V. Calculate ID at VGS = -4 V.
20 mA
2.5 mA
50 mA
5 mA
Correct answer
20 mA
What type of transmission line is characterised by a length ranging from 80 km to 240 km and includes both inductance and capacitance effects?
Short transmission line
Long transmission line
DC transmission line
Medium transmission line
Correct answer
Short transmission line
What is one of the functions of circuit breakers in a substation?
Switching equipment control
Interrupting short-circuits and overload currents
Voltage regulation
Power generation
Correct answer
Switching equipment control
Which component of the total cost of electrical energy is proportional to the energy generated (kWh)?
Fixed cost
Running cost
Depreciation cost
Semi-fixed cost
Correct answer
Fixed cost
Which types of losses in a transformer are equal to each other, resulting in maximum efficiency of the transformer?
Core loss and hysteresis loss
Eddy current loss and mechanical loss
Iron loss and copper loss
Copper loss and winding loss
Correct answer
Core loss and hysteresis loss
Identify whether the following statements with reference to magnetic circuits are true or false.
Both the statements are true
Both the statements are false
Statement 1 is true and statement 2 is false
Statement 1 is false and statement 2 is true
Correct answer
Both the statements are true
In a balanced star connection, the ratio of the magnitude of the line voltage to the magnitude of the phase voltage is
√2
\(\frac{1}{\sqrt3}\)
√3
\(\frac{1}{\sqrt2}\)
Correct answer
√2
Which part of a DC motor is responsible for creating the mechanical revolutions of the unit?
Rotor
Brushes
Commutator
Stator
Correct answer
Rotor
Identify whether the following statements related to starters in DC motors are true or false.
Both the statements are false
Statement 1 is true and statement 2 is false
Both the statements are true
Statement 1 is false and statement 2 is true
Correct answer
Both the statements are false
If a current of 2 A flowing through one coil produces flux linkage of 5 Wb-turn in the other coil, then what will be the mutual inductance between the two coils?
7.5 H
10 H
2.5 H
5 H
Correct answer
7.5 H
The voltage gain in common collector configuration of a BJT is _______.
less than one
zero
between 50 and 100
above 100
Correct answer
less than one
Two coils having self-inductance of 6 H and 24 H, respectively, are magnetically coupled. Find the maximum possible value of mutual inductance.
24 H
18 H
6 H
12 H
Correct answer
24 H
With reference to PMMC instruments, which of the following statements are correct?
I. For PMMC instruments, the scale is not uniform.
Il. PMMC instruments can be used for AC as well as DC quantities.
III. In PMMC instruments, power consumption is low.
IV. PMMC instruments offer a high torque/weight ratio.
I and II
II and IV
III and IV
I and III
Correct answer
I and II
Which type of motor requires a DC supply to the rotor to generate the rotor’s magnetic field and uses damper windings for starting?
Reluctance Motor
Permanent Magnet Synchronous Motor
Direct Current Excited Motor
Three-Phase Induction Motor
Correct answer
Reluctance Motor
What is the function of the ‘control system’ component in a load drive system?
To provide electrical power to the load
To convert electrical energy into mechanical energy
To measure the temperature of the load
To regulate the operation of the load drive
Correct answer
To provide electrical power to the load
Which of the following theorems is the dual of Norton’s theorem?
Thevenin’s theorem
Reciprocity theorem
Maximum power transfer theorem
Superposition theorem
Correct answer
Thevenin’s theorem
Identify the type of single-phase motor shown in the following figure.
Permanent-split capacitor
Capacitor-start motor
Split-phase induction motor
Shaded pole motor
Correct answer
Permanent-split capacitor
Match the oscillator circuits in column A with their respective characteristics in column B.
| Column A | Column B | ||
|---|---|---|---|
| A. | Hartley oscillator | I. | Two stage RC coupled amplifier |
| B. | Crystal oscillator | II. | LC tuned circuit |
| C. | Wien bridge oscillator | III. | Greater stability |
A - I, B - III, C - II
A - II, B - I, C - III
A - III, B - I, C - II
A - II, B - III, C - I
Correct answer
A - I, B - III, C - II
Which type of work is done by an autotransformer?
Phase shifting primary to secondary
Isolation between primary to secondary
Multiple windings
Adjustment of voltage in output side
Correct answer
Phase shifting primary to secondary
Which type of transformer uses a ring or doughnut-shaped core material, offering low leakage inductance and high inductance and Q factors?
Air core transformer
Toroidal core transformer
Ferrite core transformer
Iron core transformer
Correct answer
Air core transformer
Which component of a commercial electrical installation is responsible for protection against electrical overloads and short circuits?
Power sockets
Lighting systems
HVAC systems
Electrical panels or switchgear
Correct answer
Power sockets
Find the current ‘i3’ in the following diagram.
7 A
5 A
11 A
3 A
Correct answer
7 A
In a DC series motor, what is the relationship between speed and armature current?
Speed is independent of armature current.
Speed is directly proportional to armature current.
Speed is directly proportional to the square of armature current.
Speed is inversely proportional to armature current.
Correct answer
Speed is independent of armature current.
What is the application of overexcited synchronous motors?
Operating centrifugal pumps
Controlling voltage at the end of long transmission lines
Power factor correction for lagging loads
Generating different frequencies
Correct answer
Operating centrifugal pumps
What type of substation is responsible for transferring power from the transmission system to the distribution system of an area?
Relay substation
Collector substation
Distribution substation
Converter substation
Correct answer
Relay substation
In a single-phase series RL circuit, XL = 15 Ω and R = 20 Ω. Find the impedance of the circuit.
15 Ω
20 Ω
25 Ω
35 Ω
Correct answer
15 Ω
What are the two types of breakdowns that can occur in p-n junctions?
Avalanche and tunnelling breakdowns
Forward and reverse breakdowns
Zener and capacitive breakdowns
Voltage and current breakdowns
Correct answer
Avalanche and tunnelling breakdowns
Find the voltage across R3 in the following circuit.
4.5 V
1.5 V
7.5 V
2.5 V
Correct answer
4.5 V
Usually, the expenditure on supervision charges is ________ of the total cost.
5% to 7%
2% to 4%
8% to 10%
1% to 1.5%
Correct answer
5% to 7%
Which type of water turbine is generally suitable for high-head, low-flow applications?
Cross-flow turbine
Kaplan turbine
Pelton turbine
Francis turbine
Correct answer
Cross-flow turbine
Given a 250 : 5 current transformer used with an ammeter reading of 2.7 A, what is the line current (primary current) in the circuit?
250 A
135 A
84 A
36 A
Correct answer
250 A
With reference to tenders, which of the following statements is INCORRECT?
Tenders are invited on a tender form prescribed by the purchase department.
The earnest money is never returned to the unsuccessful contractors after disposal of the tender.
The sealed tenders are invited publicly through news-papers.
Normally, the tender offering the lowest rates is accepted.
Correct answer
Tenders are invited on a tender form prescribed by the purchase department.
Which of the following statements is INCORRECT for a reluctance motor?
A reluctance motor is cheaper than any other kind of synchronous motor.
A reluctance motor has poor efficiency.
A reluctance motor can operate on AC as well as DC supply.
The rotor of a reluctance motor rotates with constant speed.
Correct answer
A reluctance motor is cheaper than any other kind of synchronous motor.
What is the primary purpose of control rods in a nuclear reactor?
To generate electricity
To absorb excess neutrons
To transfer heat to the secondary circuit
To cool the reactor core
Correct answer
To generate electricity
The direction of rotation of a conductor in a _______ is obtained by Fleming’s left-hand rule.
alternator
DC motor
DC generator
transformer
Correct answer
alternator
If the voltage across a 5 μF capacitor is 24 V at t = 6 ms, what is the energy stored in the capacitor at that time?
720 mJ
1440 μJ
120 mJ
360 μJ
Correct answer
720 mJ
Which part of a transistor is heavily doped and emits majority carriers, either electrons or holes?
Collector
Emitter
Base and emitter
Base
Correct answer
Collector
Identify whether the following statements are true or false.
I. There is no skin effect in the DC transmission system.
Il. In DC transmission, corona losses are very large.
Statement 1 is true and statement 2 is false
Both the statements are false
Both the statements are true
Statement 1 is false and statement 2 is true
Correct answer
Statement 1 is true and statement 2 is false
What is the quality factor for the given series resonance circuit?
160
80
320
40
Correct answer
160
Calculate the speed of the 8-pole alternator if the supply frequency is 50 Hz.
1500 rpm
1000 rpm
500 rpm
750 rpm
Correct answer
1500 rpm
In a multi-plate capacitor, there are a total of nine plates in parallel. This arrangement is equivalent to _______ capacitors in parallel.
nine
eight
four
ten
Correct answer
nine
Which of the following is a limitation of Millman’s theorem?
Applicable if the circuit has no independent sources
Applicable if the circuit has only one independent source
Applicable if the circuit has no dependent sources
Applicable if the circuit has no resistance between the independent sources
Correct answer
Applicable if the circuit has no independent sources
What will be the self-inductance of the coil if an EMF of 10 V is induced in it when the current flowing through it changes at the rate of 5 A/sec?
5 H
10 H
1 H
2 H
Correct answer
5 H
What is a common technique used to reduce core losses and the magnetising component in a current transformer?
Utilising laminated cores made of insulated sheets
Decreasing the number of windings in the secondary coil
Increasing the turns ratio of the current transformer
Using thicker core materials for better conductivity
Correct answer
Utilising laminated cores made of insulated sheets
Identify whether the following statements are true or false.
Statement 1 is false and statement 2 is true
Statement 1 is true and statement 2 is false
Both the statements are false
Both the statements are true
Correct answer
Statement 1 is false and statement 2 is true
Which field control method for a DC series motor involves shunting a portion of motor current around the series field to reduce the field flux and increase the speed of the motor?
Tapped field control
Armature control method
Field diverter method
Rheostatic control method
Correct answer
Tapped field control
What is the advantage of overhead cables compared to underground cables in terms of construction?
Overhead cables are more protected against moisture and corrosion.
Overhead cables are more environmentally friendly.
Overhead cables are less expensive to construct.
Overhead cables are better insulated.
Correct answer
Overhead cables are more protected against moisture and corrosion.
Which type of electromagnetic radiation is primarily used in infrared heating to heat surfaces?
Infrared radiation
X-rays
Microwave radiation
Ultraviolet radiation
Correct answer
Infrared radiation
How does armature reaction affect the main field flux in an alternator when the load has a power factor of zero leading?
Armature reaction distorts the main field flux and does not affect its strength.
Armature reaction distorts the main field flux and weakens it.
Armature reaction strengthens the main field flux and does not distort it.
Armature reaction weakens the main field flux and reduces the generated EMF.
Correct answer
Armature reaction distorts the main field flux and does not affect its strength.
Which type of single-phase motor is known as a ‘resistance-start' motor?
Shaded-pole motor
Universal motor
Split-phase motor
Permanent-split capacitor motor
Correct answer
Shaded-pole motor
Which of the following statements is correct regarding the doping levels of the emitter, base and collector regions in a bipolar junction transistor (BJT)?
The doping levels of the emitter, base and collector are all the same.
The emitter is lightly doped, the base is heavily doped and the collector is moderately doped.
The emitter is moderately doped, the base is heavily doped and the collector is lightly doped.
The emitter is heavily doped, the base is lightly doped and the collector is moderately doped.
Correct answer
The doping levels of the emitter, base and collector are all the same.
Which of the following terms is NOT related to nuclear power plants?
Control rod
Electrostatic precipitator
Nuclear reactor
Moderator
Correct answer
Control rod
For C = 101.5 nF, determine L for the series resonant circuit if the resonant frequency is 2800 Hz.
31.83 mH
16.32 mH
46.45 mH
26.56 mH
Correct answer
31.83 mH
What are the zero power factor characteristics (ZPFC) used for in the context of alternators?
To calculate the short-circuit voltage of the alternator
To determine the synchronous speed of the alternator
To plot the armature terminal voltage per phase against field current
To assess the power factor when the alternator is loaded by reactors
Correct answer
To calculate the short-circuit voltage of the alternator
In a single-phase RL series circuit, if the current lags the supply voltage by an angle of 60°, then the voltage across the inductor leads the supply voltage by an angle of __________.
90°
60°
0°
30°
Correct answer
90°
What is the main design criterion for distributors in an electrical power transmission system?
Length
Frequency
Current-carrying capacity
Voltage drop
Correct answer
Length
Which type of electric meter is typically used for measuring energy consumption in large commercial and industrial properties with high energy needs?
Single-phase meters
Prepayment meters
Smart meters
Three-phase meters
Correct answer
Single-phase meters
What is the purpose of outcoming feeders in a distribution substation?
To carry power from the substation to distribution transformers
To protect the substation from faults
To generate electrical power
To control the voltage of the substation
Correct answer
To carry power from the substation to distribution transformers
Which of the following materials is rarely used as dielectric material in power cables?
Liquid
Solid
Compound
Gases
Correct answer
Liquid
What is the primary function of the Wind Turbine Generator (WTG) in a wind power system?
To regulate the voltage in the electrical grid
To store mechanical rotational power
To generate usable electricity from wind energy
To control the speed of the wind turbine
Correct answer
To regulate the voltage in the electrical grid
The property related to hard magnetic materials is:
low coercive force
high retentivity
high permeability
low hysteresis loss
Correct answer
low coercive force
What is the function of the moderator in a nuclear reactor during the process of nuclear fission?
Cooling down the reactor core
Slowing down the neutrons produced by fission
Increasing the reaction rate
Spinning the turbine
Correct answer
Cooling down the reactor core
Why is grounding important in the design of a substation?
To ensure room for expansion due to load growth
To protect passers-by during a short circuit in the transmission system
To protect against environmental effects
To facilitate access for maintenance
Correct answer
To ensure room for expansion due to load growth
What is the difference between transmission lines and distribution lines in an electrical power system?
Transmission lines use single-phase systems, while distribution lines use three-phase systems.
Transmission lines operate at lower voltages than distribution lines.
Transmission lines carry electricity from generating stations to substations, while distribution lines transport power to end consumers.
Transmission lines have lower current carrying capacity compared to distribution lines.
Correct answer
Transmission lines use single-phase systems, while distribution lines use three-phase systems.
What is the electrical power consumed by a circuit if a current of 4 A flows through a resistance of 5 kΩ?
800 W
800 kW
80 kW
8000 W
Correct answer
800 W
What is the result of the diffusion of electrons and holes when p-type and n-type semiconductor materials are joined to form a diode junction?
Formation of positive ions in the p-type material and negative ions in the n-type material
Creation of a layer of holes near the junction in the p-type material
Depletion of majority charge carriers in the region near the junction
Generation of an electric field that inhibits electron movement
Correct answer
Formation of positive ions in the p-type material and negative ions in the n-type material
Which type of turbine has adjustable blades and wicket gates, allowing for a wider range of operation?
Straflo turbine
Kaplan turbine
Bulb turbine
Tube turbine
Correct answer
Straflo turbine
What type of substation is used for power factor correction, metering and control of the wind farm?
Relay substation
Converter substation
Collector substation
Distribution substation
Correct answer
Relay substation
What is the Thevenin’s voltage across the a-b terminal in the given circuit?
9 V
3 V
6 V
15 V
Correct answer
9 V
With reference to I-phase transformers, match the transformer tests in column A with the purpose of the tests in column B.
| Column A | Column B | ||
|---|---|---|---|
| A. | Short circuit test | I. | Wattmeter reads the core losses |
| B. | Sumpner’s test I | II. | Wattmeter reads the full load copper losses |
| C. | Open circuit test | III. | Determines maximum temperature rise |
A - II, B - III, C - I
A - II, B - I, C - III
A - I, B - II, C - III
A - III, B - I, C - II
Correct answer
A - II, B - III, C - I
What is a brownout in the context of electrical power supply?
A drop in the electrical power supply causing a drop in voltage
Protection from power surges using surge protectors and circuit breakers
A complete loss of power to a geographic area
A phenomenon that affects high power installations, leading to partial electric discharges
Correct answer
A drop in the electrical power supply causing a drop in voltage
Find the current I2 in the following circuit.
1 A
4 A
2 A
3 A
Correct answer
1 A
What is the primary property of a dielectric material that makes it suitable for dielectric heating?
Ability to be polarised by an applied electric field
Inefficient heat dissipation
High electrical conductivity
Low electrostatic field support
Correct answer
Ability to be polarised by an applied electric field
Which of the following is NOT an application of a synchronous motor?
Servo drives
High speed compressor
Main line traction
Dot matrix printer
Correct answer
Servo drives
In circuit analysis, what is the term used to describe the closed path in a circuit where you start at a point and continue in the same direction, noting the direction of all voltage drops, and return to the same starting point?
Node
Loop
Path
Branch
Correct answer
Node
What is the purpose of damper winding in a synchronous motor?
To assist in the motor’s starting as an induction motor
To control the speed of the synchronous motor
To generate additional torque for higher efficiency
To provide a backup power source in case of a power outage
Correct answer
To assist in the motor’s starting as an induction motor
Which component is responsible for generating the time scale or time reference in a Cathode Ray Oscilloscope (CRO)?
Time-base generator
Delay line
Vertical amplifier
CRT
Correct answer
Time-base generator
What is the purpose of the trigger circuit in a Cathode Ray Oscilloscope (CRO)?
To generate the electron beam
To synchronise the horizontal and vertical deflections
To control the power supply circuit
To amplify the input signal
Correct answer
To generate the electron beam
Th the phasor diagram of an alternator, what does the angle Φ represent?
Synchronous reactance
Power factor
Leakage flux
Phase angle between voltage and current
Correct answer
Synchronous reactance
Why are energy-efficient solutions such as LED lighting and programmable thermostats incorporated into commercial electrical installations?
To raise operating costs
To increase electricity consumption
To reduce electricity consumption and lower operating costs
To improve safety measures
Correct answer
To raise operating costs
Find the number of tums of the coil shown in the following figure, if the inductance of the coil is 1.58 μH.
100
50
78
25
Correct answer
100
Which of the following is NOT a characteristic of a radial distribution system?
Power flows in only one direction
Highly reliable
Low cost
Simple construction
Correct answer
Power flows in only one direction
What is the unsaturated synchronous reactance (Xm) in an alternator if the armature resistance is neglected according to the following graph?
Xsu = Ead / Iab
Xsu = Ead Iab
Xsu = Ra + jZsu
Xsu = I / (Ra + jXsu)
Correct answer
Xsu = Ead / Iab
The susceptibility of the paramagnetic material is:
negative and small
positive and large
positive and small
negative and large
Correct answer
negative and small
In the provided circuit, which of the following represents the correct Kirchhoff’s Current Law (KCL) equation for node D?
i4 + i5 = i7
i2 = i3 + i4
i4 + i5 = -i7
i3 = i5 + i6
Correct answer
i4 + i5 = i7
An RLC series circuit has R =2 Ω, C = 20 μF and the inductance is adjusted such that the voltage across the resistance is maximum. If the applied voltage is 10 V at a frequency of 1000 rad/sec, then find the value of inductance L.
0.25 H
0.025 H
0.05 H
0.005 H
Correct answer
0.25 H
Find the current through 20 Ω resistance in the circuit shown in the following figure.
4 A
3 A
2 A
4.5 A
Correct answer
4 A
What is the resonant frequency of an RLC circuit with the given values of resistance (R = 30 Ω), inductance (L = 1.3 mH), and capacitance (C = 30 μF)?
625.23 Hz
306.63 Hz
805.91 Hz
100.53 Hz
Correct answer
625.23 Hz
With reference to wind turbines, which of the following statements are correct?
I. In a propeller-type turbine, the number of blades is three to six.
Il. The Darrieus type of turbine is an example of vertical axis turbines.
III. Propeller type turbines are rarely used.
IV. A multi-blade type turbine is an example of horizontal axis turbines.
II, III and IV
I, III and IV
I, II and IV
I, II and III
Correct answer
II, III and IV
What is the purpose of a neutral conductor in a star-connected three-phase system, and how does it help in maintaining balance?
The neutral conductor is used to increase the voltage between two phases, and it assists in load balancing.
The neutral conductor is used for grounding the system, and it helps in equalising phase voltages.
The neutral conductor is used for phase shifting, and it helps in generating higher voltage.
The neutral conductor is used for overcurrent protection, and it helps in phase separation.
Correct answer
The neutral conductor is used to increase the voltage between two phases, and it assists in load balancing.
Which materials are classified as ferromagnetic based on their permeabilities compared to free space?
Materials with permeabilities the same as that of free space
Materials with permeabilities slightly greater than that of free space
Materials with permeabilities slightly less than that of free space
Materials with permeabilities hundreds and thousands of times greater than that of free space
Correct answer
Materials with permeabilities the same as that of free space
The maximum load torque that can be applied to the shaft of an unexcited stepper motor, without causing continuous rotation, is called _______.
running torque
pull-out torque
pull-in torque
detent torque
Correct answer
running torque
Candela per square metre is the unit of ________.
luminous intensity
luminous flux
illumination
luminance
Correct answer
luminous intensity
How is the magnetomotive force per unit length denoted, and what is its symbol in equation form?
Magnetising force (H)
Magnetic permeability (μ)
Magnetic flux (Φ)
Magnetic density (B)
Correct answer
Magnetising force (H)
Which of the following statements is INCORRECT for parallel resonance?
At resonance, the power factor will be zero.
At resonance, the impedance will be maximum.
At resonance, the line current will be in phase with the applied voltage.
At resonance, the current will be minimum.
Correct answer
At resonance, the power factor will be zero.
100 questions in the full paper