ISRO SDSC Technical Assistant Electrical Engineering/Electrical Electronics Engineering 2024 Paper

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Question 1: The Geo Synchronous Solar Power station has the concept of:

A) Large array of solar cells placed in Equator region

B) Large array of solar cells placed in Geo Centre of Earth

C) Large array of solar cells synchronised in Power station

D) Large array of solar cells placed in Space Orbit

Explanation: A Geo Synchronous Solar Power station involves placing a large array of solar cells in space orbit, where the station orbits the Earth in sync with its rotation. This allows continuous exposure to sunlight, providing a constant and efficient power source.

Question 2: The distance between the starts of two consecutive coils measured in terms of coil sides is called as:

A) Commutator Pitch

B) Front Pitch

C) Winding Pitch

D) Back Pitch

Explanation: The distance between the starts of two consecutive coils measured in terms of coil sides is referred to as the winding pitch. It is an essential parameter in electrical machines and is crucial for determining the distribution and arrangement of coils in the winding.

Question 3: Which is the material used for construction of core of Electromagnets?

A) Hard magnetic materials

B) Soft Magnetic materials

C) Copper material

D) None of above

Explanation: The core of electromagnets is typically constructed using soft magnetic materials because these materials can be easily magnetized and demagnetized, making them suitable for applications where the magnetic field needs to change rapidly, such as in electromagnets.

Question 4: A bridge circuit is operating at a frequency of 2kHz. The suitable detector for obtaining balance point for null condition for the bridge can be

A) Vibration galvanometer

B) Headphones and tunable amplifiers

C) Vibration galvanometer and tunable amplifiers

D) None of the above

Explanation: The correct answer is Headphones and tunable amplifiers
The Frequency range of Headphones is from 250 Hz to 3 or 4 kHz
The Frequency range of Vibration galvanometers is from 5 Hz to 1 kHz(mostly it is used below 200 Hz)
The Frequency range of Tuneable amplifier detectors is from 1 kHz to 100 kHz.

Question 5: In a series R-L-C circuit, the Maximum voltage across the capacitor occurs at a frequency

A) Double the resonant frequency

B) Equal to resonant frequency

C) Square root times the resonant frequency

D) Below the resonant frequency

Explanation: The correct answer is Below the resonant
The maximum voltage drop across the Capacitor and as well Inductor when the circuit operates at the resonance frequency.

The resonant frequency of the RLC series circuit is given by,
$f_r = \frac{1}{2\Pi \sqrt{LC}}$
While, In a series RLC, maximum voltage across capacitor alone occurs at a frequency slightly below the resonant frequency.

This frequency is given by,
$f_c = \frac{1}{2\Pi }\sqrt{\frac{1}{LC}-\frac{R^2}{2L}}$

Question 6: The meter constant of energy meter is given by

A) Rev/kW

B) Rev/kWh

C) Rev/W

D) Rev/kWs

Explanation: The meter constant of an energy meter is given by Revolutions per kilowatt-hour (Rev/kWh). It represents the number of revolutions the disc of the energy meter makes for each kilowatt-hour of energy consumed.

Question 7: The series motor should not be started at no load because

A) Armature current is very high

B) Armature current is very low

C) Speed is very high

D) Speed is very low

Explanation: A DC series motor should always be started with load because at no load it will rotate with dangerously high speed. So, the correct answer is Speed is very high

Question 8: Floating neutral condition in a 3-phase + N distribution system in India will lead into ___________________ situation

A) Unequal line to line voltages

B) Large neutral current

C) Unbalanced load currents in three phases

D) Unequal phase to neutral voltage

Explanation: In a 3-phase + N distribution system, a floating neutral condition can lead to unequal phase-to-neutral voltages. This occurs because of the unbalanced load currents in the three phases, which results in an uneven distribution of voltages. The neutral point, not being connected to the ground, can float and cause variations in the phase-to-neutral voltages.

Question 9: The scale of voltmeter is uniform. Its type is

A) Moving Iron

B) Induction

C) Moving coil permanent magnet

D) All of the above

Explanation: A voltmeter with a uniform scale is typically associated with the moving coil permanent magnet type. This type of voltmeter uses a moving coil mechanism and a permanent magnet to measure voltage, and it is known for its linear and uniform scale.

Question 10: In an electronic ohmmeter, an op-amp is used for

A) Summer

B) Multiplier

C) Buffer amplifier

D) Integrator

Explanation: In an electronic ohmmeter, an operational amplifier (op-amp) is used as a buffer amplifier. The buffer amplifier isolates the ohmmeter from the circuit under test, preventing loading effects and ensuring accurate resistance measurements.

Question 11: Write the output expression of a logic circuit with 4 inputs A, B, C, D that will produce logic high only whenever two adjacent input variable logic high. Treat A and D are also adjacent.

A) F = AC + AD + AB + BD

B) F = AC + BD + Ā(C + D)

C) F = BC + AD + CD + AB

D) F = AB + AD + BC + BD

Explanation:

Question 12: A Power chopper converts

A) AC to DC

B) DC to DC

C) DC to AC

D) AC to AC

Explanation: There are 4 types of Converters:-
(a)Rectifier which converts AC to DC
(b)Inverter which converts DC to AC
(c)Chopper which converts DC to DC
(d)cycloconverter which converts to AC to AC

Question 13: Main components in an electronic fan regulator are _______________

A) High wattage resistance

B) IGBT

C) triac and diode

D) Transistor and diodes

Explanation:

Question 14: Which among the following is a chemical change?

A) A wet towel dries in the sun

B) Lemon juice added to tea causing its colour to change

C) Hot air rises over a radiator

D) Coffee is brewed by passing through ground coffee

Explanation:

Question 15: Wein bridge is used for measurement of

A) Resistance

B) Capacitance

C) Frequency

D) Inductance

Explanation:

Question 16: ____________ is the safe let through value of electric current through human body.

A) more than 1 ampere

B) less than 30 milli ampere

C) 230 ampere

D) 300 milli ampere

Explanation: The correct answer is option B) less than 30 milli ampere

Current (mA)	Effect	Time Duration
0.2 to 1.0	Threshold of perception	Not critical
10 to 16	Limit of ‘let go’, muscles contract	Minutes
30*	Breathing difficult, ‘safe’ limit	Seconds
50	Irregular heartbeat	1 heart beat or about 1 second
60	Respiratory problems, cannot breathe	1 heart beat or about 1 second

Question 17: A steam power generating station normally works on _______________ cycle with modifications to have heat economy and greater efficiency

A) Carnot

B) Brayton

C) Rankine

D) Otto

Explanation: A steam power generating station typically works on the Rankine cycle. The Rankine cycle is a thermodynamic cycle that describes the operation of steam power plants. Various modifications are applied to enhance heat economy and increase efficiency in power generation based on the Rankine cycle.

Question 18: A power IGBT has three terminals called

A) Collector, emitter and gate

B) Drain, source, and base

C) Drain, source, and gate

D) Collector, emitter, and drain

Explanation: The correct answer is option A) Collector, emitter and gate

Question 19: The transformer core shall have

A) High Resistance

B) High Inductance

C) Low Resistance

D) High Permeability

Explanation:

Question 20: Which of the following loads will have highest harmonics when switched ON?

A) 500 W, 230 V, 50 Hz incandescent lamp

B) 1500 W, 230 V, 50 Hz Geyser

C) 60 W, 230 V, 50 Hz destop PC

D) 50 W, 10 pole, 230 V, 50 Hz, Ceiling fan

Explanation: The correct option is C) 60 W, 230 V, 50 Hz desktop PC
Electronic devices, such as desktop PCs, often contain non-linear loads that can introduce harmonics into the electrical system when switched ON. Harmonics are multiples of the fundamental frequency and can lead to waveform distortion. Compared to resistive loads like incandescent lamps, inductive loads like a ceiling fan, or a geyser, electronic devices are more likely to generate higher harmonics due to their non-linear characteristics, making the desktop PC the option with the potential for the highest harmonics.

Question 21: Among the following, which is not directly related electrical insulation property?

A) Voltage Resistivity(VR)

B) Surface Resistivity(SR)

C) Abrasion Resistance(AR)

D) Insulation Resistance(IR)

Explanation: Abrasion Resistance (AR) is not directly related to electrical insulation properties. While Voltage Resistivity (VR), Surface Resistivity (SR), and Insulation Resistance (IR) are crucial factors determining a material's effectiveness in electrical insulation, Abrasion Resistance focuses on the material's ability to withstand wear and tear from mechanical factors like friction. Understanding these distinctions is key for selecting materials that meet both electrical and mechanical requirements for optimal performance and longevity.

Question 22: Longer coasting period for train results in

A) Higher acceleration

B) Higher retardation

C) Lower specific energy consumption

D) Higher schedule speed

Explanation: A longer coasting period for a train implies that the train is moving with little or no power applied. During coasting, the train is essentially utilizing its kinetic energy to overcome resistance. A longer coasting period results in lower specific energy consumption since the train is covering distance without actively consuming energy, contributing to better energy efficiency.

Question 23: Maximum demand on a power station is less if

A) Diversity factor is less

B) Load factor is more

C) Load factor is less

D) Diversity factor is more

Explanation: Maximum demand on a power station is less if the diversity factor is more. Diversity factor is a measure of how simultaneous the peak loads of individual consumers or substations are. A higher diversity factor implies that not all loads are at their peak simultaneously, allowing for a reduction in the overall maximum demand on the power station.

Question 24: If the surge impedance of a 20 km long underground cable is 20 ohms, then for 10 km length of the surge impedance of the cable will be:

A) 10 ohm

B) 200 ohm

C) 400 ohm

D) 20 ohm

Explanation: The correct answer is option D) 20 ohm
The surge impedance doesn't depend upon the length of the transmission line, it depends upon the characteristics of the transmission line(like diameter and spacing between the conductors).

Question 25: To measure a signal of 10 mV at 75 Hz, which one of the following instruments can be used
A. Moving coil voltmeter
B. Cathode ray oscilloscope
C. Moving iron voltmeter
D. Lux meter

A) A

B) B

C) C

D) D

Explanation: The correct answer is option B Cathode ray osciloscope
To measure a small signal of 10 mV at a specific frequency (75 Hz in this case), a cathode ray oscilloscope (CRO) is more suitable. CROs are equipped to display waveforms, and their sensitivity can be adjusted to measure small voltage signals accurately at a specified frequency. Moving coil and moving iron voltmeters are generally used for DC measurements, and a lux meter is used for measuring illuminance, not voltage.

Question 26: In order to have the impulse response of a control system approaching zero with time tending to infinity,
A. the poles of the system must have positive real parts
B. the poles of the system must lie on left half side of 's' plane
C. the zeros of the system must lie on left half side of 's' plane
D. none of the above

A) A

B) B

C) C

D) D

Explanation: The correct answer is option B) the poles of the system must lie on left half side of 's' plane
Any system is called a stable system if the output of the system is bounded for any bounded input, also the stability of any system depends on only location of poles, not on location of zeroes.
If all the poles are located on the left half of the s-plane, then the system is stable.
If one or more poles are located on the right side of the s-plane, then the system is unstable.
If one pair of poles located on the imaginary axis, then the system is marginally stable.
If more than one pair of poles located on imaginary axis, then the system is unstable.
If two or more poles located on the origin, then the system is unstable

Question 27: Two dice are thrown simultaneously. The probability that at least one of them will have six facing up is

A) 1/36

B) 1/3

C) 25/36

D) 11/36

Explanation: The correct answer is option D) 11/36
Let the two dices are Dice1 and Dice2,
A dice have 6 possible outcome(numbers 1 to 6), when two dice are thrown simultanesously the possible outcome will be 6x6=36
The probability of getting at least 6 = 1 - the probability of not getting 6
The probability of getting 6 on dice1 = The probability of getting 6 on dice2 = $\frac{1}{6}$
Therefore, the probability of not getting 6 on dice1 = the probability of not getting 6 on dice2 = $1-\frac{1}{6}=\frac{6-1}{6}=\frac{5}{6}$
The number 6 will not show in both the dice = $\left(\frac{5}{6}\right)\left(\frac{5}{6}\right)$
Hence, the probability of getting at least 6 = 1 - the probability of not getting 6=
$1-\left(\frac{25}{36}\right)=\frac{36-25}{36}=\frac{11}{36}$

Question 28: An A.C source of 200 V r.m.s supplies an active power of 600 w and reactive power of 800 VAR to a load. The r.m.s current and the power factor of the load respectively are
A. 5 A and 0.60
B. 5 A and 0.75
C. 4 A and 0.60
D. 4 A and 0.75

A) A

B) B

C) C

D) D

Explanation: The correct answer is option (A) 5 A and 0.60

Given active power (P) = 600 W, reactive power (Q) = 800 VAR, and rms voltage (V) = 200V
The apparent power (S) can be calculated as $S=\sqrt{P^2+Q^2}=\sqrt{{600}^2+{800}^2}=1000 VA.$
The rms current (I) can be calculated as $I=\frac{S}{V}=\frac{1000}{200}=5 A$
The Power factor (PF) is given by $PF=\frac{P}{S}=\frac{600}{1000}=0.60$

Question 29: Initially the circuit shown in the given figure was relaxed. If the switch is closed at t=0, the values of $i\left(0_{+}\right), \frac{di}{dt}\left(0_{+}\right) and \frac{d^{2}i}{d{t}^2}\left(0_{+}\right)$ will be respectively be

A) 0, 10 and -100

B) 0, 10 and 100

C) 10, 100 and 10

D) 100, 0 and 10

Explanation: The correct answer is option A) 0, 10 and -100
$By KVL equation$
$10 = \mathrm{iR} + L\frac{di}{dt} + V_c ⇢\left(i\right)$
$At t = 0^{+}, t = 0 and V_c = 0 (short-circuited)$
$\therefore 10 = L\frac{di}{dt}$
$\Rightarrow 10 = 1\times \frac{di}{dt}$
$\Rightarrow \frac{di}{dt}= 10$
$Differentiating equation \left(i\right), we have$
$\frac{dd\mathrm{t}}{}\left(10\right) = \frac{dd\mathrm{t}}{}(\mathrm{iR} + L\frac{di}{dt} + V_c)$
$\Rightarrow 0 = \frac{di}{dt}R + L\frac{d^{2}i}{d{t}^2} + \frac{d{V}_c}{dt}$
$\Rightarrow -\frac{di}{dt}R = L\frac{d^{2}i}{d{t}^2} [ as \frac{d{V}_c}{dt} = \frac{i}{C} = 0 ]$
$\Rightarrow 1\times \frac{d^{2}i}{d{t}^2} = -\left(10\right)\times 10$
$\Rightarrow \frac{d^{2}i}{d{t}^2} = -100$

Question 30: Armature reaction with axis at 90° to the main field is called as ___________________
A. Demagnetizing
B. Cross-magnetizing
C. Non-magnetizing
D. None of the above

A) A

B) B

C) C

D) D

Explanation: When the axis of armature reaction is at 90° to the main field, it is referred to as cross-magnetizing. This phenomenon can lead to distortion in the main magnetic field and affects the overall performance of the DC machine.

Question 31: Hydro Electric generators are basically
A. High speed alternator of smooth cylindrical type
B. Low speed alternator of Salient pole type
C. Low speed alternator of smooth cylindrical type
D. High speed alternator of Salient pole type

A) A

B) B

C) C

D) D

Explanation: .

Question 32: Which of the following is not present in cement?
A. Clay
B. Alumina
C. Alum
D. Gysum

A) A

B) B

C) C

D) D

Explanation: .

Question 33: The microprocessor contains ROM chip which contains
A. control function
B. arithmetic functions
C. instructions to execute data
D. memory functions

A) A

B) B

C) C

D) D

Explanation: .

Question 34: Let A and B be real symmetric matrices of size nxn. Then which one of the following is true?
A. A.AT = 1
B. A = A-1
C. A. B = B.A
D. (A.B)T = B.A

A) A

B) B

C) C

D) D

Explanation: .

Question 35: For a sinusoidal waveform, form factor is
A) 1.11
B) 2.12
C) 3.13
D) 4.14

A) A

B) B

C) C

D) D

Explanation: .

Question 36: Which of the following instrument is used to measure alternating current?
A. Moving Iron voltmeter
B. Permanent magnet type ammeter
C. Induction type voltmeter
D. Moving Iron Ammeter

A) A

B) B

C) C

D) D

Explanation: .

Question 37: A 10 milli henry inductor carries a sinusoidal current input of 1 A r.m.s at a frequency of 50 Hz. The average power dissipated by the inductor is
A. 0 watts
B. 0.25watts
C. 0.5 watts
D. 1.0 watts

A) A

B) B

C) C

D) D

Explanation: .

Question 38: A transformer is working at its maximum efficiency, its iron loss is 500 W, its copper loss will be
A) 250 W
B) 300 W
C) 400 W
D) 500 W

A) A

B) B

C) C

D) D

Explanation: .

Question 39: What is the main constituent of natural gas?
A. Methane
B. Ethane
C. Butane
D. Hydrogen

A) A

B) B

C) C

D) D

Explanation: .

Question 40: Which are the following are used to reduce short circuit fault currents
A. Reactors
B. Capacitors
C. Resistors
D. Combination of all of (A), (B) & (C)

A) A

B) B

C) C

D) D

Explanation: .

Question 41: The "Double conclave lens" phenomena in a CRO is observed between
A. Control grid and pre accelerating anode
B. Focussing anode and pre accelerating anode
C. Pre accelerating anode and focussing anode
D. Pre accelerating anode and accelerating anode.

A) A

B) B

C) C

D) D

Explanation: .

Question 42: When two different capacities of synchronous generators operate in parallel and supply to given load conditions and both have same governor droops, the following statement will be correct
A. The higher rated generator will share lesser load and lower rated generator will share higher load
B. The higher rated generator will share more load and lower rated generator will share lesser load
C. Both higher rated and lower rated generator will share equal load
D. None of the above

A) A

B) B

C) C

D) D

Explanation: .

Question 43: Plug setting of a relay can be altered by varying
A. Air gap of magnetic path
B. Adjustable back up stop
C. Number of ampere turns
D. None of the above

A) A

B) B

C) C

D) D

Explanation: .

Question 44: The effect of harmonics in a power distribution system is
A. Low Power factor
B. Higher losses
C. Lower eddy current loss
D. High efficiency

A) A

B) B

C) C

D) D

Explanation: .

Question 45: A synchronous generator is running over excited with excitation emf of 1.2 p.u. The synchronous reactance is 0.8 p.u. The machine is delivering a synchronous power of 0.9 p.u to the busbar. If the prime-mover input is increased by 7.5%, then the percentage change in reactive power is
A. -7.5%
B. - 3.5%
C. -5.63%
D. 7.5%

A) A

B) B

C) C

D) D

Explanation: .

Question 46: The eddy current loss in an ac electric motor is 100 watts at 50 Hz. Its loss at 100 Hz will be
A. 25 Watts
B. 400 Watts
C. 100 Watts
D. 59 Watts

A) A

B) B

C) C

D) D

Explanation: .

Question 47: The current i(t) through a 102 resistor in series with an inductance, is given by i(t) = 3 + 4sin(100t+45º) + 4sin(300t+60°) Amperes
The RMS value of the current and power dissipated in the circuit are
A. √41A, 410W respectively
B. √35A, 350W respectively
C. 5A, 250W respectively
D. 11A, 1290W respectively

A) A

B) B

C) C

D) D

Explanation: .

Question 48: In a three-phase half wave diode rectifier, if Vm is the maximum value per phase voltage then each diode is subjected to peak inverse voltage of
A. Vm
B. √3Vm
C. 2Vm
D. 3Vm

A) A

B) B

C) C

D) D

Explanation: .

Question 49: The field of an induction motor rotor rotates relatively to the stator at
A. Slip speed
B. Synchronous speed
C. Rotor Speed
D. Very low speed

A) A

B) B

C) C

D) D

Explanation: .

Question 50: The dielectric loss of a capacitor can be measured by
A. Wein bridge
B. Owen bridge
C. Schering bridge
D. Maxwell bridge

A) A

B) B

C) C

D) D

Explanation: .

Question 51:Materials which have small area of Hysteresis loop are suitable for making
A. Electromagnets
B. Permanent magnets
C. Transformer Core
D. None of the above

A) A

B) B

C) C

D) D

Explanation: .

Question 52:The values of the resistor R in the circuit shown in the figure is varied in such a manner that the power dissipated in 3Ω resistor is maximum. Under this condition, the value of R will be
A. 3Ω
B. 9Ω
C. 12Ω
D. 6Ω

A) A

B) B

C) C

D) D

Explanation: .

Question 53:

A) A

B) B

C) C

D) D

Explanation: .

Question 54: A sinusoidal waveform is mathematically represented by
A. an even function
B. an odd function
C. a function that is neither even nor odd
D. none of the above

A) A

B) B

C) C

D) D

Explanation: .

Question 55: A body moves with a constant speed along a curved path. Its acceleration
A. is zero
B. is parallel to its velocity
C. can make any arbitrary angle with its velocity
D. is perpendicular to its velocity

A) A

B) B

C) C

D) D

Explanation: .

Question 56: There are no transients in pure resistance circuits because they
A. Offer high resistance
B. Obey ohms law
C. Have no stored energy
D. Are linear circuits

A) A

B) B

C) C

D) D

Explanation: .

Question 57:

A) A

B) B

C) C

D) D

Explanation: .

Question 58: If a counter having 10 flip-flops is initially at '0', what count will, if hold after 2060 pulses?
A. 000 000 1100
B. 000 001 1100
C. 000 001 1000
D. 000 000 1110

A) A

B) B

C) C

D) D

Explanation: .

Question 59: Inverter converts
A) AC to AC
B) AC to DC
C) DC to AC
D) DC to DC

A) A

B) B

C) C

D) D

Explanation: .

Question 60: For a synchronous motor, inverted 'V' curve is the relation between
A. Field Current and Power factor
B. Field current and armature current
C. Armature current and Power factor
D. None of the above

A) A

B) B

C) C

D) D

Explanation: .

Question 61: What is the purpose of providing compensating winding in DC machine?
A. To neutralize armature reaction
B. To increase the armature reaction
C. To increase the speed
D. To reduce the speed

A) A

B) B

C) C

D) D

Explanation: .

Question 62: The arcing ground phenomenon is related___ electrical system.
A. Underground long HV AC transmission
B. Loose connection of Phase at Outdoor transformer's terminal
C. Loose connection at Earthing terminal
D. Arcing due to lightning

A) A

B) B

C) C

D) D

Explanation: .

Question 63: The diac is a
A. Transistor
B. Unidirectional device
C. Three layer device
D. Bidirectional device

A) A

B) B

C) C

D) D

Explanation: .

Question 64: The unit of luminous flux is
A) Lumen
B) Candle power
C) Lux
D) Meter candle

A) A

B) B

C) C

D) D

Explanation: .

Question 65: Advantage of using electronic devices for speed control of electric motor is
A. Fast action
B. Consumes less power
C. Compact
D. All of the above

A) A

B) B

C) C

D) D

Explanation: .

Question 66: In a practical clamping circuit, a resistor 'R' is placed across the diode. This is
A. to provide charging or discharging path for the capacitor as need arises
B. to neutralise the effect of diode's forward resistance
C. an indispensable addition
D. none of the above

A) A

B) B

C) C

D) D

Explanation: .

Question 67: In a series RIC cireuit at resonance, the magnitude of the voltage developed across the capacitor
A. is always zero
B. can never be greater than the input voltage
C. can be greater than the input voltage, however, it is 90° out of phase with the input voltage
D. can be greater than the input voltage, and is in phase with the input voltage

A) A

B) B

C) C

D) D

Explanation: .

Question 68: The address bus width of a memory of size 1024x8 bits is
A. 10 bits
B. 13 bits
C. 8 bits
D. 18 bits

A) A

B) B

C) C

D) D

Explanation: .

Question 69: Transmission line regulation is arrived by:
A. (Sending end voltage - Receiving end voltage) ÷ Receiving end voltage
B. (Receiving end voltage - Generation voltage) ÷ Generation voltage
C. (Receiving end voltage - Sending end voltage) ÷ Sending end voltage
D. None of the above

A) A

B) B

C) C

D) D

Explanation: The correct option is: A. (Sending end voltage - Receiving end voltage) ÷ Receiving end voltage
Transmission line regulation is actually calculated using the following formula: $Transmission line regulation = \frac{Sending end Voltage - Receiving end Voltage}{Receiving end Voltage}\times 100\%$
This formula represents the percentage change in voltage from the sending end to the receiving end of the transmission line.

Question 70: The main function of which of the following parts of an VFD is to change a high DC voltage into a pulsed AC voltage?
A. Inverter
B. DC Link
C. Rectifier
D. RFI filter

A) A

B) B

C) C

D) D

Explanation: The correct answer is: A. Inverter
- In a Variable Frequency Drive (VFD), the inverter is responsible for converting DC voltage from the DC link into an AC voltage with variable frequency and voltage magnitude.
- The inverter utilizes power electronic switches (such as insulated gate bipolar transistors - IGBTs) to generate a pulsed AC voltage by switching the DC voltage at high frequencies.
- This pulsed AC voltage is then filtered and smoothed to create a sinusoidal output voltage with variable frequency and voltage magnitude, allowing precise control of the speed and torque of the connected motor.

Question 71: What is the KVA load on the distribution transformer if the secondary of the 100/5A CT connected in primary of 11KV/433V is 4 Amps?
A. 1905 KVA
B. 1000 KVA
C. 1524 KVA
D. 1143 KVA

A) A

B) B

C) C

D) D

Explanation: The correct option is: C. 1524 kVA

Question 72: Which of the following is not a correct method to reduce the effects of armature reaction?
A. Increasing Reluctance of the pole tips
B. Use of Inter-poles
C. Decreasing Reluctance of pole tips
D. Increasing length of airgap at the pole tips

A) A

B) B

C) C

D) D

Explanation: The correct option is: C. Decreasing Reluctance of pole tips
Armature reaction in a DC machine refers to the effect of armature current on the distribution of magnetic flux in the machine. To reduce the effects of armature reaction, methods such as increasing the reluctance of the pole tips, using inter-poles, and increasing the length of the airgap at the pole tips are commonly employed. However, decreasing the reluctance of the pole tips would exacerbate the effects of armature reaction rather than reduce them.

Question 73: How many flipflops are required to construct MOD-31 counter?
A. 4
B. 2
C. 3
D. 5

A) A

B) B

C) C

D) D

Explanation: The correct option is D. 5
To find the minimum number of flip-flops required for a MOD-31 counter, we need to solve for n in the equation:
$2^n-1=31$
$\Rightarrow 2^n=31+1=32$
$\Rightarrow 2^n=2^5$
$\Rightarrow n=5$

Question 74: A 3 phase, 4 wire system supplies power to a balanced star connected load. The Current in each phase is 10A. The current in the Neutral wire will be
A. 10A
B. 30A
C. 40A
D. 0A

A) A

B) B

C) C

D) D

Explanation: The correct option is: D. 0A
In a balanced star-connected load supplied by a 3-phase, 4-wire system, the sum of currents in the neutral wire should ideally be zero if the load is perfectly balanced. Each phase current returning through the neutral will cancel out with the corresponding currents from the other phases.

Question 75: Buck boost transformer is generally used in ____ system.
A. HVAC
B. Servo Controlled Voltage Stabilizers
C. Sub-stations
D. Railway traction

A) A

B) B

C) C

D) D

Explanation: The correct option is: B. Servo Controlled Voltage Stabilizers Buck-boost transformers are often used in Servo Controlled Voltage Stabilizers (SCVS) to regulate voltage levels. SCVS systems utilize buck-boost transformers to compensate for variations in input voltage and ensure a stable output voltage. These stabilizers are commonly employed in industrial and commercial settings to protect sensitive equipment from voltage fluctuations.

Question 76: When the phenomenon of cogging happens in induction motor?
A. Rotor slots = stator slots
B. Rotor slots = ½ Stator slots
C. Stator slots = ½ Rotor slots
D. Rotor slots =2 x stator slots

A) A

B) B

C) C

D) D

Explanation: The correct option is: A. Rotor slots = stator slots
The phenomenon of cogging occurs in induction motors when there is a strong magnetic interaction between the stator and rotor teeth, causing the rotor to "cog" or "stick" at certain positions rather than rotate smoothly.

Cogging is most likely to occur when the number of rotor slots is equal to the number of stator slots. This alignment creates a situation where the magnetic forces between the stator and rotor teeth become more significant, leading to the cogging effect.

Question 77: A planet of solar system has mass four times and diameter twice than that of earth. The value of 'g' on this planet is
A. 4.9m/s²
B. 9.8m/s²
C. 19.6m/s²
D. 39.2m/s²

A) A

B) B

C) C

D) D

Explanation: The correct option is: B. 9.8m/s²
To find the value of acceleration due to gravity (g) on the planet, we can use the formula:
$g=\frac{G\times M}{r^2}$
Where,
G is the universal gravitational constant$(6.674\times {10}^{-11}N.m^2/k{g}^2)$
M is the mass of the planet
r is the radius of the planet
Given that the mass of the planet is four times that of Earth $(M=4\times M_{Earth})$ and the radius is twice that of Earth $(r=2\times r_{Earth})$
Substituting these values into the formula for g:
$g=\frac{G\times \left(4\times M_{Earth}\right)}{{\left(2\times r_{Earth}\right)}^2}$
$\Rightarrow g=\frac{4\times G\times M_{Earth}}{4\times \left({r^2}_{Earth}\right)}$
$\Rightarrow g=\frac{G\times M_{Earth}}{{r^2}_{Earth}}$
Since g on earth is 9.8m/s², we can conclude that g on this planet will be 9.8m/s²

Question 78: What will happen if the voltmeter is connected like an ammeter in series to the load?
A) The measurement will be too high
B) There will be no current in the circuit
C) The meter will burn out
D) High current will flow

A) A

B) B

C) C

D) D

Explanation: The correct option is: B) There will be no current in the circuit
When a voltmeter is connected like an ammeter in series with the load, it creates a short circuit in the circuit. As a voltmeter has a very high resistance compared to an ammeter, which has low resistance, effectively no current flows through the circuit.

Question 79: One of the following can act as inverse transducer
A. Electrical resistance potentiometer
B. LVDI
C. Capacitive transducer
D. Piezo electric crystals

A) A

B) B

C) C

D) D

Explanation: The correct option is: D. Piezoelectric crystals
An inverse transducer converts an electrical signal into a non-electrical quantity.
Piezoelectric crystals are a type of inverse transducer which convert electrical signals into mechanical vibrations or pressure variations, and vice versa

Question 80: Various power system faults in increasing order of severity are
A. LG, LL, LLG, LLLG
B. LLLG, LLG, LL, LG
C. LL, LG, LLLG, LLG
D. LLG, LLLG, LL, LG

A) A

B) B

C) C

D) D

Explanation: The correct option is: A. LG, LL, LLG, LLLG
In increasing order of severity, various power system faults typically progress as follows: LG (Line-to-Ground), LL (Line-to-Line), LLG (Line-to-Line-to-Ground), and LLLG (Triple Line-to-Ground). This sequence represents an escalation in fault severity, with LLLG being the most severe.

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