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Question Bank

ISRO HSFC Technical Assistant Exam (Electrical) - English

Duration: 90 · Questions: 80 · Max Marks: 80 · Language: 3

View ISRO HSFC Technical Assistant 2026 Exam Page

Electrical

1
Resistance switching is normally resorted in case of
  1. A.Air blast CB
  2. B.Bulk oil CB
  3. C.Minimum oil CB
  4. D.All types of CB
2
By transmitting power at high voltage
  1. A.it will give poor voltage regulation
  2. B.it will give better voltage regulation
  3. C.it will not effect voltage regulation
  4. D.None of these
3
Which statement about the daily load curve is valid ?
  1. A.The area under the curve gives the average demand
  2. B.The ratio of the area under the curves to the total area of rectangle in which it is contained gives the load factor for the day
  3. C.The peak of the curve gives the installed capacity of the plant
  4. D.The area of the curves divided by the number of hours gives load factor
4
High voltage Schring bridge is used to measure
  1. A.large capacitance without additional element
  2. B.small capacitance without additional element
  3. C.medium value capacitance
  4. D.None of these
5
Draw - in - system of laying underground cables has the drawback (s) of
  1. A.higher cost
  2. B.reduced current carrying capacity of the cables
  3. C.requirements of much deeper and wider trenches
  4. D.repairs, alterations or additions difficult
  5. E.all of the above except
6
Surge impedance of a transmission line is
  1. A.independent of its length
  2. B.dependent on its length
  3. C.independent on its temperature
  4. D.none of the above
7
If two synchronous generators connected in parallel loose synchronism, it will lead to
  1. A.stalling of generators
  2. B.wild fluctuations in current
  3. C.wild fluctuations in current and voltage
  4. D.None of these
8
A differential relay responds to
  1. A.algebraic difference of two or more similar electrical quantities
  2. B.vector difference of two or more similar electrical quantities
  3. C.algebraic difference between two currents
  4. D.algebraic difference between two voltages
9
The conductor carries more current on the surface in comparison to its core. This phenomenon is called the
  1. A.Skin effect
  2. B.Corona
  3. C.Ferranti effect
  4. D.Lenz's effect
10
A booster is connected in
  1. A.series with the feeder
  2. B.parallel with the feeder
  3. C.both (a) and (b) are correct
  4. D.none of these
11
Fuses have got advantages of
  1. A.cheapest type of protection
  2. B.inverse time - current characteristic
  3. C.no maintenance
  4. D.current limiting effect under short - circuit conditions
  5. E.all of the above
12
The power transmitted will be maximum when
  1. A.line reactance is high
  2. B.corona losses are minimum
  3. C.sending end voltage is more
  4. D.receiving end voltage is more
13
The connected load of a consumer is 2 kW and his maximum demand is 1.5 kW. The load factor of the consumer is
  1. A.0.75
  2. B.0.375
  3. C.1.33
  4. D.None of these
14
In a transformer, the exciting current will be in phase quadrature with the impressed voltage provided
  1. A.only the leakage impedance drop is ignored
  2. B.only the core loss is ignored
  3. C.both the leakage impedance drop and the core loss are ignored
  4. D.only the no - load copper loss is ignored
15
Which of the following techniques is used for the measurements of a.c. high frequency voltages ?
  1. A.Peak voltmeter
  2. B.Series resistance mircro - ammeter
  3. C.Resistance potential divider
  4. D.All of these
16
Use of additional shunt capacitor can be made for increasing the capability of line as it
  1. A.reduces surge impedance Z0
  2. B.increases phase shift β
  3. C.increase in α
  4. D.all of the above
17
The sag of a transmission line is least affected owing to
  1. A.weight of the conductor
  2. B.current through the conductor
  3. C.atmospheric temperature
  4. D.ice deposited on the conductor
18
In case of Impulse Thermal break down of solid insulating materials, the critical electric field is proportional to
  1. A.critical absolute temperature
  2. B.square of critical absolute temperature
  3. C.square of T0
  4. D.none of these
19
The insulation of the modern EHV lines is designed based on
  1. A.corona
  2. B.switching voltages
  3. C.lightning voltage
  4. D.all of these
20
For constant voltage transmission, the voltage drop along the line is maintained constant by installing
  1. A.capacitors
  2. B.inductors
  3. C.resistors
  4. D.synchronous phase modifiers at the receiving end
21
AC network analyser is employed for solving the problems of
  1. A.load flow
  2. B.load flow and stability
  3. C.load flow and short - circuit
  4. D.load flow, stability and short - circuit
22
The change in excitation in an alternator connected to an infinite line provides a corresponding change in
  1. A.terminal voltage
  2. B.speed of rotor
  3. C.power generated
  4. D.power factor
23
Different types of insulators used for transmission lines are
  1. A.pin type only
  2. B.suspension type only
  3. C.strain type only
  4. D.pin type, suspension type and shackle type
24
The conductor connecting consumer's terminals to the distributor is called the
  1. A.feeder
  2. B.distributor
  3. C.service main
  4. D.none of the above
25
Which of the following method or techniques can be used for the measurement of high d.c. voltages ?
  1. A.Generating voltmeter
  2. B.Electrostatic voltmeter
  3. C.Peak voltmeter
  4. D.Half effect generators
26
The ripple voltage in dc output is small if
  1. A.frequency of supply voltage is small
  2. B.the filtering capacitor is small
  3. C.load current is small
  4. D.none of these
27
The voltage measurements using uniform spark gap are
  1. A.affected by dust particles
  2. B.affected by polarity of supply
  3. C.affected by temperature
  4. D.none of these
28
Neutral earthing is provided for
  1. A.the safety of personnel from electric shock
  2. B.the safety of equipment and personnel against lightning and voltage surges
  3. C.reducing the voltage stress on lines and equipment with respect to earth under various operating and fault conditions
  4. D.controlling the earth fault currents for protective relaying
  5. E.both (c) and (d)
29
The function of Lightning arrester is
  1. A.to limiting the short - circuit fault current
  2. B.to provide path to high voltage surge to earth
  3. C.to reduce arcing
  4. D.none of these
30
In which of the following cases are delay fuses used ?
  1. A.For the protection of light circuits
  2. B.For the protection of power out - let circuits
  3. C.For the protection of fluorescent lamps
  4. D.For the protection of motors
31
In order to improve the voltage profile of the line, compensation is resorted by providing
  1. A.capacitors at the receiving end
  2. B.reactors at the receiving end
  3. C.resistors at the receiving end
  4. D.none of these
32
Skin effect in conductor is proportional to
  1. A.(diameter of conductor) 1/2
  2. B.diameter of conductor
  3. C.(diameter of conductor)2
  4. D.(diameter of conductor)4
33
The function of steel wire in an ACSR conductor is to
  1. A.compensate for skin effect
  2. B.take care of surges
  3. C.provide additional mechanical strength
  4. D.reduce inductance
34
A fault is more severe from the view point of RRRV if it is a
  1. A.Short length fault
  2. B.Medium length line fault
  3. C.Long length line fault
  4. D.None of these
35
Protective resistance to be connected between the sphere gap and the test equipment is required while measuring
  1. A.power frequency and higher frequency a.c. voltage
  2. B.power frequency and impulse voltage
  3. C.all kinds of voltages
  4. D.none of these
36
Series capacitor is used in a transmission line to
  1. A.compensate the voltage drop
  2. B.reduce line loss
  3. C.limit short circuit current
  4. D.improve load power factor
37
The passive element that is used as interconnecting element for the stable operation of interconnected system is
  1. A.reactor
  2. B.resistor
  3. C.capacitor
  4. D.resistor and capacitor
38
Corona loss in a transmission line is dependent on
  1. A.diameter of the conductor
  2. B.material of the conductor
  3. C.height of the conductor
  4. D.none of these
39
In a minimum oil circuit breaker the oil is used
  1. A.to act as circuit breaking medium only
  2. B.for circuit breaking and providing insulation
  3. C.for providing insulation only
  4. D.for none of the above purposes
40
Skin effect is
  1. A.proportional to frequency
  2. B.proportional to square of frequency
  3. C.inversely proportional to frequency
  4. D.independent of frequency
41
Rated making capacity of breaker is equal to
  1. A. X rated symmetrical breaking capacity
  2. B.2.55 X rated symmetrical breaking capacity
  3. C.1 X rated symmetrical breaking capacity
  4. D.none of these
42
The main reason for using high voltage for long distance power transmission is
  1. A.reduction in transmission losses
  2. B.reduction in time of transmission
  3. C.increase in system reliability
  4. D.none of the above
43
Bus - coupler is very essential in
  1. A.single bus - bar arrangement
  2. B.ring bus - bar arrangement
  3. C.double bus, double breaker arrangement
  4. D.main and transfer bus
44
With the rise in temperature, the insulation resistivity
  1. A.remains unchanged
  2. B.decreases linearly
  3. C.increases linearly
  4. D.reduces exponentially
45
The effect of bonding the cable is
  1. A.to increase the effective resistance and inductance
  2. B.to increase the effective resistance but reduce inductance
  3. C.to reduce the effective resistance and inductance
  4. D.to reduce the effective resistance but increase the inductance
46
Increase in temperature in overhead transmission lines causes
  1. A.increase in stress and length
  2. B.decrease in stress and length
  3. C.decrease in stress but increase in length
  4. D.none of the above
47
The insulation resistance of the cable decreases with the
  1. A.increase in length of cable
  2. B.decrease in length of cable
  3. C.electric stresses
  4. D.none of these
48
Corona has the disadvantage(s) of
  1. A.power loss
  2. B.interference with neighbouring communication circuits
  3. C.introducing the harmonics, predominately third harmonics, into the transmission lines
  4. D.all of the above
49
In a load duration curve for an intergrated power system the uppermost crest represents the energy contributed by
  1. A.base power stations
  2. B.major thermal stations
  3. C.peaking hydro or gas turbine stations
  4. D.non - conventional power stations
50
At bridge crossing and near the railway track ternary lead cables are used because they
  1. A.are of high tensile strength
  2. B.are of low coefficient of thermal expansion
  3. C.are of low specific gravity
  4. D.can withstand shocks and vibrations
51
The heat produced at the contact point owing to flow of electric current is least affected by
  1. A.temperature of the surrounding medium
  2. B.contact resistance
  3. C.magnitude of electric current flowing
  4. D.duration of flow of current
52
A stationary alternator should not be connected to the live bus - bar because
  1. A.it is likely to operate as a synchronous motor
  2. B.it will get short - circuited
  3. C.it will reduce bus - bar voltage
  4. D.all of the above
53
In a transmission system the feeder supplies power to
  1. A.transformer substations (step - up)
  2. B.service mains
  3. C.distributors
  4. D.all of the above
54
For a given amount of power to be transmitted over a certain distance with fixed power loss, the volume of copper required is
  1. A.directly proportional to voltage
  2. B.inversely proportional to voltage
  3. C.inversely proportional to the square of voltage and pf of the load
  4. D.directly proportional to the square of the voltage and pf of the load
55
Power despatch through a line can be increased by
  1. A.installing series capacitors
  2. B.installing shunt capacitors
  3. C.installing series reactor
  4. D.installing shunt reactor
56
In the figure shown which curve represents the variation of cost of generation per kWh with the load factor, for a thermal power plant ?
​
  1. A.Curve A
  2. B.Curve B
  3. C.Curve C
  4. D.Curve D
57
Under 'no load conditions the current in a transmission line is because of
  1. A.capacitance effect
  2. B.corona effect
  3. C.proximity effect
  4. D.back flow from earth
58
The only advantage of corona is that it
  1. A.produces a pleasing luminous glow
  2. B.makes line current sinusoidal
  3. C.works as a safety valve for surges
  4. D.ozone gas is produced
59
Earth wires are made of
  1. A.copper
  2. B.aluminium
  3. C.iron
  4. D.galvanised stranded steel
60
The connected load of a consumer is 2 kW and his maximum demand is 1.5 kW. The demand factor of the consumer is
  1. A.0.75
  2. B.0.375
  3. C.1.33
  4. D.none of the above
61
A lightning arrester connected between the line and earth in a power system
  1. A.protects the terminal equipment against travelling surges
  2. B.protects the terminal equipment against direct lightning stroke
  3. C.suppresses high frequency oscillations in the line
  4. D.reflects back the travelling waves approaching it
62
Oil filled cables have the advantage(s) of
  1. A.smaller overall size
  2. B.most perfect impregnation
  3. C.easy detection of fault
  4. D.all of the above
63
A bus coupler circuit breaker is utilised in a substation for
  1. A.joining the transmission line with station bus - bar
  2. B.joining main and transfer bus in a substation
  3. C.joining the generator with transfer
  4. D.joining the neutral of the generator with earth
64
The fluids used in circuit breakers should be of
  1. A.high dielectric strength and thermal stability
  2. B.non - inflammability
  3. C.are extinguishing ability
  4. D.all of the above
65
Feeder is designed mainly from the point of view of
  1. A.its current carrying capacity
  2. B.voltage drop in it
  3. C.operating voltage
  4. D.operating frequency
66
Power output per unit volume of an MHD generator is proportional to
  1. A.specific electrical conductivity of gas
  2. B.square of the magnetic field strength
  3. C.square of the fluid velocity
  4. D.all of the above
67
Increase in frequecy of transmission line causes
  1. A.no change in line resistance
  2. B.increase in line resistance
  3. C.decrease in line resistance
  4. D.decrease in line series reactance
68
A dc series generator can excite itself
  1. A.only on zero load current
  2. B.only when load current is not zero
  3. C.irrespective of the value of load current
  4. D.none of the above
69
Thermal relays are used for protection of motors against over - current owing to
  1. A.short - circuits
  2. B.heavy loads
  3. C.earth fault
  4. D.all of these
70
Transmission efficiency of a transmission line increases with the
  1. A.decrease in power factor and voltage
  2. B.increase in power factor and voltage
  3. C.increase in power factor but decrease in voltage
  4. D.increase in voltage but decrease in power factor
71
While using air - blast circuit breaker, current chopping is a phenomenon often observed when
  1. A.a long overhead line is switched off
  2. B.a bank of capacitors is switched off
  3. C.a trasformer on no - load is switched off
  4. D.none of these
72
The contact resistance of a circuit breaker is about
  1. A.20 Ω
  2. B.2 Ω
  3. C.20 mΩ
  4. D.20 μΩ
73
Metallic shielding is provided on underground cables to
  1. A.reduce thermal resistance
  2. B.reduce corona effect
  3. C.control the electrostatic voltage stress
  4. D.all of the above
74
The most economical limit of power factor correcting is governed by
  1. A.original power factor
  2. B.relative costs of the supply and power factor correction equipment
  3. C.both (a) and (b)
  4. D.none of the above
75
A short - circuit current is identified by
  1. A.heavy current flow
  2. B.voltage rise
  3. C.voltage drop
  4. D.none of these
76
Which of the following materials is not used for transmission and distribution of electrical power ?
  1. A.Tungsten
  2. B.Copper
  3. C.Aluminium
  4. D.Cadmium copper
77
Which of the following alternators will have maximum number of poles ?
  1. A.Alternator coupled to hydraulic turbine
  2. B.Alternator coupled to steam turbine
  3. C.Alternator coupled to gas turbine
  4. D.All will have same number of poles
78
In humid weather, the corona occurs at a voltage
  1. A.much less than the needed in fair weather
  2. B.much higher than that needed in fair weather
  3. C.equal to that needed in fair weather
  4. D.none of the above
79
Short - circuit currents are due to
  1. A.single phase to earth fault
  2. B.phase to phase fault
  3. C.all the three phases to earth fault
  4. D.all the three phases short - circuited
  5. E.any of the above
80
Over - current protection respond to
  1. A.increase in current above pick - up value
  2. B.single line to earth faults
  3. C.double line to earth faults
  4. D.all of the above
Question for ISRO HSFC Technical Assistant 2026 - Quiz / Questions / MCQ - Toppersexam