Islamabad Electric Supply Company IESCO Past papers Solved for Junior Engineer (Electrical BPS-17) 2019

IESCO Past papers Solved for Junior Engineer (Electrical BPS-17) 2019

IESCO Past papers Solved for Junior Engineer (Electrical BPS-17) 2019
IESCO Past papers Solved for Junior Engineer (Electrical BPS-17) 2019

IESCO Past papers for Junior Engineer (Electrical BPS-17) 2019

18-If in the transfer function of a system, there is present a zero in mirror image
position for every pole in LHS half plane, and then the system is called
A. Minimum phase system
B. Non-minimum phase system
C. All pass system
D. All stop system
19-Zeros are complex frequencies of a transfer function where the response
A. Infinite
B. Zero
C. Oscillatory
D. Exponentially decaying
20-When a control system is required to have a power level higher than the
capability of the linear electronic amplifiers, which of the following is preferred?
A. Amplidyne
B. AC servomotor
C. AC tachometer
D. Metadyne
21-Transfer function of the control system depends upon
A. System parameters alone
B. Nature of the input
C. Initial condition of input and output
D. Nature of the output
22-For a transfer function H(s)= P(s)/Q(s), where P(s) and Q(s) are polynomials in s
A. The degree of P(s) is always greater than the degree of Q(s)
B. The degree of P(s) and Q(s) are same
C. Degree of P(s) is independent of degree of Q(s)
D. Maximum degree of P(s) and Q(s) differ at most by one
23-Slope of asymptote in Bode plot of 2nd order system is …………………. per
A. 18 dB
B. 12dB
C. 06 dB
D. 03 dB
23-Which of the following control systems provides good performance if Offset is to
be avoided?
A. Proportional action
B. Proportional plus Integral action
C. Proportional plus differential action
D. Proportional plus integral action plus differential action
24-For a type 1 system, the position error arises at steady state when there is a:
A. Constant acceleration input
B. Step displacement input
C. Ramp or velocity input
D. Unit parabolic input
25-The device that can act as a complete electronic circuit is:
A. Zener diode
B. Junction diode
C. Integrated Circuit
D. Junction transistor
26-A Common emitter amplifier has a voltage gain of 50, an input impedance of 100
Ohm and an output impedance of 200 Ohms. The power gain of the amplifier is:
A. 1250
B. 500
C. 100
D. 50
E. 2000

27-The characteristics of a thyristor closely resemble to the characteristics of:
A. PN-junction
B. Constant Voltage Source
C. Constant current source
D. Thyratron gas tube
28-What is the advantage of class A operation of an amplifier
A. High gain
B. Less distortion
C. High efficiency
D. High Adeptness
29-Which of the following is an active device?
A. Electric Bulb
B. Transformer
D. Loudspeaker
30-A tangent galvanometer is:
A. An absolute instrument
B. A secondary instrument
C. A recording instruments
D. An integrating instrument
31-An N-type crystal is:
A. Neutral
B. Negatively charged
C. Positively charged
D. Insufficient information
32-A device which converts mechanical energy into electrical energy is called:
A. Electric generator
B. Transformer
C. Mechanical device
D. Amplifier
33-The Internal voltage drop in case of Silicon diode is around:
A. 2 to 5 volts
B. 0.6 to 0.7 volts
C. 5 to 10 volts
D. 10 to 20 volts
34-The rotating part of a DC generator is known as:
A. Pole
B. Stator
C. Commutator
D. Armature
35-Every chemical element has its own unique type of particle, called its:
A. Molecule
B. Electron
C. Proton
D. Atom
36-Which of the following can be measured by using Hall’s effect?
A. Magnetic field intensity
B. Electric energy
C. Electrostatic field intensity
D. Average number of holes
37-The Potential barrier in germanium p-n junction is:
A. 0.3 volt
B. 0.7 volt
C. 1 volt
D. 0.5 volt
38-A solid state detector mainly consists of a
A. Silicon diode
B. Silicon crystal
C. Transistor
D. Germanium Crystal
39-The series parallel combination of solar cells is known as:
A. Photo-combination cell
B. Photoelectric cell
C. Photovoltaic array
D. Combination diode
40-A binary digital system deals with quantities or variables which have ……….
discrete values or states.
A. 04
B. 03
C. 02
D. 05

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41-The ripple factor is …………for a half wave rectified sine wave.
A. 1.65
B. 1.45
C. 1.21
D. 1.00
42-Who discovered the thermionic emission?
A. Gamow
B. Lee de forest
C. Edison
D. Rutherford
43-In the FET, current flows along a semiconductor path called:
A. Channel
B. Drain
C. Source
D. Junction
44-Lenz’s law is a statement of law of conservation of ………………that can be
conveniently applied to the circuits involving induced currents.
A. Energy
B. Mass
C. Charge
D. Momentum
45-If the speed of shunt motor to be controlled between zero and normal running
speed N, the most practical way to achieve this would be to insert a resistance of
suitable value in:
A. Parallel with the field
B. Series with the field
C. Parallel with the armature
D. Series with the armature
46-A Charged body moving along a circle in magnetic field B=10^-2 T, a mass
m=10^5 Kg, velocity =1 m/s, and charge q= 10^7 coulomb. What is the radius of its
circular track?
A. 0.1 m
B. 10 m
C. 100 m
D. 1.0 m

47-The current generated when a conductor moves across a magnetic field is called:
A. Active emf
B. Effective emf
C. Optimum emf
D. Induced emf
48-Two coils having equal resistances, but different inductances are connected in
series. The time constant of the series combination is the:
A. Sum of the time constants of the individual
B. Average of the time constants of individual coils
C. Product of the time constants of individual coils
D. Geometric mean of the time constants of the individual coils

49-Permeance is the reciprocal of
A. Flux density
B. Resistance
C. Ampere-turns
D. Reluctance
50-A DC shunt motor is running at rated load and speed with rated supply voltage. If
the supply voltage is halved, then the speed of the motor becomes:
A. Slightly more than the rated speed
B. Slightly less than the rated speed
C. Half of the rated speed
D. Double of the rated speed
51-Which of the following is not an integrating instrument?
A. Ampere-hour meter
B. Watt-hour meter
C. Voltmeter
D. Both A & B
52-The main reason for connecting of a pulse transformer at the output stage of the
thyristor triggering circuit is to:
A. Amplify the power of the triggering pulse
B. Provide electrical isolation
C. Reduce the turn on time of the thyristor
D. Avoid spurious triggering of the thyristor due to noise
53-One electron is moving in the electric and magnetic field. It will gain energy
A. Magnetic field
B. Electric field
C. Both A and B
D. Insufficient information
54-The function of the starter of the DC motor is:
A. To limit the starting current
B. To limit the starting voltage
C. To increase the field resistance
D. To reduce armature resistance
55-A battery consists of 44 2-volt cells, each with an internal resistance of 0.12 ohm.
The voltage of each cell has fallen to 1.8 volt. It is a requirement to charge the
battery at a constant current of 4 A from a charger with an internal resistance of 2
ohm. The Applied voltage at the commencement of charge is:
A. 135.15 V
B. 163.43 V
C. 108.32 V
D. 120.67 V
E. 130.33 V
56-The ratio of starting torque to full load torque is minimum in:
A. Shunt motor
B. Series motor
C. Differential compound motor
D. Cumulative compound motor
57-Photon always propagate with speed c, but light comes into view to travel at a
speed diverse from c in an opaque medium. We can explain this fact by
……………in medium by introducing a phase change upon re-radiation.
A. Electron oscillators
B. Discharge Tube
C. Cathode rays
D. Electro-magnetic rays
58-Frog-leg winding is:
A. Same as simplex winding
B. Same as duplex winding
C. Combined lap and wave winding on a single rotor
D. Duplex wave winding on a single rotor
59-In periodic table, semiconductors belong to:
A. Third group
B. Fourth group
C. Fifth group
D. First group
60-In a DC machine without interpoles, to get improved commutation, the brush
shift angle must be:
A. Varied with change in load
B. Kept constant
C. Zero degree
D. 100 degrees
61-If the step response of an initially relaxed system is known, then the ramp
response can be obtained by:
A. Integrating the step response
B. Differentiating the step response twice
C. Integrating the step response twice
D. Differentiating the step response
62-Eddy current losses in a DC machine are given by Bft*V where V stands for:
A. Voltage generated
B. Peripheral velocity
C. Linear velocity of conductors
D. Volume of iron part
63-Second Cauer’s form of reactive network synthesis is the successful removal of
A. Poles at infinity
B. Zeros at Infinity
C. Poles at origin
D. Zeros at origin
64-If residual magnetism of a shunt generator is destroyed accidently, it may be
restored by connecting its shunt field:
A. To earth
B. To an alternator
C. To a battery
D. In reverse
65-The lines of force are circular and their direction depends upon the:
A. Voltage
B. Capacitance
C. Current
D. Resistance

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66-Commutators of 220 V DC generator have brushes which are generally made of:
A. Copper
B. Electro graphite
C. Graphite copper
D. Carbon copper
67-When a number of two port networks are connected in cascade, the individual:
A. H-matrices are multiplied
B. Ysc matrices are added
C. Zoc matrices are added
D. Chain matrices are multiplied
68-In hot wire instruments, the sensing wire is made of:
A. Copper
B. Silver
C. Platinum-iridium
D. Copper-Nickle
69-The direction of induced EMF during electromagnetic induction can be
determined by making use:
A. Lenz’s law
B. Faraday’s law
C. Ampere’s law
D. Laplace law
70-In an inductance AC circuit, the current:
A. Lags the voltage
B. Leads the voltage
C. Is in phase with the voltage
D. Both A and B
71-Capacitive susceptance is expressed in terms of:
A. Farads
B. Siemens
C. Micro-farads
D. Ohms
72-The impedance value of generator is 0.2 pu on a base value of 11Kv, 50 MVA.
The impedance value for a base value of 22KV, 100 MVA is:
A. 0.2 pu
B. 2.4 pu
C. 0.4 pu
D. 0.15 pu

73-A lightning arrester connected in the line and earth in a power system:
A. Reflects back travelling waves approaching it
B. Suppress high frequency oscillations in the line
C. Protects transmission line against direct lightning strokes
D. Protects terminal equipment against travelling surge
74-In frequency modulation, noise components which affect the amplitude can be
eliminated by using:
A. A differentiator
B. An oscillator
C. An FM limiter circuit
D. A mixer
E. A RF amplifier
75-Cost of operation of which of the following plants is least?
A. Gas turbine plant
B. Thermal power plant
C. Nuclear power plant
D. Hydroelectric plant
76-The effect of ice deposition on conductor is
(A) increased skin effect
(B) reduced corona losses
(C) increased weight
(D) reduced sag
77-The protection against direct lightening strokes and high voltage steep waves is
provided by
(A) earthing of neutral
(B) lightening arresters
(C) ground wires
(D) lightening arresters and ground wires
78-The dc compound motors are generally
A. level compound.
B. cumulative compound.
C. differential compound.
D. none of these.
79-Air standard efficiency of a diesel engine depends on
(A) compression ratio
(B) speed
(C) fuel
(D) torque.
80-In power plants cooling towers are used to
(A) cool exhaust steam
(B) cool repeated steam
(C) cool feed water
(D) cool condenser outlet water
81-Skin effect is proportional to
(A) diameter of conductor
(B) (diameter of conductor)1/2
(C) (diameter of conductor )2
(D) (diameter of conductor )2
82-The capacitor switching is easily done with
A) Air blast circuit breaker
B) Oil circuit breaker
C) Vacuum circuit breaker
D) Any one of these
83-The characteristic impedance of a transmission line depends upon
(A) shape of the conductor
(B) surface treatment of the conductors
(C) conductivity of the material
(D) geometrical configuration of the conductors
84-A Short transmission line has equivalent circuit consisting of:
A. Series inductance L and shunt capacitance G
B. Series resistance R and shunt capacitance G
C. Series resistance R and shunt capacitance C
D. Series resistance R and series inductance L
85-Shunt capacitance is usually neglected in the analysis of
(A) Short transmission lines
(B) Medium transmission lines
(C) Long transmission lines
(D) Medium as well as long transmission lines.
86-Super heated steam is always
(A) at a temperature higher than the saturation temperature corresponding to a
steam pressure
(B) at a pressure more than the boiler steam pressure
(C) separated from water particles before being supplied to turbine
(D) at a pressure less than the maximum cycle pressure.

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87-Transmission lines link
(A) service points to consumer premises
(B) distribution transformer to consumer premises
(C) receiving end station to distribution transformer
(D) generating station to receiving end station.
88-A load curve is a plot of
(A) Load versus generation capacity
(B) Load versus current
(C) Load versus time
(D) Load versus cost of power.
89-As compared to steam at entry to the turbine, which of the following will be
larger at exit?
(A) Pressure
(B) Flow rate
(C) Specific volume
(D) Specific enthalpy.
90-Total load transmitted through a 3-phase transmission line is 10,000 kW at 0.8
power factor lagging. The I2
R losses are 900 kW. The efficiency of transmission line
(A) 60% (B) 90% (C) 95% (D) 99%.
91-In high voltage transmission lines the top most conductor is
(A) R-phase conductor (B) Y- phase conductor
(C) B-phase conductor (D) Earth conductor


“The information presented in this blog post has been compiled from various engineering professionals’ accounts on social media platforms. It is intended for informational purposes only and does not necessarily represent official statements or policies of the individuals or organizations mentioned. Readers are encouraged to verify and cross-reference information independently.”

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