EIJ-49857-A 1 [Turn over
ROUGH WORK

1. Ohm's law is applicable to

Semi-conductors Vacuum tubes


Electrolytes Semiconductors and Vacuum tubes


2. The resistance between the opposite faces of 1m. cube is found to be 1. . If its length is increased to 2 with its volume remaining the same, then its resistance between the opposite faces along its length is

2 . 4 .


1 . 8 .


3. Three resistances of 3 . each are connected in delta. The value of the resistances in the equivalent star is

1.5 1 .
4. Thevenin's theorem can be applied to network containing

Passive elements only Active elements only


Linear elements only All of these


5. Which of the following is the unit of time constant of an RC network
R×ampere × second

Second
V R ×. idt
All of these
6. A floating battery is one

in which battery voltage is equal to charger voltage


in which the current in the circuit is fully supplied by battery


which gets charged and discharged simultaneously


which supplies current intermittently and also during off cycle gets charged


7. Which of the following statements is not correct

A primary cell is an electro-chemical cell


After charging, a primary cell can be again put to use


Dry cell is a primary cell


Leclanche cell is used in experiments, where constant supply of current is not needed


8. The efficiency of a solar cell can be expected in the range

10 to 15 percent 25 to 30 percent


45 to 60 percent 70 to 80 percent


9. A 10 kW electric motor drives a vehicle at an average speed of 50 Km/h. Ten, 12 100A-h batteries supply the motor, the maximum distance that the vehicle may travel before the batteries must be recharged, will be

30 Km 45 Km


60 Km 80 Km


10. A power factor of incandescent bulb is

0.8 lagging 0.8leading


Unity Zero


11. A high pass filter has a resistance R 2 k.. The lowest input frequency to be passed is 7.5 KHz. The value of suitable coupling capacitor must be

0.1 pF 1 pF


0.1 µ F 1 µ F


12. In the network shown the value of the current supplied by the battery will be


1.17 A 11.7 A


11.7 mA 117 mA


13. In a Circuit, a resistance a pure inductance and a Capacitance C are connected in parallel across a sinusoidal voltage source of V volt. The circuit current will lead the applied voltage if
I
c L c L
Ic IL None of these
s 2
14. For the initial and final values of will be respectively s(s
1 and 1 2 and 1 2 and 2 1 and 2
15. Inverse Laplace transform of 10 10 1 1)s 10 is 10 1 et] 10 1 et]
EIJ-49857-A 4 .

16. Impulse response of an R-L circuit is a

Rising exponential function


Step function


17. For a two port network to be reciprocal
Z
11 22
h
21 12

Decaying exponential function


Parabolic function


Y
21 12
AD BC O
18. In a network containing resistances and reactances the roots of the characteristic equation give for the circuit

The forced response The total response


The natural response The damped response


19. Which of the following is an example of an open loop system

Household refrigerator


Respiratory system of an animal


Stabilisation of air pressure entering into a mask


Execution of a program by a computer


20. The transfer function of a first order control system is of the type
1 1
2
Ts +1 Ts
1
Ts
Ts
21. The response of a system to an input is given by the following differential equation
d2c(t)
3
dt2 dt
The transfer function of the system is given by
5 1

s2 3s 5 s2 3s 5
3s s
2 2
s 3s 5s 3s 5

22. With the feedback system, the transient response

Decays slowly Decays rapidly


Rises slowly Rises quickly


23. A phase-lag compensation will

Improve relative stability


Increase bandwidth


24. In a stable control system saturation may cause

Conditional Stability


Overdamping
1




25. Given, the system stability is
s(1 6s)

Conditional


Marginal



Increase the speed of response


Increase overshoot


High Level Oscillations


Low Level Oscillations


Absolute


Limited


26. The number of roots in the right half of s-plane for the equation s3 4s2 s 6 0 would be


27. If the Nyquist plot cuts the negative real axis at a distance of 0.4, then the gain margin of the
system is

0.4





28. Which input yields natural response

Step input


Impulse input


29. Sinusoidal oscillators are

Stable


Marginally stable



-0.4


2.5


.

Sinusoidal input


Ramp input


Unstable


Conditionally stable


30. If the system specifications are given in time domain, best approach for designing is

Nyquist Plot Bode's Plot


Root Locus None of these


31. The velocity of a travelling electromagnetic wave in free space is given by
µ0 .0
µ0 .0
11



µ. µ.
00 00
32. Maxwell's divergence equation for the magnetic field is given by





33. The electric field lines and equipotential lines

are parallel to each other


cut each other orthogonally


34. The noise temperature of sky is about

100° K


0° K


35. The value of .
dl

Zero


4 p


along a circle of radius 2 units is

2 p


8 p




.·B


are one and the same


can be inclined to each other at any angle


273° K


30º K


36. The unit of µ0 .0 is

Farad Henry Sec2 /meter2


amp sec/volt sec. newton meter2/Coulomb2


.×
B

=.0
· 037. Which one of the statements does not pertain to the equation .B 0
.µ s ·
. ·

There are no sinks and sources for magnetic fields


Magnetic field is perpendicular to the electric field


Single magnetic pole cannot exist


B is solenoidal


38. An air filled rectangular waveguide has dimensions 6 cm, 4 cm. The cut off frequency for TE10 is

2.5 GHz 25 GHz


25 MHz 5 GHz


39. The intrinsic impedance of a lossy dielectric medium is given by

. .e µ


. .µ j .e
µ e


40. The equation V·j 0 is known as

Poissons's equation Laplace equation


Continuity equation Maxwell equation


41. Which of the following relations is correct




All of the above


42. If q stand for voltage, energy and charge then V can be expressed as dw
V

dq
dw dq
dV dV
dq dw
43. A null type of instrument as compared to a deflection type instrument has

a higher accuracy a lower sensitivity


a faster response all of the above


44. The usage of electronic instruments is becoming more extensive because they have

a high sensitivity and reliability


a fast response and compatibility with digital computers


the capability to respond to signals from remote places


all of the above


45. The input resistance of a Cathode ray Oscilloscope is of the order of

tens of ohm mega ohm


kilo ohm fraction of an ohm


46. An 0-10 A ammeter has a guaranteed accuracy of of full scale deflection. The limiting error while reading 2.5 A is




None of the above


47. A set of readings has a wide range and therefore it has

Low precision High precison


Low accuracy High accuracy


48. The voltage of a circuit is measured by a voltmeter having an input impedance comparable with the output impedance of the circuit thereby causing error in voltage measurement. This error may be called

Gross error Random error


Error caused by misuse of instrument Error caused by loading effect


49. The most stable primary atomic standard for frequency is

Caesium beam standard Hydrogen maser standard


Quartz standard Rubidium vapour standard


50. The material of wires used for making resistance standards is usually

Manganin Nichrome


Copper Phosphor Bronze


51. In a flux meter

the controlling torque is produced by weights attached to moving coil


the controlling torque is produced by springs


there is no controlling torque


none of the above


52. The relative damping in a galvanometer is 0.8. Its logarithmic decrement is approximately

0.48 1.25


4.19 -4.19


53. The power consumption in PMMC instruments is typically about

0.25 W to 2W 0.25 mW to 2 mW


25 µ W to 200 W None of the above


µ 54. A meggar is used for measurement of

low valued resistances


medium valued resistances


high valued resistances, particularly insulation resistance


all of the above


55. The moving iron voltmeters indicate

the same value for d.c. and a.c. voltages


lower values for a.c. voltages than for corresponding d.c. voltages


higher values for a.c. voltages than for corresponding d.c. voltages


none of the above


56. Electronic Voltmeters which use rectifiers employ negative feedback, this is done

to increase the overall gain to improve stability


to overcome non-linearity of diodes none of the above


57. A true rms reading Voltmeter uses two thermocouples in order

to increase sensitivity


that the second thermocouple cancels out the non-linear effects of the first thermocouple


to prevent drift in the d.c. amplifier


all of the above


58. In an electronic ohm meter, an OP-Amp is used as

Summer Multiplier


Buffer amplifier Integrator


59. A vertical amplifier for a CRO can be designed for

Only a high gain Only a broad bandwidth


A constant gain times bandwidth product All of the above


60. In CRT the focusing anode is located

between pre-accelerating and accelerating anodes


after accelerating anode


before pre-accelerating anode


none of the above


61. In a communications system, noise is most likely to affect the signal

at the transmitter in the channel


in the information source at the destination


62. Which of the following statements is true

Random noise power is inversely proportional to bandwidth


Flicker is sometimes called demodulation noise


Noise in mixers is caused by inadequate image frequency rejection


A random voltage across a resistance cannot be calculated


63. In a low-level AM system, amplifiers following the modulated stage must be

linear devices harmonic devices


class C amplifiers non-linear devices


64. A carrier is simultaneously modulated by two sine waves with modulation indices of 0.3 and 0.4; the total modulation index

is 1


cannot be calculated unless the phase relations are known


is 0.5


is 0.7


EIJ-49857-A 10
65. To provide two or more voice circuits with the same carrier, it is necessary to use

ISB Carrier reinsertion


SSB with pilot carrier Lincompex


66. One of the following cannot be used to remove the unwanted sideband in SSB, this is the

Filter system Phase-shift method


Third method Balanced modulator


67. Indicate which one of the following is not an advantage of FM over AM

Better noise immunity is obtained Lower bandwidth is required


The transmitted power is more useful Less modulating power is required


68. To prevent overloading of the last IF amplifier in a receiver, one should use

Squelch Variable sensitivity


Variable selectivity Double Conversion


69. To couple a coaxial line to a parallel-wire line, it is best to use a

Slotted line Balun


Directional coupler Quarter-wave transformer


70. High frequency waves are

absorbed by the F2 layer


reflected by the D-layer


capable of use for long distance communications on the moon


affected by the solar cycle


71. After a target has been acquired, the best scanning system for tracking is

Nodding Spiral


Conical Helical


72. Semiconductors have electrical conductivity of the order of

10-15 S/m 10-10 S/m


1.0 S/m 105 S/m


73. In an ac amplifier, smaller the internal resistance of the ac signal source

Larger the current gain Smaller the circuit voltage gain


Larger the circuit voltage gain and both


74. In an amplifier, the coupling capacitors are employed for

limiting the bandwidth


matching the impedances


controlling the output


preventing of dc mixing with input or output


75. A diac is equivalent to

Pair of Diodes Triac with two gates


Pair of four-layer SCRs Diode with two transistors


76. Silicon steel is used for transformer core because

it reduces hysteresis loss it reduces eddy current loss


it increases core permeability all of the above


77. The core in a large power transformer is built of

Cast iron Mild steel


Ferrite Silicon steel


78. A 400/200 V transformer has a pu impedance of 0.05. The HV side voltage required to circulate full load current during short circuit test is

40 V 20 V


10 V 5 V


79. Phase relationship between mmf phasor and emf phasor in a synchronous machine is

leads by 90°


lags by 90°


and are in phase


This angle depends upon the pf of the load


80. Why is it necessary to provide compensating winding in a DC motor

To help achieve good commutation


To prevent a large speed drop


To prevent commutator flash over upon sudden change in load


To reduce the main field ampere-turns


81. A synchronous motor with 5 . synchronous reactance draws a leading current of 10 A at 400 V. The induced emf is
400 j
3× 50

400
3× 50 400
3× 50


EIJ-49857-A 12
82. Which of the following statements is correct

Xd and Xq are different in a round rotor machine at lagging pf only


Xd and Xq are different in a round rotor machine at any pf


Xd and Xq are different in a salient pole machine at lagging pf only


Xd and Xq are different in a salient pole machine at any pf


83. If stator impedance is neglected, the maximum torque in an induction motor occurs at a rotor resistance of

x2 x2


sx2 x2


84. At low slip the torque slip characteristic is
T a 12 a S2
s

1
T a s
T a
s
85. A full-pitched coil in a 6-pole machine has a mechanical angle span of

30° 60°


90° 180°


86. A 230 V dc series motor is connected to 230 V ac, it will

runslowly not run at all


run with less efficiency none of these


87. In a 25-KVA 3300/230 single phase transformer the iron and full load copper losses are 350 W and 400 W respectively. The load at which the efficiency will be maximum is

25 KW 21.875 KW


25 KVA 21.875 KVA


88. A 6 pole induction motor operates on 440 50Cls supply. If the actual speed of the motor is 960 rpm, the slip will be




0.4%


89. When an induction motor runs at rated load and speed, the iron losses are

negligible very heavy


independent of supply frequency independent of supply voltage


90. Which of the following transformers is smallest

1 KVA, 50Hz 1 KVA, 200Hz


1 KVA, 400Hz 1 KVA, 600Hz


91. Two mechanically coupled alternators deliver power at 50 Hz and 60 Hz respectively. The highest speed of the alternator is

3600 rpm 3000 rpm


600 rpm 500 rpm


92. Synchronous speed is defined as the speed at which the

stator magnetic field rotates


rotor rotates on full load


93. The losses that occur in an induction motor are

stator copper loss


windage and friction losses


94. Lightning arrester should be located

away from the circuit breaker


away from the transformer


95. Corona loss is maximum in:

ACSR


unstranded wire



rotor rotates on no load


none of the above


stator iron loss


all of the above


near the circuit breaker


near the transformer


stranded wire


transposed wire


96. For a load flow solution the quantities normally specified at a voltage controlled bus are

P and Q P and


Q and P and d


97. Mho relay is normally used for protection of

Long transmission lines Medium length lines


Short length lines None of these


98. The voltages at the two ends of a line are 132 KV and its reactance is 40 ohms. The capacity of the line is

435.6 MW 217.5 MW


251.5 MW 500 MW


99. For stability and economic reasons we operate the transmission line with power angle in the range

10° to 25° 30° to 45°


60° to 75° 65° to 80°


100. Ferranti effect on long overhead lines is experienced when it is

On full load at unity pf Lightly loaded


On full load at 0.8 pf lag In all these cases


101. Load flow study is carried out for

Fault Calculations Stability Studies


System Planning LoadFrequencyControl


102. A transformer rated for 500 KVA, 11 KV/0.4 KV has an impedance of 10% and is connected to an infinite bus. The fault level of the transformer is

500 KVA 5000 KVA


None of these


103. In a pure LC parallel circuit under resonance condition, current drawn from the supply mains is
Very large V
LC


LC Zero


104. The insulation of modern EHV lines is designed based on

The lighting voltage Corona


Radio Interference SwitchingVoltage


105. Severe over-voltages are produced during arcing faults in a power system with the neutral
isolated solidly earthed
500
3 KVA
earthed through a low resistance none of these
106. The zero sequence impedance of different elements of power system is generally

equal zero


different none of these


107. Resistance switching is used in

Bulk oil circuit breakers Minimum oil circuit breakers


Air blast circuit breakers All types of breakers


108. Surge protector provides

high impedance to normal voltage low impedance to surge


both and none of these


109. Thermal protection switch is able to protect against

overload over voltage


temperature short circuit

110. Which type of plant has the minimum running cost per KWh of energy generated


dc saturation of transformer care is minimised


Hydro-Electric Plant Thermal Power Plant
Nuclear Power Plant Diesel Power Plant
111. In resonant pulse inverters
dc output voltage variation is wide
the frequency is low
the output voltage is never sinusoidal

112. The effect of d.c. saturation in a rectifier transformer is

to decrease the output


to increase the output


to decrease the a.c. components of the output


none of the above


113. In a 3-f half-wave rectifier, each diode conducts for a duration of

180° 30°


60° 45°


114. A converter which can operate in both 3-pulse and 6-pulse modes is a

1-f full converter 3-f half wave convertor


3-f semi converter 3-f full converter


115. A 1-f full bridge inverter can operate in load-commutation mode in case load consists of

RLC overdamped RLC underdamped


RLC critically damped None of these


116. In circulating-current type of dual converter, the nature of voltage across reactor is

alternating pulsating


direct triangular


117. In a 3-f full converter, the output voltage pulsates at a frequency equal to

Supply frequency, f 2f


3f 6f


118. In a single pulse modulation of PWM inverters, the pulse width is 120°. For an input voltage of
220V dc, the rms value of output voltage is
179.63 V 254.04 V
127.02 V None of these

EIJ-49857-A 16
119. In a dual converter, converters 1 and 2 work as under

1 as rectifier, 2 as inverter both as rectifiers


both as inverter none of these


120. In a constant source inverter, if frequency of output voltage is f Hz. Then frequency of voltage input to constant source inverter is

3f 4f
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ROUGH WORK