ROUGH WORK

1. The approximate voltage supplied by one cell of a lead acid battery is

0·50 V 1·11 V


1·60 V 2·00 V


2. While charging accumulators, the following care should be taken

Connect and disconnect them when the power supply is on


Keep them in well ventilated area


Acid level should be checked


Short the cells to check if they are charged fully


3. Which one of the following acts as a depolarizer in a dry cell

Carbon power Manganese dioxide


Ammonium chloride Zinc chloride


4. A solar cell converts directly

Light energy into electrical energy in dc form


Light energy into electrical energy in ac form


Heat energy into electrical energy in dc form


Heat energy into electrical energy in ac form


5. Four 4 . resistors connected in series is connected in series with a four 4 . resistors connected in parallel. The effective value of resistance is

16 . 15 .


17 . 1 .


6. The rms value of voltage shown in Fig. 1 is 20 V. The equation of voltage is

v 14·14 sin 628 t v -28·28 cos 314 t


v 28·28 cos 314 t v -14·14 cos 628 t
volt




Fig. 1
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7. Given two coupled coils of 20 mH each, then their mutual inductance M satisfies

M 20 mH M 20 mH


M 20 mH M 40 mH


8. The current passing through a coil of resistance 2 . and inductor 2 H is shown in Fig. 2. The energy absorbed by the coil is

Fig. 2

100 Joules 300 Joules


400 Joules 500 Joules


9.
Find the current through the branch A in the network shown in Fig. 3.

10.
The voltage across the coil shown in Fig. 2 is


20 V 10 V


40 V 0 V



11.
When a resistor is connected to a voltage source, it consumes a power of 5 W in the circuit and when the same is connected to a current source having the same magnitude as the voltage source, the power absorbed by is 125 W. The magnitude of the voltage source is


5 V 25 V


12·5 V 62·5 V



12.
A series circuit is connected across a constant voltage and variable frequency supply. When the frequency is varied, the current is maximum and in phase with the voltage, so that the


Voltages across R and LC are equal


Voltages across R and L are equal


Voltages across L and C are equal


Voltages across RL and C are equal



13.
In the circuit shown in Fig. find the value of resistance required for the transfer of maximum power to the load RL having a resistance of 11 ..



Fig. 3
14 A 14 A
15 A 15 A


RL


10/9 . 9/10 .


1/10 . 1/9 .


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14. In a Cathode Ray Oscilloscope, the time base signal is applied to

Y-Plates


X-Plates


either X or Y Plates


both X and Y Plates


15. The voltage and current waveforms of an element are shown in Fig. 5. The value of the element is
2 V
2 A


Fig. 5
2 H
1 H
2 F
1 F

16. The time constant of the network shown in Fig. 6 is

Fig. 6

RC/2 2RC/3


3RC/2 3RC/4


.
17. The Laplace transformation of a function is given by . The final value of s2 +.2
the function is

Zero Infinity


Unity None of the above


18. A balanced delta connected load of j3) . per phase is connected to a 440 50 Hz, 3-phase supply. The kVAR supplied is

69·70 92·93


116·16 87·12


19. The per phase impedance of a R-L load is 20 . at a frequency of 50 Hz, 3-phase supply. If the frequency is decreased, then the power factor

Remains constant Decreases


Increases is unity


20. For a given network of a voltage, 100 sin 2 pf the current is given by 5 sin pf t 30º). The value of inductive reactance is

10v5 . 20 .


10 . 10v3 .


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21. The characteristic equation of a second order system is given by s2 20 . s 100. The Un-damped natural frequency is

100 rad/sec


10 rad/sec


1000 rad/sec


20 rad/sec


22. Signal flow graph is used to obtain the

Transfer function of a system


Stability of a system


Controllability of a system


Observability of a system


23. Which semi-conductor device behaves like two SCRs in anti-parallel

UJT


Triac


Diac


FET


24. In Force-Current analogy, mass is analogous to

Current


Resistance


Capacitance


Voltage


25. Which of the following systems provides excellent transient and steady-state response

Proportional action


Proportional Differential action


Proportional Integral action


Proportional Differential Integral action


100(1+ 0·25s)
26. The transfer function of a system is given by . The corner frequencies
0·5s)
are

4 and 2 4 and 2


0·25 and 0·5 -0·25 and -0·5


27. The number of roots on the equation s3 4s2 s 6 0 that lie in the right half of s-plane is

Three Two


One Zero


28. In phase lead compensation

Both Bandwidth and overshoot decreases


Bandwidth decreases and overshoot increases


Bandwidth increases and overshoot decreases


Both Bandwidth and overshoot increases


29. For a feedback control systems of Type 1 and Type the respective values of steady-state error for ramp input are

Zero and infinite Zero and finite


Finite and zero Infinite and zero


30. The polar plot of a transfer function is shown in Fig. 7. Choose a correct statement from the following
Im G
. 8
Re G
.

The finite zero is closer to the origin than the finite pole


The finite pole is closer to the origin than the zero


The system is unstable


None of the above



31. A dc generator has 8 poles. A mechanical brush shift of 4º means a brush shift of

4º 8º


12º 16º


32. If a 200 V dc generator is run at full speed without any excitation, then its induced emf is

190 V to 200 V 90 to 100 V


2 V to 5 V Zero volt


33. In a dc series motor, at high armatures torques after saturation, the armature current is proportional to

Torque0·5 Torque


Torque1·5 Torque2


34. In dc motors, the electric braking which consumes negative power is

Plugging Counter-current braking


Dynamic braking Regenerative braking


35. A dc series motor drives a load whose torque varies as square of the speed. When the speed is 1000 rpm, the line current is 10 A. If the speed is halved, then the line current is

5 A 10 A


14·14 A 20 A


36. A 220 V dc shunt motor runs at a speed of 800 rpm. If this machine is run as a generator and takes same line current from 220 then the speed will be

Equal to 800 rpm Slightly greater than 800 rpm


Slightly less than 800 rpm Equal to 400 rpm


37. The losses that are proportional to frequency are Eddy current loss Armature copper loss Field copper loss Hysteresis loss

and are true and are true


and are true and are true


38. The test that can be used for the determination of no-load losses in a large dc shunt machine is

Break test Field test


Hopkinson's test Swinburne's test


39. An O.C. test is conducted on a 1 2 voltage ratio of a transformer. When secondary is open, the wattmeter reading on primary is 300 W. If primary is open and O.C. is conducted, the reading on the secondary is

75 W 150 W


300 W 600 W


40. The polarity of transformer is important when

The transformer is switched on with load


The transformer is switched off


The transformer is operated in parallel with another transformer


The transformer is switched on with no-load


41. The total rating of three single phase transformers connected in Delta-delta is 100 kVA. If it is operated in open delta, the total rating will be

70·7 kVA 57·7 kVA


86·6 kVA 100 kVA


42. Salient pole machines have

Large number of poles and small length to diameter ratio


Small number of poles and small length to diameter ratio


Large number of poles and high length to diameter ratio


Small number of poles and high length to diameter ratio


43. A cylindrical pole synchronous machine has maximum power output when the power angle is

Equal to 90º Greater than 90º


Less than 90º Equal to 180º


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44. If the power factor of an alternator is zero lagging, then the armature reaction is

Demagnetizing only Magnetizing only


Cross-magnetizing only Both demagnetizing and cross-magnetizing


45. In a 3-phase induction motor at full load, the ratio of frequency of rotor current to frequency of stator current is equal to

unity 1-slip


2-slip Slip


46. At slip equal to zero and slip equal to nearly zero, the torques developed by a 3-phase induction motor are

Starting torque and full load torque respectively


Starting torque and zero torque respectively


Zero torque and full load torque respectively


Zero torque and starting torque respectively


47. The equivalent rotor resistance of a 3-phase, 4 pole, 50 Hz induction motor referred from stator side is 0·2 . at a full load speed of 1450 rpm. The electrical equivalent of mechanical load is

5·8 . 6·0 .


3·0 . 2·9 .


48. A 2000 kVA, 200 Hz transformer is operated at 50 Hz. At constant flux operation, its kVA rating should be restricted to

8000 1000


500 2000


49. A 3-phase, star connected, 440 50 Hz induction motor is to be operated at 30 Hz. If air-gap flux is to be maintained constant, then the approximate per phase voltage that should be applied is

440 V 254 V


152 V 264 V


50. The running current of a 3-phase induction motor is lower than starting current because

Voltage is low Impedance is low


Slip is high Impedance is high


51. Which one of the following is Maxwell-Faraday's equation
. × D .f . × B 0
.B .D
.× E .× H Jf
.t .t
52. Conductance is analogous to

Flux Reluctance


Permeance Flux density


53. A magnetic circuit requires 1000 AT to produce a certain quantity of flux. If the exciting coil of the magnetic circuit has 100 turns and 10 . resistance, the voltage to be applied to the exciting coil is

1000 V 1 V


10 V 100 V


54. A collapsing field around a coil

Opposes flow of current Aids flow of current


Opposes decay of current Aids decay of current


55. The line integral of the vector potential A around the boundary surface S represents

Flux through surface S Flux density in the surface S


Magnetic density Current density


56. In a uniform electric field, field lines and equi-potentials

Do not intersect Intersect at 45º


Intersect at 90º Intersect at 135º


57. Lightning arrestor is located near to a

generator transformer


bus-bar circuit-breaker


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58. Divergence of the three dimensional radial vector field F is

1/r


3(ˆi ˆj 3


59. An emf of 10 V is induced in a coil of inductance 5 H. The rate of change of current is

50 A/sec 0·5 A/sec


2·0 A/sec 5·0 A/sec


60. An electro-magnetic field is radiated from

A stationary point charge A capacitor with a dc voltage


A conductor carrying a dc current An oscillating dipole


61. 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


62. The difference between the measured value and the true value is called

Gross error Relative error


Probable error Absolute error


63. If the instrument is to have a wide range, the instrument should have

Linear scale Square law scale


Logarithmic scale Exponential scale


64. For measuring rms values of any ac current at high frequency, the instrument that can be used is

Moving iron instrument Moving coil instrument


Thermo-couple instrument Electro-static instrument


65. A switched mode power supply operating at 20 kHz to 100 kHz range uses as the main switching element.

Thyristor Triac


UJT MOSFET


66. In a Megger, controlling torque is provided by

Spring Gravity


Coil Eddy current


67. For measurement of frequency, the suitable bridge is

Schering bridge Maxwell's bridge


Wein bridge All the above


68. The material used for shunts in ac instruments is

Manganin Constantan


Copper Silver


69. The pressure coil of an induction type energy meter is

Highly inductive Highly resistive


Purely inductive Purely resistive


70. The braking torque produced by a permanent magnet in a single phase energy meter is proportional to

Square of the flux of the permanent magnet


Speed of the meter


Distance of permanent magnet from the center of the revolving disc


All the above


71. An energy meter disc makes 10 revolutions in 100 seconds when a load of 500 W is connected to it. The meter constant is

1000 rev/kWh 500 rev/kWh


1440 rev/kWh 720 rev/kWh


72. A CRO screen has ten divisions on the horizontal scale. If a voltage signal v 10 sin (314 t 30º) is examined with a time base setting of 10 msec/division, the number of cycles of signal displayed on the screen will be

1 cycle 5 cycles


2·5 cycles 10 cycles


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73. The X plate and Y plate inputs to a CRO are 10 cos (100 t and 10 sin (100 t respectively. The resulting Lissajous pattern is

An inclined straight line An inclined ellipse


A circle A horizontal line


74. The amplifier used in an electronic voltmeter is

Differential amplifier Buffer amplifier


Power amplifier Wideband amplifier


75. An integrating digital voltmeter measures

peak value average value


rms value all the above


76. Power factor of a synchronous motor can be varied by varying

applied voltage supply frequency


excitation load


77. In 180º mode conduction of 3-phase inverter feeding a 3-phase induction motor, at any given time

Only one device conduct and current flows through two phases


Only two devices conduct and current flows through two phases


Three devices conduct and current flows through three phases


Four devices conduct and current flows through three phases


78. A dc chopper feeds a voltage of 230 V to a separately excited dc motor.The back emf of the motor is 210 V and armature current is discontinuous. During the time the armature current is zero, the armature voltage equal to

230 V 210 V


20 V 440 V


79. A single-phase half wave converter dc drive operates in

First fourth quadrants First quadrant only


First second quadrants Second quadrant only


80. A three-phase semi-converter can work as

Converter for firing angle a 0 to 180º


Converter for firing angle a 0 to 90º


Inverter for firing angle a 90º to 180º


Inverter for firing angle a 0 to 90º


81. If a step-up chopper has a output voltage of 100 V and the duty ratio is then the input voltage is

75 V 133 V


400 V 25 V


82. A voltage source inverter is normally employed when

Source impedance is large and load impedance is small


Source impedance is small and load impedance is large


Source impedance is large and load impedance is large


Source impedance is small and load impedance is small


83. A three-phase induction is fed from a 3-phase inverter which contain predominant 5th and 7th harmonics. Choose a correct statement from the following

Both the 5th 7th harmonics contribute positive sequence torques


Both the 5th 7th harmonics contribute negative sequence torques


5th 7th harmonics contribute negative positive sequence torques


5th 7th harmonics contribute positive negative sequence torques


84. The approximate value of slip of a 3-phase induction motor is unity for fundamental voltage fifth harmonic voltage seventh harmonic voltage

and are true and are true


and are true and are true


85. A 200 single-phase input ac voltage controller gives an output voltage of 128 V with a resistive load. The input power factor is

0·80 0·64


0·5 1·00


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86. For a lossless line, the characteristics impedance is

C/L
LC


L/C 1/LC


87. The surge impedance of a 3-phase 400 kV transmission line is 400 .. The surge impedance
loading is

400 MW 100 MW


1600 kW 400 kW


88. In a overhead transmission line

Sag2/Span constant Sag/Span2 constant


Sag/Span constant Sag×Span constant


89. Equal area criteria is applicable for

Single-machine system Two-machine system


Multi-machine system All the above


90. The transient stability limit of a power system can be appreciably increased by

Series inductance Shunt inductance


Series capacitance Shunt capacitance


91. Reactance relay is normally preferred for protection against

Phase faults Open circuit faults


Earth faults None of the above


92. Resistance switching is normally employed in

Bulk oil breakers Air-blast circuit breakers


Minimum oil breakers All the above


93. In dc circuit breakers, arc quenching is done by

Zero current interruption Low resistance interruption


High resistance interruption Normal resistance interruption


94. The rupturing capacity of a circuit breaker is measured by

Current Voltage


Active power Apparent power


95. A power system is subjected to a fault which makes the zero sequence component of current equal to zero. The nature of fault is

Double line to ground fault


Double line fault


Line to ground fault


Three-phase to ground fault


96. With positive feedback in an amplifier circuit, the gain will

Increase Decrease


Remain constant Decreases first and then remains constant


97. The phenomena of converting mechanical energy into electrical energy and vice-versa using crystals is called

Piezo-conductivity effect Piezo-magnetic effect


Piezo-electric effect Piezo-photo effect


98. In the saturation region, the JFET transfer characteristics are

Exponential Linear


Parabolic Hyperbolic


99. The common base configuration is useful when a is required.

High current gain Low output resistance


Low input resistance High voltage gain


100. Cascading of amplifier stages to obtain high power gain is done with

Common emitter stages


Common base stages


Common collector common emitter stages


Common base common collector stages


101. Vacuum diode can be used as

Detector and rectifier Rectifier and oscillator


Oscillator and Amplifier Amplifier and detector


102. Triode can be used as an amplifier only for

High frequencies Low frequencies


Very high frequencies All the above


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103. An intrinsic semi-conductor at absolute zero

Behaves like a metallic conductor Behaves like an insulator


Has a large number of holes Has a large number of electrons


104. Junction breakdown of a semi-conductor occurs

Because of manufacturing defect Because of high temperature


During forward bias During reverse bias


105. For every 10ºC rise in temperature, reverse current of a Germanium diode practically

Remains constant Becomes half


Doubles Triples


106. A positive clipper circuit always clips

Some part of upper portion of the input signal


Time period input signal


Lower portion of input signal


Both upper and lower portions of input signal


107. In a centre tapped full-wave rectifier, if the peak voltage between the centre tap and one end of secondary is 160 then the maximum voltage across the reverse biased diode is

80 V 160 V


226 V 320 V


108. The ripple factor of a full-wave rectifier without filter is

0·482 1·11


1·21 1·57


109. The function of the base in the transformer is analogous to in the triode.
Plate Cathode
Grid Heater
110. For transistor operation


Emitter-base is forward biased and Collector-base is reverse biased


Emitter-base is reverse biased and Collector-base is forward biased


Both Emitter-base and Collector-base are forward biased


Both Emitter-base and Collector-base are reverse biased


111. The state' MOSFET switch is equivalent to a

Resistor Inductor


Capacitor Battery


112. The Q-point in a voltage amplifier is selected in the middle of the active region so that

It gives distortion—free output


It needs a small dc voltage


The operating point becomes very stable


Power loss is minimum


113. The input signal to an amplifier having a gain of 100 is given by 0·5 sin 314t. The output signal is

100 sin (314 t 180º) 100 cos (314 t 180º)


200 sin (314 t 180º) 50 sin (314 t 180º)


114. A transformer audio amplifier is found to have an overall efficiency of the order of 70% is
a

Class A push-pull amplifier Class B push-pull amplifier


Single-stage class C amplifier Direct coupled amplifier


115. For tuned radio-frequency, the amplifier that can be used is

Class A amplifier Class B amplifier


Class C amplifier Class AB amplifier


116. The Silicon controlled rectifier is a

Three junction, three terminal three layer device


Three junction, three terminal four layer device


Four junction, three terminal three layer device


Four junction, four terminal four layer device


117. If an audio signal of 2 kHz is used to modulate a carrier of 500 kHz, the bandwidth of AM transmission is

2 kHz 1 MHz


250 kHz 4 kHz


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118. In frequency modulation, if depth of modulation is doubled, then power transmitted will become

Double Remain unchanged


One half times 1·41 times


119. The most stable sine-wave oscillator is

Colpitts oscillator Armstrong oscillator


Phase-shift oscillator Crystal oscillator


120. The number of flip-flops required in a decade counter is

Two Three


Four Ten


ROUGH WORK

ROUGH WORK