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lectrical ngineering Objective Questions

Page 2

1. The two windings of a transformer is

A. conductively linked

B. inductively linked

C. not linked at all

D. electrically linked

2. A salient pole synchronous motor is running at no load. Its field current is switched off. The motor

will

A. come to stop

B. continue to run at synchronous speed

C. continue to run at a speed slightly more than the synchronous speed

D. continue to run at a speed slightly less than the synchronous speed

3. The DC series motor should always be started with load because

A. at no load, it will rotate at dangerously high speed

B. it will fail to start

C. it will not develop high starting torque

D. all is true

4. In a stepper motor the angular displacement

A. can be precisely controlled

B. it cannot be readily interfaced with microcomputer based controller

C. the angular displacement cannot be precisely controlled

D. it cannot be used for positioning of work tables and tools in NC machines

5. The power factor of a squirrel cage induction motor is

A. low at light load only

B. low at heavy load only

C. low at light and heavy load bothD. low at rated load only

6. The generation voltage is usually

A. between 11 KV and 33 KV

B. between 132 KV and 400 KV

C. between 400 KV and 700 KV

D. none of the above

7. When a synchronous motor is running at synchronous speed, the damper winding produces

A. damping torque

B. eddy current torque

C. torque aiding the developed torque

D. no torque

8. If a transformer primary is energized from a square wave voltage source, its output voltage will be

A. a square wave

B. a sine wave

C. a triangular wave

D. a pulse wave


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Page 3

9. In a DC series motor the electromagnetic torque developed is proportional to

A. Ia

B. Ia2

C. 1/Ia

D. 1/Ia2

10. In a three phase induction motor running at slip ‘s’ the mechanical power developed in terms of air

gap power Pg is

A. (s-1)Pg

B. Pg/(1-s)

C. (1-s)Pg

D. (s)(Pg)

11. In a three phase induction motor the maximum torque

A. is proportional to rotor resistance r2

B. does not depend on r2

C. is proportional to sq. rt of r2

D. is proportional to r22

12. In a DC machine, the armature MMF is

A. stationary w.r.t. armature

B. rotating w.r.t. field

C. stationary w.r.t. field

D. rotating w.r.t. brushes

13. In a transformer the voltage regulation will be zero when it operates at

A. unity p.f.

B. leading p.f.

C. lagging p.f.D. zero p.f. leading

14. The maximum power in cylindrical and salient pole machines is obtained respectively at load angles

of

A. 90o, 90o

B. < 90o, 90o

C. 90o, > 90o

D. 90o, < 90o

15. The EMF induced in the primary of a transformer

A. is in phase with the flux

B. lags behind the flux by 90 degree

C. leads the flux by 90 degree

D. is in phase opposition to that of flux


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Page 4

16. The current from the stator of an alternator is taken out to the external load circuit through

A. slip rings

B. commutator segments

C. solid connections

D. carbon brushes

17. A motor which can conveniently be operated at lagging as well as leading power factors is the

A. squirrel cage induction motor

B. wound rotor induction motor

C. synchronous motor

D. DC shunt motor

18. A hysteresis motor

A. is not a self-starting motor

B. is a constant speed motor

C. needs dc excitation

D. cannot be run in reverse speed

19. The most suitable servomotor for low power applications is

A. a DC series motor

B. a DC shunt motor

C. an AC two-phase induction motor

D. an AC series motor

20. The size of a conductor used in power cables depends on the

A. operating voltage

B. power factor

C. current to be carried

D. type of insulation used

21. Out of the following methods of heating the one which is independent of supply frequency is

A. electric arc heating

B. induction heating

C. electric resistance heating

D. dielectric heating

22. In a DC shunt motor the terminal voltage is halved while the torque is kept constant. The resulting

approximate variation in speed 'ω' and armature current ' Ia ' will be

A. Both ω and Ia are doubled

B. ω is constant and Ia is doubled

C. ω is doubled while Ia is halved

D. ω is constant but Ia is halved


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Page 5

23. An alternator is delivering rated current at rated voltage and 0.8 power-factor lagging case. If it is

required to deliver rated current at rated voltage and 0.8 power-factor leading, the required

excitation will be

A. less

B. more

C. more or less

D. the same

24. A ceiling fan uses

A. split-phase motor

B. capacitor start and capacitor run motor

C. universal motor

D. capacitor start motor

25. A stepper motor is

A. a DC motor

B. a single-phase ac motor

C. a multi-phase motorD. a two phase motor

26. The ‘sheath’ is used in cable to

A. provide strength to the cable

B. provide proper insulation

C. prevent the moisture from entering the cable

D. avoid chances of rust on strands

27. The drive motor used in a mixer-grinder is a

A. DC motor

B. induction motorC. synchronous motor

D. universal motor

28. In a three phase synchronous motor

A. the speed of stator MMF is always more than that of rotor MMF

B. the speed of stator MMF is always less than that of rotor MMF

C. the speed of stator MMF is synchronous speed while that of rotor MMF is zero

D. rotor and stator MMF are stationary with respect to each other

29. In a capacitor start single-phase induction motor, the capacitor is connected

A. in series with main winding

B. in series with auxiliary winding

C. in series with both the windings

D. in parallel with auxiliary winding


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Page 6

30. A synchro has

A. a three phase winding on rotor and a single-phase winding on stator

B. a three phase winding on stator and a commutator winding on rotor

C. a three phase winding on stator and a single-phase winding on rotor

D. a single-phase winding on stator and a commutator winding on rotor

31. As the voltage of transmission increases, the volume of conductor

A. increases

B. does not change

C. decreases

D. increases proportionately

32. The size of the feeder is determined primarily by

A. the current it is required to carry

B. the percent variation of voltage in the feeder

C. the voltage across the feeder

D. the distance of transmission

33. The boundary of the protective zone is determined by the

A. location of CT

B. sensitivity of relay used

C. location of PT

D. none of these

34. In a three phase transformer, if the primary side is connected in star and secondary side is

connected in delta, what is the angle difference between phase voltages in the two cases?

A. delta side lags by -30°

B. star side lags by -30°

C. delta side leads by 30°D. star side leads by -30°

35. To achieve low PT error, the burden value should be ____________.

A. low

B. high

C. medium


36. The synchronous reactance of the synchronous machine is ______________.

A. ratio between open circuit voltage and short circuit current at constant field current

B. ratio between short circuit voltage and open circuit current at constant field current

C. ratio between open circuit voltage and short circuit current at different field current

D. ratio between short circuit voltage and open circuit current at different field current

37. In case of a universal motor, torque pulsation is minimized by _________.

A. load inertia

B. rotor inertia

C. both rotor and load inertia



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Page 8

45. An AC tachometer is just ________with one phase excited from the carrier frequency.

A. a two-phase AC servomotor

B. a two-phase induction motor

C. an AC operated universal motor

D. a hybrid stepper motor

46. The torque, in a _____________is proportional to the square of the armature current

A. DC shunt motor

B. stepper motor

C. two phase servomotor

D. DC series motor

47. The maximum power for a given excitation in a synchronous motor is developed when the power

angle is equal to

A. 0o

B. 45o

C. 60o

D. 90o

48. A commutator in a DC machine

A. reduces power loss in armature

B. reduces power loss in field circuit

C. converts the induced AC armature voltage into direct voltage

D. is not necessary

49. The speed of a DC shunt motor at no-load is ____________ higher than its speed at rated load.

A. 5 to 10%

B. 15 to 20%

C. 25 to 30%D. 35 to 40%

50. The efficiency of a transformer is mainly dependent on

A. core losses

B. copper losses

C. stray losses

D. dielectric losses

51. When two transformers are operating in parallel, they will share the load as under:

A. proportional to their impedances

B. inversely proportional to their impedances

C. 50% - 50%

D. 25%-75%

52. If the voltage is reduced to half, the torque developed by an induction motor will be reduced to

A. ¼ of original torque

B. ½ of original torque

C. 1/8 of original torque

D. 1/16 of original torque


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Page 9

53. If the phase angle of the voltage coil of a directional relay is 50o, the maximum torque angle of the

relay is

A. 130o

B. 100o

C. 50o

D. 25o

54. A 220/440 V, 50 Hz, 5 KVA, single phase transformer operates on 220V, 40Hz supply with secondary

winding open circuited. Then

A. both eddy current and hysteresis losses decreases

B. both eddy current and hysteresis losses increases

C. eddy current loss remains the same but hysteresis loss increases

D. eddy current loss increases but hysteresis loss remains the same

55. Which of the following may be value of resistivity of copper?

A. 1.7 X 10 – 6

B. 1.7 X 10 – 5

C. 1.7 X 10 – 4 D. 1.7 X 10

– 3

56. The introduction of inter poles in between the main pole improves the performance of DC machines,

because

A. the inter pole produces additional flux to augment the developed torque.

B. the flux waveform is improved with reduction in harmonics.

C. the inequality of air flux on the top and bottom halves of armature is removed.

D. a counter EMF is induced in the coil undergoing commutation.

57. The direction of rotation of hysteresis motor is reversed by

A. shift shaded pole with respect to main poleB. reversing supply lead

C. either A or B

D. neither A nor B

58. Low head plants generally use

A. Pelton Turbines

B. Francis Turbine

C. Pelton or Francis Turbine

D. Kaplan Turbines

59. Electric ovens using heating elements of _______________ can produce temperature up to 3000°C.

A. nickel

B. graphite

C. chromium

D. iron


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devilbat of symbianizedotcom Page 1

60. In DC generators, armature reaction is produced actually by

A. its field current

B. armature conductors

C. field pole winding

D. load current in armature

61. Two transformers operating in parallel will share the load depending upon their

A. rating

B. leakage reactance

C. efficiency

D. per-unit impedance

62. As compared to shunt and compound DC motors, the series DC motor will have the highest torque

because of its comparatively ____________ at the start.

A. lower armature resistance

B. stronger series field

C. fewer series turns

D. larger armature current

63. Reduction in the capacitance of capacitor-start motor, results in reduced

A. noise

B. speed

C. starting torque

D. armature reaction

64. Regenerative braking

A. can be used for stopping a motor

B. cannot be easily applied to DC series motors

C. can be easily applied to DC shunt motorsD. cannot be used when motor load has overhauling characteristics

65. At present level of technology, which of the following method of generating electric power from sea

is most advantageous?

A. tidal power

B. ocean thermal energy conversion

C. ocean currents

D. wave power

66. If the field circuits of an unloaded salient pole synchronous motor gets suddenly open circuited, then

A. the motor stops

B. it continues to run at the same speed

C. it runs at the slower speed

D. it runs at a very high speed


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Page 11

67. Electric resistance seam welding uses __________ electrodes.

A. pointed

B. disc

C. flat

D. domed

68. For LV applications (below 1 kV), ______________ cables are used.

A. paper insulated

B. plastic

C. single core cables

D. oil filled

69. No load current in a transformer:

A. lags the applied voltage by 90°

B. lags the applied voltage by somewhat less than 90°

C. leads the applied voltage by 90°

D. leads the applied voltage by somewhat less than 90°

70. In a salient pole synchronous machine (usual symbols are used):

A. x q > x d

B. x q = x d

C. x q


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Page 12

75. The line trap unit employed in carrier current relaying:

A. offers high impedance to 50 Hz power frequency signal

B. offers high impedance to carrier frequency signal

C. offers low impedance to carrier frequency signal

D. both A & C

76. For a line voltage V and regulation of a transmission line R

A. R α V

B. R α (1/V)

C. R α V2

D. R α (1/V2)

77. The breakdown mechanism in a lightly doped p-n junction under reverse biased condition is called

A. avalanche breakdown

B. zener breakdown

C. breakdown by tunneling

D. high voltage breakdown

78. In a CE-connected transistor amplifier with voltage-gain A , the capacitance Cbc is amplified by a

factor

A. Av

B. 1 + Av

C. sq. rt. of (1 + Av)

D. Av2

79. For a large values of |VDS|, a FET behaves as

A. voltage controlled resistor

B. current controlled current source

C. voltage controlled current sourceD. current controlled resistor

80. Removing bypass capacitor across the emitter leg resistor in a CE amplifier causes

A. increase in current gain

B. decrease in current gain

C. increase in voltage gain

D. decrease in voltage gain

81. For an op-amp having differential gain A and common-mode gain Ac the CMRR is given by

A. Av + Ac

B. Av / Ac

C. (Av / Ac) + 1

D. Ac / Av

82. When a step-input is given to an op-amp integrator, the output will be

A. a ramp

B. a sinusoidal wave

C. a rectangular wave

D. a triangular wave with DC bias


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Page 13

83. Hysteresis is desirable in Schmitt-trigger, because

A. energy is to be stored/discharged in parasitic capacitances

B. effects of temperature would be compensated

C. devices in the circuit should be allowed time for saturation and desaturation

D. it would prevent noise from causing false triggering

84. In a full-wave rectifier without filter, the ripple factor is

A. 0.482

B. 1.21

C. 1.79

D. 2.05

85. The minimum number of flip-flops required to construct a mod-75 counter is

A. 5

B. 6

C. 7

D. 8

86. Space charge region around a p-n junction

A. does not contain mobile carriers

B. contains both free electrons and holes

C. contains one type of mobile carriers depending on the level of doping of the p or n regions

D. contains electrons only as free carriers

87. The important characteristic of emitter-follower is

A. high input impedance and high output impedance

B. high input impedance and low output impedance

C. low input impedance and low output impedance

D. low input impedance and high output impedance

88. In a JFET, at pinch-off voltage applied on the gate

A. the drain current becomes almost zero

B. the drain current begins to decrease

C. the drain current is almost at saturation value.

D. the drain-to-source voltage is close to zero volts

89. When an amplifier is provided with current series feedback, its

A. input impedance increases and output impedance decreases

B. input and output impedances both decrease

C. input impedance decreases and output impedance increases

D. input and output impedances both increase

90. The open-loop gain of an op-amp available in the market may be around.

A. 10 –1

B. 10

C. 105

D. 102


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91. The control terminal (pin5) of 555 timer IC is normally connected to ground through a capacitor

(~0.01μF). This is to

A. protect the IC from inadvertent application of high voltage

B. prevent false triggering by noise coupled onto the pin

C. convert the trigger input to sharp pulse by differentiation

D. suppress any negative triggering pulse

92. The value of ripple factor of a half-wave rectifier without filter is approximately

A. 1.2

B. 0.2

C. 2.2

D. 2.0

93. The fan-out of a MOS-logic gate is higher than that of TTL gates because of its

A. low input impedance

B. high output impedance

C. low output impedance

D. high input impedance

94. In an intrinsic semiconductor, the Fermi-level is

A. closer to the valence band

B. midway between conduction and valence band

C. closer to the conduction band

D. within the valence band

95. The reverse – saturation current of a silicon diode

A. doubles for every 10°C increase in temperature

B. does not change with temperature

C. halves for every 1°C decrease in temperatureD. increases by 1.5 times for every 2°C increment in temperature

96. The common collector amplifier is also known as

A. collector follower

B. base follower

C. emitter follower

D. source follower

97. In class –A amplifier, the output current flows for

A. a part of the cycle or the input signal

B. the full cycle of the input signal

C. half the cycle of the input signal

D. 3/4th of the cycle of the input signal

98. In an amplifier with negative feedback

A. only the gain of the amplifier is affected

B. only the gain and bandwidth of the amplifier are affected

C. only the input and output impedances are affected

D. All of the four parameters mentioned above would be affected


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99. Wien bridge oscillator can typically generate frequencies in the range of

A. 1KHz – 1MHz

B. 1 MHz – 10MHz

C. 10MHz – 100MHz

D. 100MHz – 150MHz

100. A differential amplifier, amplifies

A. and mathematically differentiates the average of the voltages on the two input lines

B. and differentiates the input waveform on one line when the other line is grounded

C. the difference of voltages between the two input lines

D. and differentiates the sum of the two input waveforms

101. The transformer utilization factor of a half-wave rectifier is approximately

A. 0.6

B. 0.3

C. 0.9

D. 1.1

102. It is required to construct a counter to count up to 100 (decimal). The minimum number of flip-

flops required to construct the counter is

A. 8

B. 7

C. 6

D. 5

103. The power conversion efficiency of an output stage is defined as_______.

A. (load power + supply power) / supply power

B. (load power + supply power) / (load power - supply power)

C.load power / supply power

D. supply power / load power

104. A highly stable resonance characteristic is the property of a ____ oscillator.

A. Hartley

B. Colpitts

C. Crystal

D. Wien bridge

105. The gate that assumes the 1 state, if and only if the input does not take a 1 state is called

________.

A. AND gate

B. NOT gate

C. NOR gate

D. Both B & C


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106. The width of depleted region of a PN junction is of the order of a few tenths of a

___________.

A. millimeter

B. micrometer

C. meter

D. nanometer

107. For NOR circuit SR flip flop the not allowed condition is ________.

A. S=0, R=0

B. S=0, R=1

C. S=1, R=1

D. S=1, R=0

108. In negative feedback the return ratio is __________.

A. 0

B. 1

C. greater than 0

D. greater than 1

109. A phase shift oscillator uses __________________.

A. LC tuning

B. piezoelectric crystal

C. balanced bridge

D. variable frequency operation

110. The voltage gain of basic CMOS is approximately _________.

A. (gmro)/2

B. 2gmro

C. 1 / (2gmro)D. 2ro / gm

111. Transistor is a

A. current controlled current device

B. current controlled voltage device

C. voltage controlled current device

D. voltage controlled voltage device

112. A bistable multivibrator is a

A. free running oscillator

B. triggered oscillator

C. saw tooth wave generator

D. crystal oscillator

113. For a JFET, when VDS is increased beyond the pinch off voltage, the drain current

A. increases

B. decreases

C. remains constant.

D. first decreases and then increases


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114. The type of power amplifier which exhibits crossover distortion in its output is

A. Class A

B. Class B

C. Class AB

D. Class C

115. The main advantage of a crystal oscillator is that its output is

A. 50Hz to 60Hz

B. variable frequency

C. a constant frequency

D. DC

116. The lowest output impedance is obtained in case of BJT amplifiers for

A. CB configuration

B. CE configuration

C. CC configuration

D. CE with RE configuration

117. N-channel FETs are superior to P-channel FETs, because

A. they have higher input impedance

B. they have high switching time

C. they consume less power

D. mobility of electrons is greater than that of holes

118. The upper cutoff frequency of an RC coupled amplifier mainly depends upon

A. coupling capacitor

B. emitter bypass capacitor

C. output capacitance of signal source

D. inter-electrode capacitance and stray shunt capacitance

119. Just as a voltage amplifier amplifies signal-voltage, a power amplifier

A. amplifies power

B. amplifies signal current

C. merely converts the signal ac power into the dc power

D. merely converts the dc power into useful ac power

120. A radio frequency signal contains three frequency components, 870 KHz, 875 KHz and

880 KHz. The signal needs to be amplified. The amplifier used should be

A. audio frequency amplifier

B. wide band amplifier

C. tuned voltage amplifier

D. push-pull amplifier

121. An oscillator of the LC type that has a split capacitor in the circuit is

A. Hartley oscillator

B. Colpitts oscillator

C. Wien bridge oscillator

D. R-C phase shift oscillator


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Page 18

122. The function of a bleeder resistor in a power supply is

A. the same as that of load resistor

B. to ensure a minimum current drain in the circuit

C. to increase the output dc voltage

D. to increase the output current

123. In a bistable multivibrator circuit, commutating capacitor is used

A. to increase the base storage charge

B. to provide ac coupling

C. to increase the speed of response

D. to provide the speed of oscillations

124. n-type silicon is obtained by

A. doping with tetravalent element

B. doping with pentavalent element

C. doping with trivalent element

D. doping with a mixture of trivalent and tetravalent element

125. In the voltage range, Vp < VDS < BVDSS of an ideal JFET or MOSFET

A. The drain current varies linearly with VDS.

B. The drain current is constant.

C. The drain current varies nonlinearly with VDS.

D. The drain current is cut off.

126. In a voltage shunt negative feedback amplifier system, the input resistance Ri and the output

resistance Ro of the basic amplifier are modified as follows:

A. Ri is decreased and Ro increased

B. both Ri and Ro are decreased

C. both Ri and Ro are increasedD. Ri is increased and Ro is decreased

127. The use of crystal in a tunable oscillator

A. improves frequency stability

B. increases the gain of the oscillator

C. helps to obtain optimum output impedance

D. facilitates generation of wide range of frequencies

128. The large signal bandwidth of an operational amplifier is limited by its

A. Loop gain

B. slew rate

C. output impedance

D. input frequency

129. Rectification efficiency of a full wave rectifier without filter is nearly equal to

A. 51%

B. 61%

C. 71%

D. 81%


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130. When the temperature of a doped semiconductor is increased, its conductivity

A. decreases

B. increases

C. does not change

D. increases or decreases depending on whether it is p or n type

131. The main characteristics of a Darlington Amplifier are

A. high input impedance, high output impedance and high current gain

B. low input impedance, low output impedance and low voltage gain

C. high input impedance, low output impedance and high current gain

D. low input impedance, low output impedance and high current gain

132. The transconductance, gm, of a JFET is computed at constant VDS, by the following:

A. ΔID / ΔVGS

B. ΔVGS / ΔID

C. ΔVGS x ΔID

D. ΔID / (ΔVGS + ΔIDS)

133. The feedback factor β at the frequency of oscillation of a Wien bridge oscillator is

A. 3

B. 1/3

C. 1/29

D.-3/29

134. In an amplifier with negative feedback, the bandwidth is (where A = gain of the basic amplifier and

β = feedback factor)

A. increased by a factor of β

B. decreased by a factor of β

C. increased by a factor of (1+A β) D. not affected at all by the feedback

135. The ‘slew rate’ of an operational amplifier indicates ____________ ___ when a step input signal is

given.

A. how fast its output current can change

B. how fast its output impedance can change

C. how fast its output power can change

D. how fast its output voltage can change

136. In a clamping circuit, the peak-to peak voltage of the waveform being clamped is

A. affected by the clamping

B. not affected by the clamping

C. determined by the clamping voltage value

D. determined by the ratio of rms voltage of the waveform and the clamping voltage


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137. Regulation of a DC power supply is given by

A. product of no-load output voltage and full-load current

B. ratio of full-load output voltage and full-load current

C. change in output voltage from no-load to full-load

D. change in output impedance from no-load to full-load

138. A ‘literal’ in Boolean Algebra means

A. a variable in its uncomplemented form only

B. a variable with its complement

C. a variable in its complemented form only

D. a variable in its complemented or uncomplemented form

139. In an unclocked R-S flip-flop made of NOR gates, the forbidden input condition is

A. R = 0, S = 0

B. R = 1, S = 0

C. R = 0, S = 1

D. R = 1, S = 1

140. The current amplification factor in CE configuration is

A. α

B. β + 1

C. 1/ β

D. β

141. A zener diode

A. has a high forward voltage rating

B. has a sharp breakdown at low reverse voltage

C. is useful as an amplifier

D. has a negative resistance

142. The maximum possible collector circuit efficiency of an ideal class A power amplifier is

A. 15%

B. 25%

C. 50%

D. 75%

143. Negative feedback in an amplifier

A. Reduces the voltage gain

B. Increases the voltage gain

C. Does not affect the voltage gain

D. Converts the amplifier into an oscillator

144. For generating 1 kHz signal, the most suitable circuit is

A. Colpitts oscillator

B. Hartley oscillator

C. Tuned collector oscillator

D. Wien bridge oscillator


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145. The output stage of an op-amp is usually a

A. complementary emitter follower

B. transformer coupled class B amplifier

C. Class A power amplifier

D. Class B amplifier

146. When a sinusoidal voltage wave is fed to a Schmitt trigger, the output will be

A. triangular wave

B. asymmetric square wave

C. rectangular wave

D. trapezoidal wave

147. The logic gate which detects equality of two bits is

A. EX-OR

B. EX-NOR

C. NOR

D. NAND

148. The overall bandwidth of two identical voltage amplifiers connected in cascade will

A. remain the same as that of a single stage

B. be worse than that of a single stage

C. be better than that of a single stage

D. be better if stage gain is low and worse if stage gain is high

149. Field effect transistor has

A. large input impedance

B. large output impedance

C. large power gain

D. large votage gain

150. Which of the following parameters is used for distinguishing between a small signal and a large

signal amplifier?

A. voltage gain

B. frequency response

C. harmonic Distortion

D. input/output impedances

151. Which of the following parameters is used for distinguishing between a small signal and a large

signal amplifier?

A. instability

B. bandwidth

C. overall gain

D. distortion


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152. If the feedback signal is returned to the input in series with the applied voltage, the input

impedance ______.

A. decreases

B. increases

C. does not change

D. becomes infinity

153. Most of linear ICs are based on the two transistor differential amplifier because of its

A. input voltage dependent linear transfer characteristic

B. high voltage gain

C. high input resistance

D. high CMRR

154. The waveform of the output voltage for the circuit shown in Fig.1 (RC >> 1) is a

A. sinusoidal wave

B. square wave

C. series of spikes

D. triangular wave

155. A single phase diode bridge rectifier supplies a highly inductive load. The load current can be

assumed to be ripple free. The ac supply side current waveform will be

A. sinusoidal

B. constant DC

C. square

D. triangular

156. Conductance of any conductor is expressed as

A. ampere/watt

B. mhoC. volt

2/watt

D. watt/ampere2

157. The “Superposition theorem” is essentially based on the concept of

A. duality

B. linearity

C. reciprocity

D. non-linearity

158. Cells are connected in parallel in order to

A. increase the voltage available

B. reduce cost of wiring

C. increase the current available

D. reduce the time required to fully charge them after use


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159. The power factor of a purely resistive circuit is

A. zero

B. unity

C. lagging

D. leading

160. The power taken by a three phase load is given by the expression

A. 3 VL IL cos θ

B. sq. rt. of 3 VL IL cos θ

C. 3 VL IL sin θ

D. sq. rt. of 3 VL IL sin θ

161. Which of the following generating stations has the minimum running cost?

A. hydro-electric station

B. nuclear power station

C. thermal power station

D. diesel power plant

162. Which of the following motors has a high starting torque?

A. ac series motor

B. dc series motor

C. induction motor

D. synchronous motor

163. A step-up transformer increases

A. voltage

B. current

C. power

D. frequency

164. The effect of increasing the length of the air gap in an induction motor will be to increase

A. power factor

B. speed

C. magnetizing current

D. air-gap flux

165. The combined resistance of two equal resistors connected in parallel is equal to

A. one half the resistance of one resistor

B. twice the resistance of one resistor

C. four times the resistance of one resistor

D. one fourth the resistance of one resistor

166. The Q- factor of a coil is given by

A. its power factor cosine j

B. ratio of maximum energy stored & energy dissipated per cycle

C. reciprocal of its power factor

D. ratio R/Z


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Page 24

167. Voltage equation of a dc motor is

A. V = Eb + IaRa

B. Eb = V + IaRa

C. V = Eb / IaRa

D. V = Eb + Ia2Ra

168. The efficiency of a transformer is maximum when

A. it runs at half full load

B. it runs at full load

C. its Cu loss equals iron loss

D. it runs overload

169. The crawling in an induction motor is caused by

A. improper design of the machine

B. low voltage supply

C. high loads

D. harmonics developed in the motor

170. The starting winding of a single-phase motor is placed in

A. rotor

B. stator

C. armature

D. field

171. Reduction in the capacitance of a capacitor- start motor results in reduced

A. noise

B. speed

C. starting torque

D. armature reaction

172. In an AC circuit, the ratio of kW / kVA represents

A. power factor

B. load factor

C. form factor

D. diversity factor

173. The unit of inductance is

A. ohm

B. mho

C. farad

D. henry

174. Thevenin’s equivalent circuit consists of _________.

A. series combination of RTh, ETh and RL

B. series combination of RTh, ETh

C. parallel combination of RTh, ETh

D. parallel combination of RTh, ETh and RL


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Page 25

175. In an RLC circuit, the phase of the current with respect to the circuit voltage will be_________.

A. leading

B. same

C. lagging

D. depends upon the value of L and C

176. The frequency of DC supply is__________.

A. zero

B. 16 Hz

C. 50 Hz

D. 100 Hz

177. Load factor is defined as the ratio of _________.

A. Average Demand / Max. Demand

B. Max. Demand / Average Demand

C. Average Demand / Connected load

D. Connected load / Max. Demand

178. Static Capacitors are used for__________.

A. power improvement

B. current improvement

C. voltage improvement

D. power factor improvement

179. The speed of an induction motor__________.

A. decreases too much with the increase of load

B. increases with the increase of load

C. decreases slightly with the increase of load

D. remains constant with the increase of load

180. Centrifugal switch is provided for disconnecting the auxiliary winding in a_______.

A. capacitor- start motor

B. capacitor run motor

C. reluctance motor

D. hysteresis motor

181. Rotating magnetic field is produced in a ________.

A. single- phase induction motor

B. three- phase induction motor

C. DC series motor

D. AC series motor

182. The frequency of the secondary voltage of a transformer will be_________.

A. less than the frequency of the primary voltage

B. equal to the primary voltage

C. greater than the frequency of the primary voltage

D. very much greater than the frequency of the primary voltage


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Page 26

183. The demand factor for the electrical system is the ratio of

A. maximum demand to connected load

B. maximum demand to average load

C. average power to maximum power

D. relative power to total power

184. When a low resistance is connected in parallel with a high resistance, the combined resistance is

A. always more than the high resistance

B. always less than the low resistance

C. always between the high resistance & low resistance

D. either lower or higher than low resistance depending on the value of high resistance

185. A DC series motor is best suited for driving

A. lathes

B. cranes and hoists

C. shears and punches

D. machine tools

186. Transformer cores are built up from laminations rather than from solid metal so that

A. oil penetrates the core more easily

B. eddy current loss is reduced

C. less lamination is required for the windings

D. turn ratio is higher than voltage ratio

187. In a DC series motor increase in load current results in

A. decrease in speed

B. increase in speed

C. better commutation

D. increase in the back EMF

188. The starting torque of a single phase induction motor is

A. high

B. moderate

C. low

D. zero

189. An electric motor in which rotor and stator fields rotate simultaneously is called a __________

motor.

A. DC

B. induction

C. synchronous

D. universal

190. In ac circuit the product of voltage and current is known as

A. power

B. real power

C. resistive power

D. apparent power


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Page 27

191. A network that does not have either voltage or current sources is called

A. active network

B. passive network

C. resistive network

D. dummy network

192. The power factor at resonance in RLC circuit is

A. zero

B. unity

C. 0.5 lagging

D. 0.5 leading

193. Transformer core is laminated to

A. reduce the copper losses

B. reduce the core losses

C. reduce the eddy current losses

D. none of these

194. Star – delta starter of an induction motor

A. inserts resistance in rotor circuit

B. inserts resistance in stator circuit

C. applies reduced voltage to rotor

D. applies reduced voltage to stator

195. Stator core of an induction motor is made of

A. laminated cast iron

B. mild steel

C. silicon steel stampings

D. soft wood

196. Watt hour is the unit of

A. electric power

B. electric capacity

C. electric energy

D. electric charge

197. A battery is a source of

A. DC voltage

B. single phase AC voltage

C. three phase AC voltage

D. AC or DC voltage

198. Which DC motors has approximately constant speed?

A. series motor

B. shunt motor

C. cumulatively compound motor

D. all of the above


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Page 28

199. Resistance of a wire is r ohms. The wire is stretched to double its length, then its resistance in ohms

is

A. r/2

B. 4r

C. 2r

D. r/4

200. An electric machine will have high efficiency when

A. input/output ratio is low

B. reactive power is more

C. kWh consumption is low

D. losses are low

201. Which type of loss is not common to transformers and rotating machines?

A. eddy current loss

B. copper loss

C. hysteresis loss

D. windage loss

202. The difference between the synchronous speed and the actual speed of an induction motor is

known as

A. regulation

B. back lash

C. slip

D. lag

203. In two wattmeter method of power measurement, if one of the wattmeter shows zero reading,

then it can be concluded that

A. power factor is unityB. power factor is zero

C. power factor is 0.5 lagging

D. power factor is 0.5 leading

204. Which of the following will remain the same in all parts of a series circuit?

A. voltage

B. current

C. power

D. resistance

205. Which single phase motor would you select for a tape recorder?

A. reluctance motor

B. hysteresis motor

C. synchronous motor

D. universal motor


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Page 29

206. Under the condition of resonance, RLC series circuit behaves as a,

A. purely resistive circuit

B. purely inductive circuit

C. capacitive circuit

D. reactive circuit

207. During charging, the electrolyte of a lead acid cell becomes

A. stronger

B. weaker

C. water

D. dilute

208. As compared to shunt and compound motors, series motor have the highest torque because of its

comparatively __________ at the start.

A. lower armature resistance

B. stronger series field

C. fewer series turns

D. larger armature current

209. The voltage ratio of the transformer is given as

A. ES / EP

B. TS / TP

C. TP / TS

D. EP / TS

210. The relationship between the frequency of ac wave and the time period is given by

A. f = T

B. f = 1 / T2

C. f = 1 / TD. f = T

2

211. Which of the following power plant has the maximum efficiency?

A. thermal

B. hydroelectric

C. nuclear

D. diesel

212. Which of the following components are all active components?

A. a resistor and an inductor

B. a diode, a BJT and an FET

C. a capacitor, and an inductor

D. an operational amplifier, a BJT and thermionic triode

213. In forward mode NPN BJT, if we increase the voltage VCC, the collector current increases

A. due to ohm’s law, higher VCC causes higher current

B. due to base width decrease less carrier recombines in the base region

C. as the gradient of the minority carriers in the base region becomes steeper

D. due to both the reasons B and C


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Page 3

214. The barrier voltage (Vr or Vo) in a junction diode is the effect of

A. the p-side and n-side of the junction forming a battery

B. the emf required to move the holes fast enough to have the mobility equal to that of the

electrons

C. the recombination of charge carriers across the junction leaving behind the opposite charged

ions

D. the voltage needed to make the semiconductor material behave as a conductor

215. An emitter follower has high input impedance because

A. large emitter resistance is used

B. large biasing resistance is used

C. there is negative feedback in the base emitter circuit

D. the emitter-base junction is highly reverse biased

216. In a differential amplifier an ideal CMRR is

A. infinity

B. zeroC. –1

D. +1

217. FET is advantageous in comparison with BJT because of

A. high input impedance

B. high gain-bandwidth product

C. its current controlled behavior

D. high noise immunity

218. The emission of electrons in a vacuum diode is achieved by

A. electrostatic fieldB. magnetic field

C. heating

D. electron bombardment

219. The color code of a resistor of nominal value 2.7KΩ ± 10% is

A. red, violet, red and silver

B. red, violet, yellow and gold

C. red, violet, orange and silver

D. red, violet, red and gold

220. Capacitor that can have the highest capacitance value is

A. mica

B. paper

C. electrolytic

D. ceramic


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Page 31

221. The equivalent current-source representation for a voltage-source with open circuit voltage 12 V

and internal resistance 3 ohms is

A. a current-source of strength 4A in shunt with a resistance of 6 Ω

B. a current –source of strength 4A in series with a resistance of 3 Ω

C. a current-source of strength 4A in shunt with a resistance of 3 ohms

D. a current-source of strength 4A in shunt with a resistance of 36 ohms

222. An intrinsic semiconductor at absolute zero temperature

A. has a large number of holes

B. behaves like an insulator

C. behaves like a metallic conductor

D. has few holes and same number of electrons

223. For the operation of a depletion-type N-MOSFET, the gate voltage has to be

A. low positive

B. high positive

C. high negative

D. zero

224. The typical operating voltage for LED’s ranges from

A. 0.2 V to 0.6 V

B. 6 V to 10 V

C. 1.5 V to 2.5 V

D. 9 V to 10 V

225. Capacitors for integrated circuits

A. cannot be made using diffusion techniques

B. can be made with very high values of capacitance

C. are always discrete components connected externallyD. can be made using silicon dioxide as the dielectric

226. Which one of the following statements is not true?

A. capacitance is a measure of a capacitor’s capability to store charge.

B. a capacitor offers high impedance to ac but very low impedance to dc.

C. a capacitor is also used as bypass capacitor.

D. capacitors are used to couple alternating voltages from one circuit to another and at the same

time to block dc voltage from reaching the next circuit.

227. In a Zener diode large reverse current is due to

A. collision

B. presence of impurities

C. rupture of bonds

D. lower resistance in reverse biased region


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Page 32

228. JFET has main drawback of

A. having low input impedance

B. having high output impedance

C. being noisy

D. having small gain-bandwidth product

229. A UJT has

A. stable negative resistance characteristics

B. low firing current

C. use as a waveform generator

D. all of the above

230. For thermionic emission

A. a material with high work function is preferable

B. a material with low work function is preferable

C. the work function of the material has no importance

D. none of these is true

231. Ideal operational amplifier has input impedance of

A. 1MW

B. infinity

C. zero

D. 1Ω

232. The CE configuration amplifier circuits are preferred over CB configuration amplifier circuits

because they have

A. lower amplification factor

B. larger amplification factor

C. high input resistance and low output resistanceD. none of these

233. The most commonly used type of electron emission in electron tubes is

A. photo-electron emission

B. thermionic emission

C. field emission

D. secondary emission

234. A device whose characteristics are very close to that of an ideal current source is

A. a gas diode

B. a BJT in CB mode

C. a BJT in CE mode

D. a triode

235. In an N-type semiconductor, the concentration of minority carriers mainly depends upon

A. the doping technique

B. the number of donor atoms

C. the temperature of the material

D. the quality of the intrinsic material, Ge or Si


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Page 33

236. When forward bias is applied to a junction diode, it

A. increases the potential barrier

B. decreases the potential barrier

C. reduces the majority-carrier current to zero

D. reduces the minority-carrier current to zero

237. The theoretical maximum efficiency of a Bridge rectifier circuit is

A. 48.2%

B. 81.2%

C. 82%

D. 40.6%

238. A switching voltage regulator can be of the following type:

A. step-down

B. step-up

C. inverting

D. none of these

239. A UJT contains

A. four pn junctions

B. three pn junctions

C. two pn junctions

D. one pn junction

240. The foundation on which an IC is built is called

A. an insulator

B. a base

C. a waferD. a plate

241. X-ray tubes make use of

A. thermionic emission

B. secondary emission

C. high field emission

D. photoelectric emission

242. Which of the following components are all active components?

A. a resistor and a capacitor

B. a microphone, a LCD and a Thyratron

C. an electric bulb, a transformer and a varactor diode

D. an SCR, a vacuum diode and an LED

243. Doping materials are called impurities because they

A. decrease the number of charge carriers

B. change the chemical properties of semiconductors

C. make semiconductors less than 100 percent pure

D. alter the crystal structures of the pure semiconductors


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244. Avalanche breakdown is primarily dependent on the phenomenon of

A. collision

B. doping

C. ionization

D. recombination

245. In a rectifier, larger the value of shunt capacitor filter

A. larger the peak-to-peak value of ripple voltage

B. larger the peak current in the rectifying diode

C. longer the time that current pulse flows through the diode

D. smaller the dc voltage across the load

246. The main reason why electrons can tunnel through a P-N junction is that

A. they have high energy

B. barrier potential is very low

C. depletion layer is extremely thin

D. impurity level is low

247. If a change in base current does not change the collector current, the transistor amplifier is said to

be

A. Saturated

B. Cut-off

C. Critical

D. Complemented

248. The extremely high input impedance of a MOSFET is primarily due to the

A. absence of its channel

B. negative gate-source voltage

C. depletion of current carriersD. extremely small leakage current of its gate capacitor

249. After firing an SCR, the gating pulse is removed. The current in the SCR will

A. remains the same

B. immediately fall to zero

C. rise up

D. rise a little and then fall to zero

250. In the context of IC fabrication, metallization means

A. connecting metallic wires

B. forming interconnecting conduction pattern and bonding pads

C. depositing Sio2 layer

D. covering with a metallic cap

ee objective q 1

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