SSC junior Engineer Exam 2012

1. The emf induced per phase in a three phase star connected synchronous generator having the following data: Distribution factor = 0.955; Coil-span factor = 0.966; Frequency = 50 Hz, Flux per pole = 25 mwb; Turns per phase = 240, emf per phase is ?

A) 2128.36 Volts
B) 1228.81 Volts
C) 869.46 Volts
D) 1737.80 Volts

... Answer is B)
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2. In a 1-phase transformer, the copper loss at full load is 600 Watts. At half of the full load the copper loss will be ?

A) 150 Watts
B) 75 Watts
C) 600 Watts
D) 300 Watts

... Answer is A)
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3. An auto transformer used with a sodium vapour lamp should have high ?

A) winding resistance
B) leakage reactance of windings
C) V A rating
D) transformation ratio

... Answer is B)
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4. In an auto-transformer, the number of turns in primary winding is 210 and in secondary winding is 140. If the input current is 60A, the currents in output and in common winding are respectively ?

A) 40 A, 20 A
B) 40A, 100 A
C) 90 A, 30 A
D) 90A, 150A

... Answer is C)
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5. A 3-phase transformer has its primary connected in delta and secondary in star. Secondary to primary turns ratio per phase is 6. For a primary voltage of 200 V, the secondary voltage would be ?

A) 2078 V
B) 693 V
C) 1200 V
D) 58 V

... Answer is A)
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6. A resistance and another circuit element are connected in series across a dc voltage V. The voltage across the second element is V initially and zero after time. The other element is pure ?

A) capacitance
B) resistance
C) both (A) and (B)
D) inductance

... Answer is D)
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7. For RLC ac series circuit at resonance the current is ?

A) minimum at leading p.f.
B) minimum at lagging p.f.
C) maximum at unity p.f.
D) maximum at leading p.f

... Answer is C)
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8. A series R-L-C circuit resonates at 1 MHz. At frequency 1.1 MHz the circuit impedence will be ?

A) resistive
B) will depend on the relative amplitude of R, L and C
C) capacitive
D) inductive

... Answer is D)
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9. The equivalent resistance between terminals X and Y of the network shown is ?

A) 8 ?
B) 100/3 ?
C) 40/3 ?
D) 20/3 ?

... Answer is C)
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10. Application of Thevenin's Theorem in a circuit results in ?

A) an ideal voltage source
B) an ideal current source
C) a current source and an impedance in parallel
D) a voltage source and an impedance in series

... Answer is D)
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11. A current of i = 6 + 10 sin (100 pt) + 20 sin (200 pt) is flowing through a series combination of a PMMC and moving iron instrument. Ratio of the two currents as registered by the M.I. and PMMC meter is i = 6 + 10 sin (100 pt) + 20 sin (200 pt) ?

A) 1.81
B) 3.11
C) 2.82
D) 2.63

... Answer is C)
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12. Three resistances 5? each are connected in star. Values of equivalent delta resistances are ?

A) 1.5? each
B) 2.5? each
C) 5/3? each
D) 15? each

... Answer is D)
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13. A 120 V, 60 W incandescent lamp has to be operated from 220 V, 50 c/s, 1 phase A.C. supply. In order to do this, a circuit element has to be connected in series with the lamp. Which one of the following series element is preferable ?

A) Pure capacitance
B) Pure inductance or capacitance
C) Resistance
D) Pure inductance

... Answer is A)
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14. The bandwidth of an ac series circuit consisting of R, L and C is ?

A) L/R
B) R/L
C) L/RC
D) RC/L

... Answer is B)
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15. For balanced 3-phase supply system, the phasor sum of the line currents is NOT zero if the load is ?

A) Balanced delta connected
B) Unbalanced delta connected
C) Balanced star connected
D) Unbalanced star connected

... Answer is D)
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16. At series resonance of an A.C R-L-C circuit the impressed voltage is ?

A) equal to the resistive drop.
B) equal to the capacitive drop
C) greater than the resistive drop.
D) equal to the inductive drop.

... Answer is A)
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17. In a series RLC circuit R = 20 ?, XL = 30? and XC = 30?. If the supply voltage across the combination is v = 100 sin (100pt + 300) Volts, the instantaneous current and the power factor of the circuit are respectively ?

A) i = 3.536 sin (100pt + 300) Amps, p.f. = 0.866
B) i = 5 sin (100pt + 300) Amps, p.f. = unity
C) i = 3.536 sin (100 pt + 300) Amps, p.f. = unity
D) i = 5 sin (100pt + 300) Amps, p.f = 0.866

... Answer is B)
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18. The rms value of the alternating current given by the equation i = 50 sin (314t – 100) + 30 sin (314t – 200) is ?

A) 41.23 A
B) 58.31 A
C) 38.73 A
D) 77.43 A

... Answer is A)
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19. A series R-L-C circuit will have unity power factor if operated at a frequency of ?

A) 1/(2p * root LC)
B) LC
C) 1/(LC)
D) 1/root(LC)

... Answer is A)
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20. In a balanced 3-phase system, the current coil of a wattmeter is inserted in line 1 and the potential coil across 2 and 3. If the wattmeter reads 100 W, the reactive power drawn by the 3-phase load is ?

A) 100 VAR
B) 50 VAR
C) 173.2 VAR
D) 141.4 VAR

... Answer is C)
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21. An electric iron is rated at 230 V, 400 W, 50 Hz. The voltage rating 230 V ?

A) peak value
B) average value
C) peak-to-peak value
D) rms value

... Answer is D)
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22. A non- sinusoidal periodic waveform is free from DC component, cosine components and even harmonics. The waveform has ?

A) half wave and even function symmetry.
B) half wave and odd function symmetry
C) only odd function symmetry
D) only half wave symmetry

... Answer is B)
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23. A periodic train of rectangular pulses x(t) with a time period of 25 seconds, has a pulse width of 9 seconds as shown in Figure. The RMS value of the waveform is ?

A) 10 V
B) 6 V
C) 3.6 V
D) 2.16 V

... Answer is C)
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24. The time constant of the network shown in the figure is ?

A) CR/4
B) CR/2
C) CR
D) 2 CR

... Answer is C)
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25. In the series RC circuit, the voltage across C starts increasing, the moment the circuit is switched to V Volts D.C. The rate of increase of voltage across C at the instant just after the switch is closed (i.e. at t= 0+) is ?

A) RV/C
B) CV/R
C) V/RC
D) R/CV

... Answer is C)
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26. Form factor of an alternating wave is ?

A) Form factor = Average value / rms value
B) Form factor = (rms value) squre / Average value
C) Form factor = rms value / Average value
D) Form factor = rms value * Average value

... Answer is C)
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27. The phase difference between the following voltage and current waves, v = 311 sin (100pt + 300) Volts, i = 17 sin (100pt – 200) Amps ?

A) 20
B) 50
C) 10
D) 30

... Answer is B)
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28. Match the items given in List–I and those in List–II Select your answers using codes given in the lists: List –I List-II (Temperature Coefficient of Resistance) (a) Aluminium ----- Positive (b) Manganin ----- Negligibly small (c) Carbon ----- Negative ?

A) N m
B) R K
C) A S
D) M S

... Answer is ALREADY MATCHED)
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29. Which of the following materials possesses the least resistivity ?

A) Iron
B) Manganin
C) Aluminium
D) Copper

... Answer is D)
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30. The resistances of insulations, in general,______with temperature rise ?

A) decreases
B) increases rapidly
C) increases slowly
D) does not change

... Answer is A)
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31. A 10 µF and a 20 µF capacitor are in series. The combination is supplied at 150 V from a sinusoidal voltage source. The voltage across the 20 µF capacitor is ?

A) 75 V
B) 125 V
C) 100 V
D) 50 V

... Answer is D)
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32. The conditions at which the following potential divider is independent of frequency, may be ?

A) R1/R2 = C1/C2
B) R1/R2 = C2/C1
C) R1CI <<1, R1R2 <<1
D) R1 + R3 =1/C1+1/C2

... Answer is D)
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33. Which of the following is the best conductor of electricity ?

A) Warm water
B) Salt water
C) Cold water
D) Distilled water

... Answer is B)
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34. SI unit of electricalenergy is ?

A) Watt-Second
B) Joule
C) KWh
D) Volt-Ampere-Second

... Answer is B)
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35. The wave shape of current flowing through an inductor is ?

A) N m
B) R K
C) A S
D) M S

... Answer is A)
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36. Two wires A and B of the same material but of different lengths L and 2L have the radius r and 2r respectively ?

A) 1: 4
B) 1: 8
C) 1: 1
D) 1: 2

... Answer is C)
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37. A 20 micro farad capacitor is connected across an ideal voltage source. The current in the capacitor ?

A) will be very high at first, then exponentially decay and at steady state will become zero
B) will be zero at first, then exponentially rise
C) will be very high at first, then exponentially decay
D) None of these are true

... Answer is A)
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38. In general, if a sine wave is fed into a Schmitt trigger, the output will be ?

A) a square wave
B) a saw-tooth wave
C) an amplified sine wave
D) M S

... Answer is A)
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39. Sawal ?

A) to hold the output voltage to a constant value
B) to bias the transistor
C) to clip the output voltage
D) to protect the base-emitter junction

... Answer is D)
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40. FETs are ?

A) either unipolar or bipolar
B) unipolar devices
C) bipolar devices
D) None of these

... Answer is B)
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41. In the circuit, forward resistance of the diode D is 2 ? and its reverse resistance is infinitely high. A list consists of meters (List-I) and another list shows the meter readings (List-II). ?

A) N m
B) R K
C) A S
D) M S

... Answer is UPDATE SOON)
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42. In the figure, D is an ideal diode. If the rms value of the input voltage is 50 V, then the rms current through 100 ? is ?

A) 0.5/root2
B) 0.25
C) 0.5
D) 0.5 root2

... Answer is A)
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43. Which of the following materials is a semiconductor ?

A) Chromium
B) Selenium
C) Bismuth
D) Silica

... Answer is B)
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44. In a rectifier circuit, the primary function of the filter is to ?

A) control the DC level of the output voltage
B) remove ripples from the rectified output
C) minimise AC input variations AC
D) suppress odd harmonics in the rectifier output

... Answer is B)
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45. In an R-L series circuit R = 20 ?, L = 0.056 H and the supply frequency is f = 50 Hz. The magnitude of impedance of the circuit is ?

A) 26.64 OHM
B) 20 OHM
C) 37.6 OHM
D) 20.056 OHM

... Answer is A)
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46. A pure sinusoidal current is being rectified. For the given maximum value of sinusoidal current if rms value of half wave rectified current is 50 A, then the rms value of full wave rectification will be ?

A) 50/pA
B) 100/p A
C) 100A
D) 70.7 A

... Answer is D)
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47. Under thermal equilibrium in a pure semiconductor the ratio of the number of holes to the number of conduction electrons is ?

A) 1/2
B) infinity
C) 1
D) 2

... Answer is C)
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48. As per IE rules the maximum allowable variation between declared and actual voltage at consumer's premises should be ?

A) ± 4%
B) ± 4.5%
C) ± 3.5%
D) ± 3%

... Answer is D)
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49. Alternator used in hydel power station has more number of poles in it than that used in thermal power station, because ?

A) speed of the prime mover may be changed whenever required
B) power generated by the alternator may be changed according to demand
C) speed of its prime mover is less
D) power generated by this alternator is less

... Answer is C)
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50. The connected load of a consumer is 2 KW and the maximum demand is 1.5 KW. The demand factor of the consumer is ?

A) 1.33
B) 0.75
C) 0.375
D) none of these

... Answer is B)
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51. In the thyrite lightning arrester the resistance ?

A) is high at low current and low at high current
B) is low at low current and high at high current
C) increases linearly with the applied voltage
D) decreases linear with the applied voltage

... Answer is D)
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52. A consumer is offered the following rate of tariff. He has to pay a fixed charge of ` 1,000 per month and a running charge of ` 4.50 per unit consumed. If the consumer runs a motor load of 1 KW at 0.85 power factor lagging on an average of 15 hours per day, his annual bill is ?

A) 25637.50
B) 36637.50
C) 40985.29
D) 32941.88

... Answer is B)
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53. Glare is caused due to ?

A) excessive lighting contrast in the field of vision
B) excessive luminance
C) both of (A) and (B)
D) none of (A) and (B)

... Answer is C)
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54. Which of the following method is suitable for heating of conducting medium ?

A) Induction heating
B) Eddy current heating
C) Both (A) and (B)
D) Radiant heating

... Answer is C)
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55. Furnaces used for cremation use ?

A) Dielectric heating
B) Arc heating
C) Resistance heating
D) Induction heating

... Answer is C)
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56. In a fluorescent tube circuit high voltage surge is produced by ?

A) Heater
B) Electrode
C) Starter
D) Choke

... Answer is D)
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57. In AC operated electromechanical contactors, the problem of chattering is eliminated by AC ?

A) increasing the conductor cross section
B) Using aluminium instead of copper as conductor material
C) laminating the electromagnet core
D) placing copper shading band on pole face of electromagnet

... Answer is D)
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58. Magnetic blow out coils are generally used in ?

A) vacuum circuit breaker
B) air break circuit breaker
C) air blast circuit breaker
D) oil circuit breaker

... Answer is B)
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59. The pitch factor for a full pitched winding of a synchronous machine is ?

A) 0.5
B) 0.9
C) 0.0
D) 1.0

... Answer is D)
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60. An ac meter of resistance Rm and reactance Xm is connected in series with a resistance RS.A shunt of impedance (Rsh + jXsh) is applied in parallel to the existing combination of meter and Rs. The current division across the two branches will be independent of frequency when ?

A) Xm/(Rm+Rs) =Xsh/Rsh
B) Rs/Rm =Rsh/Xsh
C) Rm/Xm = Xsh/Rsh
D) (Rs+Rm)squre + (Xm)squre = (Rsh)squre +(Xsh)squre

... Answer is D)
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61. In phantom loading arrangement, energy consumption in the calibration test of wattmeter is reduced because of ?

A) th separate application of low voltage supply across current coil
B) no common point between the two coils.
C) the reduced loss in current coil and pressure coil
D) the absence of load in the test set.

... Answer is D)
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62. In the measurement of power in a balanced 3- phase circuit by two-wattmeter method if the two wattmeters show equal readings. then the power factor of the circuit is ?

A) zero
B) unit
C) 0.8 lagging
D) 0.8 leading

... Answer is B)
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63. Two meters X and Y required 40 mA and 50 mA respectively for full scale deflection. Then ?

A) Both are equally sensitive.
B) Data are insufficient to comment
C) X is more sensitive than
D) Y is more sensitive than

... Answer is C)
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64. The house hold energy meter is ?

A) recording instrument
B) indicating instrument
C) integrating instrument
D) None of these

... Answer is C)
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65. A Ballistic galvanometer of constant equal to 1 micro-coulomb/degree gives a throw of 22.50, when a capacitor discharges through the meter. If a battery of 15 V is used to recharge the capacitor, value of capacitance is ?

A) 22.5µF
B) 10µF
C) 1.5µF
D) 15µF

... Answer is C)
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66. A potentiometer is used to measure the voltage between two points of a D.C. circuit, which is found to be 1.2 V. This is also measured by a voltmeter, which is found to be 0.9 V. The resistance of the voltmeter is 60 k ?

A) 60 kilo ohm
B) 20 kilo ohm
C) 45 kilo ohm
D) 80 kilo ohm

... Answer is B)
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67. A load is connected to supply. A current transformer (CT) and a potential transformer (PT) is used in between load and supply. A power factor of 0.5 is measured at the secondary side of CT and PT. If phase angle error of CT and PT are 0.4degree and 0.7degree, power factor of the load is ?

A) Cos60.3
B) Cos58.9
C) Cos59.7
D) Cos61.1

... Answer is D)
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68. During the measurement of a low resistance using a potentiometer, the following readings were obtained: Voltage drop across unknown resistance = 0.531 Volt. Voltage drop across a 0.1 Ohm standard resistance connected in series with the unknown = 1.083 Volt. Value of the unknown resistor is ?

A) 49.03 milli ohm
B) 108.3 milli ohm
C) 20.4 milli ohm
D) 53.1 milli ohm

... Answer is A)
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69. Which one of the following types of instruments does suffer from error due to magnetic hysteresis ?

A) Induction type
B) Electrodynamic
C) Moving Iron
D) PMMC

... Answer is C)
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70. Which one of the following does not employ a null method of measurement ?

A) Megger
B) DC potentiometer
C) Kelvin double bridge
D) AC potentiometer

... Answer is A)
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71. In star-delta starting of three-phase induction motor the starting voltage is reduced to ?

A) 3 times of normal voltage
B) 3 times of normal voltage.
C) 3 1 times of normal voltage
D) 3 1 times of normal voltage.

... Answer is D)
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72. An electromagetic torque is produced as an interaction between a flux and current. The angle between flux and current is 450. If this angle is changed to 300, flux increases by 100% and current reduces by 25% then the torque ?

A) increases to 183.7% of the original
B) reduces to 81.6% of the original
C) reduces to 54.4% of the original
D) reduces to 66.7% of the original

... Answer is A)
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73. Maximum temperature limit for class F insulation is ?

A) 130 0C
B) 120 0C
C) 105 0C
D) 155 0C

... Answer is D)
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74. Match List–I (Types of motors) with List–II (Characteristics) and select the appropriate response. dc series motor (1) Constant speed (b) dc shunt motor (2) High starting torque ?

A) N m
B) R K
C) A S
D) M S

... Answer is A)
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75. The motor characteristics best suited for traction purpose are those of ?

A) d.c. series motor
B) synchronous motor
C) induction motor
D) d.c. shunt motor

... Answer is A)
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76. If the starting torque of a 3 phase induction motor is Tst for DOL starting, that for star-delta starting of the same motor is ?

A) Tst/3
B) Tst/root3
C) root3 Tst
D) 3 Tst

... Answer is A)
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77. The iron loss in a 100 KVA transformer is 1 KW and full load copper losses are 2 KW. The maximum efficiency occurs at a load of ?

A) 100KVA
B) 70.7 KVA
C) 141.4 KVA
D) 50 KVA

... Answer is B)
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78. Which one of the following is correct ?

A) The effect of air gap flux on armature current of a synchronous machine is called armature reaction
B) The effect of armature current on main flux of a synchronous machine is called armature reaction.
C) The effect of armature current on air gap flux of a synchronous machine is called armature reaction
D) The effect of field current on main flux of a synchronous machine is called armature reaction

... Answer is B)
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79. A lap wound dc generator having 250 armature conductor runs at 1200 rpm. If the generated emf is 200 V, then the operating flux of the D.C. generator is ?

A) 0.08 wb
B) 0.04 wb
C) 0.06 wb
D) 0.02 wb

... Answer is B)
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80. The highest speed attainable by d.c. shunt motor is ?

A) much higher than no-load speed
B) much lower than no-load speed
C) ideally infinite
D) equal to no-load speed

... Answer is D)
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81. The direction of rotation of a D.C. shunt motor can be reversed by interchanging ?

A) the armature terminals only
B) either field or armature terminals
C) the supply terminals
D) the field terminals only

... Answer is B)
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82. AC series motors are built with as few turns as possible to reduce ?

A) flux
B) reactance
C) iron losses
D) speed

... Answer is B)
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83. Based on revolving field theory, the forward on backward frequencies of the rotor emf of a 4- pole, 50 Hz, single- phase induction motor when running at 1300 rpm in the same direction of the forward field are respectively ?

A) 107.69 Hz, 7.69 Hz
B) 93.33 Hz, 6.67 Hz
C) 7.69 Hz, 107.69 Hz
D) 6.67 Hz, 93.33 Hz

... Answer is D)
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84. Three lamps are in circuit as shown in Figure. At what condition 100 W lamp will have the maximum brightnes ?

A) K1 is closed, K2 is open and K3 is also open
B) Key K1 is closed, K2 is open and K3 is closed
C) Key K1 is open, K2 is closed and K3 is open
D) Both (B) and (C)

... Answer is C)
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85. Given two coupled inductors Ll and L2 having their mutual inductance M. The relationship among them must satisfy ?

A) M > L1L2
B) M <= L1L2
C) M = L1L2
D) M > (L1 + L2)/2

... Answer is B)
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86. If the length of a bar of magnetic material is increased by 20% and the cross-sectional area is decreased by 20% then the reluctance is ?

A) increased by 50%
B) remaining same
C) decreased by 33%
D) increased by 67%

... Answer is A)
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87. Two coupled inductors L1 = 0.2 H and L2 = 0.8 H, have coefficient of coupling K = 0.8. The mutual inductance M is ?

A) 0.16 H
B) 0.02 H
C) 0.32 H
D) 0.24 H

... Answer is C)
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88. A coil with a certain number of turms has a specified time constant. If the number of turns is doubled, its time constant would ?

A) become four fold
B) get halved
C) remain unaffected
D) become doubled

... Answer is D)
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89. The iron loss per unit frequency in a ferromagnetic core, when plotted against frequency, is a ?

A) Straight line with positive slope
B) Straight line with negative slope
C) Parabola
D) Constant

... Answer is A)
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90. The mutual inductance between two closely coupled coils is 1 H. if the turns of one coil is decreased to half and those of the other is doubled, the new value of the mutual inductance would be ?

A) 1/4 H
B) 1 H
C) 2 H
D) 1/2 H

... Answer is B)
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91. Following graph shows the loss characteristics of a sheet of ferromagnetic material against varying frequency f. Pi, is the iron loss at frequency f, Hysteresis and eddy current losses of the sheet at 100 Hz are ?

A) 10 W, 100 W
B) 10 W, 50 W
C) 1 W, 5 W
D) 1 W, 10 W

... Answer is D)
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92. Hysteresis losses are present in iron core coil when ?

A) the current in the coil is alternating
B) the current is unsymmetrical alternating only
C) the current in the coil is d.c. only
D) the current in the coil is sinusoidal only.

... Answer is A)
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93. Eddy current loss in ferromagnetic core is proportional to ?

A) square of frequency
B) square root of frequency
C) frequency
D) reciprocal of frequency

... Answer is A)
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94. Two inductors have self inductances of 9 mH and 25 mH. The mutual inductance between the two is 12 mH. The coefficient of inductive coupling between the two inductors is ?

A) 18.75
B) 0.25
C) 0.8
D) 1.25

... Answer is D)
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95. The magnetic materials that are used to prepare permanent magnets should have ?

A) steeply rising magnetisation curve
B) small hysteresis loop
C) high Retentivity
D) low coercive force

... Answer is C)
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96. Poles of d.c. machines are often laminated to reduce ?

A) eddy current loss
B) iron weight
C) armature reaction
D) hysteresis loss

... Answer is A)
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97. Universal motor is a _______motor ?

A) series
B) single phase induction
C) synchronous
D) shunt

... Answer is A)
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98. Which of the following motors can work satisfactorily on both AC and DC ?

A) Series motor
B) Shunt motor
C) Induction motor
D) Synchronous motor

... Answer is A)
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99. Two alternators rated 40 MVA and 60 MVA respectively are working in parallel and supplying a total load of 80 MW. Speed regulation of both the alternators is 5%. The load sharing between them will be ?

A) 30 MW, 50 MW
B) 36 MW, 44 MW
C) 40 MW each
D) 32 MW, 48 MW

... Answer is D)
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100. Slip of a 3-phase induction motor may be expressed as ?

A) rotor copper loss/rotor core loss
B) rotor copper loss/rotor power input
C) rotor copper loss/total input power
D) rotor power input/rotor copper loss

... Answer is B)
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