Bihar State Power Holding Corporation LTD. JE Electrical (BSPHCL)2016

1. The number of slip rings of a single phase and three phase converters is ?

A) 1 and 3 respectively
B) 2 and 6 respectively
C) 2 and 3 respectively
D) 1 and 6 respectively

... Answer is C)
A slip ring is an electromechanical device that allows the transmission of power and electrical signals from a stationary to a rotating structure.


In a single phase rotary converter two number of slip rings, One for phase and one for neutral.


1 slip ring for each phase . So, in 3 phase Slip Ring Induction Motor, there will be 3 slip-rings.
The rotor winding of the motor is star connected, and the three leads of phase winding are connected to three slip rings.

2. A Silicon Controlled Rectifer (SCR) can withstand a maximum junction temperature of 1200C with an ambient temperature of 75C. If the SCR has thermal resistance from junction to Ambient as 1.50 C/W, the maximum internal power dissipation allowed is ?

A) 80 W
B) 60 W
C) 50 W
D) 30 W

... Answer is D)
Explanation will provide as soon as possible.

3. Metallic copper is a ?

A) diamagnetic substance
B) ferromagnetic substance
C) paramagnetic substance
D) ferrimagnetic substance

... Answer is A)
Explanation will provide as soon as possible.

4. Which of the following motors is preferred for automatic drives ?

A) Squirrel cage induction motor
B) Synchronous motors
C) Repulsion motor
D) Ward Leonard controlled dc motors

... Answer is D)
Explanation will provide as soon as possible.

5. A 3 phase slip ring induction motor is wound for 4 poles on stator and 6 poles on rotor. When 3–phase balanced voltage source at 50 Hz is applied to the motor, it will run at ?

A) 0 rpm
B) 700 rpm
C) 1000 rpm
D) 1500 rpm

... Answer is A)
Explanation will provide as soon as possible.

6. A good heating element should have ?

A) high resistivity and low melting point
B) low resistivity and high melting point
C) high resistivity and high melting point
D) low resistivity and low melting point

... Answer is C)
Explanation will provide as soon as possible.

7. Field control of a DC shunt motor gives which one of the following drives ?

A) constant speed drive
B) Constant torque drive
C) Variable load speed drive
D) Constant KW drive

... Answer is D)
Explanation will provide as soon as possible.

8. If the base current of a BJT is 250 µA and emitter current is 15 mA, then the common base current gain will be ?

A) 41
B) 55
C) 59
D) 95

... Answer is C)
Explanation will provide as soon as possible.

9. Voltage regulation of an alternator may be zero if ?

A) the machine runs at very low loads
B) the load power factor is leading
C) the load power factor is lagging
D) it is loaded beyond its full-load capacity

... Answer is B)
Explanation will provide as soon as possible.

10. Hall effect can be used
(i) to find type of semiconductor
(ii) to find carrier concentration
(iii) to measure conductivity

A) Only i
B) Only ii
C) Only iii
D) i,ii and iii

... Answer is D)
Explanation will provide as soon as possible.

11. Reactance relay is ?

A) Voltage operated and Current restrained
B) Directional unit operated and Current restrained
C) Current operated and Directional unit restrained
D) Directional unit operated and Voltage restrained

... Answer is C)
Explanation will provide as soon as possible.

12. The equivalent decimal and binary numbers of the given hexadecximal number (7BF)16 are ?

A) 1983; 0111 1011 1111
B) 1983; 0111 1011 1110
C) 1982; 0111 1011 1110
D) 1982; 0111 1011 1111

... Answer is A)
Explanation will provide as soon as possible.

13. The input and output voltages of a CE amplifier is ?

A) equal
B) 1800 Out of phase
C) always negative
D) in phase

... Answer is B)
Explanation will provide as soon as possible.

14. At resonant frequency for a series RLC circuit, the magnitude and phase of the voltage across C and L are respectively ?

A) equal and same in phase
B) equal and opposite in phase
C) unequal and same in phase
D) unequal and opposite in phase

... Answer is B)
Explanation will provide as soon as possible.

15. What is the frequency range of VHF electromagnetic waves ?

A) 30–300 kHz
B) 30–3000 kHz
C) 30–300MHz
D) 30–3000 MHz

... Answer is C)
Explanation will provide as soon as possible.

16. To reduce corona loss, what should be the shape of a conductor ?

A) Circular
B) Flat
C) Oval
D) Can be of any shape

... Answer is A)
Explanation will provide as soon as possible.

17. The speed of a three phase induction motor will increase, if the ?

A) number of poles of he stator winding is increased
B) number of poles of the stator winding is decreased
C) frequency of the stator supply is decreased
D) resistance of rotor circuit is increased

... Answer is B)
Explanation will provide as soon as possible.

18. The motor preferred for boom hoist in case of travelling cranes is ?

A) AC slip ring motor
B) Squirrel cage induction motor
C) Synchronous motor
D) Ward Leonard controlled DC shunt motor

... Answer is A)
Explanation will provide as soon as possible.

19. A differential amplifier has a differential gain of 28000 and CMRR is 60 dB. What will be the value of common mode gain ?

A) Ac = 0.125
B) Ac = 0.33
C) Ac = 3
D) Ac = 28

... Answer is D)
Explanation will provide as soon as possible.

20. Operations Management deals with which of the following ?

A) Manufacturing Process
B) Transportation and Logistics
C) Inventory Management and Purchase
D) Enterprises Resources Planning and Controlling

... Answer is A)
Explanation will provide as soon as possible.

21. For a NAND gate, when one or more inputs are low, then the output will be ?

A) alternately high and low
B) low
C) High
D) High or low depending on relative magnitude

... Answer is C)
Explanation will provide as soon as possible.

22. A short circuit test performed on a 25 KVA 2300/230 V transformer gives the measured value of the resistance as 0.8 Ω and 0.009 Ω on the two sides of the transformer. Its total equivalent resistance in Ω referred to LV side will be ?

A) 0.017 Ω
B) 0.09 Ω
C) 0.908 Ω
D) 1.7 Ω

... Answer is A)
Explanation will provide as soon as possible.

23. A bistable multivibrator is a ?

A) triggered oscillator
B) free running oscillator
C) saw tooth wave generator
D) crystal oscillator

... Answer is A)
Explanation will provide as soon as possible.

24. The reduced form of the Boolean expression AB BC AC + + is ?

A) AB + AC
B) AB + C
C) AC B+
D) AC+BC

... Answer is D)
Explanation will provide as soon as possible.

25. Distribution feeders are generally protected with ?

A) Directional relays at Infeed buses and Nondirectional relays at Load buses
B) Non–directional relays at Infeed buses and Directional relays at Load buses
C) Directional relays at Infeed buses and at load buses
D) Non-Directional relays at Infeed buses and at Load buses

... Answer is B)
Explanation will provide as soon as possible.

26. The latching current of a Silicon Controlled Rectifier is 20 mA. Its holding current could be ?

A) 10 mA
B) 21 mA
C) 40 mA
D) 60 mA

... Answer is D)
Explanation will provide as soon as possible.

27. You are responsible for transmitting a fixed amount of power over a fixed distance with a fixed line loss. What will be the amount of copper required to do it using a 3–phase, 3– wire system when compared to that of using a single-phase, 2–wire line system ?

A) one-fourth
B) three-fourth
C) one-third
D) half

... Answer is B)
Explanation will provide as soon as possible.

28. In DC welding ?

A) both electrode and work piece are positive
B) both electrode and work piece are negative
C) electrode is made positive and work piece negative
D) electrode is made negative and work piece positive

... Answer is D)
Explanation will provide as soon as possible.

29. A PCM system uses a uniform quantizer followed by a 6 bit encoder. The system bit rate is 60 Mbits/sec. The maximum bandwidth of the message signal for which this system operates satisfactorily would be ?

A) 2.5 MHz
B) 4.5 MHz
C) 5 MHz
D) 10 MHz

... Answer is C)
Explanation will provide as soon as possible.

30. The approximate efficiency of a 3–phase, 50 Hz, 4 pole induction motor running at 1455 rpm is 1455 rpm ?

A) 94%
B) 96%
C) 97%
D) 98%

... Answer is C)
Explanation will provide as soon as possible.

31. What will be the neutralizer inductive reactance in ohms for neutralising the 90%of line to earth capacitance of 1µF at 50 Hz ?

A) 1179
B) 1061
C) 1210
D) 950

... Answer is A)
Explanation will provide as soon as possible.

32. The phase sequence in a balanced 3-phase 4 wire AC system is RYB. If the voltage of R phase is 230∠0 0V, then for Y phase it is (Notations/symbols carry their usual meaning) ?

A) 230∠+1200 V
B) 230∠+600 V
C) 230∠+900 V
D) 230∠–1200V

... Answer is D)
Explanation will provide as soon as possible.

33. What is the function of megger ?

A) To measure power
B) To measure low resistance
C) To measure insulation resistance
D) To measure voltage

... Answer is C)
Explanation will provide as soon as possible.

34. The output of a JK flip-flop with asynchronous preset and clear inputs is '1'. The output can be changed to '0' with one of the following coneditions by applying ?

A) J = 0, K = 0, and using a clock
B) J = 1, K = 0 and using the clock
C) a synchronous preset input
D) J = 1, K = 1 and using the clock

... Answer is D)
Explanation will provide as soon as possible.

35. An auto transformer having 1250 turns is connected across a 250 V AC supply. What will be the secondary voltage obtained, if a tap is taken at 800th turn ?

A) 800 V
B) 200 V
C) 165 V
D) 160 V

... Answer is D)
Explanation will provide as soon as possible.

36. When two coupled coils of equal selfinductance are connected in series in one way, the net inductance is 6 mH and when they are connected in another way, the net inductance is 2 mH. What is the maximum value of net inductance, when they are connected in parallel in suitable way ?

A) 1.5 mH
B) 3 mH
C) 4 mH
D) 8 mH

... Answer is A)
Explanation will provide as soon as possible.

37. Which one of the following meters exhibits creeping phenomena ?

A) Ammeter
B) Voltmeter
C) Watt meter
D) Energy meter

... Answer is D)
Explanation will provide as soon as possible.

38. The rotor power output of a 3 phase induction motor is 12 kW and the corresponding slip is 4%. The rotor copper loss will be ?

A) 500 W
B) 525 W
C) 550 W
D) 600 W

... Answer is B)
Explanation will provide as soon as possible.

39. In a single phase full converter, the maximum value of firing angle for rectifier operation will be ?

A) 300
B) 450
C) 600
D) 900

... Answer is D)
Explanation will provide as soon as possible.

40. For protection of a 10 MVA, 132 kV/6.6 kV delta-star connected transformer, what will be turn ratio of current transformer on high voltage side in differential protrection scheme to circulate a current 5 A in pilot wires ?

A) 874.75: 5/1.732
B) 43.73: 5/1.732
C) 43.73: 5
D) 874.75: 5

... Answer is C)
Explanation will provide as soon as possible.

41. For a signal, which is amplitude modulated to a depth of 90% by a sinusoidal signal, what will be the ratio of transmitted power to the power of unmodulated carrier ?

A) 0.5
B) 0.81
C) 1.405
D) 1.5

... Answer is C)
Explanation will provide as soon as possible.

42. A commutator having a diameter of 76 cm rotates at 600 rpm. If the width of the brush is 1.5 cm, the approximate time of commutation is ?

A) 0.83 msec
B) 0.72 msec
C) 0.63 msec
D) 0.5 msec

... Answer is C)
Explanation will provide as soon as possible.

43. Which of the following types of motor is preferred for smooth and precise speed control over a wide range operation ?

A) Synchronous motor
B) Squirrel cage induction motor
C) Wound rotor induction motor
D) DC motor

... Answer is D)
Explanation will provide as soon as possible.

44. As compared to power MOSFET, a BJT has ?

A) lower switching losses but higher conduction loss
B) higher switching losses and higher conduction loss
C) higher switching losses but lower conduction loss
D) lower switching losses and lower conduction

... Answer is C)
Explanation will provide as soon as possible.

45. Swinburne's method CANNOT be used for determining the efficiency of a DC series motor, because ?

A) it is not advisable to run a series motor on no load
B) a series motor takes excessive current at no load
C) a series motor develops a very high starting torque
D) It is not possible to load dc series motor in steps

... Answer is A)
Explanation will provide as soon as possible.

46. Two identical 3000 kVA, 3-phase synchronous generators operate in parallel. The governor of the first is so adjusted that frequency drops from 50 Hz at no load to 47 Hz at full load. The corresponding drop for the second machine is 50 Hz to 48 Hz. What is the maximum load at unity power factor that can be delivered without overloading either of the machines ?

A) 2000 kW
B) 3000 kW
C) 5000 kW
D) 6000 kW

... Answer is C)
Explanation will provide as soon as possible.

47. Which of the following is minimised by laminating the core of a transformer ?

A) Hysteresis loss
B) eddy current loss
C) Heat loss
D) Copper loss

... Answer is B)
Explanation will provide as soon as possible.

48. For controlling the speed of an induction motor the supply frequency is increased by 10%. For maximum torque to remain constant, the supply voltage must ?

A) be decreased by 10%
B) be increased by 10%
C) remain constant
D) be reduced or increased by 20%

... Answer is B)
Explanation will provide as soon as possible.

49. Above the curie temperature, Ferro-magnetic material behaves like ?

A) paramagnetic
B) diamagnetic
C) anti-ferromagnetic
D) ferromagnetic

... Answer is A)
Explanation will provide as soon as possible.

50. What will be the continuous rating of a 100 kW motor if the duty cycle is 10 minute for full load 3/4 th of full load for next 10 minute for half load for next 20 minutes and no load for next 20 minutes and cycle repeats ?

A) 54.45 kW
B) 58.63 kW
C) 73.21 kW
D) 82.0 kW

... Answer is B)
Explanation will provide as soon as possible.

51. Match List-1 with List-2 and select the correct answer using the codes given below for each list List-1 (SCR Ratings List-2 (Protective Element)
i. di/dt limit 1. Snubber circuit
ii. dv/dt limit 2. Heat Sink
iii. i2 t 3. Series reactor
iv. Junction temperature limit 4. To avoid runway speed on no load

A) i-1, ii-2, iii-3, iv-4
B) i-3, ii-1, iii-4, iv-2
C) i-3, ii-4, iii-2, iv-1
D) i-4, ii-3, iii-1, iv-2

... Answer is B)
Explanation will provide as soon as possible.

52. A 100 kVA, 1100V/440 V, 50 Hz single phase transformer has 100 turns on the low voltage winding. The number of turns on the high voltage winding will be ?

A) 40
B) 125
C) 250
D) 500

... Answer is C)
Explanation will provide as soon as possible.

53. If B is the total number of branches of the graph and N is the number of nodes, then the total number of links (L) should be ?

A) (B+N+1)
B) (B–N–1)
C) (B–N+1)
D) (B+N+1)

... Answer is C)
Explanation will provide as soon as possible.

54. A 4 pole dc shunt motor working on 250 V takes a current of 2 A, when running at no load at 1000 rpm. Armature resistance and shunt field resistance are 0.2 Ω and 250 Ω respectively. What will be the percentage speed drop, if the motor takes 51 A at a certain load ?

A) 2.98
B) 3.9
C) 4.8
D) 5.9

... Answer is B)
Explanation will provide as soon as possible.

55. When an alternator is feeding an infinite bus bar ?

A) the excitation controls the reactive power output and the governor setting controls the real power output
B) the excitation controls both the real and reactive power output
C) the excitation controls the terminal voltage and the governor setting controls the real power output
D) the governor setting controls the terminal voltage

... Answer is A)
Explanation will provide as soon as possible.

56. In cascade converter, if Pm and Pg represents the number of poles on the AC and DC ends, then the synchronous speed corresponding to the sum of the poles of both machines is ?

A) 120 f/Pm
B) 120 f/Pg
C) 120 f/(Pm+Pg)
D) 120 f/(Pm–Pg)

... Answer is C)
Explanation will provide as soon as possible.

57. Which of the following is the most common type of power plants used in ships for generating electrical power ?

A) Diesel Engines
B) Hydraulic turbines
C) Nuclear power plants
D) Steam accumulators

... Answer is A)
Explanation will provide as soon as possible.