SSC ELECTRICAL

EEMCQS

SSC Jr. Engg. (Electrical) - 2014 by Bikshan Ghosh Assistant Engineer(Electrical) – Public Works Department, Govt. of West Bengal

Previous Five Year Question Papers With Answers (Key Only)

2014

EEMCQS

Staff Selection Commission – 2014 Recruitment to the post of

Junior Engineer (ELECTRICAL) Previous Five Year Question Papers With Answers (Key Only)

Multiple Choice Questions (Technical Questions Only)

By Er. Bikshan Ghosh M.E.( Electrical Engg.) First Class First & Silver Madelist, Bengal Engg. & Science University, Shibpur 2

CONTENTS Syllabus

4

Scheme of Examination

6

SSC JE (Electrical) Question Paper – 2013

8

Solution(Key) to SSC JE (Electrical) Question Paper – 2013

27

SSC JE (Electrical) Question Paper – 2012

28

Solution(Key) to SSC JE (Electrical) Question Paper – 2012

47

SSC JE (Electrical) Question Paper – 2011

48

Solution(Key) to SSC JE (Electrical) Question Paper – 2011

57

SSC JE (Electrical) Question Paper – 2010

58

Solution(Key) to SSC JE (Electrical) Question Paper – 2010

66

SSC JE (Electrical) Question Paper – 2009

67

Solution(Key) to SSC JE (Electrical) Question Paper – 2009

74

SSC JE (Electrical) Practice Paper – I

75

Solution(Key) to SSC JE (Electrical) Practice Paper – I

85

3

SYLLABUS Electrical Engineering Basic Concepts : Concepts of resistance, inductance, capacitance, and various factors affecting them. Concepts of current, voltage, power, energy and their units. Circuit Law : Kirchhoff‘s law, Simple Circuit solution using network theorems. Magnetic Circuit : Concepts of flux, mmf, reluctance, Different kinds of magnetic materials, Magnetic calculations for conductors of different configuration e.g. straight, circular, solenoidal, etc. Electromagnetic induction, self and mutual induction. AC Fundamentals : Instantaneous, peak, R.M.S. and average values of alternating waves, Representation of sinusoidal wave form, simple series and parallel AC Circuits consisting of R.L. and C, Resonance, Tank Circuit. Poly Phase system – star and delta connection, 3 phase power, DC and sinusoidal response of R-Land R-C circuit. Measurement and Measuring Instruments : Measurement of power (1 phase and 3 phase, both active and re-active) and energy, 2 wattmeter method of 3 phase power measurement. Measurement of frequency and phase angle. Ammeter and voltmeter (both moving oil and moving iron type), extension of range wattmeter, Multimeters, Megger, Energy meter AC Bridges. Use of CRO, Signal Generator, CT, PT and their uses. Earth Fault detection. Electrical Machines : (a) D.C. Machine – Construction, Basic Principles of D.C. motors and generators, their characteristics, speed control and starting of D.C. Motors. Method of braking motor, Losses and efficiency of D.C. Machines. (b) 1 phase and 3 phase transformers – Construction, Principles of operation, equivalent circuit, voltage regulation, O.C. and S.C. Tests, Losses and efficiency. Effect of voltage, frequency and wave form on losses. Parallel operation of 1 phase /3 phase transformers. Auto transformers. (c) 3 phase induction motors, rotating magnetic field, principle of operation, equivalent circuit, torque-speed characteristics, starting and speed control of 3 phase induction motors. Methods of braking, effect of voltage and frequency variation on torque speed characteristics. Fractional Kilowatt Motors and Single Phase Induction Motors : Characteristics and applications. Synchronous Machines - Generation of 3-phase e.m.f. armature reaction, voltage regulation, parallel operation of two alternators, synchronizing, control of active and reactive power. Starting and applications of synchronous motors. Generation, Transmission and Distribution – Different types of power stations, Load factor, diversity factor, demand factor, cost of generation, inter-connection of power 4

stations. Power factor improvement, various types of tariffs, types of faults, short circuit current for symmetrical faults. Switchgears – rating of circuit breakers, Principles of arc extinction by oil and air, H.R.C. Fuses, Protection against earth leakage / over current, etc. Buchholtz relay, Merz-Price system of protection of generators & transformers, protection of feeders and bus bars. Lightning arresters, various transmission and distribution system, comparison of conductor materials, efficiency of different system. Cable – Different type of cables, cable rating and derating factor. Estimation and Costing : Estimation of lighting scheme, electric installation of machines and relevant IE rules. Earthing practices and IE Rules. Utilization of Electrical Energy : Illumination, Electric heating, Electric welding, Electroplating, Electric drives and motors. Basic Electronics : Working of various electronic devices e.g. P N Junction diodes, Transistors (NPN and PNP type), BJT and JFET. Simple circuits using these devices.

5

SCHEME OF EXAMINATION The examination will be conducted in two stages: A. Written Test (500 marks) B. Interview (100 marks) A. Written Test Papers Paper-I Objective type (OMR Answer Sheets will be provided for this Paper)

Paper-II Conventional Type

Subjects (i) General Intelligence & Reasoning (ii) General Awareness (iii) Part –A General Engineering (Civil & Structural) OR Part-B General Engineering (Electrical) OR Part-C General Engineering (Mechanical) Part –A General Engineering (Civil & Structural) OR Part – B General Engineering (Electrical) OR Part-C General Engineering (Mechanical)

Maximum Marks 50

Duration 2 Hours

50

100

2 Hours

300

B. Personality Test (Interview)

Maximum Marks : 100

NOTE-I: Only those candidates who secure at least the minimum qualifying marks in the written examination as may be fixed by the Commission at its discretion, will be eligible to appear in the Interview. The interview will be held at places as may be decided by the Commission. NOTE-II: SC/ST candidates called for interview will be paid TA as per Government Orders. However, no TA is payable to any candidate for appearing in the written examination.

6

NOTE-III: Canvassing in any form whatsoever will lead to cancellation of the candidates. Note-IV: The Commission may, its discretion fix minimum qualifying standards in interview.

7

SSC JE (Electrical) – 2013 ‘Question Paper’ Q. No. 1. Resistance temperature coefficient of copper at 20°C is (A) 0.0045/°C

(B) 0.0017/°C

(C) 0.00393/°C

(D) 0.0038/°C

Q. No. 2. The load characteristics of dc shunt generator is determined by (A) the voltage drop in armature resistance (B) the voltage drop due to armature reaction, voltage drop due to decreased field current and voltage drop in armature resistance (C) the voltage drop due to armature reaction and voltage drop in armature resistance (D) the voltage drop due to armature reaction, voltage drop due to decreased field current and voltage drop in armature resistance and field resistance. Q. No. 3. How many watt-seconds are supplied by a motor developing 2 hp (British) for 5 hours? (A) 2.6856×107 watt-seconds

(B) 4.476×105 watt-seconds

(C) 2.646×107 watt-seconds

(D) 6.3943×106 watt-seconds

Q. No. 4. A 4-pole generator is running at 1200 rpm. The frequency and time period of the emf generated in its coil are respectively (A) 50 Hz, 0.02 sec.

(B) 40 Hz, 0.025 sec.

(C) 300 Hz, 0.00333 sec.

(D) 240 Hz, 1/2400 sec.

Q. No. 5. The voltage wave 𝑣 = 𝑉𝑚 sin⁡ (𝜔𝑡 − 15°) volt is applied across an ac circuit. If the current leads the voltage by 10° and the maximum value of current is I m, then the equation of current is (A) 𝑖 = 𝐼𝑚 sin⁡ (𝜔𝑡 + 5°) amps

(B) 𝑖 = 𝐼𝑚 sin⁡ (𝜔𝑡 − 25°) amps

(C) 𝑖 = 𝐼𝑚 sin⁡ (𝜔𝑡 + 25°) amps

(D) 𝑖 = 𝐼𝑚 sin⁡ (𝜔𝑡 − 5°) amps

Q. No. 6. The average value of current (Iav) of sinusoidal wave of peak value (I m) is (A) Iav=Im/2

(B) Iav=(𝜋/2)×Im

(C) Iav=(2/𝜋)×Im

(D) Iav=Im/ 2

8

𝑑𝜑

Q. No. 7. The emf induced in a coil is given by 𝑒 = −𝑁. 𝑑𝑡 , where ‘e’ is the induced emf, N is number of turns and ‘d𝜑’ is the instantaneous flux linkage with the coil in time ‘dt’. The negative sign in above expression is due to (A) Hans Christian Oersted

(B) Andre-Marie Ampere

(C) Michael Faraday

(D) Emil Lenz

Q. No. 8. The mutual inductance between two coils having self inductances 3 henry and 12 henry and coupling coefficient 0.85 is (A) 12.75 henry

(B) 5.1 henry

(C) 0.425 henry

(D) 1.7 henry

Q. No. 9. Two parallel conductors carrying current in opposite directions will exert on each other (A) an attractive force

(B) a repulsive force

(C) an axial force

(D) no force

Q. No. 10. The unit of reluctance of magnetic circuit is (A) AT/m

(B) Weber/m

(C) AT/Weber

(D) Weber/AT

Q. No. 11. In indicating instrument the springs are mainly used to (A) conduct the current to the coil

(B) hold the pivot in position

(C) control the pointer movement

(D) reduce the vibration of the pointer

Q. No. 12. A balanced 3-phase, 3-wire supply feeds balanced star connected resistors. If one of the resistors is disconnected, then the percentage reduction in load will be (A) 33.33

(B) 50

(C) 66.67

(D) 75

Q. No. 13. The total flux at the end of a long permanent bar magnet is 100×10 -6 Wb..The end of this magnet is withdrawn through a 1000 turn coil in 1/20 seconds. The induced emf in the coil is (A) 20.0 V

(B) 2.0 V

(C) 0.2 V

(D) 0.02 V

9

Q. No. 14. The single phase Induction Motor(IM) which does not have centrifugal switch is (A) capacitor start single phase IM (B) resistance split single phase IM (C) capacitor start capacitor run single phase IM (D) permanent capacitor run single phase IM Q. No. 15. When a multiplier is added to an existing volt meter for extending its range, its electromagnetic damping (A) remains unaffected (B) increases (C) decreases (D) changes by an amount depending on the controlling torque Q. No. 16. Phasor diagram of load voltage (V), current in pressure coil (I P) and current in current coil (IC) is shown in figure when an electrodynamic wattmeter is used to measure power. The reading of the wattmeter will be proportional to

(A) cos⁡ (𝛽 + 𝜓)

(B) cos⁡𝜓

(C) cos β cos 𝜓

(D) cos 𝛽 cos⁡ (𝛽 + 𝜓)

Q. No. 17. An ammeter of resistance R m is placed in an arrangement as shown in the figure. Material of Rm, Rsh is copper whereas that of Rs, Rx is manganin. The condition for which the meter performance is compensated against the temperature, is

10

1

1

𝑚

𝑠ℎ

1

1

𝑠

𝑥

(A) 𝑅 + 𝑅 = 𝑅 + 𝑅

(B) 𝑅𝑚 𝑅𝑠ℎ = 𝑅𝑠 𝑅𝑥

(C) 𝑅𝑚 +𝑅𝑠ℎ = 𝑅𝑠 +𝑅𝑥

(D)

𝑅𝑚 𝑅𝑠

=

𝑅𝑠ℎ 𝑅𝑥

Q. No. 18. If a 110 V, 50 Hz is supplied across a PMMC voltmeter of full-scale range 0220 V and internal resistance of 10 kΩ, reading of the voltmeter will be (A) 0 V

(B) 110 2 V

(C) 78 V

(D) 55 V

Q. No. 19. To maximize the driving torque in an induction type instrument, flux produced by shunt coil and series coil should be (A) in phase with each other (B) in quadrature with each other (C) displaced by 45° with respect to each other (D) out of phase with respect to each other Q. No. 20. To minimize the error due to lead and contact resistances, low resistances used in electrical measurement work are provided with (A) guard rings

(B) four terminals

(C) thick insulation

(D) metal shields

Q. No. 21. In reference to the figure, the voltage waveform v(t) is measured by a PMMC, a PMMC combined with bridge rectifier and a moving iron (MI) instrument. Two lists are provided thereafter:

Instrument

List of instrument reading

a. PMMC

i. 5 V

b. PMMC rectifier

ii. 2.75 V 11

c. M.I.

iii. 2.5 V

The correct option relating the instruments and their reading is (A) a-i, b-ii, c-iii

(B) a-iii, b-ii, c-i

(C) a-ii, b-iii, c-i

(D) a-iii, b-i, c-ii

Q. No. 22. The switching transistor as shown, carries in the collector side an rms current of 8 mA. If the frequency of rectangular pulse train v i is 50 Hz, then on-time of the transistor is

(A) 20 ms

(B) 6.4 ms

(C) 12.8 ms

(D) 16 ms

Q. No. 23. In electronic circuits, for blocking the DC component of a voltage signal, a/an ____________ is connected in series with the voltage source. (A) capacitor

(B) diode

(C) resistor

(D) inductor

Q. No. 24. For n-type semiconductor, the doping material is (A) teteravalent

(B) pentavalent

(C) trivalent

(D) bivalent

Q. No. 25. An attenuator probe as shown, is connected to an amplifier of input capacitance 0.1 𝜇𝐹. Value of C that must be connected across 100 kΩ to make the overall gain independent of frequency, is

12

(A) 0.01 μF

(B) 0.1 μF

(C) 1 μF

(D) 10 μF

Q. No. 26. Silicon content in iron lamination is kept within 5% as it (A) makes the material brittle

(B) reduces the curie point

(C) increases the hysteresis loss

(D) increases the cost

Q. No. 27. A wattmeter is marked 15 A/30 A, 300 V/600 V and its scale is marked up to 4500 watts. When the meter is connected for 30 A, 600 V, the point indicated 2000 watts. The actual power in the circuit is (A) 2000 watts

(B) 4000 watts

(C) 6000 watts

(D) 8000 watts

Q. No. 28. Examine the two statements ‘A’ and ‘R’ and select your answer. Statement A: Switching of a lamp in house produces noise in a radio. Statement R: Switching operation produces arc across separating contacts. (A) Both A and R are true and R is a correct explanation of A (B) Both A and R are true and R is not a correct explanation of A (C) A is true but R is false (D) A is false but R is true Q. No. 29. The small pockets of air in the high voltage cable provided ____________ relative permittivity, ____________ electric field at these sites breakdown is likely to be initiated. (A) high, high

(B) low, low

(C) low, high

(D) high, low

Q. No. 30. The capacitance measured between any two cores of a 3-core cable with the sheath earthed is 3 𝜇𝐹. The capacitance per phase will be (A) 1.5 𝜇𝐹

(B) 6 𝜇𝐹

(C) 1 𝜇𝐹

(D) None of the above

Q. No. 31. In an insulated cable having core diameter d and overall diameter D, the ratio of maximum to minimum dielectric stress is given by

13

(A) (𝐷/𝑑)1/2

(B) (𝐷/𝑑)2

(C) 𝐷/𝑑

(D) 𝑑/𝐷

Q. No. 32. Compared to the braking capacity of a circuit breaker, its making capacity should be (A) more (B) less (C) equal (D) the two are unrelated to each other Q. No. 33. In case of frosted GLS lamps, frosting is done by (A) acid etching

(B) ammonia

(C) ozone

(D) salt water

Q. No. 34. If the supply polarity to the armature terminal of a separately excited d.c. motor is reversed, the motor will run under (A) Plugging condition

(B) Regenarative breaking condition

(C) Dynamic breaking condition

(D) Normal motoring condition

Q. No. 35. For welding purpose, the secondary of transformer used should be capable of carrying (A) high voltage, high current

(B) high voltage, low current

(C) low voltage, high current

(D) low voltage, low current

Q. No. 36. Which of the following is correct? (A) Load factor = Capacity factor × Utilization factor (B) Utilization factor = Capacity factor × Load factor (C) Capacity factor = Load factor × Utilization factor (D) Load factor has no relation with capacity factor and utilisation factor Q. No. 37. In a motor starter, the electromechanical contractor provides inherent protection against (A) over-current

(B) short-circuit

(C) single-phasing

(D) under-voltage 14

Q. No. 38. Resistance switching is normally employed for (A) bulk oil breakers

(B) minimum oil breakers

(C) air blast circuit b reakers

(D) all of A, B and C

Q. No. 39. If the angular frequency of an alternating voltage is ω, then the angular frequency of instantaneous real power absorbed in an ac circuit is (A) 2 ω

(B) ω

(C) 3 ω

(D) ω/2

Q. No. 40. For the configuration below, of the transistor, what is the value of R? Given 𝛽=45.

(A) 85.64 k

(B) 63.14 k

(C) 72.15 k

(D) 91.18 k

Q. No. 41. In a balanced 3-phase circuit, the line current is 12 A. When the power is measured by two wattmeter method, one wattmeter reads 11 kW while the other reads zero. Power factor of the load is (A) 0

(B) 0.5

(C) 0.866

(D) 1.0

Q. No. 42. Two lossy capacitors with equal capacitance values and power factor of 0.01 and 0.02 are in parallel, and the combination is supplied from a sinusoidal voltage source. The power factor of the combination is (A) 0.03

(B) 0.015

(C) 0.01

(D) 0.0002

15

Q. No. 43. A voltmeter when connected across a dc supply, reads 124 V. When a series combination of the volt meter and unknown resistance X is connected across the supply, the meter reads 4 V. If the resistance of the voltmeter is 50 kΩ, the value of X is (A) 1550 kΩ

(B) 1600 kΩ

(C) 1.6 kΩ

(D) 1.5 MΩ

Q. No. 44. The purpose of providing a choke in the tube-light is (A) to eliminate the corona effects (B) to avoid radio interference (C) to improve power factor (D) to limit current to appropriate value Q. No. 45. In a 3-phase 400 V, 4-wire system, two incandescent lamps, one having 230 V, 100 W specification and the other 230 V, 200 W are connected between R phaseneutral and Y phase-neutral respectively. If the neutral wire breaks (A) 100 W lamp will fuse first (B) 200 W lamp will fuse first (C) both the lamp will fuse together (D) both the lamp will glow Q. No. 46. In the circuit, v is the input voltage applied across the capacitor of 2 F. Current through the capacitor is

16

Q. No. 47. In a semiconductor, the resistivity (A) depends on temperature

(B) depends on the voltage

(C) depends on the current through it

(D) None of the above

Q. No. 48. A geyser is operated from 230 V, 50 c/s mains. The frequency of the instantaneous power consumed by the geyser is (A) 25 c/s

(B) 50 c/s

(C) 100 c/s

(D) 150 c/s

Q. No. 49. Ampere-second is the unit of (A) emf

(B) power

(C) electric charge

(D) energy

Q. No. 50. If the insulation resistance of 2 m long sample of a cable is 10 MΩ, then the 8m sample of the same will have an insulation resistance of (A) 40 MΩ

(B) 2.2 MΩ

(C) 2 MΩ

(D) 5.5 MΩ

Q. No. 51. A inductor is supplied from a sinusoidal voltage source. The magnetic field energy in the inductor changes from peak value to minimum value in 10 msec. The supply frequency is (A) 50 Hz

(B) 25 Hz

(C) 1 Hz

(D) 100 Hz

Q. No. 52. Two 2000 Ω, 2 watt resistors are connected in parallel. Their combined resistance value and wattage ratting are (A) 1000 Ω, 2 watt

(B) 1000 Ω, 4 watt

(C) 2000 Ω, 4 watt

(D) 2000 Ω, 2 watt

Q. No. 53. We have three resistances each of value 1 Ω, 2 Ω and 3 Ω. If all the resistances are to be connected in a circuit, how many different values of equivalent resistance are possible? (A) Five

(B) Six

(C) Seven

(D) Eight

Q. No. 54. One B.O.T unit is

17

(A) 100 kWh

(B) 10 kWh

(C) 1 kWh

(D) 0.1 kWh

Q. No. 55. An electric heater draws 1000 watts from a 250 V source. The power drawn from 200 V source is (A) 800 W

(B) 640 W

(C) 1000 W

(D) 1562.5 W

Q. No. 56. Three 3 μF capacitors are in series. A 6 μF capacitor is in parallel with this series arrangement. The equivalent capacitance of the combination is (A) 7 μF

(B) 15 μF

(C) 3.6 μF

(D) 1 μF

Q. No. 57. A solenoid of inductance 250 mH and resistance 10 Ω is connected to a battery. The time taken for the magnetic energy 1/4 th of its maximum value is (A) loge(2)

(B) 10-3loge(2)

(C) 25loge(2)

(D) (1/40)loge(2)

Q. No. 58. The peak value of the output voltage of half-wave rectifier is 100 V. The r.m.s value of the half-wave rectifier output voltage will be (A) 100 V

(B) 50 V

(C) 70.7 V

(D) 35.35 V

Q. No. 59. The given circuit represents a

(A) monostable multivibrator

(B) astable multivibrator

(C) Schmitt trigger

(D) bistable multivibrator 18

Q. No. 60. The input resistance of a FET is of the order of (A) 100 Ω

(B) 10 kΩ

(C) 1 MΩ

(D) 100 MΩ

Q. No. 61. In a series R-L circuit supplied from a sinusoidal voltage source, voltage across R and L are 3 V and 4 V respectively. The supply voltage is then (A) 7 V

(B) 1 V

(C) 3.5 V

(D) 5 V

Q. No. 62. In squirrel cage induction motor, the rotor conductors are (A) open circuited (B) short circuited via end rings (C) short circuited via external resistances (D) None of the above Q. No. 63. A 3-phase synchronous motor is started by utilizing the torque developed in (A) the high-speed steam turbine

(B) the damper winding on the rotor

(C) the damper winding on the stator

(D) the low-speed water-turbine

Q. No. 64. If the frequency of input voltage of a transformer is increased keeping the magnitude of the voltage unchanged, then (A) both hysteresis loss and eddy current loss in the core will increase (B) hysteresis loss will increase but eddy current loss will decrease (C) hysteresis loss will increase but eddy current loss will remain unchanged (D) hysteresis loss will decrease but eddy current loss will increase Q. No. 65. Two single-phase ac motors A and B operate from a 1000 V supply. A consumes 2 KW at a power factor of 0.8 (lagging) and B consumes 1 kW at a power factor of 0.5 (lagging). The total current drawn from the supply is approximately (A) 4.5 A

(B) 2.1 A

(C) 4.41 A

(D) 9 A

Q. No. 66. The high-voltage and low-voltage winding resistances of a distribution transformer of 100 kVA, 1100/220 volts, 50 Hz are 0.1 Ω and 0.004 Ω respectively. The

19

equivalent resistances referred to high-voltage side and low-voltage side are respectively (A) 2.504 Ω and 0.2 Ω

(B) 0.2 Ω and 0.08 Ω

(C) 0.10016 Ω and 2.504 Ω

(D) 0.008 Ω and 0.10016 Ω

Q. No. 67. A dc motor has an armature resistance of 0.06 Ω and series field resistance of 0.08 Ω. The motor is connected to a 400 V supply. The line current is 20 A when the speed of the machine is 1100 rpm. When the line current is 50 A and the excitation is increased to 30%, speed of the machine in rpm is (A) 1100

(B) 1003

(C) 837

(D) 938

Q. No. 68. The voltage across R, L and C are 3 V, 14 V and 10 V respectively as in the figure. If the voltage source is sinusoidal, then the input voltage (r.m.s) is

(A) 10 V

(B) 5 V

(C) 2.5 V

(D) 15 V

Q. No. 69. In 1-phase series RL circuit fed by voltage source, the resistance and reactance values are 4 Ω each. In this circuit (A) the current leads the voltage by 45°

(B) the current lags the voltage by 45°

(C) the current lags the voltage by 60°

(D) None of the above

Q. No. 70. Superposition theorem require as many circuits to be solved as there are (A) nodes

(B) sources

(C) loops

(D) None of the above

Q. No. 71. Application of Norton’s theorem in a circuit results in (A) a current source and an impedance in parallel 20

(B) a voltage source and an impedance in series (C) an ideal voltage source (D) an ideal current source Q. No. 72.

The voltage (v) vs. current (i) curve of the circuit is shown below:

Internal resistance of the source e is (A) 24 Ω

(B) 4 Ω

(C) 10 Ω

(D) 14 Ω

Q. No. 73. Value of the load impedance 𝑍𝐿 for which the load consumes maximum power is

21

(A) 50 Ω at a power factor of 0.6 lead

(B) 50 Ω at a power factor of 0.6 lag

(C) 30 Ω at a power factor of unity

(D) None of the above

Q. No. 74. A tank circuit consists of (A) an inductor and a capacitor connected in series (B) an inductor and a capacitor connected in parallel (C) a pure inductance and a pure capacitance connected in series (D) a pure inductance and a pure capacitance connected in parallel Q. No. 75. The instantaneous power of a 1-phase series circuit supplying R-L load from a sinusoidal voltage source has in each cycle (A) negative twice, zero four times (B) zero twice, negative once (C) negative four times, zero twice (D) negative twice, zero once Q. No. 76. In a series R-L-C circuit, the “Q-factor” is given by 1

𝐿

(A) 𝑄 = 𝑅

𝐶

1

𝐶

(C) 𝑄 = 𝑅

(B) 𝑄 = 𝑅 (D) 𝑄 = 𝑅

𝐿

𝐿 𝐶 𝐶 𝐿

Q. No. 77. In an ac circuit, V = (200 + j40) V and I = (30 – j 10) A. The active and reactive power of the circuit are respectively (A) 6400 W, 800 VAR capacitive

(B) 6400 W, 800 VAR inductive

(C) 5600 W, 3200 VAR capacitive

(D) 5600 W, 3200 VAR inductive

Q. No. 78. Three equal impedances are first connected in delta across a 3-phase balanced supply. If the same impedances are connected in star across the same supply (A) phase currents will be 1/3rd of the previous value (B) line currents will be 1/3rd of the previous value (C) power consumed will be 1/3rd of the previous value (D) power consumed will be 3 times the previous value Q. No. 79. The average value of the voltage wave v = 110 + 175 sin (314 t - 25°) volts is 22

(A) 100 V

(B) 175 V

(C) 165.57 V

(D) 206.7 V

Q. No. 80. A current from an ac source bifurcates into two branches A and B in parallel. Branch A is an inductor with 30 μH inductance and 1 Ω resistance. Branch B is another inductor with inductance L and 1.5 Ω resistance. For the ratio of currents in the branches to be independent of supply frequency, value of L should be (A) 30.5 μH

(B) 20 μH

(C) 45 μH

(D) 29.5 μH

Q. No. 81. A universal motor is one which (A) can run on any value of supply voltage (B) has infinitely varying speed (C) can operate ac as well as dc voltage (D) can work as single-phase or three-phase motor Q. No. 82. The speed-torque characteristic of a dc series motor operating from constant voltage supply is (A)

(B)

(C)

(D)

Q. No. 83. Match List I (Machine) with List II (graph) and select the appropriate response. List I List II a. DC Motor

(i) Circle diagram 23

List I

List II

b. DC Generator

(ii) V-curve

c. Alternator

(iii) Circle diagram

d. Induction motor

(iv) Circle diagram

(A) a-(iv), b-(iii), c-(i), d-(ii)

(B) a-(iii), b-(iv), c-(ii), d-(i)

(C) a-(iv), b-(iii), c-(ii), d-(i)

(D) a-(iii), b-(iv), c-(i), d-(ii)

Q. No. 84. A voltage source having an open-circuit voltage of 150 V and internal resistance of 75 Ω, is equivalent to a current source of (A) 2 A in series with 75 Ω

(B) 2 A in parallel with 37.5 Ω

(C) 2 A in parallel with 75 Ω

(D) 1 A in parallel with 150 Ω

Q. No. 85. A 300 kW alternator is driven by a prime mover of speed regulation 4% while the prime mover of another 200 kW alternator has a speed regulation of 3%. When operating in parallel, the total load they can take without any of them being overloaded is (A) 500 kW

(B) 567 kW

(C) 425 kW

(D) 257 kW

Q. No. 86. The commutator in a dc machine acts as (A) a mechanical inverter

(B) a mechanical rectifier

C) current controller

(D) either (A) or (B)

Q. No. 87. The purpose of using dummy coil in a dc machine is to (A) eliminate harmonics developed in the machine (B) eliminate armature reaction (C) bring mechanical balance of the armature (D) bring mechanical balance of the body of the motor Q. No. 88. If the centrifugal fuse of a single-phase resistance split induction motor does not operate after starting of the motor, the motor (A) will run above normal speed (B) will run below normal speed (C) will draw very small current 24

(D) will draw very high current and over-heated Q. No. 89. Alternators are usually designed to generate which type of ac voltage? (A) With fixed frequency

(B) With variable frequency

(C) Fixed current

(D) Fixed power factor

Q. No. 90. Three inductors each of 60 mH are connected in delta. The value of inductance of each arm of the equivalent star connection is (A) 10 mH

(B) 15 mH

(C) 20 mH

(D) 30 mH

Q. No. 91. The magnetic field energy in an inductor changes from maximum value to minimum value in 5 msec when connected to an ac source. The frequency of the source in Hz is (A) 500

(B) 200

(C) 50

(D) 20

Q. No. 92. In the circuit as shown, voltage measured between A, B is found to be 70 V. Value of M is

(A) 30 mH

(B) 100 mH

(C) 200 mH

(D) 70 mH

Q. No. 93. Two coupled coils, connected in series, have an equivalent inductance of 16 mH or 8 mH depending on the connection. The mutual inductance between the coils is (A) 12 mH

(B) 8 2 mH

(C) 4 mH

(D) 2 mH

Q. No. 94. Tesla is the unit of

25

(A) electric flux density

(B) magnetic flux intensity

(C) electric field intensity

(D) magnetic flux density

Q. No. 95. Which of the following is a valid value of coefficient of coupling between two inductors? (A) 1.414

(B) 0.9

(C) 1.732

(D) 17.32

Q. No. 96. An inductor with ferromagnetic core supplied from a sinusoidal voltage source with frequency ‘f’. The current drawn by the inductor will be (A) sinusoidal with frequency ‘f’

(B) sinusoidal with frequency ‘2f’

(C) a sawtooth wave

(D) non-sinusoidal with frequency ‘f’

Q. No. 97. For a 6-pole dc machine with wave wound armature, the number of brushes required is (A) 2

(B) 4

(C) 6

(D) 12

Q. No. 98. Functions of interpoles in a dc machine is to (A) reduce field winding heating

(B) improve commutation

(C) compensate for air-gap variation

(D) reduce losses

Q. No. 99. The commutator segments of dc machine are made of (A) tungsten

(B) hard-drawn copper

(C) soft copper

(D) electrolytic copper

Q. No. 100. Which of the following is a speed control method of three-phase squirrel cage induction motor? (A) Plugging method

(B) Star-delta switch method

(C) Pole-changing method

(D) Centrifugal clutch method

End of Paper

26

‘Solution Keys’ QNO. ANS

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

[ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [

C B A B D C D B B C C B B D C C D A B B B C A B A A D A C B C A B A C C D C A A B B D D A D A C C B

QNO. ANS

] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ]

51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100

27

[ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [ [

B B D C B A D B C D D B B C C B C B B B A D A D A A D C A C C C C C C D C D A C C A D D B D A B B C

] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ] ]

SSC JE (Electrical) – 2012 ‘Question Paper’ Q. No. 1. The wave shape of current flowing through an inductor is

The wave shape of voltage drop (v) across the inductor is (A)

(B)

(C)

(D)

Q. No. 2. Two wires A and B of the same material but of different lengths L and 2L have the radius r and 2r respectively. The ratio of specific resistance will be (A) 1 : 8

(B) 1 : 1

(C) 1 : 2

(D) 1 : 4

Q. No. 3. A 20 𝜇F capacitor is connected across an ideal voltage source. The current in the capacitor (A) None of these are true (B) will be zero at first, then exponentially decay 28

(C) will be very high at first, then exponentially decay (D) will be very high at first, then exponentially decay and at steady state becom zero Q. No. 4. In general, if a sine wave is fed into a Schmitt trigger, the output will be (A) a saw-tooth wave

(B) an amplified sine wave

(C) a triangular wave

(D) a square wave

Q. No. 5. In the given circuit the function of the diode D is

(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 Q. No. 6. FETs are (A) None of these

(B) unipolar devices

(C) bipolar devices

(D) either unipolar or bipolar

Q. No. 7. In the circuit, forward resistance of the diode D is 2 Ω and its reverse resistance is infinitely high.

29

A list consists of meters (List – I) and another list shows the meter readings (List – II). List – I

List – II

(i) PMMC

(a) 7.07 A

(ii) Hot wire

(b) 4.5 A (c) 10 A (d) 12.5 A

Which one of the options given here is correct to indicate the type of meter (List – I) and its reading (List – II)? (A) (i)⟶(b), (ii) ⟶ (d)

(B) (i)⟶(a), (ii) ⟶ (b)

(C) (i)⟶(b), (ii) ⟶ (a)

(D) (i)⟶(a), (ii) ⟶ (c)

Q. No. 8. 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 Ω is

(A) 0.25 A

(B) 0.5 A

(C) 0.5 2 A

(D) 0.5/ 2 A

Q. No. 9. Which of the following materials is semiconductor? (A) Selenium

(B) Bismuth

(C) Silica

(D) Chromium

Q. No. 10. In a rectifier circuit, the primary function of the filter is to (A) remove ripples from the rectified output (B) minimise AC input variation (C) suppress odd harmonics in rectifier output (D) control the DDC level of the output voltage 30

Q. No. 11. In an R – L series circuit R = 20 Ω, L = 0.056 H and the supply frequency is f = 50 Hz. The magnitude of impedance of the circuit is (A) 20.0 Ω

(B) 37.6 Ω

(C) 20.056 Ω

(D) 26.64 Ω

Q. No. 12. 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) 100/π A

(B) 100 A

(C) 70.7 A

(D) 50/π A

Q. No. 13. Under thermal equilibrium in a pure semiconductor the ratio of the number of holes to the number of conduction electrons is (A) infinity

(B) 1

(C) 2

(D) 1/2

Q. No. 14. As per IE rules the maximum allowable variation between declared and actual voltage at consumer’s premises should be (A) ±4.5%

(B) ±3%

(C) ±3.5%

(D) ±4%

Q. No. 15. Alternator used in hydel power station has more number of poles in it than that used in thermal power station, because (A) power generated by the alternator may be changed according to demand (B) speed of its prime mover is less (C) power generated by this alternator is less (D) speed of the prime mover may be changed whenever required Q. No. 16. 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) None of these

(B) 0.75

(C) 0.375

(D) 1.33

Q. No. 17. In a thyrite lightning arrester the resistance (A) is low at low current and high at high current

31

(B) increases linearly with the applied voltage (C) decreases linearly with the applied voltage (D) is high at low current and low at high current Q. No. 18. A consumer is offered the following rate of tariff. He has to pay a fixed charge of Rs. 1,000/- per month and a running charge of Rs. 4.50/0 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) Rs. 36,637.50/-

(B) Rs. 40,985.29/-

(C) Rs. 32,941.88/-

(D) Rs. 25,637.50/-

Q. No. 19. Glare is caused due to (A) both of (B) and (C) (B) excessive lighting contrast in the field of vision (C) excessive luminance (D) none of (B) and (C) Q. No. 20. Which of the following method is suitable for heating of conducting medium? (A) both (C) and (D)

(B) Radiant heating

(C) Eddy current heating

(D) Induction heating

Q. No. 21. Furnaces used for cremation use (A) Arc heating

(B) Resistance heating

(C) Induction heating

(D) Dielectric heating

Q. No. 22. In a fluorescent tube circuit high voltage surge is produced by (A) Electrode

(B) Starter

(C) Choke

(D) Heater

Q. No. 23. In AC operated electromechanical contactors, the problem of chattering is eliminated by (A) using aluminium instead of copper as conductor material (B) laminating the electromagnet core (C) placing copper shading band on pole face of electromagnet 32

(D) increasing the conductor cross-section Q. No. 24. Magnetic blowout coils are generally used in (A) air break circuit breaker

(B) air blast circuit breaker

(C) oil circuit breaker

(D) vacuum circuit breaker

Q. No. 25. The pitch factor of a full pitched winding of a synchronous machine is (A) 0.9

(B) 0.0

(C) 1.0

(D) 0.5

Q. No. 26. 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 branch will be independent of frequency when

(A)

𝑅𝑠 2 +𝑋 2 𝑅𝑚 𝑚

𝑅

𝑋

𝑋

(B) 𝑅𝑚 = 𝑅𝑠ℎ

= 𝑋𝑠ℎ

𝑚

𝑠ℎ

2 2 (C) (𝑅𝑠 + 𝑅𝑚 )2 + 𝑋 2 = 𝑅𝑠ℎ + 𝑋𝑠ℎ

(D) 𝑅

𝑋𝑚

𝑚 +𝑅𝑠

𝑠ℎ

𝑅

= 𝑋 𝑠ℎ 𝑠ℎ

Q. No. 27. In phantom loading arrangement, energy consumption in the calibration test of wattmeter is reduced because of (A) no common point between the two coils (B) the reduced loss in current coil and pressure coil (C) the absence of load in the test set (D) the separate application of low voltage supply across current coil Q. No. 28. In the measurement of power in a balanced 3-phase circuit by two-wattmeter method if the two-wattmeter show equal readings, then the power factor of the circuit is (A) unity

(B) 0.8 lagging

(C) 0.8 leading

(D) zero 33

Q. No. 29. Two meters X and Y requires 40 mA and 50 mA respectively for full scale deflection. Then (A) Data are insufficient to comment (B) X is more sensitive than Y (C) Y is more sensitive than X (D) Both are equally sensitive Q. No. 30. The household energy meter is (A) None of these

(B) indicating instrument

(C) integrating instrument

(D) recording instrument

Q. No. 31. A Ballistic galvanometer of constant equal to 1 micro-coulomb/degree gives a throw of 22.5°, when a capacitor discharges through the meter. If a battery of 15 V is used to recharge the capacitor, value of capacitance is (A) 10 𝜇F

(B) 1.5 𝜇F

(C) 1.5 𝜇F

(D) 22.5 𝜇F

Q. No. 32. A potentiometer is used to measure the voltage between two points of a dc 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 kΩ. The input resistance between two points (A) 20 kΩ

(B) 45 kΩ

(C) 80 kΩ

(D) 60 kΩ

Q. No. 33. 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 0.4° and 0.7°, power factor of the load is (A) cos 58.9°

(B) cos 59.7°

(C) cos 61.1°

(D) cos 60.3°

Q. No. 34. During the measurement of a low resistance using a potentiometer, the following readings were obtained: Voltage drop across unknown resistance = 0.531 V. Voltage drop across a 0.1 ohm standard resistance connected in series with the unknown = 1.083 V. Value of the unknown resistance is 34

(A) 108.3 mΩ

(B) 20.4 mΩ

(C) 53.1 mΩ

(D) 49.03 mΩ

Q. No. 35. Which one of the following types of instruments does suffer from error due to magnetic hysteresis (A) Electrodynamic

(B) Moving iron

(C) PMMC

(D) Induction type

Q. No. 36. Which one of the following does not employ a null method of measurement? (A) DC potentiometer

(B) Kelvin double bridge

(C) AC potentiometer

(D) Megger

Q. No. 37. In star-delta starting of three-phase induction motor the starting voltage is reduced to (A) 3 times of normal voltage

(B) 1/3 times of normal voltage

(C) 1/ 3 times of normal voltage

(D) 3 of normal voltage

Q. No. 38. An electromagnetic torque is produced as an interaction between a flux and current. The angle between flux and current is 45 °. If this angle changed to 30°, flux increases by 100% and current reduces by 25%, then the torque (A) reduces to 81.6% of the original

(B) reduces to 54.4% of the original

(C) reduces to 66.7% of the original

(D) increases to 183.7% of the original

Q. No. 39. Maximum temperature limit for class F insulation is (A) 120 °C

(B) 105 °C

(C) 155 °C

(D) 130 °C

Q. No. 40. Match List – I (Types of motors) with List – II (Characteristics) and select the appropriate response: List – I

List – II

(a) PMMC

(1) Constant speed

(b) Hot wire

(2) High starting torque

(A) (a)⟶(2), (b) ⟶ (1)

(B) (a)⟶(1), (b) ⟶ (1)

(C) (a)⟶(2), (b) ⟶ (2)

(D) (a)⟶(1), (b) ⟶ (2)

35

Q. No. 41. The motor characteristics best suited for traction purpose are those of (A) synchronous motor

(B) induction motor

(C) d.c. shunt motor

(D) d.c. series motor

Q. No. 42. 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) 3 Tst

(C) 3Tst

(D) Tst/3

Q. No. 43. 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) 70.7 kVA

(B) 141.4 kVA

(C) 50 kVA

(D) 100 kVA

Q. No. 44. Which one of the following is correct? (A) The effect of armature current on main flux of a synchronous machine is called armature reaction (B) The effect of armature current on air gap flux of a synchronous machine is called armature reaction (C) The effect of field current on main flux of a synchronous machine is called armature reaction (D) The effect of air gap flux on armature current of a synchronous machine is called armature reaction Q. No. 45. 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 dc generator is (A) 0.04 Wb

(B) 0.06 Wb

(C) 0.02 Wb

(D) 0.08 Wb

Q. No. 46. The highest speed attainable by dc shunt motor is (A) much lower than no-load speed

(B) ideally infinite

(C) equal to infinite speed

(D) much higher than no-load speed

Q. No. 47. The direction of rotation of a dc shunt motor can be reversed by interchanging (A) either field or armature terminals 36

(B) the supply terminals

(C) the field terminals only

(D) the armature terminals only

Q. No. 48. AC series motors are built with as few turns as possible to reduce (A) reactance

(B) iron losses

(C) speed

(D) flux

Q. No. 49. Based on revolving field theory, the forward and 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) 93.33 Hz, 6.67 Hz

(B) 7.69 Hz, 107.69 Hz

(C) 6.67 Hz, 93.33 Hz

(D) 107.69 Hz, 7.69 Hz

Q. No. 50. Three lamps are in circuit as shown in figure. At what condition 100 W lamp wil have the maximum brightness?

(A) Both (B) and (C) (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) Key K1 is closed, K2 is open and K3 is also open Q. No. 51. Given two coupled inductors L1 and L2 having their mutual inductance M. The relationship among them must satisfy (A) M ≤ L1L2

(B) M = L1L2

(C) M ≥ (L1 + L2)/2

(D) M > L1L2

Q. No. 52. If the length of a bar of magnetic material is increased by 20% and the crosssectional area is decreased by 20%, then the reluctance is (A) remaining same

(B) decreased by 33%

37

(C) increased by 67%

(D) increased by 50%

Q. No. 53. 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) 0.02 H

(B) 0.32 H

(C) 0.24 H

(D) 0.16 H

Q. No. 54. A coil with a certain number of turns has a specified time constant. If the number of turns is doubled, its time constant would (A) get halved

(B) remain unaffected

(C) become doubled

(D) become four fold

Q. No. 55. The iron loss per unit frequency in a ferromagnetic core, when plotted against frequency, is a (A) straight line with negative slope

(B) parabola

(C) constant

(D) straight line with positive slope

Q. No. 56. 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 H

(B) 2 H

(C) ½ H

(D) ¼ H

Q. No. 57. Following graph shows the loss characteristics of a sheet of ferromagnetic material against varying frequency f. P i is the iron loss at frequency f, Hysteresis and eddy current losses of the sheet at 100 Hz are

(A) 10 W, 50 W

(B) 1 W, 5 W

(C) 1 W, 10 W

(D) 10 W, 100 W

Q. No. 58. Hysteresis losses are pre sent in iron core coil when (A) the current is unsymmetrical alternating only 38

(B) the current in the coil is dc only (C) the current in the coil is sinusoidal only (D) the current in the coil is alternating Q. No. 59. Eddy current loss in ferromagnetic core is proportional to (A) square root of frequency

(B) frequency

(C) reciprocal of frequency

(D) square of frequency

Q. No. 60. 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 inductor is (A) 0.25

(B) 0.8

(C) 1.25

(D) 18.75

Q. No. 61. The magnetic materials that are used to prepare permanent magnets should have (A) small hysteresis loop (B) high retentivity (C) low coercive force (D) steeply rising magnetisation curve Q. No. 62. Poles of dc machines are often laminated to reduce (A) iron weight

(B) armature reaction

(C) hysteresis loss

(D) eddy current loss

Q. No. 63. Universal motor is a ___________ motor. (A) single phase induction

(B) synchronous

(C) shunt

(D) series

Q. No. 64. Which of the following motors can work satisfactorily on both AC and DC? (A) Shunt motor

(B) Induction motor

(C) Synchronous motor

(D) Series motor

Q. No. 65. 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 alternators is 5%. The load sharing between them will be 39

(A) 36 MW, 44 MW

(B) 40 MW

(C) 30 MW, 50 MW

(D) 32 MW, 48 MW

Q. No. 66. Slip of a 3-phase induction motor may be expressed as (A) rotor copper loss/rotor power input (B) rotor copper loss/total power input (C) rotor power input/rotor copper loss (D) rotor copper loss/rotor core loss Q. No. 67. 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) 1228.81 Volts

(B) 869.46 Volts

(C) 1737.80 Volts

(D) 2128.36 Volts

Q. No. 68. 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) 75 Watts

(B) 600 Watts

(C) 300 Watts

(D) 150 Watts

Q. No. 69. An auto transformer used with a sodium vapour lamp should have high (A) leakage reactance of winding (B) VA rating (C) transformation ratio (D) winding resistance Q. No. 70. In an auto-transformer, the number of turns in primary winding is 210 and in secondary winding is 140. If the input current is 60 A, the currents in output and in common winding are respectively (A) 40 A, 100 A

(B) 90 A, 30 A

(C) 90 A, 150 A

(D) 40 A, 20 A

Q. No. 71. 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 40

(A) 693 V

(B) 1200 V

(C) 58 V

(D) 2078 V

Q. No. 72. A resistance and another circuit element are connected in series across a dc voltage V. The voltage across the second element is VV initially and zero after time. The other element is pure (A) both (B) and (D)

(B) resistance

(C) inductance

(D) capacitance

Q. No. 73. For RLC ac series circuit at resonance the current is (A) minimum at lagging p.f.

(B) maximum at unity p.f.

(C) maximum at leading p.f.

(D) minimum at leading p.f.

Q. No. 74. A series R-L-C circuit resonates at 1 MHz. At frequency 1.1 MHz the circuit impedance will be (A) will depend on the relative amplitude of R, L and C (B) capacitive (C) inductive (D) resistive Q. No. 75. The equivalent resistance between terminals X and Y of the network shown is

(A)

100

(C)

20

3

9

Ω

(B)

Ω

40 3

Ω

(D) 8 Ω

Q. No. 76. A application of Thevenin’s Theorem in a circuit results in (A) an ideal current source (B) a current source and an impedance in parallel 41

(C) a voltage source and an impedance in series (D) an ideal voltage source Q. No. 77. A current of i = 6 + 10 sin (100 πt) + 20 sin (200 πt) is flowing through a series combination of PMMC and moving iron instrument. Ratio of the two currents as registered by the MI and PMMC meter is (A) 3.11

(B) 2.82

(C) 2.63

(D) 1.81

Q. No. 78. Three resistances 5 Ω each are connected in star. Values of equivalent delta resistances are (A) 2.5 Ω each

(B) 5/3 Ω each

(C) 15 Ω each

(D) 1.5 Ω each

Q. No. 79. A 120 V, 60 W incandescent lamp has to be operated from 220 V, 50 c/s, 1 phase ac 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 inductance or capacitance

(B) Resistance

(C) Pure inductance

(D) Pure capacitance

Q. No. 80. The bandwidth of an ac series circuit consisting of R, L and C is (A) R/L

(B) L/RC

(C) RC/L

(D) L/R

Q. No. 81. For balanced 3-phase supply system, the phasor sum of the line currents is NOT zero if the load is (A) unbalanced delta connected

(B) balanced star connected

(C) unbalanced star connected

(D) balanced delta connected

Q. No. 82. At series resonance of an ac R-L-C circuit the impressed voltage is (A) equal to capacitive drop

(B) greater than resistive drop

(C) equal to inductive drop

(D) equal to the resistive drop

Q. No. 83. In a series RLC circuit R = 20 Ω, X L = 30 Ω and XC = 30 Ω. If the supply voltage across the combination is v = 100 sin (100 πt + 30°) Volts, the instantaneous current and the power factor of the circuit are respectively (A) i = 5 sin (100 πt + 30°) Amps, p.f. = unity 42

(B) i = 3.536 sin (100 πt + 30°) Amps, p.f. = unity (C) i = 5 sin (100 πt + 30°) Amps, p.f. = 0.866 (D) i = 3.536 sin (100 πt + 30°) Amps, p.f. = 0.866 Q. No. 84. The rms value of the alternating current given by the equation i = 50 sin (314t – 10°) + 30 sin (314t – 20°) is (A) 58.31 A

(B) 38.73 A

(C) 77.43 A

(D) 41.23 A

Q. No. 85. A series R-L-C circuit will have unity power factor if operated at a frequency of (A) LC (B) 1/(LC) (C) 1/ LC

(D) 1/(2π LC )

Q. No. 86. 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) 50 VAR

(B) 100 VAR

(C) 141.4 VAR

(D) 173.2 VAR

Q. No. 87. An electric iron is rated at 230 V, 400 W, 50 Hz. The voltage rating 230 V refers to (A) peak-to-peak value

(B) average value

(C) peak value

(D) rms value

Q. No. 88. 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) only odd function symmetry (C) only half wave symmetry (D) half wave and odd function symmetry Q. No. 89. 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

43

(A) 6 V

(B) 3.6 V

(C) 2.16 V

(D) 10 V

Q. No. 90. The time constant of the network shown in the figure is

(A) CR/2

(B) CR

(C) 2 CR

(D) CR/4

Q. No. 91. 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 dc generator is (A) 0.04 Wb

(B) 0.06 Wb

(C) 0.02 Wb

(D) 0.08 Wb

Q. No. 92. Form factor of an alternating wave is (rms value )2

(A) Form factor = average

rms value

(B) Form factor = average

valu e

(C) Form factor = rms value × average value

(D) Form factor =

value

average value rms value

Q. No. 93. The phase difference between the following voltage and current waves, v = 311 sin (100 πt + 30°) Volts i = 17 sin (100 πt – 20°) Amps (A) 50°

(B) 10°

(C) 30°

(D) 20° 44

Q. No. 94. Match the items given in List – I and those in List – II List – I

List – II (Temperature Coefficient of Resistance)

(a) Aluminium

(P) Negligibly small

(b) Manganin

(Q) Positive

(c) Carbon

(R) Negative

(A) a ⟶ Q, b ⟶ P, c ⟶ R

(B) a ⟶ P, b ⟶ Q, c ⟶ R

(C) a ⟶ R, b ⟶ P, c ⟶ Q

(D) a ⟶ R, b ⟶ Q, c ⟶ P

Q. No. 95. Which of the following materials possesses the least resistivity? (A) Manganin

(B) Aluminium

(C) Copper

(D) Iron

Q. No. 96. The resistances of insulations, in general, __________ with temperature rise. (A) increases rapidly

(B) increases slowly

(C) does not change

(D) decreases

Q. No. 97. A 10 𝜇F and 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 then (A) 125 V

(B) 100 V

(C) 50 V

(D) 75 V

Q. No. 98. The conditions at which the following potential divider is independent of frequency, may be

(i) R1/R2 = C1/C2 (ii) R1/R2 = C2/C1 45

(iii) R1C1 0, 𝑑𝛿 = 0

where, P & δ

have their usual meaning. Q. 56. The p.u. impedance of a 100 KVA, 50 Hz, 1-phase transformer is 0.8 p.u.. Now with 200 KVA as base the new p.u. impedance will be A. 1.6 p.u.

B. 0.4 p.u.

C. 0.8 p.u.

D. 3.2 p.u.

Q. 57. When four resistances of 2W & 1W; 5W & 2W; 10W & 5W and 15W & 10 W are connected in parallel, the greatest power is absorbed by A. 2 W & 1 W in parallel

B. 5 W & 2 W in parallel

C. 10 W & 5W in parallel

D. 15 W & 10 W in parallel

Q. 58. The cut-in voltage of a silicon diode is approx. A. 0.7 volt

B. 0.3 volt

C. 1.4 volt

D. None of the above.

Q. 59. Two equal resistors R connected in series across a voltage source V dissipate power P. What would be the power dissipated in the same resistors when they are connected in parallel across the same voltage source? 82

A. 4P

B. P

C. 2P

C. 16P

Q. 60. Specific resistance is measured in A. mho C. ohm – cm

D. ohm/cm D. ohm/cm

Q. 61. The Boolean expression, (A + AB) gets simplified to A. A + B

B. A

C. B

D. AB

Q. 62. The slip of an induction motor normally does not depend on A. rotor speed

B. synchronous speed

C. shaft torque

D. core-loss component

Q. 63. A simple phase transformer has a maximum efficiency of 90% at full load and unity power factor. Efficiency at half load at the same power factor is A. 86.7%

B. 88.26%

C. 88.9%

D. 87.8%

Q. 64. A three-phase, 33 kV oil circuit breaker is rated 1200 A, 2000 MVA, 3 s. The symmetrical breaking current is A. 1200 A

B. 3600 A

C. 35 kA

D. 104.8 kA π

Q. 65. The period of the signal x t = 8sin⁡ (0.8πt + 4 ) is A. 0.4π s

B. 0.8π s

C. 1.25 s

D. 2.5 s

Q. 66. The inductance of a long solenoid of length 1000 mm wound uniformly with 3000 turns on a cylindrical paper tube of 60 mm diameter is A. 3.2 μH

B. 3.2 mH

C. 32.0 mH

D. 3.2 H

Q. 67. In the figure below, the value of the source voltage is

83

A. 12 V

B. 30 V

C. 24 V

D. 44 V

Q. 68. An ideal op-amp has A. Infinite input impedance

B. Infinite voltage gain

C. Infinite CMRR

D. All of the above

Q. 69. The most important criterion for the parallel operation of two transformers is A. Both of them must have same voltage ratio B. Both of them must have same polarity C. Both of them must have same X/R ratio D. Any of the above Q. 70. Inflammable articles like plastic, wooden materials etc. are generally heated using A. Induction heating

B. Dielectric heating

C. Resistance heating

D. None of the above

End of Paper

84

Solution to Practice Paper – I 1. B

2. C

3. B

4. A

5. A

6. B

7. A

8. B

9. C

10. B

11. D

12. A

13. C

14. B

15. C

16. B

17. C

18. B

19. A

20. C

21. B

22. B

23. D

24. A

25. A

26. C

27. C

28. C

29. B

30. D

31. C

32. B

33. C

34. B

35. D

36. C

37. B

38. B

39. C

40. B

41. B

42. C

43. B

44. B

45. A

46. A

47.A

48. B

49. B

50. D

51. D

52. C

53. C

54. C

55.C

56. A

57. A

58. A

59. A

60. D

61. B

62. D

63. D

64. C

65. D

66. C

67. B

68. D

69. B

70.B

The End

85