MV-March 2018-ESAS - Engineering Sciences and Allied Subjects PDF

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Engineering Sciences and Allied Subjects...

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MULTIPLE CHOICE 1. A material best suited for manufacturing of fuse wire is A. Aluminum B. Silver C. Lead

D. Copper

2. In the fleming’s left hand rule, thumb always represents A. Voltage B. Current C. direction of force on conductor D. Magnetic Field 3. The net reactance in a series RLC circuit is A. XL B.XC

C. XC + XL

D. XL – XC

4. Two resistors R1 and R2 are connected in parallel. R1 is twice of R2. If the current in R1 is I, what is the current in R2? A. I B. 2I C.4I D. I/2 5. The ampere – hour capacity of battery depends on A. The thickness of the plates B. The strength of the electrolytes C. The area of the plates D. the distance between the plates 6. A Y – Δ connected transformer has a turns ratio of 1. If the primary line current is 5 amperes, what is the secondary line current? A. 5A B. 15A C. 8.66A D. 2.89A 7. In a certain county the energy consumption is expected to double in 10 years. Calculate the growth rate. A. 4% B. 3.96% C. 13.85% D. 6.93% 8. The condition in Ohm’s law is that A. ratio V/I should be constant C. The temperature should remain constant

B. current should be proportional to voltage D. the temperature should vary

9. Two single – phase transformers with equal ratings and turns ratio are operated in parallel to supply a load of 300 KVA, 0.80 lagging power factor. Transformer A has a resistance of 2.5% and a reactance of 5.5%. Transformer B has a resistance of 2.0% and a reactance of 5.5%. Find the KVA load of each transformer. A. 147.7, 152.2 B.148.7, 151.5 C. 149.7, 150.5 D. 150.7, 149.5 10. If an electrical network having one or more than one voltage source, is transformed into equivalent electrical network with a single voltage source (which is short circuit current of previous circuit) with parallel internal resistance of the network with all current source replaced by their internal resistance. The above illustration is called

A. Thevenin’s theorem C. Norton’s theorem

B. Reciprocity theorem D. Superposition theorem

11. What is the power given V = 4 sin 3t and I = 3 sin 3t? A. 16 sin (3t)2 B. 16 sin2(3t) C. 8 (1 – 6cos3t)

D. 16 (1 – 6cos3t)

12. A 40µF capacitor is supplied with a voltage of v(t) = 100sin377t. Find the current equation. A. 1.51sin(377 t – 90°) B. 1.51sin377t C. 1.51cos(377t + 90°) D. 1.51cos 377t 13. A 20 mH inductor draws a current of i(t) = 100 sin 100t. Find the voltage equation. A. 200sin100t B. 200cos100t C. 2000sin100t D. 2000cos100t 14. For the phase unbalance load A. the power factor of each phase will be proportional to the load B. the power factor of each phase will be the same C. the power factor of at least one of the phases must be leading D. the power factor of each phase may be different 15. Cellular phone operate in the frequency range of A. EHF B. VHF

C. UHF

D. SHF

16. A medium unshaded lamp hangs 8 m directly above the table. To what distance should it be lowered to increase the illumination to 2 times its former value? A. 2.34 m B. 5.66 m C. 4 m D.4.64 m 17. The resistance of a copper wire at 30 °C is 50 Ω. If the temperature coefficient of copper at 0 °C is 0.00427, what is the resistance at 100 °C? A. 72.26 Ω B. 63.24 Ω C. 54.25 Ω D.58.15 Ω 18. What is the maximum allowable voltage drop for lighting circuit? A. 3% B. 5% C. 2%

D. 10%

19. What is the maximum allowable voltage drop for feeder? A. 1% B. 2% C. 3%

D. 5%

20. Fiber optic operates on the principle of A. Refraction B. Reflection

D. Dispersion

C. Diffraction

21. ________ color is reserved for grounding equipment wire only. A. white B. green C. yellow

D. grey

22. Overhead lines are protected from lightning by the use of I. overhead ground conductors II. Surge arresters A. I only B. II only C. either I or II

D. both I and II

23. An inductance of 20 mH is connected in parallel with a capacitance of 80 µF. What is the frequency when XL = XC? A. 100 Hz B. 150 Hz C. 128.5 Hz D. 125.8 Hz 24. A horizontal power line carries a current of 90 A. Compute the magnetic field at a point 1.5 m below A. 1.2 x 10-5 T B. 1.2 x 10-4 T C. 1.2 x 10-3 T D. 1.2 x 10-2 T 25. The synchroscope is an instrument used to indicate the A. speed of a motor B. phase relationship between the current and the voltage C. phase relationship between two voltages D. phase relationship between the true power and the reactive power 26. A three – phase transmission line of a two – conductor bundle is arranged horizontally with a spacing of 8 m between bundle centers. Each conductor is ACSR, 1,272,000 cmils Pheasant with GMR of 0.0466 ft. The spacing between conductors of the bundle is 45 cm. Find the per unit serious reactance of the line if its length is 160 km and base is 100 MVA, 345 KV. A. 0.069 pu B. 0.059 pu C. 0.049 pu D. 0.039 pu 27. The current flowing in the armature conductors of a dc motor is A. ac B. dc C. ac as well as dc

D. transients

28. A string insulator has 5 units. The voltage across the bottom most unit is 30% of the total voltage. A. 60% B. 66.67% C. 75% D. 83.33% 29. For a single line to ground fault the zero sequence current is given by j3.0 pu. The current carried by the neutral during the fault is A. j 1 pu B. j 3 pu C. j 9 pu D. j 6 pu 30. Two single – phase transformers each rated 75 KVA are connected in V or open delta to serve a 3 – phase load of 120 KW at 0.80 power factor lagging. Determine the size in KVAR of the capacitor needed to prevent overloading of the transformers. A. 40.25 B. 41.28 C. 45.24 D. 43.50 31. A time of 10 milliseconds is required for the current on a series RL dc circuit to reach 90% of its final steady state value. What is the time constant in seconds for the circuit? A. 3.39 ms B. 4.34 ms C. 3.86 ms D. 4.25 ms

32. The armature current drawn by any dc motor is proportional to A. the voltage applied to the motor B. the torque required C. the flux required in the motor D. the speed of the motor 33. Fault level means A. voltage at the point of fault C. the flux required in the motor

B. fault current D. fault MVA

34. A bulb having a rating of 220 volts, 75 watts is to be connected to a 110 volts source. What power will it draw if connected across 100 volts source? A. 37.5 watts B. 9.375 watts C. 75 watts D.18.75 watts 35. A capacitor is charged 0.23 watt – second of energy at a voltage of 48 volts. What is its capacitance? A. 180 µF B. 240 µF C. 200 µF D. 220 µF 36. A 20 – HP, 110 v dc shunt motor has an efficiency of 88% and an exciting current of 4 amperes and an armature resistance of 0.1 ohms. What is the starting resistance required for full – load torque? A. 0.69 Ω B. 0.96 Ω C. 0.92 Ω D. 0.46 Ω 37. A coil of 50 – ohm resistance and 150 mH inductance is connected in parallel with a 50 - µF capacitor. What is the power factor of the circuit? A. 70% B. 70% leading C. 80% lagging D. 80% leading 38. A 220 – volt dc shunt motor runs at 500 rpm with an armature current of 50 amperes and an armature resistance of 0.1 Ω. Calculate the speed if the torque is halved? A. 510.8 rpm B. 508.6 rpm C. 505.8 rpm D. 502.8 rpm 39. A 150 0 MVA, 13.8 – KV, Y – connected, 3Ф, 60 – Hz alternator is operating at rated voltage and at no – load when a three – phase faults occurs at its terminals. If the sub transient reactance of the alternator is j0.2 pu, calculate the current the instant the fault occurs. A. 10, 870 amps B. 6,276 amps C. 32,611 amps D. 31,380 amps 40. The capacitive reactance of a transmission line is 90,000 ohms per kilometer. Find the total capacitive reactance if the transmission line is 50 km long. A. 90,000 Ω B. 4.5 x 106 Ω C. 180,000 Ω D. 1,800 Ω 41. A generating station supplies peak load of 12,000 KW, 9,000 KW, and 6,000 KW. Calculate the maximum demand of the station and the energy it supplies in a year if its diversity factor and its average annual load factor is 1.2 and 0.7, respectively. A. 27,000 KW, 137.97 x 106 KWHR B. 22,500 KW, 137.97 x 106 KWHR 6 C. 27,000 KW, 5.75 x 10 KWHR D. 22,500 KW, 5.75 x 106 KWHR

58. Which of the following is an active element of a circuit? A. Ideal current source B. Resistance C. Inductance D. Capacitance 59. A 200 µH coil has a Q of 250 at resonance frequency of 800 KHZ. What is the effective resistance of the coil? B. 2 Ω C. 4 Ω D. 8 Ω A. 1 Ω 60. Find the capacitive susceptance per mile of a single – phase line operating at 60 Hz. The conductor is Partridge with an outside diameter of 0.642 in, and spacing is 20 ff between centers A. 5.10 x 10-4 mho/mi to neutral B. 0.1961 x 104 mho/mi to neutral 6 C. 5.10 x 10- mho/mi to neutral D. 0.1961 x 106 mho/mi to neutral 61. Which wave form will have minimum rms value if they have the same peak value of voltage? A. Square Wave B. Sine Wave C. Triangular Wave D. Full Wave rectified sine wave 62. The line currents in amperes in phases a, b and c respectively are 500 + j150, 100 – j600, and -300 + j600. Determine the zero sequence component of phase a current. A. -100 – j50 amps B. -100 + j50 amps C. 100 – j50 amps D. 100 + j50 amps 63. The minimum armature current of a synchronous motor corresponds to operation at A. 0.8 p.f. lagging B. unity p.f. C. 0 p.f. leading D. 0 p.f lagging 64. A 10 – KW, 110 volts dc series generator has a 2 – volts brush drop, an armature resistance R a of 0.1Ω and series field resistance RS of 0.05Ω. Calculate the generated emf when delivering rated current at rated speed. A. 110 v B. 130.25 v C. 115.56v D. 125.64 v 65. Lap winding is best suited for _________ voltage, __________ current dc generators. A. high, low B. low, high C. high, high D. low, low 66. A three – phase motor is rated 50 – HP, 440 volts and 85% power factor. What is the rated current of the motor efficiency is 89%? A. 57.5 A B. 64.7 A C. 55A D.59A 67. The phase b line voltage and the phase a line current of a balanced three phase system are V = 220 sin (ωt + 210°) and I = 10 sin (ωt – 30°) respectively. What is the power of the system? A. 1,905 W B. 5,716 W C. 3,300 W D. 3,810 W

68. A 200.5 current transformer is used with a 10 – amps ammeter. If the meter reads 4.5 amps, determine the line current. A. 400A B. 20A C. 45A D. 180A 69. What is the relative permittivity of vacuum? A. unity B. 8.854 x 10-12

C.8.854

D. zero

70. On tripling the number of turns of a coil the inductance A. becomes 9 times as large B. 3 times C. 1/3 D. will remain same 71. A 1.5 MΩ resistor is connected in series with a 20 µF capacitor. The voltage source is 120 volts dc. Determine the current at t = 10 seconds after the switch is closed. A. 80 µA B. 63.85µA C. 32.64 µA D. 57.32 µA 72. A dc ammeter has an internal resistance of 0.1 ohm. A shunt of 1.01 x 10-3 ohm is connected to the ammeter. What is the multiplier of the set up? A. 80 B. 50 C. 100 D. 10 73. The field circuit of a 200 KW, 230 KW volts shunt generator is 8A when running full – load at rated terminal voltage. If the combined brush and armature resistance is 0.03 Ω. Solve for the electrical efficiency of the generator. A. 88.9% B. 85.7% C. 93.5% D. 81.7% 74. A parking lot is to be illuminated by four floodlights placed on each corner of the lot mounted on 7 meters high poles. The parking lot measures 25 m x 20 m. If each lamp has an output of 5000 candelas, calculate the illumination at the center of the lot. A. 51.44 lux B. 26.25 lux C. 6.43 lux D. 12.86 lux 75. An external resistance is added in series with the filled of a dc shunt motor. When the motor runs, the effect of resistance is A. to reduce the speed of the motor B. to increase the speed of the motor C. to reduce the armature current drawn by the motor D. to reduce the losses 76. The PTs of a 220 KV transmission line have a ratio of 132.76 KV/66.375 c and are connected wye – wye. A voltmeter connected line to ground read s 66 volts, what is the transmission line voltage? A. 228.65 KV B. 220.10 KV C. 223.15 KV D. 225.25 KV 77. What is the speed of an induction motor of four poles if the percent slip is 3%? A. 1,764 prm B. 1,756 rpm C. 1,746 rpm D. 1,730 rpm

78. A 3 – phase synchronous motor runs at full – load speed of 1,200 rpm. If the load is reduced to one – half of rated, calculate its speed regulation. A. 100% B. 50% C. 0% D. 86.6% 79. Which of the following is not the method of arc dispersion? A. oil immersion contacts B. magnetic blow out of arc C. use of rectifiers D. deionization of arc path 80. During load shedding A. system voltage is reduced C. system power factor is changed

B. some load are switch off D. system frequency is reduced

81. The capacitor in a series RC circuit at steady state is: A. open circuit B. short circuit C. transient circuit

D. coupled circuit

82. A lead storage battery is rated at 12 volts. If the internal resistance is 0.01 Ω, what is the maximum power that can be delivered to the load? A. 1,200 watts B. 7,200 watts C.1, 800 watts D. 3,600 watts 83. Two No.8 copper conductors are placed 15 – cm apart with a GMR of 1, 27 x 10-3m. If the length of the line is 4 – km, find the value of the line inductance. D. 7.63 mH A. 9.65 mH B. 6.85 mH C. 5.78 mH 84. There is no zero sequence component of the fault current for A. Line to line fault B. Single line to ground fault B. Symmetrical fault D. Double line to ground fault 85. A diesel generator set burn fuel with a heating value of 18,000 BTU per lb. The diesel engine has an efficiency of 30% and the alternator has an efficiency of 95%. Determine the fuel cost component of producing one KWHR if the diesel costs ₱ 2.80 per lb. A. ₱ 0.15 B. ₱ 2.15 C. ₱ 3.28 D. ₱ 1.86 86. The ratio of lumens reaching the work piane divided by the total lumens generated by the light is: A. Room ratio B. Coefficient of utilization C. illumination factor D. Maintenance factor 87. A. 50 Ω resistance is connected in series with a coil having 25 Ω resistance and 150 mH inductance. The circuit is connected toa voltage source of 200 sinωt. Calculate the instantaneous current. A. 2.7 sinωt B. 2.1 sin(ωt – 37°) C.1.7 sin(ωt + 37°) D. 5.11 sin(ωt – 37°) 88. What is 1013 ergs/sec in KW?

A. 1,000 KW B. 2,000 KW C. 1,800 KW D. 3,000 KW 89. Find the rotor frequency of an induction motor having 4 poles if the rotor speed is 1,746 rpm. A. 60 HZ B. 1.8 HZ C. 3 HZ D. 50 HZ 90. The conductors of a 30 – km long transmission line have a triangular configuration. The conductors are placed 4ft apart. Each conductor has 336.4 MCM ACSR and its diameter is 0.75 inch. Find the capacitive reactance per phase? B. 1,354 Ω/phase C. 7,717 Ω/phase D. 8,261 Ω/phase A. 5,389 Ω/phase 91. The secondary current of a 20 – KV/ 7.97 – KV autotransformer is 100 amperes. Determine the current that flows through the common winding. A. 60 amps B. 100 amps C. 70 amps D. 50 amps 92. A winding is short pitched by 60 degrees electrical. Its pitch factor is: A. 0.5 B. 0.707 C.0.966

D.0.866

93. When the excitation of an unloaded salient pole synchronous motor suddenly gets disconnected, then A. the motor stops B. it runs at the same speed C. it runs at lower speed D. it runs at very high speed 94. Sensitivity of a voltmeter is expressed as A. Volts/ohm B. Ohms/Volt

C Ohms-Volt

D. 1/Ohm-Volt

95. Two conductors carrying 50 amperes and 75 amperes respectively are placed 10 cm apart. Calculate the force between them per meter. A. 0.075 N/m B. 100 N/m C. 0.0075 N/m D. 10 N/m 96. A coil has resistance of 3 Ω and an inductance of 0.01 H is connected in series with a capacitor across a voltage source of 220 volts. What must be the capacitance of the capacitor in order that maximum current occurs at 60HZ? A. 3.77 B. 703.6 µF C. 0.03 µF D. 512.45 µF 97. In a T – T connected transformer, if the terminal voltage in the primary side is 220 volts, what is the voltage across the teaser transformer? A. 127 volts B. 190 volts C. 220 volts D. 110 volts 98. At a certain point of the system network the positive, negative and zero sequence impedances are 0.25 pu, 0.25 pu, 0.3 pu, respectively. The base MVA is 100. The level at that point is 34.5 KV. Determine the zero sequence current for a one line to ground fault. A. 6,275 A B. 7,516 A C. 8,132 A D. 2,091 A

99. The dc armature winding in which the coil sides are placed a pole pitch apart is called _____ winding A. Multiplex B. Full – Pitch C. Fractional – pitch D. Pole – pitch 100. A power plant gets water from a dam from a height of 100 m at the rate of 1,000 cubic meters per minute. If the overall efficiency of the plant is 75%, what is the KW output of the plant? A. 12,250 KW B. 5,250 KW C. 7,550 KW D. 15,250 KW...