DIAGNOSTIC-EXAM_EE.pdf

EE DIAGNOSTIC EXAM INSTRUCTION: Select the correct 7. A 3-phase alternator rated 50 MVA, answer for each of the following 22 kV has a synchronous reactance questions. Mark only one answer for per phase of 5 pu on its thermal each item....

EE DIAGNOSTIC EXAM INSTRUCTION: Select the correct 7. A 3-phase alternator rated 50 MVA, answer for each of the following 22 kV has a synchronous reactance questions. Mark only one answer for per phase of 5 pu on its thermal each item. rating. Find the pu value of this MULTIPLE CHOICE reactance on a base of 100 MVA and 220 kV. 1. A bulb having a rating of 220 V, A. 20 pu C. 0.25 pu 75 W is to be connected to a 110 B. 0.15 pu D. 0.1 pu V source. Find the power will it 8. A nichrome wire is 1 m long and 1 draw. x 10-6 m2 in cross-sectional area. A. 37.5 W C. 75 W B. 9.375 W D. 18.75 W When connected to a potential difference of 2 V, a current of 4 2. A cylindrical core 50 cm long and A exists in the wire. The 5 cm2 in cross section is wound resistivity of this nichrome is: with 500 turns of wire. Find the A. 1 x 10-7 Ω-m C. 4 x 10-7 Ω-m inductance of the coil. Assume the B. 2 x 10 Ω-m -7 D. 5 x 10-7 Ω-m core has a permeability of 2000. 9. A balanced 3-phase, 3-wire system A. 0.628 H C. 0.152 H B. 0.748 H D. 0.347 H supplies power to two balanced connected loads: 6 kW, 0.8 pf 3. A series LC circuit has an lagging and 12 kW, 0.833 pf inductance of 200 uH, a leading. If the current in each capacitance of 300 pF and a Q of line is 8 A, find the line to line 60. Find the upper cut-off voltage. frequency. A. 1.20 kV C. 1.46 kV A. 655 kHz C. 650 kHz B. 1.12 kV D. 1.32 kV B. 653 kHz D. 645 kHz 10. The current in an inductor is 4. Power in a balanced 3-phase system given by i = 5 + 16t amperes. The is measured by two-wattmeter self-induced emf in it is 10 mV. method and is found that the ratio Find the energy stored in the of the two wattmeter readings is inductor at t = 1 second. 2:1. Find the pf of the system. A. 137.8 mJ C. 13.78 mJ A. 0.866 C. 0.5 B. 1.378 mJ D. 1,378 mJ B. 0.707 D. unity 11. A single-phase transmission 5. A 10 kVA, 2400/240 V transformer line, 50 km long, is made up of has a primary winding resistance hard drawn copper conductors 500 of 6 Ω and a secondary resistance mils in diameter. Find the loop of 0.06 Ω. Find the full load resistance. Resistivity of hard copper loss. drawn copper is 1.77 uΩ-cm. A. 201 W C. 176 W A. 6.99 Ω C. 5.46 Ω B. 105 W D. 208 W B. 7.14 Ω D. 8.79 Ω 6. A 6-pole generator with fixed 12. A conductor has an area of 40,000 excitation develops an emf of 100 CM. What is the diameter of this V when operating at 1500 rpm. Find conductor in inches? the operating speed in order to A. 0.60 C. 0.50 develop 120 V. B. 0.20 D. 0.40 A. 1250 rpm C. 1042 rpm B. 1500 rpm D. 1800 rpm 13. Find the resistance connected in series with a capacitance of 4 uF will give the circuit a time constant of 2 s. A. 200 kΩ C. 250 kΩ B. 175 kΩ D. 500 kΩ Page 1 of 4  EE DIAGNOSTIC EXAM 14. Find the distance from an 21. Two identical capacitors, each isolated positive point charge of with capacitance C, are connected 10 nC in order to produce an in parallel and the combination is electric potential of 100 V. connected in series to a third A. 1.8 m C. 0.45 m identical capacitor. The B. 0.9 m D. 0.75 m equivalent capacitance of this arrangement is: 15. A 3-phase, 4-wire, balanced A. C C. 2C/3 system supplies a lighting load of B. 3C/2 D. 2C 40 A, 30 A, and 20 A, respectively in the three phases. Find the 22. A 4-pole induction motor running current in the neutral wire. with 5% slip is supplied by a 60- A. 17.32 A C. 16.49 A Hz synchronous generator. B. 15.41 A D. 18.12 A Determine the speed of the motor. A. 1,674 rpm C. 1,728 rpm 16. A 2000/400-V single phase B. 1,710 rpm D. 1,692 rpm transformer has an equivalent resistance of 0.03 pu and an 23. Two identical coupled coils have equivalent reactance of 0.08 pu. an equivalent inductance of 100 mH Find the voltage regulation at 0.8 when connected in series aiding pf lagging. and 50 mH in series opposing. Find A. 6.2% C. 8.1% the value of the self inductance B. 7.3% D. 9.4% of each coil. A. 37.5 mH C. 22.5 mH 17. At rated load, the rotational B. 62.5 mH D. 12.5 mH losses of a 240 V dc shunt motor is 900 W. The armature and field 24. Three single-phase transformers resistances are 0.15 Ω and 94 Ω. rated 40 MVA, 13.2kV/80kV are If the rated current of the motor connected in delta/wye on a 13.2kV is 145 A, find the horsepower transmission line. Find the output. secondary line voltage. A. 41 hp C. 45 hp A. 80 kV C. 23 kV B. 43 hp D. 47 hp B. 146 kV D. 138 kV 18. An electric heater takes a 25. Two 30 Ω resistors are connected current of 1.5 A at 220 V. Find in series. When a resistor R is the amount of heat produced in one connected across one of them, the minute. total circuit resistance is 40 Ω. A. 4.3 kcal C. 5.5 kcal Find the ohmic value of R. B. 6.6 kcal D. 7.2 kcal A. 20 C. 25 B. 15 D. 10 19. Three capacitors of capacitance 2 uF, 4 uF, and 6 uF respectively 26. The maximum flux density in the are connected in series to a 220- core of a 250/3000-V, 50 Hz V dc source. Find the voltage single-phase transformer is 1.2 T. across the 2 uF capacitor. If the emf per turn is 8 V, find A. 40 V C. 80 V the cross-sectional area of the B. 120 V D. 60 V core. A. 240 cm2 C. 360 cm2 20. A fluorescent lamp draws a B. 300 cm 2 D. 450 cm2 current of 1 A at 0.5 pf lagging from a 220 V, 60 Hz source. Find the overall pf when a 7uF capacitor is connected across the lamp. A. 0.855 C. 0.868 B. 0.883 D. 0.871 Page 2 of 4  EE DIAGNOSTIC EXAM 27. What is the capacitance per 33. An alternating current is given kilometer of two parallel wires 7 by i= 141.4 sin 314t. Find the mm in diameter placed 30 cm apart instantaneous value when t is 3 from each other in air? ms. A. 625 x 10-9 F/km A. 114.35 A C. 115.34 A B. 62.5 x 10-9 F/km B. 113.25 A D. 116.53 A C. 6.25 x 10-12 F/km D. 6.25 x 10-9 F/km 34. It is found that resistance of a wire increases from 50 Ω at 15°C 28. Find the impedance which absorbs to 60 Ω at 55°C. Find the a complex power of 4600 VA at temperature coefficient at 0°C of angle 30° at 230 V. the conductor material. A. 9.95 + j4.75 A. 0.00555 C. 0.00588 B. 8.25 + j5.75 B. 0.00541 D. 0.00606 C. 9.95 + j5.75 D. 8.25 + j4.75 35. A 3-phase, 400 V, 50 Hz, 4-pole synchronous motor has a load angle 29. A charged capacitor is connected of 10 electrical degrees. Find its across a 10 kΩ resistor and equivalent mechanical degree. allowed to discharge. The A. 10° C. 20° potential difference across the B. 6° D. 5° capacitor drops to 37% of its original value after a time of 7 36. A 4-pole 60 Hz three-phase wye s. Find the capacitance of the connected induction motor has a capacitor. mechanical rotational loss of A. 400 uF C. 600 uF 500W. At 5% slip, the motor B. 500 uF D. 700 uF delivers 30 hp at the shaft. Find the mechanical torque. 30. A 120 V dc shunt motor has an A. 128 N-m C. 113 N-m armature and shunt field B. 150 N-m D. 103 N-m resistances of 0.05Ω and 60Ω, respectively. Find the starting 37. A series RL circuit with R = 100 rheostat resistance, in series Ω; L = 50 H, is supplied to a dc with armature to limit the source of 100 V. Find the time armature starting current to 60 A. taken for the current to rise 70% A. 1.95 Ω C. 2.25 Ω of its steady-state value. B. 1.25 Ω D. 1.75 Ω A. 0.3 s C. 0.2 s B. 0.6 s D. 0.8 s 31. A factory load of 900 kW at 0.6 pf lagging is to be increased to 38. Find the line current delivered 0.9 by the addition of a to a 3-phase, 480-V, 60-hp, 3- synchronous motor that takes 450 phase motor if it operates at a pf kW. At what power factor must this of 0.70 and efficiency of 0.8. motor operate? A. 92 A C. 101 A A. 0.648 C. 0.713 B. 85 A D. 96 A B. 0.636 D. 0.745 39. The power transmitted by a shaft 32. Find the induced emf in a 150cm2 of a dc motor is 20 hp. If the circular coil having 100 turns torque is 222 N-m, find the speed. when the field strength passing A. 642 rpm C. 525 rpm through the coil changes from 0 to B. 756 rpm D. 589 rpm 0.001 Wb/m2 in 0.1 s at a constant rate. A. 0.010 V C. 0.025 V B. 0.015 V D. 0.020 V Page 3 of 4  EE DIAGNOSTIC EXAM 40. A transformer has a core loss of 47. What is the total flux of light 64 W and copper loss of 144 W when emitted from a source having a it is carrying 20% overload. Find uniform intensity of 150 the percentage load when the candlepower? transformer operates at maximum A. 150 lm C. 1,885 lm efficiency. B. 572 lm D. 1,088 lm A. 80% C. 67% B. 75 % D. 87% 48. A series RLC circuit has a reactance of 121 Ω and an 41. At a certain current, the energy impedance of 135 Ω. Find the power stored in an iron-cored coil is consumed in the circuit when the 1000 J and its copper loss is 2000 total potential difference is 120 W. Find the time constant of the V. coil. A. 47 W C. 95 W A. 0.25 s C. 1 s B. 106 W D. 240 W B. 0.50 s D. 2 s 49. A 90-slot stator has a 3-phase, 42. Two batteries A and B having emfs 6-pole winding. Each coil spans of 12 V and 8 V and internal from slot 1 to 14. Find the pitch resistances of 2 Ω and 1 Ω factor. respectively are connected in A. 0.978 C. 0.916 parallel across a 10 Ω resistor. B. 0.946 D. 0.982 Find the current delivered by the 50. A hydroelectric generating 12 V battery. station is supplied from a A. 1.63 A C. 1.75 A B. 1.52 A D. 1.88 A reservoir of capacity 5x10 cubic 6 meters at a head of 200 meters. 43. Find the magnetic field at a Find the total energy available in point 50 mm from a wire carrying kWhr if the overall efficiency is a current of 3 A. 75%. A. 0.16 G C. 0.14 G A. 2.725 x 106 kWhr B. 0.18 G D. 0.12 G B. 2.044 x 106 kWhr C. 5.450 x 106 kWhr 44. A 40 uF capacitor is charged to D. 4.088 x 106 kWhr store 0.2 J of energy. An unchanged 60 uF capacitor is then connected in parallel with the first. Find the energy stored on the 60 uF capacitor. A. 0.032 J C. 0.048 J B. 0.024 J D. 0.036 J 45. An alternator has 8 poles. Find its speed in order to develop 60 Hz frequency. A. 900 rpm C. 800 rpm B. 1000 rpm D. 500 rpm 46. The sequence components of phase c current of a 3-phase system are as follows: Ic0 = 0, Ic1 = 18.4∠88.4° A, and Ic2 = 3.23∠48.2° A. Find the phase b current in amperes. A. 19.24∠-218° C. 19.24∠218° B. 18∠42° D. 18∠-42° Page 4 of 4