Basic Electrical FAQs

Basic Electrical FAQs Single Phase Motors: Fill in the blanks with appropriate words: 1. In capacitor motors, the capacitor is connected in ....................... with the starting winding. 2. In ceiling fans generally ...................... motors are used. 3. In shaded pole motors the shading coil is normally made of ................... 4. A universal motor has ...................... starting torque. 5. The capacitor used on ceiling fans has capacitance of few ...................... farads. 6. A shaded pole type motor is generally not used because it has poor ..................... 7. For high speed and high starting torque ....................... motor is preferred. 8. Single phase motors are generally fitted with ........................ bearings. 9. The running winding of a split phase induction motor has .................. resistance and ......................... reactance. 10. A capacitor motor has ....................... starting torque than equally rated slip phase induction motor. 11. The starting torque and current taken by a repulsion motor depends on the .......................... . 12. The advantage of repulsion motor over other single phase motors is ................................. 13. For applications demanding high speed of the order of 5000. rpm, a ............................ motor is suitable. 14. For recorded players a ...................... motor is suitable. 15. The single phase motor suitable for signal devices is ...................... motor. Get all answers at once: 1.series ----- 2.capacitor ----- 3.copper ----- 4.high ----- 5.micro ----6.starting torque----- 7.universal ----- 8.ball -----9.low,high -----10.higher -----11.brush position----- 12.high efficiency-----13. universal -----14.hysteresis ----- 15.reluctance 16. The rotor of a hysteresis motor is made of a material having high ......................... and .............................. 17. In case of hysteresis motors the power factor is ...................:....... 18. If 8 micro F capacitor is used on 200 W capacitor motor, the value of capacitor to be used on 600 W capacitor will be .............................. 19. The ............................ motor has unsymmetrical rotor. 20. Any motor may become hot when subjected to ............................ 21. The power factor of an ac series motor can be improved by ........................... the inductance of field and armature winding. 22. The starting torque of a capacitor motor is ................................ 23. In electric clocks ................................. motor is used. Get Answer: synchronous Nani

24. Only ................................. motor is capable of running on ac as well as dc. 25. The speed-torque characteristics of a repulsion induction motor resemble to that of dc .................................... motor. 26. A shaded pole motor has ............................... initial cost and ........................... maintenance cost. 27. Commutator, capacitor and centrifugal switch are not provided in case of .......................... motor. 28. Power to weight ratio is highest in case of ......................... motor. 29. The stator of a shaded pole motor resembles that of ............................... motor. 30. In shaded pole motors the direction of rotation is from .......................... pole to .............................. pole. Get all answers at once: 16.hysteresis loss, retentivity ----- 17.low ----- 18. (20μF) ----- 19.reluctance ----- 20.overload ----21.decreasing ----- 22.low ----- 23. synchronous-----24.universal ----- 25.compound ----- 26. low, low----- 27.shaded pole----- 28.universal ----- 29.hysteresis ----- 30. main, shaded 31. A 22 gauge wire will be .............................. as compared to a 20 gauge wire. 32. AC series motors of a large size are used in ................................. 33. Most of the single phase motors are designed to run in ........................... horse power range. 34. In capacitor motors, the current is in ........................... with that in the main winding. 35. An amplidyne is a ............................... field machine. 36. The rotor of a .................................. motor has no protrusions, teeth or windings. 37. The rotor of a hysteresis motor must be of ........................... material. 38. The rotating magnetic field in a hysteresis motor magnetizes the metal of the rotor and induces .................................. within it. 39. In a hysteresis motor when the motor reaches synchronous speed, the stator flux ceases to sweep across the rotor and the rotor acts like a ................................... 40. The characteristics of a universal motor resembles that of dc ............................... motor. 41. Table fan motor ratings arc usually less than ............................... watts. 42. A pistol drill is usually fitted with a ................................ motor. 43. Gear trains are often used in ...................................... motors to obtain operating speeds. 44. Ball bearings offer less friction as compared to ................................. bearings. 45. The rotor shaft of a universal motor is made of............................... 46. The direction of rotation of the reluctance start motor is always from the .................................... air gap to the .................................... air gap. 47. Hysteresis motors are made in low horse power range usually below ...................................... H.P. 48. For the same load a dc series motor will have .............................. speed as compared to a dc series motor. Nani

49. Electronic speed controllers for single phase motors use ...................... and ................................. 50. A reluctance motor will operate as sub-synchronous reluctance motor when the number of salient poles on the rotor is ................................... than the number of electrical poles on the stator. Get all answers at once: 31.thinner ----- 32.railway locomotives----- 33.fractional ----- 34.quadrature ----- 35.cross ----36.hysteresis ----- 37.magnetic ----- 38.poles ----- 39.permanent magnet ----- 40.series -----41. (100)----- 42.universal -----43.universal -----44.bush ----- 45.mild steel ----- 46- wide, narrow 47. (1/100) ----- 48.higher ----- 49. diacs, triacs ----- 50. greater State whether the following statements related to Synchronous Motors are true (T) or false (F): 1. The speed of rotation of a synchronous motor of P number of poles with supply frequency fr, is given by 120 f / P. 2. If the field current of a synchronous motor is varied while its shaft load remains constant, then the reactive power consumed by the motor will vary. 3. A synchronous motor has small starting torque. 4. Damper windings in a synchronous motor assist in increasing the stability of the motor. 5. A synchronous motor must be brought upto synchronous speed before it is loaded. 6. The pony motor should have at least two poles more than the number of poles on the synchronous motor to be started. 7. One of the advantage of synchronous motor over induction motor is that its torque is less sensitive to change in supply voltage. 8. Synchronous motor always runs at unit power factor. 9. In a synchronous motor the magnitude of the emf induced in the stator due to revolving flux depends upon rotor flux only. 10. In a synchronous motor, under no load running conditions, the angle between induced voltage and supply voltage will be zero. 11. A synchronous motor can be started on no load using damper windings. 12. A synchronous motor can run over wide range of power factors. 13. The rotor winding of the synchronous motor is excited by the revolving field. 14. The speed of a synchronous motor depends on the frequency of emf generated. 15. A synchronous motor is a self-starting constant speed constant torque motor. 16. In case the dc excitation of a synchronous motor is disconnected, it will stop running. 17. An advantage of synchronous motor over a slip ring induction motor is that the power factor of the motor can be controlled. 18. A synchronous condenser is a stationary device. 19. The common method of starting modem synchronous motors is by induction motor principle. 20. An over excited synchronous motor has lagging power factor.

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Get all answers at once: 1.T ----- 2.T ----- 3.F ----- 4.T ----- 5.T ----- 6.F ----- 7.T ----- 8.F -----9.F -----10.T -----11.T ----12.T -----13.F -----14.F ----- 15.F ----- 16.T ----- 17.T ----- 18.F ----- 19.T ----- 20.F State whether the following statements related to Single Phase Motor are true (T) or false (F): 1. In case of single phase motors, pulsating flux is set up instead of revolving field as in 3-phase motors. 2. In split-phase induction motors, two windings are provided. 3. In split-phase induction motors, two windings arc connected in parallel. 4. In split-phase induction motor, both the windings arc connected during starling. 5. A shaded pole motor has laminated salient poles. 6. In shaded pole motors, the winding is provided on poles. 7. A universal motor can be operated on single phase or three phase supply. 8. Normally the direction of rotation of a shaded pole motor cannot be reversed. 9. The starting torque of a single phase motor can be improved by connecting a capacitor in series with the starting winding. 10. In capacitor motors paper capacitor is used. 11. Shaded pole type motor has leading power factor. 12. The electrical connection between stator and rotor is through a condenser. 13. Starting winding is provided on single phase motor to make it self-starting. 14. In a capacitor motor the capacitance helps in splitting single phase into two phase supply. 15. A shaded pole motor is the only single phase motor which is inherently self-starting. 16. In a mixer-grinder, universal motor is used. 17. The principle of operation of a single phase induction motor depends upon rotating magnetic fields. 18. A repulsion motor is fitted with a commutator. 19. A repulsion motor receives its armature current by induction. 20. A repulsion motor can be directly switched on line. Get all answers at once: 1.T ----- 2.T ----- 3.T ----- 4.F ----- 5.T ----- 6.T ----- 7.F ----- 8.T -----9.T -----10.T -----11.F ----12.T -----13.T -----14.T ----- 15.T ----- 16.T ----- 17.T ----- 18.T ----- 19.T ----- 20.T

State whether the following statements related to Generation of Electric Power are true (T) or false (F): 1. In economizer, the heat of flue gases is used to reheat the steam. 2. Air meters are used in power plants to heat air used for combustion of coal. 3. Corrosion of air pre heater tube can be minimized by limiting the cooling of the flue gas to a Nani

temperature above the dew point 4. Air from air pre heater is sent to forced draft fans. 5. In a silver oxide cell depolarization is accompanied by oxide of silver. 6. Slow neutrons are very efficient in causing fission of uranium 235. 7. A gas turbine power plant suits as peak load plant 8. Steam coal is not suitable for steam boilers. 9. Still process is used for removing sulphur dioxide from flue gases. 10. A perfect heat absorber is also a perfect radiator. 11. A black body absorbs all the incident radiation striking it. 12. Pulverized fuel enters the boiler furnace through striker. 13. A jet aircraft has no propeller. 14. Steam generated in boilers for power plants is invariably dry and saturated. 15. Benson boiler is a drumless once through boiler. 16. Protium is the isotope of hydrogen having the mass number 1. 17. The mass of proton is approximately equal to that of electron. 18. Radon is a radioactive element one of of the heaviest gases known. 19. Rank classification of coal is based on the percentage of fixed carbon and heat content. 20. Rare earths are 15 in number. 21. Read vapor pressure is used for nuclear fuels. 22. The total amount of solid material in grams contained in 1 kg of sea water is called salinity. 23. No moderator is used in fast breeder reactors. 24. Semi-water gas is a mixture of carbon monoxide carbon dioxide, hydrogen and nitrogen. 25. Silica gel is a desiccant. Get all answers at once: 1.F ----- 2.T ----- 3.T ----- 4.F ----- 5.T ----- 6.T ----- 7.T ----- 8.F -----9.T -----10.T -----11.T ----12.F -----13.T -----14.F ----- 15.T ----- 16.T ----- 17.F ----- 18.T ----- 19.T ----- 20.T ----- 21.F ----22.T ----- 23.T ----- 24.T -----25.T

State whether the following statements related to Economics of Power Generation are true (T) or false (F): 1. Obsolescence is - due to technological advancements. 2. Need for unskilled labor is maximum in case of thermal power plants. 3. Depreciation is a fixed cost for a power plant. 4. The ratio of connected load to maximum demand is known as demand factor. 5. In case of domestic consumers the maximum demand occurs in the night. 6. There is an inherent reserve in most electrical supply systems in that the load can be decreased by dropping the voltage. Nani

7. Area under a load curve gives energy consumed. 8. Less costly power plants even having high fuel consumption are preferred for peak load. 9. Diversity factor is always less than one. 10. Salvage value of a plant is always zero. 11. Depreciation of a plant depends on the useful life of the plant. 12. Load curve of a power plant has always positive slope. 13. A power plant having maximum demand more than installed capacity will have utilization factor of less than unity. 14. In two part tariff, the consumer with low power factor will be charged more on account of demand charges. 15. In two part tariff energy charges do not depend on power factor. 16. Power factor of electric heater, is always lagging. 17. Industrial plants generally have leading power factor. 18. Running charges of a power plant are directly proportional to the kWH generated. 19. Spinning reserve is the generating capacity connected to the bus bars and ready to take load when switched on. 20. Fuel consumption depends on the installed capacity of the plant. 21. For a generator at a particular load, when incremental heat rate is equal to heat rate, it will work at maximum efficiency. 22. While selecting units continuous rating of generators is taken into account. 23. Transmission lines also form a part of capital cost of the plant. 24. A tariff is the rate of charge 1 kW hr of the electric energy supplied to a consumer. Get all answers at once: 1.T ----- 2.T ----- 3.T ----- 4.F ----- 5.T ----- 6.T ----- 7.T ----- 8.T ----- 9.F -----10.F ----- 11.F ----12.F ----- 13.F ----- 14.T ----- 15.T ----- 16.F ----- 17.F ----- 18.T ----- 19.T ----- 20.F ----- 21.T ----- 22.T ----- 23.T ----- 24.T

State whether the following statements related to transmission and distribution are true (T) or false (F): 1. Guy wires are generally galvanized. 2. Soft drawn copper wires are cold-drawn to size and then annealed. 3. The surge resistance for overhead lines is 500 ohms. 4. In modern power stations generation voltage range from 6.3 kV to 33 kV. 5. In order to maintain the frequency and voltages at their prescribed value at all times, it is necessary to maintain the balance of active power and reactive power in the system. 6. In generation system at any instant the generation should be exactly equal to the demand. 7. Synchronous condensers provide flexible control of power factor as compared to that by shunt capacitors.

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8. V-strings are suitable for single circuit lines. 9. As an insulator material, toughened glass insulators have greater puncture strength. 10. The life of a toughened glass insulator is greater than that of porcelain insulator. 11. In long transmission lines incident and reflected waves travel in opposite directions. 12. The characteristic impedance of a long transmission line is independent of the length of the line. 13. For a loss less line the characteristic impedance is called surge impedance. 14. Corona reduces the effect of surges. 15. Corona discharges emit radiations which induce noise signals in the communication channel. 16. In short lines A = 1. B = Z, C = 0 and D = A. 17. In nominal T line D = A, C = Y and B = Z (1 + (YZ)/4) 18. Galloping frequency may be of the order of 50 to 100 Hz.. 19. Armour rods on conductors are provided to reduce the amplitude of vibrations. 20. The choice of economic span length of transmission lines depends on size, material and number of conductors. 21. A booster is connected in parallel with feeder. Get all answers at once: 1. T ----- 2. T ----- 3. T ----- 4. T ----- 5. T ----- 6. T ----- 7. T ----- 8. T ----- 9. T ----- 10. T ----- 11. T ----- 12.T ----- 13.T ----- 14.T ----- 15.T ----- 16.T ----- 17.T ----- 18.F ----- 19.T ----- 20.T ----- 21.F

State whether the following statements related to circuit breakers are true (T) or false (F): 1. The voltage across the circuit breaker pole after final current zero is recovery voltage. 2. Air circuit breakers are used for voltages above 12 kV. 3. Double pressure type SF6 circuit breaker is also known as Puffer type. 4. Air blast circuit breakers and SF6 circuit breakers are preferred for EHV applications. 5. Arcing contacts of circuit-breakers are generally made of copper tungsten alloy. 6. The are plays important role in the behavior of circuit breaker. 7. The arc has a brightly burning core of high temperature ranging from 6000 K to 25000 K. 8. SF6 is a heavy, colorless and chemically inert gas. 9. SF6 gas is electro-positive. 10. In oil circuit breakers transformer oil is used. 11. . An isolator does not have any current making or current breaking capacity. 12. SF6 circuit breaker takes minimum time for installation. 13. A triple pole isolator has three identical poles, with operate simultaneously. Nani

14. Isolators operate under no current conditions. 15. Non-linear resistors are used in lightning arresters. 16. Switching over-voltages are proportional to system voltages. 17. Switching over-voltages arise from energizing of uncharged line can be reduced by the use of high voltage shunt reactors. 18. The damage caused by surge depends on steepness of the wave-front. 19. Bulk oil circuit breaker is used for outdoor UHV application. 20. In electro-magnetic relays the restraining torque is given by springs. Get all answers at once: 1.T ----- 2.F ----- 3.F ----- 4.T ----- 5.T ----- 6.T ----- 7.T ----- 8.T -----9.F -----10.T -----11.T ----12.T -----13.T -----14.T ----- 15.T ----- 16.T ----- 17.T ----- 18.T ----- 19.F ----- 20.T State whether the following statements related to Electric Machine Design are true (T) or false (F): 1. Hard rubber is obtained by increased sulphur content and extended vulcanization treatment. 2. Ceramics are unaffected by chemical action. 3. B-type insulation is largely used in commutators, wedges of slots and capacitors. 4. H-type insulation is used in traction motors. 5. C-type insulation includes press board and vulcanized natural rubber. 6. Florentine, foulard and excelsior are silky fabrics. 7. PVC is obtained by combination of acctylene and hydrogen chloride in the presence of catalyst like oxides at a temperature of 323 K. 8. SF6 has high dielectric strength and is non inflammable. 9. Square section of the transformer core requires less copper wire than equivalent rectangular section. 10. Gum, starch, asphalt are useful for binding laminates of wood. 11. For liquid insulating materials the dielectric strength increases with rise in temperature. 12. Mineral insulating oils are obtained from the fractional distillation of crude petroleum. 13. Transformer oil is flammable 2nd sludging type oil. 14. Sulphur hexafluoride is used as insulating material in turbo-generators. 15. Hydrogen is used in large turbo-generators primary as a dielectric. 16. Oil varnish is obtained by dissolving shellac in methylated spirit 17. Lacquer is obtained by dissolving nitrocellulose in ketone. 18. The base material of black varnish is bitumen. 19. Smaller is the number of slots, the more is the distortion in the field flux. 20. The dielectric strength of PVC is around 30 kV/mm. 21. PVC can be safely used up to temperatures of 250 0 C.

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Get all answers at once: 1.T ----- 2.T ----- 3.T ----- 4.T ----- 5.F ----- 6.T ----- 7.T ----- 8.T -----9.T -----10.T -----11.F ----- 12.T -----13.F -----14.F ----- 15.F ----- 16.F ----- 17.T ----- 18.T ----- 19.T ----- 20.T ----- 21.F State whether the following statements related to Computation are true (T) or false (F): 1. If the number of leaves in a tree is not a power of 2, then the tree is not a binary tree. 2. The union of two equivalence relations is also an equivalence relation. 3. All subsets of regular sets are regular. 4. The relation r with scheme (x, y) satisfies the function dependency x -> y. The tuples <1,2 > and < 2,2 > can both be in r simultaneously. 5. There is a linear-time algorithm for testing the planarity of finite graphs. 6. Every infinite cyclic group is ionospheric to the infinite cyclic group of integers under addition. 7. Regularity is preferred under the operation of string reversal. Get all answers at once: 1.T ----- 2.T ----- 3.F ----- 4.T ----- 5.F ----- 6.F ----- 7.F

Synchronous Generator Multiple Choice Questions of Synchronous Generator 1. In an alternator, voltage drops occurs in (A) armature resistance only (B) armature resistance and leakage reactance (C) armature resistance, leakage reactance and armature reaction (D) armature resistance, leakage reactance, armature reaction and earth connections. 2. The magnitude of various voltage drops that occur in an alternator, depends on (A) power factor of the load (B) load current (C) power factor x load current (D) power factor x (load current)2. 3. In an alternator, at lagging power factor, the generated voltage per phase, as compared to that at unity power factor (A) must be same as terminal voltage (B) must be less than the terminal voltage (C) must be more than the terminal voltage (D) must be 1.41 time the terminal voltage. 4. The power factor of an alternator depends on (A) Load Nani

(B) Speed of rotor (C) Core losses (D) Armature losses. 5. Which kind of rotor is most suitable for turbo alternators which arc designed to run at high speed ? (A) Salient pole type (B) Non-salient pole type (C) Both (A) and (B) above (D) None of the above. 6. Salient poles are generally used on (A) high speed prime movers only (B) medium speed prime movers only (C) low speed prime movers only ( D) low and medium speed prime movers. 7. The frequency of voltage generated in an alternator depends on (A) number of poles (B) rotative speed (C) number of poles and rotative speed (D) number of poles, rotative speed and type of winding. 8. The frequency of voltage generated by an alternator having 8 poles and rotating at 250 rpm is (A) 60 Hz (B) 50 Hz (C) 25 Hz (D) 16 2/3 Hz. 9. An alternator is generating power at 210 V per phase while running at 1500 rpm. If the need of the alternator drops to 1000 rpm, the generated voltage per phase will be (A) 180 V (B) 150 V (C) 140 V (D) 105 V. 10. A 10 pole AC generator rotates at 1200 rpm. The frequency of AC voltage in cycles per second will be (A)120 (B) 110 (C) 100 (D) 50. 11. The number of electrical degrees passed through in one revolution of a six pole synchronous Nani

alternator is (A)360: (B)720 (C) 1080 (D)2160 . 12. Fleming's left hand rule may be applied to an electric generator to find out (A) direction of rotor rotation (B) polarity of induced emf (C) direction of induced emf (D) direction of magnetic field. 13. If the input to the prime mover of an alternator is kept constant but the excitation is changed, then the (A) reactive component of the output is changed (B) active component of the output is changed (C) power factor of the load remains constant (D) power factor of the load reduces. 14. An alternator is said to be over excited when it is operating at (A) unity power factor (B) leading power factor (C) lagging power factor (D) lagging to leading power factor. 15. When an alternator is running on no load the power supplied by the prime mover is mainly consumed (A) to meet iron losses (B) to meet copper losses (C) to meet all no load losses (D) to produce induced emf in armature winding. Get all answers at once: 1.C ----- 2.B ----- 3.C ----- 4.A ----- 5.B ----- 6.D ----- 7.C ----- 8.D -----9.C -----10.C -----11.C ----- 12.C -----13.A -----14.C ----- 15.C 16. As the speed of an alternator increases (A) the frequency increases (B) the frequency decreases (C) the frequency remains constant but power factor decreases (D) none of the above. 17. For an alternator when the power factor of the load is unity Nani

(A) the armature flux will have square waveform (B) the armature flux will be demagnetising (C) the armature flux will be cross-magnetising (D) the armature flux will reduce to zero. 18. The driving power from the prime mover driving the alternator is lost but the alternator remains connected to the supply network and the field supply also remains on. The alternator will (A) get burnt (B) behave as an induction motor but will rotate in the opposite direction (C) behave as a synchronous motor and will rotate in the same direction (D) behave as a synchronous motor but will rotate in a reverse direction to that corresponding to generator action. 19. If the input of the prime mover of an alternator is kept constant but the excitation is changed, then (A) the active component of the output is changed (B) the reactive component of the output is changed (C) power factor of the load remains constant (D) power factor of the load changes from lagging to leading. 20. For 50 Hz system the maximum speed of an alternator can be (A) approximately 3600 rpm (B) approximately 3000 rpm (C) 3600 rpm (D) 3000 rpm. 21. Voltage characteristic of an alternator is shown in figure. Which curve represents the characteristics for leading power factor ?

(A) A (B) B (C) C (D) D. 22. In the above figure, the characteristic for unity power factor is represented by the curve maked Nani

(A) A (B) B (C)C (D )D. Questions 23 to 26 refer to the following data: In a 50 kVA, star connected 440 V, 4-phase 50 Hz alternator, the effective armature resistance is 0.25 ohm per phase. The synchronous reactance is 3.2 ohm per phase and leakage reactance is 0.5 ohm per phase. 23. Full load output current at unity power factor will be (A) 65.6 A (B) 55.4 A (C) 45.6 A (D) 35.4 A. 24. Full load line voltage will be (A) 500 V (B) 471 V (C) 450 V (D) 435 V. 25. No load line voltage will be (A) 600 V (B) 599 V (C)592V (D) 580 V. 26. Percentage regulation of the alternator is approximately (A) 55% (B) 45% (C) 35% (D) 25%. 27. In order that two alternators be put in parallel, which of the following factors should be identical for both ? (A) Voltage (B) Frequency (C) Phase sequence (D) All of the above. 28. When two alternators are running in parallel, their RKVA load share is changed by changing their ................ while their kW load share is changed by changing their .............. (A) excitation, driving torque Nani

(B) driving torque, excitation (C) excitation, excitation (D) driving torque, driving torque. 29. Two-alternators are running in parallel. If the driving force of both the alternators is changed, this will result in change is (A) frequency (B) back emf (C) generated voltage (D) all of the above. 30. A three phase alternator has a phase sequence of RYB for its three output voltages. In case the field current is reversed, the phase sequence will become (A) RBY (B) RYB (C) YRB (D) none of the above. Get all answers at once: 16.A ----- 17.C ----- 18.C ----- 19.B ----- 20.D ----- 21.D ----- 22.C ----- 23.A -----24.B -----25.C ----- 26.D ----- 27.D -----28.A -----29.A ----- 30.B 31. The armature reaction of an alternator influences (A) windage losses (B) operting speed (C) generated voltage per phase (D) waveform of voltage generated. 32. For the same power rating, a lower voltage alternator will be (A) more efficient (B) larger in size (C) operating at high rpm (D) more costly. 33. An alternator is supplying 10A to an inductive load at 220 V, while running at 1000 rpm. Now if the speed of the alternator is reduced to 750 rpm but the field current remains unchanged, the load current will become (A) 18 A (B) 13.3 A (C) 10 A (D) 7.5 A. 34. Dampers in a large generator (A) increase stability

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(B) reduce voltage fluctuations (C) reduce frequency fluctuations. 35. An alternator is rated for 75 kW at 0.8 power factor. It means that (A) alternator has 4 poles (B) alternator can supply 75 kW at 0.8 power factor (C) alternator can supply power only to loads having power factor 0.8 only (D) the peak efficiency of alternator occurs only at 75 kW load having 0.8 lagging power factor. 36. The regulation of an alternator is (A) the reduction in terminal voltage when alternator is loaded (B) the variation of terminal voltage under the conditions of maximum and minimum excitation (C) the increase in terminal voltage when load is thrown off (D) the change in terminal voltage from lagging power factor to leading power factor. 37. A magnetisation curve represents the relationship between (A) reactive and non-reactive components of voltage (B) exciting currents and terminal voltage (C) power factor and terminal voltage (D) magnetic flux and armature current. 38. In an alternator if the armature reaction produces demagnetisation of the main field, the power factor should be (A) Zero, lagging load (B) Zero, leading load (C) Unity. 39. In an alternator if the armature reaction produces magnetisation of the main field the power factor should be (A) Zero, lagging load (B) Zero, leading load (C) Unity. 40. When an alternator is supplying unity power factor load, the armature reaction will produce (A) magnetisation of the main field (B) demagnetisation of the main field (C) distortion of the main field. 41. An alternator has full load regulation of 4% when the power factor of the load is 0.8 lagging while alternator runs at 1500 rpm. The full load regulation of 1400 rpm for 0.8 pf lagging load will be (A) 15/14 x 4 percent (B) 14/15 x 4 percent (C) 4 percent Nani

(D) Depends on other factors also. 42. The Potier's triangle separates the (A) iron losses and copper losses (B) field mmf and armature mmf (C) stator voltage and rotor voltage (D) armature leakage reactance and armature reaction mmf. 43. In the Potier's triangle, the Potier reactance drop per phase is 22 volts per phase at 88 amperes per phase. The Potier's reactance per phase is (A) 0.22 (B) 0.25 (C) 0.30 (D) 0.44. 44. Two alternators are running in parallel. The excitation of one of the alternator is increased. The result will be (A) machine with excess excitation will burn (B) both machines will start vibrating (C) power output will decrease (D) wattless component will change. 45. The power output of an alternators is 100 kW. In order that the tangent of pf angle may be 0.8 lagging, the KVAR rating must be (A) 80 cosφ KVAR (B) 80 sin φ KVAR (C) 80 KVAR (D) -80 KVAR. Get all answers at once: 31.C ----- 32.B ----- 33.C ----- 34.A ----- 35.B ----- 36.C ----- 37.B ----- 38.A ----- 39.A ----- 40.C -----41.C ----- 42.D -----43.B -----44.D ----- 45.D 46. The power output of an alternator is 40 kW and KVAR component is - 25. What will be the value of tanφ (φ being the power factor angle) ? (A) 0.625 lagging (B) 0.625 leading (C) 0.375 lagging (D) 0.375 leading. 47. When short pitch coils of 160 are used in an alternator, which harmonic component will not be present in the output emf ? (A) third (B) fifth Nani

(C) seventh (D) ninth. 48. A 120 MW turbo alternator is supplying power to 80 MW load at p.f. lagging. Suddenly the steam supply to the turbine is cut off and the alternator remains connected to the supply network and the field supply also remains on. What will happen to the alternator ? (A) The stator winding of the alternator will get burnt (B) The rotor winding of the alternator will get burnt (C) The alternator will continue to run as a synchronous motor rotating in the same direction (D) The alternator will continue to run as a synchronous motor rotating in the opposite direction. 49. The figure shows the characteristics of an alternator. Which curve represents synchronous impedance ?

(A) curve A (B) curve B (C) curve C (D) curve D. 50. In the above figure (Figure of Question 49) which curve represents short circuit ? (A) curve A (B) curve B (C) curve C (D) curve D. 51. In the above figure which curve represents open circuit voltage ? (A) curve A (B) curve B (C) curve C (D) curve D. 52. For a peripheral speed of 314 m/s, a 2 pole cylindrical machine will have maximum diameter of

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(A) 255 cm (B) 235 cm (C) 200 cm (D) 170 cm. 53. The rotor of the salient pole alternator has 24 poles. The number of cycles of emf in one revolution would be (A) 24 (B) 12 (C) 6 (D) 4. 54. Two alternators A and B are sharing an inductive load equally. If the excitation of alternator A is increased (A) alternator B will deliver more current and alternator A will deliver less current (B) alternator B will deliver less current and alternator A will deliver more current (C) both will continue to share load equally (D) both will deliver more current. 55. Desirable feature for the parallel operation of two alternators is (A) both should have same resistance (B) both should have same reactance (C) both should have less of resistance as compared to synchronous reactance (D) both should have more of resistance as compared to synchronous reactance. 56. Alternators used in aircraft systems usually have frequency of (A) 25 Hz (B) 50 Hz (C) 100 Hz (D) 400 Hz. 57. High frequency on aircraft alternators is selected in order to (A) free the systems from external disturbance (B) compensate for high speeds (C) compensate for high altitudes (D) reduce the bulk. 58. A 20 pole ac generator rotates at 600 rpm. The periodic time of current in seconds per cycle is (A) 0.009 (B) 0.004 (C) 0.008 (D) 0.01. Nani

59. What kind of rotor is most suitable for turbo alternators ? (A) salient pole type (B) non-salient pole type (C) both (A) and (B) above (D) none of the above. 60. The synchronizing power developed in one of the alternators, when two alternators are running in parallel, will load the same alternator in which it is developed and reduce its speed (A) True (B) False Get all answers at once: 46.B ----- 47.D ----- 48.C ----- 49.A ----- 50.C ----- 51.D ----- 52.C ----- 53.B ----- 54.B ----- 55.C ----- 56.D ----- 57.D ----- 58.D ----- 59.B ----- 60.A 61. If the input to the prime mover of an alternator is kept constant but the excitation is changed then the (A) reactive component of the output is changed (B) active component of the output is changed (C) power factor of load remains constant. 62. If two machines are running in synchronism and the voltage of one machine is suddenly increased (A) the machines will burn (B) both machines will stop (C) synchronising torque will be produced to restore further synchronism. 63. In an alternator, at 0.8 lagging power factor, the generated voltage per phase is 240 V to give a rated terminated voltage ' V '. If the power factor of load increases to unity, the generated voltage per phase must be (A) 260 V (B) 250 V (C) 240 V (D) 225 V. 64. The advantage of salient poles in an alternator is (A) reduce noise (B) reduced windage loss (C) adoptability to low and medium speed operation (D) reduce bearing loads and noise.

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65. Magnetisation curves for no load and full load unity power factor are shown in figure below. Which is the magnetisation curve for full load 0.8 power factor ? (A) curve A (B) curve B (C) curve C (D) curve D. 66. At a particular instant a turbo alternator is generating 80 MW at 0.8 power factor lagging. Now if the steam supply valve to the steam turbine is further opened and the excitation is not changed (A) the speed of the alternator will increase but kW delivered will remain unchanged (B) the speed of the alternator will increase and kW delivered will also increase (C) the speed of the alternator will remain unchanged but it can meet more kW demand (D) the speed of the alternator will remain unchanged but it will deliver more kVA. 67. Two alternators A and B are sharing a resistive load (p.f. = 1 ) equally. Now if the excitation of alternator A is increased (A) alternator A will become lagging and alternator B will become leading (B) alternator A will become leading and alternator B will become lagging (C) both alternators will continue to operate on unity power factor (D) both alternators will operate on lagging power factor (E) both alternators will operate on leading power factor. 68. The advantage of providing damper winding in alternators is (A) elimination of harmonic effects (B) provide a low resistance path for the currents due to unbalancing of voltage (C) oscillations are provided when two alternators operate in parallel (D) all of the above. 69. When two alternators are running in exactly synchronism, the synchronising power wil be (A) zero (B) sum of the output of two (C) unity (D) 0.707. Nani

Questions 70 to 72 refer to the figure given below :

70. Load characteristic curves for an alternator are shown. The curves are drawn for 0.8 pf lagging, 0.8 p.f. leading, 0.7 p.f. leading and 0.9 p.f. lagging. Which curve represents the characteristics for 0.8 p.f. leading ? (A) curve A (B) curve B (C) curve C (D) curve D. 71. Which curve represents the data for 0.8 p.f. lagging ? (A) curve A (B) curve B (C) curve C (D) curve D. 72. Which curve represents the data for 0.9 p.f. lagging ? (A) curve A (B) curve B (C) curve C (D) curve D. 73. The balanced short circuit current of a three phase alternator is 25 amperes at 1500 rpm. For the same field current, the balanced short current at 1400 rpm will be (A)18 A (B) 27 A (C) 20 A (D) 20*(2)1/2A 74. A three phase alternator has a phase sequence of RYB for its three output voltages, for clockwise rotation. Now if the alternator is rotated anticlockwise, the phase sequence will be (A) RYB (B) RBY Nani

(C) BYR (D) none of the above. 75. In a synchronous machine, if the field flux axis is ahead of the armature field axis, in the direction of rotation, the machine working as (A) asynchronous motor (B) asynchronous generator (C) synchronous motor (D) synchronous generator. Get all answers at once: 61.A ----- 62.C ----- 63.D ----- 64.C ----- 65.D ----- 66.C ----- 67.A ----- 68.D ----- 69.A ----- 70.C ----- 71.A ----- 72.B -----73.C ----- 74.B ----- 75.D 76. In synchronous alternator, which of the following coils will have emf closer to sine waveform ? (A) concentrated winding in full pitch coils (B) concentrated winding in short pitch coils (C) distributed winding in full pitch coils (D) distributed winding in short pitch coils. 77. An alternator has rated field current of 4 A. The alternator develops 180 V while drawing a field current of 2 A at 750 rpm. If the field current is made 4 A at 750 rpm generated voltage could be (A) 400 V (B) 380 V (C) 60V (D) 330 V. 78. The armature reaction of an alternator will be completely magnetizing in case the load power factor is (A) unity (B) 0.707 (C) zero lagging (D) zero loading. 79. Which of the following is not an integral part of synchronous generator system ? (A) prime mover (B) distribution transformer (C) excitation system (D) protection system. 80. For turbo generators the range of excitation voltage is (A) 10 to 20 V (B) 30 to 100 V

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(C) 100 to 800 V (D) 1000 to 1800 V. 81. In case of low speed hydrogenerators, the short circuit ratio is usually (A) 0.1 to 0.5 (B) 0.5 to 0.6 (C) 0.6 to 1.0 (D) 1.0 to 1.5. 82. The permissible duration for which a generator of rated frequency 50 Hz can run at 46 Hz is (A) zero (B) one cycle (C) one second (D) one minute. 83. The permissible duration in supply . frequency is (A) ± 2 % (B) ± 5 % (C) ± 10 % (D) ± 25 %. 84. The regulation of an alternator is likely to be negative in case of (A) high speed alternators (B) slow speed alternators (C) lagging power factor of the load (D) leading power factor of the load. Questions 85 to 88 refer to the data given below: A phase, 50 Hz, 6600 V, alternator is rated at 6600 kW at 0.8 power factor and a full load efficiency of 90%. 85. kVA is rating of the alternator is (A) 750 kVA (B) 7500 kVA (C) 75000 kVA (D) 750000 kVA. 86. The current rating of the alternator is (A) 65.63 A (B) 656.3 A (C) 6563 A (D) 65630 A. 87. The input to the alternator is Nani

(A) 666.6 kW (B) 6666 kW (C) 66660 kW (D) 666,600 kW. 88. If the input. to an alternator remains unaltered, but excitation is changed then which of the following will not change ? (A) kVA output (B) kW output (C) power factor (D) all of the above. 89. Which of the following method is likely to give the voltage regulation more than the actual value ? (A) Synchronous reactance method (B) MMF method (C) Zero power factor method (D) None of the above. 90. The effect of cross magnetization in an alternator field is to make the output (A) true sinusoidal (B) non-sinusoidal (C) harmonic free (D) none of the above. Get all answers at once: 76.D ----- 77.D ----- 78.D ----- 79.B ----- 80.C ----- 81.D ----- 82.C ----- 83.A ----84.D ----- 85.B ----- 86.C ----- 87.B ----- 88.B ----- 89.A ----- 90.B

Synchronous Motors Multiple Choice Questions of Synchronous Motors 1. Synchronous motor can operate at (A) Lagging power factor only (B) Leading power factor only (C) Unity power factor only (D) Lagging, leading and unity power factor only. 2. An unexcited single phase synchronous motor is (A) reluctance motor (B) repulsion motor Nani

(C) universal motor (D) AC series motor. 3. The maximum power developed in the synchronous motor will depend on (A) rotor excitation only (B) maximum value of coupling angle (C) supply voltage only (D) rotor excitation supply voltage and maximum value of coupling angle. 4. In case the field of a synchronous motor is under excited, the power factor will be (A) leading (B) lagging (C) zero (D) unity. 5. A synchronous motor is switched on to supply with its field windings shorted on themselves. It will (A) not start (B) start and continue to run as an induction motor (C) start as an induction motor and then run as synchronous motor (D) bum immediately. 6. When the excitation of an unloaded salient pole synchronous motor gets disconnected (A) the motor will bum (B) the motor will stop (C) the motor will ran as a reluctance motor at the same speed (D) the motor will run as a reluctance motor at a lower speed. 7. The damping winding in a synchronous motor is generally used (A) to provide starting torque only (B) to reduce noise level (C) to reduce eddy currents (D) to prevent hunting and provide the starting torque. 8. The back emf set up in the stator of a synchronous motor will depend on (A) rotor speed only (B) rotor excitation only (C) rotor excitation and rotor speed (D) coupling angle, rotor speed and excitation. 9. A synchronous motor is a useful industrial machine on account of which of the following reasons ? I. It improves the power factor of the complete installation

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II. Its speed is constant at all loads, provided mains frequency remains constant III. It can always be adjusted to operate at unity power factor for optimum efficiency and economy. (A) I only (B) II only (C) III only (D) I, II and III. 10. Which of the following is an unexcited single phase synchronous motor ? (A) A.C. series motor (B) Universal motor (C) Reluctance motor (D) Repulsion motor. 11. An over excited synchronous motor draws current at (A) lagging power factor (B) leading power factor (C) unity power factor (D) depends on the nature of load. 12. With the increase in the excitation current of synchronous motor the power factor of the motor will (A) improve (B) decrease (C) remain constant (D) depend on other factors. 13. The armature current of a synchronous motor has large values for (A) low excitation only (B) high excitation only (C) both low and high excitation (D) depends on other factors. 14. A synchronous motor is switched on to supply with its field windings shorted on themselves. It will (A) not start (B) start and continue to run as an induction motor (C) start as induction motor and then run as a synchronous motor. 15. If the field of a synchronous motor is under excited, the power factor will be (A) lagging (B) leading (C) unity. Nani

Get all answers at once: 1.D ----- 2.A ----- 3.D ----- 4.B ----- 5.C ----- 6.B ----- 7.D ----- 8.B -----9.D -----10.C -----11.B ----12.A -----13.C -----14.C ----- 15.A 16. When the excitation of an unloaded salient-pole synchronous motor suddenly gets disconnected (A) the motor stops (B) it runs as a reluctance motor at the some speed (C) it runs as a reluctance motor at a lower speed. 17. The armature current of the synchronous motor has large values for (A) low excitation only (B) high excitation only (C) both high and low excitation. 18. What is the ratio of no load speed to full load speed of a 200 kVA, 12 pole, 2200 V, 3 phase, 60 Hz synchronous motor ? (A) 1 (B) 1.1 (C) 1.21 (D) infinite. 19. If a synchronous motor drops too far behind, the power it takes from the supply also increases too much, and the armature tries to get accelerated, until it is in correct position. Sometimes, some motor overshoots the marks and then the process of acceleration-retardation continues. This phenomenon is known as (A) synchronization (B) hunting (C) pulling out (D) swinging. 20. The maximum value of torque that a synchronous motor, can develop without losing its synchronism, is known as (A) breaking torque (B) synchronizing torque (C) pull out torque (D) slip torque. 21. In a synchronous motor if the back emf generated in the armature at no load is approximately equal to the applied voltage, then (A) the torque generated is maximum (B) the excitation is said to be zero percent (C) the excitation is said to be 100% (D) the motor is said to be fully loaded.

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22. A synchronous motor is connected to supply voltage V drawing current /. Resultant of v and back emf Eb is represented by E in the figure. From this diagram it can be concluded that

(A) power factor it lagging (B) the resultant of V and Eb is consumed by synchronous impedance (C) current I leads the applied voltage by I (D) motor is running on full load. 23. A 3 phase, 400 V, 50 Hz salient pole synchronous motor is fed from an infinite bus and is running at no load. Now if the field current of the motor is reduced to zero (A) the motor will stop (B) the motor will run (C) the motor will run at synchronous speed (D) the motor will run at less than synchronous speed. 24. The purpose of embedding the damper winding in the pole face is to (A) eliminate hunting and provide adequate starting torque (B) reduce windage losses (C) eliminate losses on account of air friction (D) reduce bearing friction. 25. A synchronous motor is switched on to supply with its field windings shorted on themselves. It will (A) not start (B) start but continue to run as an induction motor (C) start as an induction motor and then run as a synchronous motor. 26. In case of a synchronous motor we have I. Load

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II. Speed III. DC excitation. The magnitude of stator back emf depends on (A) I only (B) I and II only (C) III only (D) I, II and III. 27. Which of the following motors is non-self starling ? (A) squirrel cage induction motor (B) wound rotor induction motor (C) synchronous motor (D) DC series motor. 28. The back emf in the stator of a synchronous motor depends on (A) speed of rotor (B) rotor excitation (C) number of poles (D) flux density. 29. Which motor can conveniently operate on lagging as well as leading power factor ? (A) squirrel cage induction motor (B) wound rotor induction motor (C) synchronous motor (D) any of the above. 30. A synchronous motor working on leading power factor and not driving any mechanical, is known (A) synchronous induction motor (B) spinning motor (C) synchronous condenser (D) none of the above. Get all answers at once: 16.A ----- 17.C ----- 18.A ----- 19.B ----- 20.B ----- 21.C ----- 22.B ----- 23.C -----24.A -----25.B ----26.C ----- 27.C -----28.B -----29.C ----- 30.C 31. The constant speed of a synchronous motor can be changed to new fixed value by (A) changing the applied voltage (B) interchanging any two phases (C) changing the load (D) changing the frequency of supply. Nani

32. A 3 phase, 400 V, 50 Hz synchronous motor is operating at zero power factor lagging with respect to the excitation voltage. The armature reaction mmf. produced by the armature current will be (A) demagnetizing (B) magnetizing (C) cross-magnetizing (D) none of the above. 33. In a synchronous motor, the torque angle is (A) the angle between the rotating stator flux and rotor poles (B) the angle between magnetizing current and back emf (C) the angle between the supply voltage and the back emf (D) none of the above. 34. A 3 phase, 400 V, 50 Hz, 4 pole synchronous motor has a load angle of 10° electrical. The equivalent mechanical degrees will be 35. (A) 10° (B)5√2 degrees (C) 5 degrees (D) 1 degree. 35. A 3 phase, 400 V, 50 Hz synchronous motor has fixed excitation. The load on the motor is doubled. The torque angle, φi will become nearly (A) φr /2 (B) φr (C)2 φr (D) √ 2 φr 36. The hunting in a synchronous motor takes place when (A) friction in bearings is more (B) air gap is less (C) load is variable (D) load is constant. 37. V curves for a synchronous motor represent relation between (A) field current and speed (B) field current and power factor (C) power factor and speed (D) armature current and field current. 38. The breakdown. torque of a synchronous motor varies as (A)1 /(applied voltage ) Nani

(B) 1/(applied voltage )2 (C) applied voltage (D) (applied voltage)2. 39. Hunting in a synchronous motor cannot be due to (A) variable frequency (B) variable load (C) variable supply voltage (D) windage friction. 40. When the excitation of an unloaded salient pole synchronous motor suddenly gets disconnected (A) the motor stops (B) it runs as a reluctance motor at the same speed (C) it runs at a reluctance motor at a lower speed. 41. Which synchronous motor will be smallest in size ? (A) 5 HP, 500 rpm (B) 5 HP, 375 rpm (C) 10 HP, 500 rpm (D) 10 HP, 375 rpm. 42. A synchronous machine has its field winding on the stator and armature winding on the rotor. Under steady running conditions, the air-gap field (A) rotates at synchronous speed with respect to stator (B) rotates at synchronous speed with direction of rotation of the rotor (C) remains stationary with respect to stator (D) remains stationary with respect to rotor. 43. If the field of a synchronous motor is under-excited, the power factor will be (A) unity (B) lagging (C) leading (D) more than unity. 44. The name plate of an induction motor reads 3 phase. 400 V, 50 Hz. 0.8 of lagging, 1440 rpm. On similar lines the name plate of a synchronous motor should read (A) 3 phase, 400 V, 50 Hz, 0.8 pf lagging, 1500 rpm (B) 3 phase, 400 V. 50 Hz, 0.8 pf leading, 1500 rpm (C) 3 phase, 400 V, 50/60 Hz, 0.8 pf lagging, 1500 rpm (D) 3 phase. 400 V, 50/60 Hz, 0.8 pf leading, 1500 rpm. 45. In which coil the emf generated will be more, for given flux distribution and number of turns (A) Full pitch coil Nani

(B) Short pitch coil (C) Long pitch coil (D) Equal emf will be generated in all cases. Get all answers at once: 31.D ----- 32.B ----- 33.A ----- 34.C ----- 35.C ----- 36.C ----- 37.D ----- 38.C ----- 39.D ----- 40.A -----41.B ----- 42.C -----43.B -----44.B ----- 45.A 46. In a synchronous motor which loss does not vary with load ? (A) Copper losses (B) Hysteresis losses (C) Windage losses (D) None of the above. 47. In a 3-phase. 400 V, 50 Hz salient pole synchronous motor, the maximum power is obtained when the load angle is (A) 45° (B) less than 90° (C) 90° (D) more than 90°. 48. A high starting torque synchronous motor has (A) simplex rotor (B) phase wound damper (C) five slip rings (D) all of the above. 49. In a three phase synchronous motor, the magnitude of field flux (A) varies with speed (B) varies with load (C) remains constant at all loads (D) varies with power factor. 50. The parameter connected with the operation of a synchronous motor are I. Speed II. Power factor III. Armature current. When the excitation of the motor is varied, which parameters vary along with it (A) I only (B) II only (C) II and III only (D) I, II and III. Nani

51. A 3 phase, 400 V, 50 Hz salient pole synchronous motor is running on no load. If there is break in the excitation winding of the motor (A) the motor will stop (B) the winding will get overheated (C) the motor will run as reluctance motor at the rated rpm (D) the motor will run as reluctance motor at lower rpm. 52. In the figure shown with curve represents the variation of synchronous reactance for a synchronous motor with field current ?

(A) curve A (B) curve B (C) curve C (D) curve D. 53. A synchronous motor is said to be 'floating' when it operates (A) on no load and without losses (B) on constantly varying load (C) on pulsating load (D) on high load and variable supply voltage. 54. The negative phase sequences in a three phase synchronous motor exist when (A) motor is overloaded (B) motor is under loaded (C) unbalanced voltage is supplied (D) motor armature is hot. 55. The field winding of a synchronous motor is shorted. A variable voltage is now supplied to the stator. The result will be (A) stator winding will bum (B) motor will not run (C) motor will rotate at synchronous speed on light load (D) motor will rotate at a speed which is less than the synchronous speed. Nani

56. In a three phase synchronous motor, the poles (A) are along the resultant air-gap flux wave φ r (B) arc opposite to φ r (C) lag φ r (D) lead φ r 57. A 3 phase synchronous motor is running clockwise. In case the direction of its field current is reversed (A) the motor will continue to run in the same direction (B) the motor will run in the reverse direction (C) the motor will stop (D) the winding of the motor will burn. 58. The speed regulation of a 3 phase synchronous motor is (A) 5% (B) 1% (C) 0.4% (D) zero. 59. When E is the supply voltage and R is the rotor resistance per phase, the mechanical power develop by a synchronous motor per phase is given by (A) V2R (B) V2/2R (C) V2/4R (D) 2V/3R 60. In a synchronous motor, the synchronizing power comes into action when (A) rotor speed is equal to synchronous speed (B) rotor speed is less than synchronous speed (C) rotor speed is more than synchronous speed (D) rotor speed is either less or more than synchronous speed. Get all answers at once: 46.C ----- 47.B ----- 48.D ----- 49.C ----- 50.C ----- 51.A ----- 52.D ----- 53.A ----- 54.C ----- 55.D ----- 56.C ----- 57.A ----- 58.D ----- 59.C ----- 60.D 61. The size of a synchronous motor decreases with the increase in (A) speed (B) horse power rating (C) flux density Nani

(D) all of the above. 62. The flux density used in synchronous motor is around (A) 0.05 to 0.46 wb/m2 (B) 0.5 to 0.6 wb/m2 (C) 5 to 6 wb/m2 (D) 50 to 60 wb/m2. 63. In a synchronous motor if the saturation is neglected, then the short circuit ratio (SCR) will be related to the synchronous reactance (xd) as (A) SCR (B) SCR = (xd)2 (C) SCR = 1/ (xd)2 (D) SCR = 1/ (xd). 64. In synchronous motor out of the following losses, which one will have the highest proportion ? (A) Stator copper losses (B) Friction and windage losses (C) Eddy current losses (D) Iron losses. 65. Which of the following losses is not dissipated by the stator core surface in a synchronous motor ? (A) Copper losses in the slot portion of the conductors (B) Eddy current losses in the conductors (C) Iron losses in the stator (D) Windage losses. 66. The speed of a synchronous motor (A) reduces as load increases (B) increases as load increases (C) adjusts itself to new equilibrium speed whenever load changes (D) always remains constant. 67. Which of the following devices can be used as a phase advancer ? (A) 3 phase induction motor squirrel cage type (B) 3 phase induction motor-slip ring type (C) Synchronous motor working at leading power factor (D) Synchronous motor working at lagging power factor. 68. When a synchronous motor is connected to an infinite bus, while operating on leading power factor . Nani

(A) the excitation voltage will be less than the supply voltage (B) the excitation voltage will be more than the supply voltage (C) the excitation voltage will be equal to the supply voltage (D) the excitation voltage will be independent of the supply voltage. 69. In a synchronous motor (A) total number of rotor slots = total number of stator slots (B) total number of rotor slots is more than total number of stator slots (C) total number of rotor slots is less than the total number of stator slots. 70. In a synchronous motor during hunting if the rotor speed becomes more than the synchronous speed (A) negative phase sequence currents are generated (B) harmonics are developed in the armature circuit (C) damper bars develop induction generator torque (D) field excitation increases. 71. If a synchronous motor fails to pull into synchronism after applying dc field current, the probable clause may be (A) high core losses (B) low field current (C) high field current (D) low short circuit ratio. 72. In case of a 3 phase synchronous motor, maximum speed variation is (A) 10% (B) 5% (C) 3% (D) zero. 73. The synchronous motors are not self-starting because (A) stator is not used (B) starting winding is not provided (C) the direction of instantaneous torque on the rotor reverses after half cycle (D) there is no slip. Questions 74 to 75 refer to the Figure.

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74. In the figure above, the curves for leading power factors are (A) A and B (B) C and D (C) On left of line XY (D) On right of line XY 75. In the curves represent characteristics for 0, 10, 20 and. 30 kW, not necessarily in that order, then curve for 0 kW is expected to be (A) A (B)B (C) C (D) D. Get all answers at once: 61.C ----- 62.B ----- 63.D ----- 64.D ----- 65.D ----- 66.D ----- 67.C ----- 68.B ----69.C ----- 70.C ----- 71.B ----- 72.D -----73.C ----- 74.D ----- 75.D

Multiple Choice Questions of Synchronous Motors (76-90): 76. The curve for 20 k W is expected to be

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(A) A (B) B (C) C (D) D. 77. In a synchronous motor hunting can be minimized (A) by using damper bars (B) by using a flywheel (C) by designing the motor for adequate synchronizing power (D) by any of the above methods. 78. A three phase 400 V, 50 Hz synchronous motor is working at 50 percent load. In case an increase in the field current of the motor causes a reduction in the armature current, it can be concluded that (A) the motor is delivering reactive power to the mains (B) the motor is absorbing reactive power to the mains (C) the motor is neither absorbing nor delivering reactive power. 79. Inverted V-curves for a synchronous motor show (A) Variation of power factor with dc field current when load on the motor remains constant (B) Variation of field current and supply voltage when excitation remains constant (C) Variation of power factor and supply voltage when motor is hunting (D) none of the above. 80. The armature current of the synchronous motor has large values for (A) low excitation only (B) high excitation only (C) both low and high excitation. 81. In which range the cost of a synchronous motor can be comparable to the cost of a induction motor ? (A) Low HP high speed (B) High HP low speed (C) High HP high speed (D) Low HP low speed. 82. Insulation resistance test on synchronous motor can be conducted to measure which of the following resistances ? (A) Stator winding to earthed frame (B) Rotor winding to earthed shaft (C) Phase to phase winding resistance (D) All of the above. 83. Which curve represents the open circuit characteristic of a synchronous motor Nani

(A) Curve A (B) Curve B (C) Curve C (D) Curve D. 84. During short circuit test which of the following is short circuited ? (A) Armature terminals (B) One of the phase windings of stator (C) AH phase windings of stator (D) All phase windings of stator and armature. 85. The duration of sudden short circuit test on a synchronous motor is usually (A) about one second (B) about one minute (C) about one hour (D) 40 minutes. 86. The maximum torque which a synchronous will develop at rest for any angular positions of the rotor, at rated stator supply voltage and frequency, is known as (A) Reluctance torque (B) Synchronous torque (C) Locked-rotor torque (D) Pull up torque. 87. The maximum constant load torque under which a synchronous motor will pull into synchronism at rated rotor supply voltage and frequency is known as (A) Synchronous torque (B) Pull in torque (C) Pull up torque (D) Pull out torque. 88. The maximum sustained torque which a synchronous motor will develop at synchronous Nani

speed for 1 mm with rated frequency and rated field current is known as (A) Pull out torque (B) Reluctance torque (C) Synchronous torque (D) Average torque. 89. The total steady state to drive synchronous motor and the load at synchronous speed is known as (A) Synchronous torque (B) Asynchronous torque (C) Reluctance torque (D) Pull-up torque. 90. The space angle between the axis of the stator revolving magnetic field and the rotor-pole axis, both looked and running at synchronous speed, is known as (A) angle of lead (B) power angle (C) power factor angle (D) reactive power angle. Get all answers at once: 76.A ----- 77.D ----- 78.B ----- 79.A ----- 80.C ----- 81.B ----- 82.D ----83.A ----- 84.A ----- 85.A ----- 86.C ----- 87.B ----- 88.A ----- 89.A ----- 90.B

Generation of Electric Power Multiple Choice Questions of Generation of Electric Power 1. Out of the following which one is not a unconventional source of energy ? (A) Tidal power (B) Geothermal energy (C) Nuclear energy (D) Wind power. 2. Pulverized coal is (A) coal free from ash (B) non-smoking coal (C) coal which bums For long time (D) coal broken into fine particles. 3. Heating value of coal is approximately (A) 1000-2000 kcal / kg (B) 2000-4000 kcal / kg (C) 5000-6500 kcal / kg Nani

(D) 9000-10,500 kcal / kg. 4. Water gas is a mixture of (A) CO2 and O2 (B) O2and H2 (C) H2, N2 and O2 (D) CO, N2 and H2. 5. Coal used in power plant is also known as (A) steam coal (B) charcoal (C) coke (D) soft coal. 6. Which of the following is considered as superior quality of coal ? (A) Bituminous coal (B) Peat (C) Lignite (D) Coke. 7. In a power plant, coal is carried from storage place to boilers generally by means of (A) bucket (B) V-belts (C) trolleys (D) manually. 8. Live storage of coal in a power plant means (A) coal ready for combustion (B) preheated coal (C) storage of coal sufficient to meet 24 hour demand of the plant (D) coal in transit. 9. Pressure of steam in condenser is (A) atmospheric pressure (B) more than pressure (C) slightly less than pressure (D) much less than pressure. 10. Equipment used for pulverizing the coal is known as (A) Ball mill (B) Hopper (C) Burner Nani

(D) Stoker. 11. Power plants using coal work closely on known which of the following cycle ? (A) Otto cycle (B) Binary vapor cycle (C) Brayton cycle (D) Rankine cycle. 12. Critical pressure of water is (A) 1 kg / cm2 (B) 100 kg / cm2 (C) 155 kg / cm2 (D) 213.8 kg / cm2. 13. The efficiency of a thermal power plant improves with (A) increased quantity of coal burnt (B) larger quantity of water used (C) lower load in the plant (D) use of high steam pressures. 14. Which of the following contributes to the improvement of efficiency of Rankine cycle in a thermal power plant ? (A) Reheating of steam at intermediate stage (B) Regeneration use of steam for heating boiler feed water (C) Use of high pressures (D) All of the above. 15. Steam pressures usually used in thermal power plants are (A) 5 kg/cm2 to 10 kg / cm2 (B) 50 kg/cm2 to 100 kg / cm2 (C) 110 kg/cm2 to 170 kg / cm2 (D) 200 kg/cm2 to 215 kg / cm2 Get all answers at once: 1.C ----- 2.D ----- 3.C ----- 4.D ----- 5.A ----- 6.A ----- 7.B ----- 8.C -----9.D -----10.A -----11.D ----12.D -----13.D -----14.D ----- 15.C 16. When pulverized fuel is not used, the equipment used for supplying coal to the boiler is (A) Heater (B) Stoker (C) Burner (D) Skip hoist. Nani

17. Burning of low grade fuel can be improved by (A) Blending with better quality (B) Oil assisted ignition (C) Pulverizing (D) Any of the above. 18. As steam expands in turbine (A) its pressure increases (B) its specific volume increases (C) its boiling point increases (D) its temperature increases. 19. Water is supplied to a boiler (A) at atmospheric pressure (B) at slightly more than atmospheric pressure (C) at 100 cm/kg2 (D) at more than the steam pressure on the boiler. 20. Which of the following enters the super heater of a boiler ? (A) Cold water (B) Hot water (C) Wet steam (D) Super-heated steam. 21. Super heated steam is always (A) at a temperature higher than the saturation temperature corresponding to a steam pressure (B) at a pressure more than the boiler steam pressure (C) separated from water particles before being supplied to turbine (D) at a pressure less than the maximum cycle pressure. 22. The equipment installed in power plants to reduce air pollution due to smoke is (A) Induced draft fans (B) De-super heaters (C) Electrostatic precipitators (D) Re-heaters. 23. Permissible pH value of water for boilers is (A) 1 (B) 7 (C) slightly more than 7 (D) 10. 24. A condenser in a thermal power plant condenses steam combing out of Nani

(A) Boiler (B) Super-heater (C) Economizer (D) Turbine. 25. Which of the following, is not a high pressure boiler ? (A) Loeffler boiler (B) Lancashire boiler (C) Velox boiler (D) Lamont boiler. 26. What is the maximum size of steam turbine usually being installed, for thermal power plants ? (A) 120 MW (B) 250 MW (C) 500 MW (D) 1000 MW. 27. Overall thermal efficiency of a steam power station is in the range (A) 18-24% (B) 30-40% (C) 44-62% (D) 68-79%. 28. Which of the following is not the voltage at which power is usually transmitted (A)132 kV (B) 66 kV (C) 33 kV (D) 20 kV. 29. Most of the generators in thermal power plants run at (A) 3000 rpm (B)1500 rpm (C) 1000 rpm (D) 750 rpm. 30. In regenerative cycle, bled steam is (A) discharged to atmosphere (B) condensed in steam condenser (C) used to beat feed water for boiler (D) is mixed with steam supplied to turbine. Get all answers at once: 16.B ----- 17.D ----- 18.B ----- 19.D ----- 20.C ----- 21.A ----- 22.C ----- 23.C -----24.D -----25.B Nani

----- 26.C ----- 27.A -----28.D -----29.A ----- 30.C 31. Standard frequency usually for electric supply is (A) 50 Hz (B) 60 Hz (C) 50 to 60 Hz (D) 50 to 55 Hz. 32. In power station practice "spinning reserve" is (A) reserve generating capacity that is in operation but not in service (B) reserve generating capacity that is connected to bus and ready to take the load (C) reserve generating capacity that is available for service but not in operation (D) capacity of the part of the plant that remains under maintenance. 33. Bagasse is (A) low quality coal (B) a fuel consisting of wood (C) fibrous portion of sugarcane left after extracting the juice (D) a kind of rice straw. 34. Low grade fuels have (A) low moisture content (B) low ash content (C) low calorific value (D) low carbon content. 35. Which variety of coal has lowest calorific value? (A) Steam-coal (B) Bituminous coal (C) Lignite (D) Anthracite. 36. In a steam locomotive the engine is (A) Single cylinder (B) Vertical (C) Condensing (D) Non-condensing. 37. The boilers using lignite as fuel do not use (A) under feed stoker (B) traveling grate stoker (C) spreader stoker Nani

(D) all of the above. 38. In a steam turbine cycle, the lowest pressure occurs in (A) turbine inlet (B) boiler (C) condenser (D) super heater. 39. Steam pressure in modem thermal plants of 100 MW and above capacity may be exacted to be (A) 10 kg/cm2 (B) 50 kg/cm2 (A) up to 100kg/cm2 (D) more than 100 kg/cm2. 40. The overall efficiency of a boiler in a thermal power plant is of the order of (A)10% (B) 25 to 30% (C) 40 to 50% (D) 70 to 80%. 41. Chemical composition of coal is given by (A) Proximate analysis (B) Ultimate analysis (C) Orast analysis (D) All of the above. 42. Which coal will have highest ash content ? (A) Bituminous coal (B) Grade I steam coal (C) Coking coal (D) Lignite. 43. Ash content of most of the Indian coals is around (A) 1% (B) 5% (C) 10% (D) 20%. 44. Ash content of coal can be reduced by (A) slow burning (B) washing (C) pulverizing Nani

(D) mixing with high grade coal. 45. A 100 MW thermal power-plant will consume nearly how many tonnes of coal in one hour ? (A) 50 tonnes (B) 150 tonnes (C) 1500 tonnes (D) 15,000 tonnes. Get all answers at once: 31.A ----- 32.B ----- 33.C ----- 34.C ----- 35.C ----- 36.D ----- 37.A ----38.C ----- 39.D ----- 40.D -----41.B ----- 42.D -----43.D -----44.B ----- 45.A 46. The steam consumption per kWh of electricity generated in a modem power plant is of the order of (A) 1-2 kgs (B) 2-4 kgs (C) 5-7 kgs (D) 10-12 kgs. 47. For low head and high discharge, the hydraulic turbine used is (A) Kaplan turbine (B) Francis turbine (C) Pelton wheel (D) Jonual turbine. 48. Soot is virtually nothing but (A) ash (B) cinder (C) gas (D) carbon 49. In pumped storage (A) Power is produced by means of pumps (B) Water is stored by pumping to high pressures (C) Downstream water is pumped up-stream during off load periods (D) Water is re circulated through turbine. 50. If the air standard efficiency of. a thermodynamic cycle is given as η= 1 - ( k ( r-1 ) ) / ( rk-1 ) where r = compression ratio, k = Cp/ Cv the cycle is (A) Lenoir cycle (B) Brayton cycle (C) Atkinson cycle Nani

(D) None of the above. 51. A graphical representation between discharge and time is known as (A) Monograph (B) Hectograph (C) Topograph (D) Hydrograph. 52. Cost of operation of which plant is least ? (A) Gas turbine plant (B) Thermal power plant (C) Nuclear power plant (D) Hydroelectric plant. 53. In a hydro-electric plant a conduct system for taking water from the intake works to the turbine is known as (A) Dam (B) Reservoir (C) Penstock (D) Surge tank. 54. A Pelton wheel is (A) inward flow impulse turbine (B) Outward flow impulse turbine (C) Inward flow reaction turbine (D) Axial flow impulse turbine. 55. Running away speed of a Pelton wheel is (A) Actual operating speed on no load (B) Full load speed (C) No load speed when governor mechanism fails (D) 90% greater than the normal speed. 56. Spouting velocity is (A) Ideal velocity of jet (B) 50% of ideal velocity of jet (C) Actual velocity of jet (D) Velocity of jet under specified conditions. 57. Outward radial flow turbines (A) are impulses turbines (B) are reaction turbines (C) are partly impulse partly reaction turbines Nani

(D) may be impulse or reaction turbines. 58. A Francis turbine is (A) Inward flow reaction turbine (B) Inward flow impulse turbine (C) Outward flow reaction turbine (D) Outward flow impulse turbine. 59. A Kaplan turbine is (A) a high head mixed flow turbine (B) an impulse turbine, inward flow type (C) an reaction turbine, outward flow type (D) low head axial flow turbine. 60. In turbulent flow (A) the fluid particles move in orderly manner (B) momentum transfer is on molecular scale only (C) shear stresses are generally larger than in laminar flow (D) cohesion is more effective than momentum transfer in causing shear stress. Get all answers at once: 46.C ----- 47.A ----- 48.D ----- 49.C ----- 50.A ----- 51.D ----- 52.D ----53.C ----- 54.D ----- 55.C ----- 56.A ----- 57.D ----- 58.A ----- 59.D ----- 60.C 61. An impulse turbine (A) always operates submerged (B) makes use of a draft tube (C) is most suited for low head installations (D) operates by initial complete conversion to kinetic energy. 62. In an impulse turbine (A) water must be admitted over the whole circumference of the wheel (B) it is net possible to regulate the flow without loss (C) wheel must run full and be-kept entirely submerged in water below the tail race (D) the pressure in the driving fluid as it moves over the vane, is atmospheric. 63. In binary vapor cycle (A) steam at 2 different pressures is used (B) steam is expanded in 2 turbines (C) two fluids are used (D) vapor and liquid are used as working substances. 64. Steam engine used in locomotive is (A) single acting, condensing type (B) single acting, non-condensing type Nani

(C) double acting, non-condensing type (D) double acting, condensing type. 65. In a thermal power plant cooling towers are used to (A) condense low pressure steam (B) cool condensed steam (C) cool water used in condenser for condensing steam (D) cool feed water of boiler. 66. Major constituent of methane gas is (A) CO (B) methane (C) oxygen (D) hydrogen. 67. Caking is (A) making cakes of coal out of fine powders (B) a variety of free burning coals (C) coal produced from burning of wood in inert atmosphere (D) in boiler furnace some coals become plastic and form lumps or masses of coal. 68. 1 atomic mass unit is equal to (A) 1.66 x 10 -27 kg (B) 1.66 x 10-25 kg (C) 1.66 x 10 -17 kg (D) 1.66 x 10-10 kg. 69. Particles having the same atomic number but different mass numbers arc called (A) Positrons (B) Beta particles (C) Isotopes (D) Decayed panicles. 70. Which of the following material can be used as a moderator ? (A) Graphite (B) Heavy water (C) Beryllium (D) Any of the above. 71. In closed cooling system (A) hot water is re circulated after cooling (B) water does not flow

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(C) air and water cooling is simultaneously used (D) constant supply of fresh water for cooling is required. 72. A gas turbine works on (A) Carnot cycle (B) Brayton cycle (C) Dual cycle (D) Rankine cycle. 73. Maximum efficiency of an open cycle gas turbine is nearly (A) 30% (B) 40% (C) 50% (D) 60%. 74. Compressor used in gas turbines is (A) reciprocating compressor (B) plunger type compressor (C) screw compressor (D) multistage axial flow compressor. 75. Which auxiliary of gas turbine consumes most of the power ? (A) Burner (B) Combustion chamber (C) Compressor (D) Fuel pump. Get all answers at once: 61.D ----- 62.D ----- 63.C ----- 64.C ----- 65.C ----- 66.B ----- 67.D ----- 68.A ----- 69.C ----- 70.D ----- 71.A ----- 72.B -----73.A ----- 74.D ----- 75.C 76. Gas turbine is widely used in (A) pumping stations (B) aircraft (C) locomotives (D) automobiles. 77. In aircraft using gas turbine, the cycle used is (A) Simple (B) Regeneration (C) Reheating (D) Reheating with regeneration. 78. Overall efficiency of gas turbine is Nani

(A) equal to Rankine cycle efficiency (B) equal to Carnot cycle efficiency (C) more than Otto or Diesel cycle efficiency (D) less than Diesel cycle efficiency. 79. In the figure, constant volume cycle is represented by

(A) 1245 (B)1235 (C) 12461 (D) 12345. 80. The cycle 1236 represents (A) Otto cycle (B) Dual cycle (C) Constant pressure cycle (D) Atkinson cycle. 81. Diesel cycle is represented by (A) 1236 (B) 1246 (C) 1245 (D) 1285. 82. Which cycle cannot be represented in the given figure ? (A) Otto cycle (B) Constant pressure cycle (C) Carnot cycle (D) Brayton cycle. 83. The horse power of a Diesel locomotive is of the order of (A) 100 to 200 (B) 500 to 1000 (C) 2000 to 2500 Nani

(D) 10.000 to 12,000. 84. A Diesel engine consumes Diesel oil nearly at the rate of (A) 180 to 200 gm/BHP hr (B) 400 to 450 gm/BHP hr (C) 600 to 750 gm/BHP hr (D) 1 kg/BHP hr. 85. The compression ratio in case of diesel engines is (A) 5 to 7 (B) 7 to 10 (C) 14 to 22 (D) 25 to 36. 86. The firing order of a four cylinder engine is (A)1-2-4-3 (B)1-4-2-3 (C) 1-2-3-4 (D)1-3-2-4. 87. The performance of engines of different HP, RPM and sizes can be compared on the basis of (A) specific fuel consumption (B) compression ratio (C) clearance volume (D) cylinder volume. 88. Advantage of hydro-electric power station is (A) low operating cost (B) free from pollution problems (C) no fuel transportation problems (D) all of the above. 89. Which engine will have highest efficiency, between given temperature limits ? (A) Carnot cycle (B) Otto cycle (C) Diesel cycle (D) Dual cycle. 90. Which if (he following is a non-petroleum fuel ? (A) Benzol (B) Methyl alcohol (C) Ethyl alcohol (D) All of the above. Nani

Get all answers at once: 76.B ----- 77.A ----- 78.D ----- 79.B ----- 80.D ----- 81.C ----- 82.D ----- 83.C ----- 84.A ----- 85.C ----- 86.A ----- 87.A ----- 88.D ----- 89.A ----- 90.D

Transmission and Distribution Multiple Choice Questions of Transmission and Distribution 1. Which of the following is not the transmission voltage in America ? (A) 66 kV (B) l32kV (C) 264 kV (D) 400 kV 2. Which of the following is usually not the generating voltage ? (A) 6.6 kV (B) 9.9 kV (C) 11kV (D) 13.2 kV. 3. Boosters are basically (A) inductors (B) capacitors (C) transformers (D) synchronous motors. 4. Which of the following is not the distribution system normally used (A) 3 phase-4 wire (B) 3 phase-3 wire (C) Single phase - 3 wire (D) Single phase -4 wire. 5. Conductors for high voltage transmission lines are suspended from towers (A) to reduce clearance from ground (B) to increase clearance from ground (C) to reduce wind and snow loads (D) to take care of extension in length during summer. 6. Transmission efficiency increases as (A) voltage and power factor both increase (B) voltage and power factor both decrease (C) voltage increases but power factor decreases (D) voltage decreases but power factor increases. Nani

7. With same maximum voltage to earth, which ac system (with p.f. 0.8) will require more copper as compared to dc 2 wire system (A) single phase. 2 wire (mid point earthed) (B) single phase. 3 wire (neutral=1/2 outer) (C) three phase three wire (D) three phase-four wire (neutral = outer). 8. When alternating current passes through a conductor (A) it remains uniformly distributed throughout the section of conductor (B) portion of conductor near the surface carries more current as compared to the core (C) portion of conductor near the surface carries less current as compared to the core (D) entire current passes through the core of the conductor. 9. The fact that a conductor carries more current on the surface as compared to core, is known as (A) skin effect (B) corona (C) permeability (D) unsymmetrical fault. 10. The effective resistance of a conductor will be the same as ohmic resistance when (A) current is in true sine wave form (B) voltage is low (C) power factor is unity (D) Current is uniformly distributed in the conductor cross-section. 11. Skin effect results in (A) reduced effective resistance but increased effective internal reactance of the conductor (B) increased effective resistance but reduced effective internal reactance of. the conductor (C) reduced effective resistance as well as effective internal reactance (D) increased effective resistance as well as effective internal reactance. 12. Skin effect depends on (A) size of the conductor (B) frequency of the current (C) resistivity of the conductor material (D) all of the above. 13. The skin effect of a conductor will reduce as the (A) diameter increases (B) frequency increases (C) permeability of conductor material increases

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(D) resistivity of conductor material increases. 14. Skin effect is proportional to (A) diameter of conductor (B) (diameter of conductor)1/2 (C) (diameter of conductor )2 (D) (diameter of conductor )2. 15. In overhead transmission lines the effect of capacitance can be neglected when the length of line is less than (A) 200 km (B) 160 km (C) 100 km (D) 80 km. Get all answers at once: 1.C ----- 2.B ----- 3.C ----- 4.D ----- 5.B ----- 6.A ----- 7.D ----- 8.B -----9.A -----10.D -----11.B ----12.D -----13.D -----14.C ----- 15.D 16. For constant voltage transmission the voltage drop is compensated by installing (A) synchronous motors (B) capacitors (C) inductors (D) all of the above. 17. The disadvantage of constant voltage transmission is (A) short circuit current of the system is increased (B) load power factor in heavy loads (C) large conductor area is required for same power transmission (D) air of the above. 18. The surge impedance for over head line is taken as (A) 10-20 ohms (B) 50-60 ohms (C) 100-200 ohms (D) 1000-2000 ohms. 19. Pin insulators are normally used up to voltage of about (A)100kV (B) 66 kV (C) 33 kV (D) 25 kV.

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20. Strain type insulator arc used where the conductors arc (A) dead ended (B) at intermediate anchor towers (C) any of the above (D) none of the above. 21. For 66 kV lines the number of insulator discs used are (A) 3 (B) 5 (C) 8 (D) 12. 22. Ten discs usually suggest that the transmission line voltage is (A) 11 kV (B) 33 kV (C) 66 kV (D) 132 kV. 23. The effect of corona is (A) increased energy loss (B) increased reactance (C) increased inductance (D) all of the above. 24. Corona usually occurs when the electrostatic stress in the air around the conductor succeeds (A) 30 kV (maximum value)/cm (B) 22 kV (maximum value)/cm (C) 11 kV (rms value)/cm (D) 6.6 kv (rms value)/cm. 25. Corona effect can be detected by (A) hissing sound (B) faint luminous flow of bluish color (C) presence of ozone detected by odor (D) all of the above. 26. The current drawn by the line due to corona losses is (A) sinusoidal (B) square (C) non-sinusoidal 27. Presence of ozone as a result of corona is harmful because (A) it gives bad odor Nani

(B) it corrodes the material (C) it transfers energy to the ground (D) reduces power factor. 28. Between two supports, due to sag the conductor takes the form of (A) catenary (B) triangle (C) ellipse (D) semi-circle. 29. The inductance of a single phase two wire line is given by (D is the distance between conductors and 2v is the diameter of conductor) (A) 0.4 loge (D/r) mH/km (B) 0.55 loge (D/r) mH/km (C) 0.4 loge (r/D) mH/km (D) 0.55 loge (r/D) mH/km. 30. The effect of ice deposition on conductor is (A) increased skin effect (B) reduced corona losses (C) increased weight (D) reduced sag. Get all answers at once: 16.A ----- 17.A ----- 18.C ----- 19.D ----- 20.C ----- 21.B ----- 22.D ----- 23.A -----24.A ----- 25.D ----- 26.C ----- 27.B -----28.A -----29.A ----- 30.C 31. The effect of wind pressure is more predominant on (A) transmission lines (B) neutral wires (C) insulator (D) supporting towers. 32. Which of the following statement is correct ? (A) Wind pressure reduces corona effects (B) Ice on conductors improves power factor (C) Wind pressure is taken to act in a direction at right angles to that for ice (D) Wind pressure and ice on conductors together improve regulation of power transmitted. 33. Which of the following statements is incorrect ? (A) As the temperature rises the tension in the transmission line decreases (B) As temperature rises the sag in transmission lines reduces (C) Tension and sag in transmission lines are complementary to each other. Nani

34. Wooden poles for supporting transmission lines are used for voltages up to (A) 440 V (B)11 kV (C) 22 kV (D) 66 kV. 35. If K is the volume of cable conductor material required to transmit power, then for the transmission of the same power, the volume of cable conductor required for single phase 2 wise AC system is (A) 2k (B) k cosφ (C) k/ cos2φ (D) 2k/ cos2p 36. Maximum permissible span for wooden poles is (A) 10 meter (B) 20 meters (C) 60 meters (D) 200 meters. 37. When transformers or switchgears are to be installed in a transmission line, the poles used are (A) I type (B) J type (C) H type (D) L type. 38. For improving life, steel poles are galvanized. Galvanizing is the process of applying a layer of (A) paint (B) varnish (C) tar coal (D) zinc. 39. The disadvantage of transmission lines as compared to cables is (A) exposure to lightening (B) exposure to atmospheric hazards like smoke, ice, etc. (C) inductive interference between power and communication circuits (D) all of the above. 40. ACSR conductor implies (A) All conductors surface treated and realigned (B) Aluminum conductor steel reinforced (C) Anode current sinusoidally run Nani

(D) Anodized Core Smooth Run. 41. The surge resistance of transmission lines is about (A) 50 ohms (B) 100 ohms (C) 250 ohms (D) 500 ohms. 42. During storm the live conductor of public electric supply breaks down and touches the earth. The consequences will be (A) supply voltage will drop (B) supply voltage will increase (C) current will flow to earth (D) no current will flow in the conductor. 43. In transmission system a feeder feeds power to (A) service mains (B) generating stations (C) distributors (D) all of the above. 44. For transmission lines the standing wave ratio is the ratio of (A) maximum voltage to minimum voltage (B) maximum current to minimum voltage (C) peak voltage to rms voltage (D) maximum reactance to minimum reactance. 45. In a transmission line following arc the distributed constants (A) resistance and inductance only (B) resistance, inductance and capacitance (C) resistance, inductance, capacitance and short conductance. Get all answers at once: 31.D ----- 32.C ----- 33.C ----- 34.C ----- 35.D ----- 36.C ----- 37.C ----- 38.D ----39.D ----- 40.B -----41.D ----- 42.C -----43.C -----44.A ----- 45.C 46. The bundling of conductors is done primarily to (A) reduce reactance (B) increase reactance (C) increase ratio interference (D) reduce radio interference. 47. Which of the following regulation is considered to be the best (A) 2%

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(B) 30% (C)70% (D) 98%. 48. The characteristic impedance of a transmission line depends upon (A) shape of the conductor (B) surface treatment of the conductors (C) conductivity of the material (D) geometrical configuration. of the conductors. 49. For a distortion-less transmission line (G = shunt conductance between two wires) (A) R/L = G/C (B) RL=GC (C) RG=LC (D)RLGC=0 50. Guard ring transmission line (A) improves power factor (B) reduces earth capacitance of the lowest unit (C) reduces transmission losses (D) improves regulation. 51. When the power is to be transmitted over a distance of 500 km, the transmission voltage should be in the range (A) 33 kV - 66 kV (B) 66 kV - 100 kV (C) 110 kV - 150 kV (D) 150kV - 220kV. 52. A relay used on long transmission lines is (A) mho's relay (B) reactance relay (C) impedance relay (D) no relay is used. 53. Total load transmitted through a 3 phase transmission line is 10,000 kW at 0.8 power factor lagging. The I2R losses are 900 kW. The efficiency of transmission line is (A) 60% (B) 90% (C) 95% (D) 99%. 54. Litz wires are used for intermediate frequencies.to overcome

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(A) corona effect (B) skin effect (C) radio interference (D) all of the above. 55. In order to reduce skin effect at UHF (A) conductors are painted (B) conductors are anodized (C) copper lubes with silver plating are used (D) copper rods with silver plating are used. 56. Shunt capacitance is usually neglected in the analysis of (A) Short transmission lines (B) Medium transmission lines (C) Long transmission lines (D) Medium as well as long transmission lines. 57. The chances of corona are maximum during (A) summer heat (B) winter (C) dry weather (D) humid weather. 58. The power transmitted will be maximum when (A) Sending end voltage is more (B) Receiving end voltage is more (C) Reactance is high (D) Corona losses are least. 59. Neglecting losses in a transmission system, if the voltage is doubled, for the same power transmission, the weight of conductor material required will be (A) four times (B) double (C) half (D) one fourth. 60. When two conductors each of radius r are at a distance D, the capacitance between the two is proportional to (A) loge (D/r) (B) loge (r/D) (C) 1/loge (D/r) (D) 1/loge (r/D). Nani

Get all answers at once: 46.A ----- 47.A ----- 48.D ----- 49.A ----- 50.B ----- 51.D ----- 52.A ----- 53.B ----- 54.B ----- 55.C ----- 56.A ----- 57.D ----- 58.A ----- 59.D ----- 60.C 61. In a transmission line having negligible resistance the surge impedance is (A) (L+C)1/2 (B) (C/L)1/2 (C) (1/LC)1/2 (D) (L/C)1/2 62. A relay used on short transmission lines is (A) Reactance relay (B) Mho's relay (C) Impedance relay (D) None of the above. 63. In case the characteristic impedance of the line is equal to the load impedance (A) all the energy will pass to the earth (B) all the energy will be lost in transmission losses (C) the system will resonate badly (D) all the energy sent will be absorbed by the load. 64. For a properly terminated line (A) ZR=ZO (B) Z/R > ZO (C) ZR < ZO (D) ZR =Z0 = 0. 65. The dielectric strength of air at 250C and 76 cm/Hg is (A) 1 kV/cm (B) 1 kV/mm (C) 3 kV/cm (D) 30 kV/cm. 66. The chances of corona are maximum in (A) domestic wiring (B) distribution lines (C) transmission lines (D) all of the above. 67. Transmission lines link (A) service points to consumer premises Nani

(B) distribution transformer to consumer premises (C) receiving end station to distribution transformer (D) generating station to receiving end station. 68. In case of open circuit transmission lines the reflection coefficient is (A) 1 (B) 0.5 (C) -1 (D) Zero. 69. Impedance relay is used on (A) Short transmission lines (B) Medium transmission lines (C) Long transmission line (D) All the transmission lines. 70. Which type of insulators are used on 132 kV transmission lines ? (A) Pin type (B) Disc type (C) Shackle type (D) Pin and shackle type. 71. String efficiency can be improved by (A) using Longer cross arm (B) grading the insulator (C) using a guard ring (D) any of the above. 72. Minimum horizontal clearance of a low voltage transmission line from residential buildings must be (A) 11/2 feet (B) 3 feet (C) 4 feet (D) 8 feet. 73. If a 66 kV lines passes over a residential building, the minimum vertical clearance from the roof of the building must be (A) 8 feet (B) 12 feet (C) 13 feet (D) 16 feet. 74. Alternating current power is transmitted at high voltage

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(A) to safeguard against pilferage (B) to minimize transmission losses (C) to reduce cost of generation (D) to make the system reliable. 75. Stranded conductors arc used for transmitting, power at high voltages because of (A) increased tensile strength (B) better wind resistance (C) ease-in handling (D) low cost. Ans: C all answers at once: 61.D ----- 62.A ----- 63.D ----- 64.D ----- 65.D ----- 66.C ----- 67.D ----- 68.D ----- 69.B ----- 70.B ----- 71.D ----- 72.C -----73.C ----- 74.B ----- 75.C

1. Electronic control systems have the serious draw‐backs of (a) low reliability (b) operational difficulty (c) temperature sensitiveness (d) all of above 2. The system whose characteristic equation has the following roots is marginally stable (a) ‐j, j, ‐1,1 (b) ‐3,‐2,0 (c) ‐2+3j, ‐2‐3j, ‐2 (d) ‐3,‐2,‐1 3. A phase log compensation will (a) improve relative stability (b)increase the speed of response (c)increase band‐width (d) increase overshoot 4. For Nyquist plot we use a. open loop function b. closed loop function c. characteristic equation d. any of the above 5. A system with gain margin close to unity or a phase margin close to zero is a. highly stable b. oscillatory c. relatively stable d. none of these 6. Root locus diagram exhibits the a. frequency response of a system b. poles of the transfer function for a set of parameter values c. bandwidth of system d. all of the above 7. Increase in the gain K makes the system a. more stable b. unstable c. none of above 8. The transfer function of a system is used to determine a. the output for a given input b. the type of system Nani

c. the input for a given output d. the steady state gai n 9. In a servo system the voltage induced in the control transformer rotor is the a. error voltage b. driving voltage c. opposing voltage d. none of these 10. With the feedback system, the transient response a. decays slowly b. decays rapidly c. rises slowly d. rises quickly 11. An open loop control system has its (a) control action independent of the output or desired quantity (b) controlling action, depending upon human judgment (c) internal system changes automatically taken care of (d) both (a) and (b) (e) all (a),(b) and (c) 12. A servo system must have (a) feedback system (b) power amplifier to amplify error (c) capacity to control position or its derivative (d) all of these (e) none of these 13. The major disadvantage of a feedback system may be (a) Inaccuracy (b) inefficiency (c) Unreliability (d) instability (e) Insensitivity 14. Properties of a transfer function (a) It is ratio of two polynomials is S and assumes zero initial conditions (b) It depends on system elements and not input and output of the system (c) Coefficients of the powers of S in denominator and numerator are all real constant. The order of denominator is usually greater than or equal to the order of numerator (d) All of these (e) It is a function which transfer one physical system into another physical system. 15. The classical analogous of a simple lever is (a) Capacitor bridge (b) transformer (c) mutual inductor (d) either of these 16. Two blocks G1(s) and G2(s) can be cascaded to get resultant transfer function as (a) G1(s) + G2(s) (b) G1(s) / G2(s) (c) G1(s) G2(s) (d) 1+G1(s) G2(s) (e) 1‐G1(s)G2(s) (f) two blocks cannot be cascaded Nani

17. The principles of homogeneity and super position can be applied to (a) linear time invariant system (b) non‐linear time invariant system (c) digital control system (d) both (a) and (b) 18. Pick up the nonlinear system (a) automatic voltage regulator (b) d.c. servomotor with high field excitation (c) temperature control of a furnaces using thermistor (d) speed control using SCR (e) all of these 19. Signal flow graph (SFG) is a (a) polar graph (b) semi log graph (c) log log graph (d) a special type of graph for analyzing modem control system (e) a topological representation of a set of differential equations 20. Disadvantages of magnetic amplifier (a) time lag, less flexible, non‐sinusoidal waveform (b) low power consumption and isolation of the active circuit (c) saturation of the core (d) all of these 21. Pick up false statement regarding magnetic amplifiers (a) The gate coil of an ideal magnetic amplifier has either zero or infinite inductance (b) Resistance of control and gate winding is very small (c) Magnetic amplifier gas dropping load characteristics (d) Magnetic amplifiers are not used to control the speed of d.c. shunt motor (e) Magnetic amplifiers can be used in automatic control of electric drivers of higher rating. 22. High power amplification is achieved by using (a) push pull amplifier (b) amplidyne (c) magnetic amplifier (d) DC amplifier (e) D.C. generator 23. Pick up false statement regarding servomotors (a) The d.c. servomotors are lighter than equivalent a.c. servomotors (b) The d.c. servomotors develops higher starting and reversing torque than equivalent a.c. servomotor. (c) A drag cup a.c. servomotor has one windings on stator and other on rotor (d) Output power of servomotors varies from 1/20 W to 100 W 24. To reduce steady state error (a) decrease natural frequency (b) decrease damping (c) increase damped frequency (d) increase time constant (f) increase gain constant of the system 25. A good factor for Mp should be (a) less than 1 (b) lying between 1.1 and 1.5 (c) more than 2.2 Nani

(d) zero (e) infinity 26. Pick up false statement. Routh‐Hurwitz criterion (a) is used for determining stability of a system (b) is an algebraic procedure (c) gives the exact location of roots of the characteristic equation (d) does not indicate relative degree of stability or instability 27. Which of the following is the time domain method of determining stability of a control system (a) Bode plot (b) Nyquist plot (c) Nicholos chart (d) Routh‐Hurwitz array (e) Constant M and (fy) locus (f) Root locus technique 28. The technique which gives transient response quickly as well as stability information is (a) Nyquist plot (b) Routh‐Hurwitz criteria (c) Bode plot (d) Root locus plot (e) Nichols plot 29. The bandwidth can be increased by use of (a) phase lag network (b) phase lead network (c) both (a) and (b) in cascade (d) both (a) and (b) in parallel (e) none of these 30. Nyquist plot is drawn on (a) semi log graph paper (b) log log graph paper (c) polar graph paper (d) centimeter graph paper 31. If the gain margin is positive and the phase margin is negative the system is (a) stable (b) unstable (c) indeterminist 32. The Bode plot is applicable to (a) all phase network (b) minimum phase network (c) maximum phase network (d) lag lead network (e) none of these 33. The valid relation between setting time ts and rise time tr is (a) tr>ts (b) ts>tr (c) ts=tr (d) none of these 34. As a root moves further away from imaginary axis the stability (a) increases (b) decreases (c) not affected Nani

(d) none of these 35. Flat frequency response means that the magnitude ratio of output to input over the bandwidth is (a) variable (b) zero (c) constant (d) none of above 36. How many octaves are between 200 Hz and 800 Hz (a) Two octave (b) One octave (c) Four octave (d) None of above 37. Human system can be considered as (a) open loop system (b) close loop system with single feedback (c) close loop system with multivariable feedback (d) none of these 38. In a feedback system the transient response (a) Decays at constant rate (b) gets magnified (c) decays slowly (d) decays more quickly 39. Transfer function of a system is used to calculate (a) the steady state gain (b) the main constant (c) the order of system (d) the output for any given input (e) all of the above 40. Transfer function of a system is defined as the ratio of output to input in (a) Laplace transform (b) Z‐transform (c) Fourier transform (d) Simple algebraic form 41. Introduction of feedback decreases the effect of (a) disturbances (b) noise signals (c) error signals (d) all the above 42. The system response of a system can be best tested with (a) unit impulse input signal (b) ramp input signal (c) sinusoidal input signal (d) exponentially decaying input signal 43. Which of the following is a closed loop system (a) electric switch (b) car starter (c) de generator (d) auto‐pilot for an aircraft 44. Which of the following is used as an error detector (a) potentiometer (b) field controlled ac motor (c) amplidyne Nani

(d) armature controlled ac motor 45. The break away point of root loci are (a) open loop poles (b) closed loop poles (c) open loop zeros (d) closed loop zeros 46. Noise in a control system can be kept low by (a) reducing the bandwidth (b) attenuating such frequencies at which external signals get coupled into the system (c) both (a) and (b) (d) none of these 47. Main cause of absolute instability in the control system is (a) parameters of controlling system (b) parameters of controlled system (c) parameters of feedback system (d) error detector where the two signals are compared 48. Basically a controller is (a) a amplifier (b) a clipper (c) a comparator (d) a summer 49. A system with gain margin close to unity or a phase margin close to zero is (a) highly stable (b) highly oscillatory (c) relatively stable (d) none of these 50. Which of following elements is not used in an automatic control system (a) sensor (b) error detector (c) oscillator (d) final control element 51. AC systems are usually preferred to the DC systems in control applications because (a) AC systems are cheaper (b) AC systems are more stable (c) AC systems have better performance characteristics and smaller in size (d) all of these 52. A system has the transfer function (1‐s)/(1+s); It is known as (a) low pass system (b) high pass system (c) all pass system (d) none of the above 53. In control systems, excessive bandwidth should be avoided because (a) noise is proportional to bandwidth (b) it leads to low relative stability (c) it leads to slow speed of response (d) none of these 54. In most systems, an increase in gain leads to (a) larger damping ratio (b) smaller damping ratio (c) constant damping ratio Nani

(d) none of these 55. A step function is applied to the input of a system and output is of the form y = t, the system is (a) stable (b) unstable (c) not necessarily stable (d) conditionally stable 56. Which of the following can be magnified by magnetic amplifier (a) voltage (b) current (c) power (d) none of above 57. The inductance is not used in lag network because of (a) big size (b) time delay and hysteresis losses (c) high reactance (d) none of these 58. Saturation in a stable control system can cause (a) conditional stability (b) over damping (c) low level oscillations (d) high level oscillations 59. Excessive noise in control systems can cause (a) reduction in bandwidth (b) reduction in gain (c) saturation in amplifying stages (d) oscillations 60. The type‐0 system has (a) net pole at the origin (b) no pole at the origin (c) simple at one origin (d) two poles at the origin

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