Heating and Welding. 1. Which of the following is an advantage of heating by electricity? (a) Quicker operation (b) Higher efficiency (c) Absence of flue gases (d) All of the above Ans: d 2. ________ has the highest value of thermal conductivity. (a) Copper (b) Aluminum (c) Brass (d) Steel Ans: a 3. Which of the following heating methods has maximum power factor? (a) Arc heating (b) Dielectric heating (c) Induction heating (d) Resistance heating Ans: d 4. Method has leading power factor (a) Resistance heating (b) Dielectric heating (c) Arc heating (d) Induction heating Ans: b 5. Is used for heating non-conducting materials. (a) Eddy current heating (b) Arc heating (c) Induction heating (d) Dielectric heating Ans: d 6. Which of the following methods of heating is not dependent on the frequency of supply? (a) Induction heating (b) Dielectric heating (c) Electric resistance heating FOLLOWERS (d) All of the above Ans: c 7. When a body reflects entire radiation incident on it, then it is known as (a) White body (b) Grey body (c) Black body (d) Transparent body Ans: a 8. for the transmission of heat from one body to another (a) Temperature of the two bodies must be different (b) Both bodies must be solids (c) Both bodies must be in contact (d) At least one of the bodies must have some source of heating Ans: a 9. Heat transfer by condition will not occur when (a) Bodies are kept in vacuum (b) Bodies are immersed in water (c) Bodies are exposed to thermal radiations (d) Temperatures of the two bodies are identical Ans: d 10. A perfect black body is one that (a) Transmits all incident radiations (b) Absorbs all incident radiations (c) Reflects all incident radiations (d) Absorbs, reflects and transmits all incident radiations Ans: b
11. Heat is transferred simultaneously by condition, convection and radiation (a) Inside boiler furnaces (b) During melting of ice (c) Through the surface of the insulted pipe carrying steam (d) From refrigerator coils to freezer of a refrigerator Ans: a 12. The process of heat transfer during the reentry of satellites and missiles, at very high Speeds, into earth's atmosphere is known as (a) Ablation (b) Radiation (c) Viscous dissipation (d) Irradiation Ans: a 13. Which of the following has the highest value of thermal conductivity? (a) Water (b) Steam (c) Solid ice (d) Melting ice Ans: c 14. Induction heating process is based on which of the following principles? (a) Thermal ion release principle (b) Nucleate heating principle (c) Resistance heating principle (d) Electro-magnetic induction principle Ans: d 15. Which of the following insulating materials was suitable for low temperature applications? (a) Asbestos paper (b) Diatomaceous earth (c) 80 percent magnesia (d) Cork Ans: b 16. A non-dimensional number generally associated with natural convection heat transfer is (a) Prandtl number (b) Grashoff number (c) Pecelet number (d) Nusselt number Ans: b 17. The temperature inside a furnace is usually measured by which of the following? (a) Optical pyrometer (b) Mercury thermometer (c) Alcohol thermometer (d) Any of the above Ans: a 18. Which of the following will happen if the thickness of refractory wall of furnace is increased? (a) Heat loss through furnace wall will increase (b) Temperature inside the furnace will fall (c) Temperature on the outer surface of furnace walls will drop (d) Energy consumption will increase Ans: c 19. The material of the heating element for a furnace should have (a) Lower melting point (b) Higher temperature coefficient (c) High specific resistance (d) all of the above Ans: c
20. In a resistance furnace the atmosphere is (a) Oxidizing (b) Deoxidizing c) Reducing (d) neutral Ans: a 21. By which of the following methods the temperature inside arc nace can be varied? (a) By disconnecting some of the heating elements (b) By varying the operating voltage (c) By varying the current through heating elements (d) By any of the above method Ans: d 22. In induction heating ______ is abnormally high. (a) Phase angle (b) Frequency (c) current (d) Voltage Ans: b 23. by the use of which of the following, high frequency power supply for induction furnaces Can be obtained? (a) Coreless transformers (b) Current transformers (c) Motor-generator set (d) Multi-phase transformer Ans: c 24. Induction furnaces are employed for which of the following? (a) Heat treatment of castings (b) Heating of insulators (c) Melting aluminum (d) none of the above Ans: a 25. In an electric room heat convector the method of heating used is (a) Arc heating (b) Resistance heating (c) Induction heating (d) Dielectric heating Ans: b 26. In a domestic cake baking oven the temperature is controlled by (a) Voltage variation (b) Thermostat (c) auto-transformer (d) series-parallel operation Ans: d 27. In an electric press mica is used (a) As an insulator (b) As a device for power factor improvement (c) For dielectric heating (d) for induction heating Ans: a 28. Induction heating takes place it which of the following? (a) Insulating materials (b) Conducting materials which are magnetic (c) Conducting materials which are non-magnetic (d) Conducting materials which may or may not be magnetic Ans: d 29. For heating element high resistivity material is chosen to (a) Reduce the length of heating element (b) Increase the life of the heating element (c) Reduce the effect of oxidation (d) Produce large amount of heat Ans: a
30. In resistance heating highest working temperature is obtained from heating elements made of (a) Nickel copper (b) nichrome (c) Silicon carbide (d) Silver Ans: c 31. for intermittent work which of the following furnaces is suitable? (a) Indirect arc furnace (b) Core less furnace (c) Either of the above (d) None of the above Ans: a 32. Due to which of the following reasons it is desirable to have short arc length? (a) To achieve better heating (b) To increase the life of roof refractory (c) To have better stirring action (d) To reduce problem of oxidation (e) All of the above Ans: e 33. In the indirect resistance heating method, maximum heat-transfer takes place by (a) Radiation (b) convection (c) conduction (d) any of the above Ans: a 34. Properly of low temperature co-eflficient of heating element is desired due to which of the following reasons? (a) To avoid initial rush of current (b) To avoid change in kW rating with temperature (c) Both (a) and (b) (d) Either (a) or (b) Ans: c 35. Which of the following methods is used to control temperature in resistance furnaces? (a) Variation of resistance (b) Variation of voltage (c) Periodical switching on and off of the supply (d) All of the above methods Ans: d 36. It is desirable to operate the arc furnaces at power factor of (a) Zero (b) 0.707 lagging (c) unity (d) 0.707 leading Ans: b 37. Radiations from a black body are proportional to (a) T1 (b) T2 (c) T3 (d) T* Ans: d 38. In arc furnace the function of choke is (a) To stabilize the arc (b) To improve, power factor (c) To reduce severity of the surge (d) None of the above Ans: a 39. Ajax Wyatt furnace is started when (a) it is filled below core level (b) it is filled above core level (c) it is fully empty (d) none of the above Ans: b
40. In electric press, mica is used because it is _______ conductor of heat but/and ________ conductor of electricity. (a) bad, good (b) bad, bad (c) good, bad (d) good, good Ans: 41. Resistance variation method of temperature control is done by connecting resistance elements in (a) Series (b) parallel (c) series-parallel connections (d) star-delta connections (e) All of the above ways Ans: e 42. Hysteresis loss and eddy current loss are used in (a) Induction heating of steel (b) Dielectric heating (c) Induction heating of brass (d) Resistance heating Ans: a 43. In heating the ferromagnetic material by induction heating, heat is produced due to (a) Induced current flow through the charge (b) Hysteresis loss taking place below curie temperature (c) due to hysteresis loss as well as eddy current loss taking place in the charge (d) None of the above factors Ans: c 44. Radiant heating is used for which of the following? (a) Annealing of metals (b) Melting of ferrous metals (c) Heating of liquids in electric kettle (d) Drying of paints and varnishes Ans: d 45. Which of the following devices is necessarily required for automatic temperature control in a furnace? (a) Thermostat (b) Thermocouple (c) Auto-transformer (d) Heating elements of variable resis-tance material Ans: b 46. For radiant heating around 2250°C, the heating elements are made of (a) Copper alloy (b) Carbon (c) Tungsten alloy (d) Stainless steel alloy Ans: c 47. The electrode of a direct arc furnace is made of (a) Tungsten (b) Graphite (c) Silver (d) Copper Ans: b 48. Direct arc furnaces have which of the following power factors? (a) Unity (b) Low, lagging (c) Low, leading (d) Any of the above Ans: b 49. In direct arc furnace, which of the following has high value? (a) Current (b) Voltage (c) Power factor (d) All of the above Ans: a
50. Which of the following is an advantage of eddy current heating? (a) The amount of heat generated can be controlled accurately (b) The area of the surface over which heat is produced can be accurately controlled (c) Heat at very high rate can be gene-rated (d) All of the above Ans: d
Industrial Drives . 1. The selection of an electric motor for any application depends on which of the following factors ? (a) Electrical characteristics (b) Mechanical characteristics (c) Size and rating of motors (d) Cost (e) All of the above Ans: e 2. For a particular application the type of electric-and control gear are determined by which of the following considerations? (a) Starting torque (b) Conditions of environment (c) Limitation on starting current (d) Speed control range and its nature (e) All of the above Ans: e 3. Which of the following motors is preferred for traction work ? (a) Universal motor (b) D.C. series motor (c) Synchronous motor (d) Three-phase induction motor Ans: b 4. Which of the following motors always starts on load ? (a) Conveyor motor (b) Floor mill motor (c) Fan motor (d) All of the above Ans: d 5. is preferred for automatic drives. (a) Squirrel cage induction motor (b) Synchronous motors (c) Ward-Leonard controlled D.C. motors (d) Any of the above Ans: c
6. When the load is above _____ a synchronous motor is found to be more economical. (a) 2 kW (b) 20 kW (c) 50 kW (d) 100 kW Ans: d 7. The load cycle for a motor driving a power press will be (a) Variable load (b) Continuous (c) Continuous but periodical (d) Intermittent and variable load Ans: d 8. Light duty cranes are used in which of the following? (a) Power houses (b) Pumping stations (c) Automobile workshops (d) All of the above Ans: d 9. While selecting an electric motor for a floor mill, which electrical characteristics will be of least significance? (a) Running characteristics (b) Starting characteristics (c) Efficiency (d) Braking Ans: d 10. Which of the following motors are pre-ferred for overhead travelling cranes? (a) Slow speed motors (b) Continuous duty motors (c) Short time rated motors (d) None of the above Ans: c 11. is preferred for synthetic fibre mills. (a) Synchronous motor (b) Reluctance motor (c) Series motor (d) Shunt motor Ans: b 12. Ward-Leonard controlled D.C. drives are generally used for ______ excavators. (a) Light duty (b) Medium duty (c) Heavy duty (d) All of the above Ans: c 13. Which of the following motors is used for elevators? (a) Induction motor (b) Synchronous motor (c) Capacitor start single phase motor (d) Any of the above Ans: a 14. Which part of a motor needs maximum attention for maintenance? (a) Frame (b) Rearing (c) Stator winding (d) Rotor winding Ans: b 15. Need frequent starting and stopping of electric motors, (a) Paper mills (b) Grinding mills (c) Air-conditioners (d) Lifts and hoists Ans: d
16. Which feature, while selecting a.motor for centrifugal pump, will be of least significance? (a) Starting characteristics (b) Operating speed(c) Horse power (d) Speed control Ans: d 17. _______ motor is a constant speed motor. (a) Synchronous motor (b) Schrage motor (c) Induction motor (d) Universal motor Ans: a 18. The starting torque in case of centrifugal pumps is generally (a) Less than running torque (b) Same as running torque (c) Slightly more than running torque (d) Double the running torque Ans: a 19. Which of the following motors are best for the rolling mills ? (a) Single phase motors (b) Squirrel cage induction motors (c) Slip ring induction motors (d) D.C. motors Ans: d 20. is not a part of ball bearing ? (a) Inner race (b) Outer race (c) Cage (d) Bush Ans: d 21. The starting torque of a D.C. motor is independent of which of the following? (a) Flux (b) Armature current (c) Flux and armature current (d) Speed Ans: d 22. Rotor of a motor is usually supported on _______ bearings. (a) ball or roller (b) needle (c) bush (d) thrust Ans: a 23. For which of the following applications D.C. motors are still preferred? (a) High efficiency operation (b) Reversibility (c) Variable speed drive (d) High starting torque Ans: c
24. In a paper mill where constant speed is required (a) synchronous motors are preferred (b) A.C. motors are preferred (c) individual drive is preferred (d) group drive is preferred Ans: c 25. A reluctance motor (a) is provided with slip rings (b) requires starting gear (c) has high cost (d) is compact Ans: d 26. The size of an excavator is usually expressed in terms of (a) 'crowd' motion (b) angle of swing (c) cubic metres (d) travel in metres Ans: c 27. For blowers which of the following motor is preferred? (a) D.C. series motor (b) D.C. shunt motor (c) Squirrel cage induction motor (d) Wound rotor induction motor Ans: b 28. Belted slip ring induction motor is almost invariably used for (a) water pumps (b) jaw crushers (c) centrifugal blowers (d) none of the above Ans: b 29. Which of the following is essentially needed while selecting a motor? (a) Pulley (b) Starter (c) Foundation pedal (d) Bearings Ans: b 30. Reluctance motor is a (a) variable torque motor (b) low torque variable speed motor (c) self starting type synchronous motor (d) low noise, slow speed motor Ans: c 31 method of starting a three phase induction motor needs six terminals. (a) Star-delta (b) Resistance starting (c) Auto-transformer (d) none of the above Ans: a 32. In ______ method of staging three phase induction motors the starting voltage is not reduced. (a) auto-transformer (b) star-delta (c) slip ring (d) any of the above Ans: c 33. In jaw crushers a motor has to often start against ______ load. (a) Heavy (b) medium (c) normal (d) low Ans: a
34. For a motor-generator set which of the following motors will be preferred? (a) Synchronous motor (b) Slip ring induction motor (c) Pole changing induction motor (d) Squirrel cage induction motor Ans: a 35. Which of the following motors is usually preferred for kiln drives ? (a) Cascade controlled A.C. motor (b) Slip ring induction motor (c) Three phase shunt wound com-mutator motor (d) Any of the above Ans: d 36. Heat control switches are used in (a) Transformers (b) Cooling ranges (c) Three phase induction motors (d) Single phase Ans: b 37 has relatively wider range of speed control. (a) Synchronous motor (6) Ship ring induction motor (c) Squirrel cage induction motor (d) D.C. shunt motor Ans: d 38. in squirrel cage induction motors which of the following methods of starting cannot be used? (a) Resistance in rotor circuit (b) Resistance in stator circuit (c) Auto-transformer starting (d) Star-delta starting Ans: a 39. In which of the following applications the load on motor changes in cyclic order ? (a) Electric shovels (b) Cranes (c) Rolling mills (d) All of the above Ans: d 40. Flame proof motors are used in (a) Paper mills (b) Steel mills (c) Moist atmospheres (d) Explosive atmospheres Ans: d 41. Which of the following machines has heavy fluctuation of load? (a) Printing machine (b) Punching machine (c) Planer (d) Lathe Ans: b
42. For derries and winches which of the following drives can be used? (a) Pole changing squirrel cage motors (b) D.C. motors with Ward-leonard con-trol (c) A.C. slip ring motors with variable resistance (d) Any of the above Ans: d 43. Battery operated scooter for braking uses (a) Plugging (b) Mechanical braking (c) Regenerative braking (d) rheostatic braking Ans: b 44 has least range of speed control. (a) Slip ring induction motor (b) Synchronous motor (c) D.C. shunt motor (d) Schrage motor Ans: b 45. has the least value of starting torque to full load torque ratio. (a) D.C. shunt motor (b) D.C. series motor (c) Squirrel cage induction motor (d) Slip ring induction motor Ans: c 46. In case of _______ speed control by injecting e.m.f. in the rotor circuit is possible, (a) d.c. shunt motor (b) schrage motor (c) synchronous motor (d) slip ring induction motor Ans: d 47. A pony motor is used for the starting which of the following motors ? (a) Squirel cage induction motor (b) Schrage motor (c) Synchronous motor (d) None of the above Ans: c 48. In ________ the speed can be varied by changing the position of brushes. (a) slip ring motor (b) schrage motor (c) induction motor (d) repulsion motor Ans: b 49. In which of the following applications variable speed operation is preferred? (a) Exhaust fan (b) Ceiling fan (c) Refrigerator (d) Water pump Ans: b
50. Heavy duty cranes are used in (a) ore handling plants (b) steel plants (c) heavy engineering workshops (d) all of the above Ans: d 51. The travelling speed of cranes varies from (a) 20 to 30 m/s (b) 10 to 15 m/s (c) 5 to 10 m/s (d) 1 to 2.5 m/s Ans: d 52. Besides a constant speed a synchronous rotor possesses which of the following advantages? (a) Lower cost (b) Better efficiency (c) High power factor (d) All of the above Ans: c 53. By the use of which of the following D.C. can be obtained from AC.? (a) Silicon diodes (b) Mercury arc rectifier (c) Motor generator set (d) any of the above Ans: d 54. Which of the following motors is preferred when quick speed reversal is the main consideration? (a) Squirrel cage induction motor (b) Wound rotor induction motor (e) Synchronous motor (d) D.C. motor Ans: d 55. Which of the following motors is preferred when smooth and precise speed control over a wide range is desired? (a) D.C. motor (b) Squirrel cage induction motor (c) Wound rotor induction motor (d) Synchronous motor Ans: a 56. For crane travel which of the following motors is normally used? (a) Synchronous motor (b) D.C. differentially compound motor (c) Ward-Leonard controlled D.C. shunt motor (d) AC. slip ring motor Ans: d 57. The capacity of a crane is expressed in terms of(a) type of drive (b) span (c) tones (d) any of the above Ans: c
58. The characteristics of drive for crane hoisting and lowering are which of the following ? (a) Precise control (b) Smooth movement (c) Fast speed control (d) All of the above Ans: d 59. Which of the following motors is preferred for boom hoist of a travelling crane ? (a) Single phase motor (b) Synchronous motor (c) A.C. slip ring motor (d) Ward-Leonard controlled D.C. shunt motor Ans: c 60. A wound rotor induction motor is preferred, as compared to squirrel cage induction motor, when major consideration is (a) slop speed operation (b) high starting torque (c) low windage losses (d) all of the above Ans: b 61. Which of the following motors has series characteristics ? (a) Shaded pole motor (b) Repulsion motor (c) Capacitor start motor (d) None of the above Ans: b 62. Which of the following happens when star-delta starter is used ? (a) Starting voltage is reduced (b) Starting current is reduced (c) Both (a) and (b) (d) None of the above Ans: c 63. For a D.C. shunt motor which of the following is incorrect 7 (a) Unsuitable for heavy duty starting (b) Torque varies as armature current (c) Torque-armature current is a straight line (d) Torque is zero for zero armature current Ans: a 64. For which of the following applications motor has to start with high acceleration? (a) Oil expeller (b) Floor mill (c) Lifts and hoists (d) Centrifugal pump Ans: c
65. Which of the following types of motor enclosure is safest? (a) Totally enclosed (b) Totally enclosed fan cooled (c) Open type (d) Semi closed Ans: b 66. While selecting motor for an air conditioner which of the following characteristics is of great importance? (a) Type of bearings (b) Type of enclosure (c) Noise (d) Arrangement for power transmis¬sion (e) None of the above Ans: c 67. The diameter of the rotor shaft for an electric motor depends on which of the following ? (a) r.p.m. only (b) Horse power only (c) Horse power and r.p.m. (d) Horse power, r.p.m. and power factor Ans: c 68. Which of the following alternatives will be cheaper? (a) A 100 H.P. AC. three phase motor (b) Four motors of 25 H.P. each (c) Five motors of 20 H.P. each (d) Ten motors of 10 H.P. each Ans: a 69. The cost of an induction motor will increase as (a) Horse power rating increases but r.p.m. decreases (b) Horse power rating decreases but r.p.m. increases (c) Horse power rating and operating speed increases (d) Horse power rating and operating speed decreases Ans: a 70. In series motor which of the following methods can be used for changing the flux per pole? (a) Tapped field control (b) Diverter field control (c) Series-parallel control (d) Any of the above Ans: d
Electric Traction 1. Which of the following is an advantage of electric traction over other methods of traction? (a) Faster acceleration (b) No pollution problems (c) Better braking action (d) All of the above Ans: a 2. Which of the following is the voltage for single phase A.C. system? (a) 22 V (b) 440 V (c) 5 kV (d) 15 kV (e) None of the above Ans: a 3. Long distance railways use which of the following? (a) 200 V D.C. (b) 25 kV single phase A.C. 10. (c) 25 kV two phase A.C. (d) 25 kV three phase A.C. Ans: b 4. The speed of a locomotive is controlled by (a) flywheel (b) gear box (c) applying brakes 11. (d) regulating steam flow to engine Ans: b 5. Main traction systems used in India are, those using (a) electric locomotives (b) diesel engine locomotives (c) steam engine locomotives (d) diesel electric locomotives (e) all of the above Ans: e 6, in India diesel locomotives are manu¬factured at (a) Ajmer (b) Varanasi (c) Bangalore (d) Jamalpur Ans: b 7. For diesel locomotives the range of horsepower is (a) 50 to 200 (b) 500 to 1000 (c) 1500 to 2500 (d) 3000 to 5000 Ans: c 8. _______ locomotive has the highest operational availability. (a) Electric (b) Diesel (c) Steam Ans: a
9. The horse power of steam locomotives is (a) up to 1500 (b) 1500 to 2000 (c) 2000 to 3000 (d) 3000 to 4000 Ans: a 10. The overall efficiency of steam locomotive is around (a) 5 to 10 percent (b) 15 to 20 percent (c) 25 to 35 percent (d) 35 to 45 percent Ans: a 11. In tramways which of the following motors is used? (a) D.C. shunt motor (b) D.C. series motor (c) A.C. three phase motor (d) AC. single phase capacitor start motor Ans: b 12. In a steam locomotive electric power is provided through (a) Overhead wire (b) battery system (c) Small turbo-generator (d) diesel engine generator Ans: c 13. Which of the following drives is suitable for mines where explosive gas exists? (a) Steam engine (b) Diesel engine (c) Battery locomotive (d) any of the above Ans: c 14. In case of locomotives the tractive power is provided by (a) Single cylinder double acting steam engine (b) Double cylinder, single acting steam engine (c) Double cylinder, double acting steam engine (d) Single stage steam turbine Ans: c 15. Overload capacity of diesel engines is usually restricted to (a) 2 percent (b) 10 percent (c) 20 percent (d) 40 percent Ans: a 16. In case of steam engines the steam pressure is (a) 1 to 4 kgf/cm2 (b) 5 to 8 kgf/cm2 (c) 10 to 15 kgf/cm2 (d) 25 to 35 kgf/cm2 Ans: c 17. The steam engine provided on steam locomotives is (a) Single acting condensing type (b) Single acting non-condensing type (e) Double acting condensing type (d) Double acting non-condensing type Ans: b
18. Electric locomotives in India are manufactured at (a) Jamalpur (b) Bangalore (c) Chittranjan (d) Gorakhpur Ans: c 19. The wheels of a train, engine as well as bogies, are slightly tapered to (a) reduce frietion (b) increase friction (c) facilitate braking (d) facilitate in taking turns Ans: d 20. Automatic signalling is used for which of the following trains ? (a) Mail and express trains (b) Superfast trains (c) Suburban and Urban electric trains (d) All trains Ans: b 21. The efficiency of diesel locomotives is nearly (a) 20 to 25 percent (b) 30 to 40 percent (c) 45 to 55 percent (d) 60 to 70 percent Ans: a 22. The speed of a superfast train is (a) 60 kmph (b) 75 kmph (c) 100 kmph (d) more than 100 kmph Ans: d 23. The number of passanger coaches that can be attached to a diesel engine locomotive on broad gauge is usually restricted to (a) 5 (b) 10 (c) 14 (d) 17 Ans: b 24. Which of the following state capitals is not on broad gauge track ? (a) Lucknow (b) Bhopal (c) Jaipur (d) Chandigarh Ans: c 25. Which of the following is the advantage of electric braking ? (a) It avoids wear of track (b) Motor continues to remain loaded during braking (c) It is instantaneous (d) More heat is generated during braking Ans: a
24. Which of the following braking systems on the locomotives is costly ? (a) Regenerative braking on electric locomotives (b) Vacuum braking on diesel locomo-tives (c) Vacuum braking on steam locomo-tives (d) All braking systems are equally costly Ans: a 27. Tractive effort is required to (a) overcome the gravity component of train mass (b) overcome friction, windage and curve resistance (c) accelerate the train mass (d) do all of the above Ans: d 28. For given maximum axle load tractive efforts of AC. locomotive will be (a) less than that of D.C. locomotive (b) more than that of D.C. locomotive (c) equal to that of D.C. locomotive (d) none of the above Ans: b 29. Co-efficient of adhesion reduces due to the presence of which of the following? (a) Sand on rails (b) Dew on rails (c) Oil on the rails (d) both (b) and (c) Ans: d 30. Due to which of the following co-efficient of adhesion improves ? (a) Rust on the rails (b) Dust on the rails (c) Sand on the rails (d) All of the above Ans: d 31. Quadrilateral speed-time curve pertains to which of the following services ? (a) Main line service (b) Urban service (c) Sub-urban service (d) Urban and sub-urban service Ans: d 32. Which of the following is the disadvantage of electric traction over other systems of traction? (a) Corrosion problems in the under-ground pipe work (b) Short time power failure interrupts traffic for hours (c) High capital outlay in fixed instal-lations beside route limitation (d) Interference with communication lines (e) All of the above Ans: c
33. Co-efficient of adhesion is (a) high in case of D.C. traction than in the case of AC. traction (b) low in case of D.C. traction than in the case of AC. traction (c) equal in both AC. and D.C. traction (d) any of the above Ans: b 34. Speed-time curve of main line service differs from those of urban and suburban services on following account (a) it has longer free running period (b) it has longer coasting period (c) accelerating and braking periods are comparatively smaller (d) all of the above Ans: d 35. The rate of acceleration on suburban orurban services is restricted by the consideration of (a) Engine power (b) Track curves (c) Passenger Discomfort (d) Track size Ans: c 36. The specific energy consumption of a train depends on which of the following? (a) Acceleration and retardation (b) Gradient (c) Distance covered (d) All of the above Ans: d 37. The friction at the track is proportional to (a) 1/speed (b) l/(speed)2 (c) speed (d) none of the above Ans: c 38. The air resistance to the movement of the train is proportional to (a) speed (b) (speed) (c) (speed) (d) 1/speed Ans: b 39. The normal value of adhesion friction is (a) 0.12 (b) 0.25 (c) 0.40 (d) 0.75 Ans: b 40. The pulsating torque exerted by steam locomotives causes which of the following? (a) Jolting and skidding (b) Hammer blow (c) Pitching (d) All of the above Ans: a
41. Which of the following braking systems is used on steam locomotives? (a) Hydraulic system (b) Pneumatic system (c) Vacuum system (d) none of the above Ans: c 42. Vacuum is created by which of the following? (a) Vacuum pump (b) Ejector (c) Any of the above (d) None of the above Ans: c 43. The resistance encountered by a trainin motion is on account of (a) Resistance offered by air (b) Friction at the track (c) Friction at various parts of the rolling stock (d) all of the above Ans: d 44. Battery operated trucks are used in (a) steel mills (b) power stations (c) narrow gauge traction (d) factories for material transportation Ans: d 45. Method can bring the locomotive to dead stop. (a) Plugging braking (b) Rheostatic braking (c) Regenerative braking (d) None of the above Ans: a 46. The value of co-efficient of adhesion will be high when rails are (a) Greased (b) wet (c) sprayed with oil (d) cleaned with sand Ans: d 47. The voltage used for suburban trains in D.C. system is usually (a) 12 V (b) 24 V (c) 220 V (d) 600 to 750 V Ans: d 48. for three-phase induction motors which of the following is the least efficient method of speed control? (a) Cascade control (b) Pole changing (c) Rheostatic control (d) Combination of cascade and pole changing Ans: c 49. Specific energy consumption becomes (a) More on steeper gradient (b) more with high train resistance (c) Less if distance between stops is more (d) all of the above Ans: d 50. In main line service as compared to urban and suburban service (a) Distance between the stops is more (b) Maximum speed reached is high (c) Acceleration and retardation rates are low (d) all of the above Ans: d
51. Locomotive having monomotor bogies (a) Has better coefficient of adhesion (b) Are suited both for passanger as well as freight service (c) has better riding qualities due to the reduction of lateral forces (d) has all above qualities Ans: d 52. Series motor is not suited for traction duty due to which of the following account ? (a) Less current drain on the heavy load torque (b) Current surges after temporary switching off supply (c) Self relieving property (d) Commutating property at heavy load Ans: b 53. When a bogie negotiates a curve, reduction in adhesion occurs resulting in sliding. Thus sliding is acute when (a) wheel base of axles is more (b) degree of curvature is more (c) both (a) and (b) (d) none of the above Ans: c 54. Energy consumption in propelling the train is required for which of the following? (a) Work against the resistance to motion (b) Work against gravity while moving up the gradient (c) Acceleration (d) All of the above Ans: d 55. An ideal traction system should have (a) easy speed control (b) high starting tractive effort (c) equipment capable of with standing large temporary loads (d) all of the above Ans: d 56. have maximum unbalanced forces (a) Diesel shunters (b) Steam locomotives (c) Electric locomotives (d) Diesel locomotives Ans: b 57. Specific energy consumption is affected by which of the following factors ? (a) Retardation and acceleration values (b) Gradient (c) Distance between stops (d) All of the above Ans: d
58. In case of ________ free running and coasting periods are generally long. (a) main-line service (b) urban service (c) sub-urban service (d) all of the above Ans: a 59. Overhead lines for power supply to tramcars are at a minimum height of (a) 3 m (b) 6 m (c) 10 m (d) 2 m Ans: c 60. The return circuit for tramcars is through (a) Neutral wire (b) rails (c) cables (d) common earthing Ans: b 61. Specific energy consumption is least in _______ service. (a) main line (b) urban (c) suburban Ans: a 62. Locomotives with monometer bogies have (a) uneven distribution of tractive effect (b) suitability for passanger as well as freight service (c) lot of skidding (d) low co-efficient of adhesion Ans: b 63 _______ was the first city in India to adopt electric traction. (a) Delhi (b) Madras (c) Calcutta (d) Bombay Ans: d 64 _______ frequency is not common in low frequency traction system (a) 40 Hz (b) 25 Hz (c) 16 Hz Ans: a 65. For 25 kV single phase system power supply frequency is (a) 60 Hz (b) 50 Hz (c) 25 Hz (d) 16 Hz Ans: b 66. Power for lighting in passanger coach, in a long distance electric train, is provided (a) directly through overhead electric line (b) through individual generator of bogie and batteries (c) through rails (d) through locomotive Ans: b 67. In India, electrification of railway track was done for the first time in which of the following years ? (a) 1820—1825 (b) 1880—1885 (c) 1925—1932 (d) 1947—1954 Ans: c 68. Suri transmission is (a) electrical-pneumatic (b) mechanical-electrical (c) hydro-mechanical (d) hydro-pneumatic Ans: c
69. In case of a steam engine an average coal consumption per km is nearly (a) 150 to 175 kg (b) 100 to 120 kg (c) 60 to 80 kg (d) 28 to 30 kg Ans: d 70. Which of the following happens in Kando system ? (a) Three phase A.C. is converted into D.C. (b) Single phase A.C. is converted into D.C. (c) Single phase supply is converted into three phase system (d) None of the above Ans: c 71. For which of the following locomotives the maintenance requirements are the least? (a) Steam locomotives (b) Diesel locomotives (c) Electric locomotives (d) Equal in all of the above Ans: b 72. Which of the following methods is used to control speed of 25 kV, 50 Hz single phase traction? (a) Reduced current method (b) Tap changing control of transformer (c) Series parallel operation of motors (d) All of the above Ans: b 73. If the co-efficient of adhesion on dry rails is 0.26, which of the following could be the value for wet rails? (a) 0.3 (b) 0.26 (c) 0.225 (d) 0.16 Ans: d 74 watt-hours per tonne km is usually the specific energy consumption for suburban services. (a) 15—20 (b) 50—75 (c) 120—150 (d) 160—200 Ans: b 75. The braking retardation is usually in the range (a) 0.15 to 0.30 km phps (b) 0.30 to 0.6 km phps (c) 0.6 to 2.4 km phps (d) 3 to 5 km phps (e) 10 to 15 km phps Ans: d 76. The rate of acceleration on suburban orurban service is in the range (a) 0.2 to 0.5 km phps (b) 1.6 to 4.0 km phps (c) 5 to 10 km phps (d) 15 to 25 km phps Ans: b 77. The coasting retardation is around (a) 0.16 km phps (b) 1.6 km phps (c) 16 km phps (d) 40 km phps Ans: a
Control Systems 1. In an open loop control system (a) Output is independent of control input (b) Output is dependent on control input (c) Only system parameters have effect on the control output (d) None of the above Ans: a 2. For open control system which of the following statements is incorrect? (a) Less expensive (b) Recalibration is not required for maintaining the required quality of the output (c) Construction is simple and maintenance easy (d) Errors are caused by disturbances Ans: b 3. A control system in which the control action is somehow dependent on the output is known as (a) Closed loop system (b) Semiclosed loop system (c) Open system (d) None of the above Ans: a 4. In closed loop control system, with positive value of feedback gain the overall gain of the system will (a) decrease (b) increase (c) be unaffected (d) any of the above Ans: a 5. Which of the following is an open loop control system ? (a) Field controlled D.C. motor (b) Ward leonard control (c) Metadyne (d) Stroboscope Ans: a 6. Which of the following statements is not necessarily correct for open control system ? (a) Input command is the sole factor responsible for providing the control action (b) Presence of non-linearities causes malfunctioning (c) Less expensive (d) Generally free from problems of non-linearities Ans: b
7. In open loop system (a) the control action depends on the size of the system (b) the control action depends on system variables (c) the control action depends on the input signal (d) the control action is independent of the output Ans: d 8. has tendency to oscillate. (a) Open loop system (b) Closed loop system (c) Both (a) and (b) (d) Neither (a) nor (b) Ans: b 9. A good control system has all the following features except (a) good stability (b) slow response (c) good accuracy (d) sufficient power handling capacity Ans: b 10. A car is rtyining at a constant speed of 50 km/h, which of the following is the feedback element for the driver ? (a) Clutch (b) Eyes (c) Needle of the speedometer (d) Steering wheel (e) None of the above Ans: c 11. The initial response when tne output is not equal to input is called (a) Transient response (b) Error response (c) Dynamic response (d) Either of the above Ans: a 12. A control system working under unknown random actions is called (a) computer control system (b) digital data system (c) stochastic control system (d) adaptive control system Ans: c13. An automatic toaster is a ______ loop control system. (a) open (b) closed (c) partially closed (d) any of the above Ans: a 14. Any externally introduced signal affecting the controlled output is called a (a) Feedback (b) stimulus (c) signal (d) gain control Ans: b
15. A closed loop system is distinguished from open loop system by which of the following? (a) Servomechanism (b) Feedback (c) Output pattern (d) Input pattern Ans: b 16 is a part of the human temperature control system. (a) Digestive system (b) Perspiration system (c) Ear (d) Leg movement Ans: b 17. By which of the following the control action is determined when a man walks along a path? (a) Brain (b) Hands (c) Legs (d) Eyes Ans: d 18. Is a closed loop system. (a) Auto-pilot for an aircraft (6) Direct current generator (c) Car starter (d) Electric switch Ans: a 19. Which of the following devices are commonly used as error detectors in instruments? (a) Vernistats (b) Microsyns (c) Resolvers (d) Any of the above Ans: d 20. Which of the following should be done to make an unstable system stable? (a) The gain of the system should be decreased (b) The gain of the system should be increased (c) The number of poles to the loop transfer function should be increased (d) The number of zeros to the loop transfer function should be increased Ans: b 21. Increases the steady state accuracy. (a) Integrator (b) Differentiator (c) Phase lead compensator (d) Phase lag compensator Ans: a 22. A.C. servomotor resembles (a) two phase induction motor (b) Three phase induction motor (c) direct current series motor (d) universal motor Ans: a
23. As a result of introduction of negative feedback which of the following will not decrease? (a) Band width (b) Overall gain (c) Distortion (d) Instability Ans: a 24. Regenerative feedback implies feedback with (a) oscillations (b) step input (c) negative sign (d) positive sign Ans: d 25. The output of a feedback control system must be a function of (a) reference and output (b) reference and input (e) input and feedback signal (d) output and feedback signal Ans: a 26. is an open loop control system. (a) Ward Leonard control (b) Field controlled D.C. motor (c) Stroboscope (d) Metadyne Ans: b 27. A control system with excessive noise, is likely to suffer from (a) saturation in amplifying stages (b) loss of gain (c) vibrations (d) oscillations Ans: a 28. Zero initial condition for a system means (a) input reference signal is zero (b) zero stored energy (c) ne initial movement of moving parts (d) system is at rest and no energy is stored in any of its components Ans: d 29. Transfer function of a system is used to calculate which of the following ? (a) The order of the system(b) The time constant (c) The output for any given input (d) The steady state gain Ans: c 30. The band width, in a feedback amplifier. (a) remains unaffected (b) decreases by the same amount as the gain increase (c) increases by the sane saaaajajt as the gain decrease (d) decreases by the same amount as the gain decrease Ans: c 31. On which of the following factors does the sensitivity of a closed loop system to gain changes and load disturbances depend ? (a) Frequency (b) Loop gain (c) Forward gain (d) All of the above Ans: d
32. The transient response, with feedback system, (a) rises slowly (b) rises quickly (c) decays slowly (d) decays quickly Ans: d 33. The second derivative input signals modify which of the following? (a) The time constant of the system (b) Damping of the system (c) The gain of the system (d) The time constant and suppress the oscillations (e) None of the above Ans: d 34. Which of the following statements is correct for any closed loop system ? (a) All the co-efficients can have zero value (6) All the co-efficients are always non-zero (c) Only one of the static error co-efficients has a finite non-zero value (d) None of the above Ans: c 35. Which of the following statements is correct for a system with gain margin close to unity or a phase margin close to zero ? (a) The system is relatively stable (b) The system is highly stable (c) The system is highly oscillatory (d) None of the above Ans: c 36. Due to which of the following reasons excessive bond width in control systems should be avoided ? (a) It leads to slow speed of response (b) It leads to low relative stability (c) Noise is proportional to band width (d) None of the above Ans: c 37. In a stable control system backlash can cause which of the following ? (a) Underdamping (b) Overdamping (c) Poor stability at reduced values of open loop gain (d) Low-level oscillations Ans: d 38. In an automatic control system which of the following elements is not used ? (a) Error detector (b) Final control element (c) Sensor (d) Oscillator Ans: d
39. In a control system the output of the controller is given to (a) Final control element (b) amplifier (c) Comparator (d) sensor (e) None of the above Ans: a 40. A controller, essentially, is a (a) Sensor (b) clipper (c) Comparator (d) Amplifier Ans: c 41. Which of the following is the input to a controller? (a) Servo signal (b) Desired variable value (c) Error signal (d) Sensed signal Ans: 42. The on-off controller is a _____ system. (a) digital (b) linear (c) non-linear (d) discontinuous Ans: 43. The capacitance, in force-current analogy, is analogous to (a) momentum (b) velocity (c) displacement (d) mass Ans: d 44. The temperature, under thermal and electrical system analogy, is considered analogous to (a) Voltage (b) Current (c) Capacitance (d) Charge (e) none of the above Ans: a 45. In electrical-pneumatic system analogy the current is considered analogous to (a) velocity (b) pressure (c) air flow (d) air flow rate Ans: d 46. In liquid level and electrical system analogy, voltage is considered analogous to (a) Head (b) Liquid flow (c) Liquid flow rate (d) None of the above Ans: a 47. The viscous friction co-efficient, in force-voltage analogy, is analogous to (a) Charge (b) Resistance (c) Reciprocal of inductance (d) Reciprocal of conductance (e) none of the above Ans: b 48. In force-voltage analogy, velocity is analogous to (a) Current (b) charge (c) inductance (d) capacitance Ans: a 49. In thermal-electrical analogy charge is considered analogous to (a) Heat flow (b) Reciprocal of heat flow (c) Reciprocal of temperature (d) Temperature (e) None of the above Ans: d
50. Mass, in force-voltage analogy, is analogous to (a) Charge (b) Current (c) Inductance (d) Resistance Ans: c 51. The transient response of a system is mainly due to (a) Inertia forces (b) Internal forces (c) Stored energy (d) Friction Ans: c 52 signals will become zero when the feedback signal and reference signs are equal. (a) Input (b) Actuating (c) Feedback (d) Reference Ans: b 53. A signal other than the reference input that tends to affect the value of controlled variable is known as (a) Disturbance (b) command (c) control element (d) Reference input Ans: a 54. The transfer function is applicable to which of the following? (a) Linear and time-in variant systems (b) Linear and time-variant systems (c) Linear systems (d) Non-linear systems (e) None of the above Ans: a 55. From which of the following transfer function can be obtained ? (a) Signal flow graph (b) Analogous table (c) Output-input ratio (d) Standard block system (e) None of the above Ans: a 56 is the reference input minus the primary feedback. (a) Manipulated variable (b) Zero sequence (c) Actuating signal (d) Primary feedback Ans: c 57. The term backlash is associated with (a) Servomotors (b) Induction relays (c) Gear trains (d) Any of the above Ans: 58. with feedback _____ increases. (a) System stability (b) Sensitivity (c) gain (d) effects of disturbing signals Ans: a
59. By which of the following the system response can be tested better ? (a) Ramp input signal (b) Sinusoidal input signal (c) Unit impulse input signal (d) Exponentially decaying signal Ans: c 60. In a system zero initial condition means that (a) The system is at rest and no energy is stored in any of its components (b) The system is working with zero stored energy (c) The system is working with zero reference signal Ans: a 61. In a system low friction co-efficient facilitates (a) reduced velocity lag error (b) increased velocity lag error (c) increased speed of response (d) reduced time constant of the system Ans: a 62. Hydraulic torque transmission system is analog of (a) amplidyne set (b) resistance-capacitance parallel circuit (c) motor-generator set (d) any of the above Ans: 63. Spring constant in force-voltage analogy is analogous to (a) capacitance (b) reciprocal of capacitance (c) current (d) resistance Ans: b 64. The frequency and time domain are related through which of the following? (a) Laplace Transform and Fourier Integral (b) Laplace Transform (c) Fourier Integral (d) Either (b) or (c) Ans: a 65. An increase in gain, in most systems, leads to (a) smaller damping ratio (b) larger damping ratio (c) constant damping ratio (d) none of the above Ans: a
66. Static error co-efficients are used as a measure of the effectiveness of closed loop systems for specified ________ input signal. (a) Acceleration (b) Velocity (c) Position (d) all of the above Ans: d 67. A conditionally stable system exhibits poor stability at (a) Low frequencies (b) Reduced values of open loop gain (c) Increased values of open loop gain (d) none of the above Ans: b 68. The type 0 system has ______ at the origin. (a) No pole (b) Net pole (c) Simple pole (d) Two poles (e) None of the above Ans: a 69. The type 1 system has ______ at the origin. (a) No pole bb (b) Net pole b (c) Simple pole (d) Two poles Ans: c 70. The type 2 system has at the origin. (a) No net pole (b) Net pole (c) Simple pole (d) two poles Ans: d 71. The position and velocity errors of a type-2 system are (a) Constant, constant (b) Constant, infinity (c) Zero, constant (d) Zero, zero Ans: c 72. Velocity error constant of a system is measured when the input to the system is unit _______ function. (a) Parabolic (b) Ramp (c) Impulse (d) Step Ans: b 73. In case of type-1 system steady state acceleration is (a) Unity (b) Infinity (c) Zero (d) 10 Ans: b 74. If a step function is applied to the input of a system and the output remains below a certain level for all the time, the system is (a) not necessarily stable (b) stable (c) unstable (d) always unstable (e) any of the above Ans: a 75. Which of the following is the best method for determining the stability and transient response? (a) Root locus (b) Bode plot (c) Nyquist plot (d) none of the above Ans: a
76. Phase margin of a system is used to specify which of the following? (a) Frequency response (b) Absolute stability (c) Relative stability (d) Time response Ans: c 77. Addition of zeros in transfer function causes which of the following? (a) Lead-compensation (b) Lag-compensation (c) Lead-lag compensation (d) None of the above Ans: b 78. technique is not applicable to nonlinear system ? (a) Nyquist Criterion (b) Quasi linearization (c) Functional analysis (d) Phase-plane representation Ans: a 79. In order to increase the damping of a badly underdamped system which of following compensators may be used ? (a) Phase-lead (b) Phase-lag (c) Both (a) and (b) (d) Either (a) and (b) (e) None of the above Ans: a 80. The phase lag produced by transportation relays (a) is independent of frequency (b) is inverseh'proportional to frequency (c) increases linearly with frequency (d) decreases linearly with frequency Ans: c 81. In a stable control system saturation can cause which of the following? (a) Low-level oscillations (b) High-level oscillations (c) Conditional stability (d) over damping Ans: a 82. Which of the following can be measured by the use of a tacho-generator ? (a) Acceleration (b) Speed (c) Speed and acceleration (d) Displacement (e) None of the above Ans: b
83 is not a final control element. (a) Control valve (b) Potentiometer (c) Electro-pneumatic converter (d) Servomotor Ans: b 84. Which of the following is the definition of proportional band of a controller? (a) The range of air output as measured variable varies from maximum to minimum (b) The range of measured variables from set value (c) The range of measured variables through which the air output chan¬ges from maximum to minimum (d) Any of the above (e) None of the above Ans: c 85. In pneumatic control systems the control valve used as final control element converts (a) pressure signal to electric signal (b) pressure signal to position change (c) electric signal to pressure signal (d) position change to pressure signal (e) none of the above Ans: b 86. Pressure error can be measured by which of the following ? (a) Differential bellows and straingauge (b) Selsyn (c) Strain gauge (d) Strain gauge and potentiometer Ans: a 87. Which of the following devices is used for conversion of co-ordinates? (a) Microsyn (b) Selsyn (c) Synchro-resolver (d) Synchro-transformer Ans: c 88. The effect of error damping is to (a) provide larger settling lime (b) delay the response (c) reduce steady state error (d) any of the above (e) none of the above Ans: c 89 technique gives quick transient and stability response (a) Root locus (b) Bode (c) Nyquist (d) Nichols Ans: a 90. A phase lag lead network introduces in the output (a) lag at all frequencies (b) lag at high frequencies and lead at low frequencies (c) lag at low frequencies and lead at high frequencies (d) none of the above Ans: c
91. Which of the following is the non-linearity caused by servomotor? (a) Static friction (b) Backlash (c) Saturation (d) None of the above Ans: c 92 can be extended to systems which are time-varying? (a) Bode-Nyquist stability methods (b) Transfer functions (c) Root locus design (d) State model representatives Ans: d 93. When the initial conditions of a system are specified to be zero it implies that the system is (a) At rest without any energy stored in it (b) Working normally with reference input (c) Working normally with zero reference input (d) At rest but stores energy Ans: d 94. Which of the following is an electromechanical device? (a) Induction relay (b) Thermocouple (c) LVDT (d) Any of the above (e) None of the above Ans: c 95. A differentiator is usually not a part of a control system because it (a) reduces damping (b) reduces the gain margin (c) increases input noise (d) increases error Ans: c 96. If the gain of the critical damped system is increased it will behave as (a) Oscillatory (b) Critically damped (c) Over damped (d) under damped (e) None of the above Ans: d 97. In a control system integral error compensation _______ steady state error (a) increases (b) minimizes (c) does not have any effect on (d) any of the above Ans: b 98. With feed back _____ reduces. (a) system stability (b) system gain (c) system stability and gain (d) none of the above Ans: b 99. An amplidyne can give which of the following characteristics? (a) Constant current (b) Constant voltage (c) Constant current as well as constant voltage (d) Constant current, constant voltage and constant power (e) None of the above Ans: d
100. Which of the following can be measured by LVDT? (a) Displacement (b) Velocity (c) Acceleration (d) Any of the above Ans: d 101 directly convert temperature into voltage. (a) Thermocouple (b) Potentiometer (c) Gear train (d) LVDT (e) None of the above Ans: a 102. The transfer function technique is considered as inadequate under which of the following conditions? (a) Systems having complexities and non-linearities (b) Systems having stability problems (c) Systems having multiple input dis¬turbances (d) All of the above Ans: d 103. Which of the following is the output of a thermocouple? (a) Alternating current (b) Direct current (c) A.C. voltage (d) D.C. voltage (e) None of the above Ans: d 104. A.C. servomotor is basically a (a) Universal motor (b) single phase induction motor (c) Two phase induction motor (d) Three phase induction motor Ans: c 105. The first order control system, which is well designed, has a (a) small bandwidth (b) negative time constant (c) large negative transfer function pole (d) none of the above Ans: c 106. Which of the following is exhibited by Root locus diagrams? (a) The poles of the transfer function for a set of parameter values (b) The bandwidth of the system (c) The response of a system to a step input (d) The frequency response of a system (e) None of the above Ans: a
Measurement and Instrumentation 1. The use of _____ instruments is merely confined within laboratories as stand¬ardizing instruments. (a) absolute (b) indicating (c) recording (d) integrating (e) none of the above Ans: a 2. Which of the following instruments indicate the instantaneous value of the electrical quantity being measured at the time at which it is being measured? (a) Absolute instruments (b) Indicating instruments (c) Recording instruments (d) Integrating instruments Ans: b 3. _____ instruments are those which measure the total quantity of electricity delivered in a particular time. (a) Absolute (b) Indicating (c) Recording (d) Integrating Ans: d 4. Which of the following are integrating instruments? (a) Ammeters (b) Voltmeters (c) Wattmeters (d) Ampere-hour and watt-hour meters Ans: d 5. Resistances can be measured with the help of (a) Wattmeters (b) voltmeters (c) ammeters (d) Ohmmeters and resistance bridges (e) all of the above Ans: d 6. According to application, instruments are classified as (a) Switch board (b) portable (c) both (a) and (b) (d) moving coil (e) moving iron (f) both (d) and (e) Ans: c 7. Which of the following essential features is possessed by an indicating instrument? (a) Deflecting device (b) Controlling device (c) Damping device (d) All of the above Ans: d 8. A _____ device prevents the oscillation of the moving system and enables the latter to reach its final position quickly (a) Deflecting (b) controlling (c) Damping (d) any of the above Ans: c 9. The spring material used in a spring control device should have the following property. (a) Should be non-magnetic (b) Most be of low temperature co-efficient (c) Should have low specific resistance (d) should not be subjected to fatigue (e) All of the above Ans: e
10. Which of the following properties damping oil must possess? (a) Must be a good insulator (b) Should be non-evaporating (c) Should not have corrosive action upon the metal of the vane (d) The viscosity of the oil should not change with the temperature (e) All of the above Ans: e 11. A moving-coil permanent-magnet instrument can be used as _____ by using a low resistance shunt. (a) ammeter (b) voltmeter (c) flux-meter (d) ballistic galvanometer Ans: a 12. A moving-coil permanent-magnet instrument can be used as flux-meter (a) by using a low resistance shunt (b) by using a high series resistance (c) by eliminating the control springs (d) by making control springs of large moment of inertia Ans: c 13. Which of the following devices may be used for extending the range of instruments ? (a) Shunts (b) Multipliers (c) Current transformers (d) Potential transformers (e) All of the above Ans: e 14. An induction meter can handle current upto (a) 10 A (b) 30 A (c) 60 A (d) 100 A Ans: d 15. For handling greater currents induction wattmeters are used in conjunction with (a) potential transformers(b) current transformers (c) power transformers (d) either of the above (e) none of the above Ans: b 16. Induction type single phase energy meters measure electric energy in (a) kW (b) Wh (c) kWh (d) VAR (e) None of the above Ans: c 17. Most common form of A.C. meters met with in every day domestic and industrial installations are (a) mercury motor meters (b) commutator motor meters (c) induction type single phase energy meters (d) all of the above Ans: c 18. Which of the following meters are not used on D.C. circuits (a) Mercury motor meters (b) Commutator motor meters (c) Induction meters (d) None of the above Ans: c
19. Which of the following is an essential part of a motor meter ? (a) An operating torque system (b) A braking device (c) Revolution registering device (d) All of the above Ans: d 20. A potentiometer may be used for (a) measurement of resistance (b) measurement of current (c) calibration of ammeter (d) calibration of voltmeter (e) all of the above Ans: e 21 is an instrument which measures the insulation resistance of an electric circuit relative to earth and one another, (a) Tangent galvanometer (b) Meggar (c) Current transformer (d) none of the above Ans: b 22. The household energy meter is (a) an indicating instrument (b) a recording instrument (c) an integrating instrument (d) none of the above Ans: c 23. The pointer of an indicating instrument should be (a) Very light (b) very heavy (c) either (a) or (b) (d) neither (a) nor (b) Ans: a 24. The chemical effect of current is used in (a) D.C. ammeter hour meter (b) D.C. ammeter (c) D.C. energy meter (d) none of the above Ans: a 25. In majority of instruments damping is provided by (a) Fluid friction (b) spring (c) eddy currents (d) all of the above Ans: c 26. An ammeter is a (a) Secondary instrument (b) Absolute instrument (c) Recording instrument (d) Integrating instrument Ans: a 27. In a portable instrument, the controlling torque is provided by (a) Spring (b) gravity (c) eddy currents (d) all of the above Ans: a 28. The disc of an instrument using eddy current damping should be of (a) Conducting and magnetic material (b) Non-conducting and magnetic material (c) Conducting and non-magnetic material (d) none of the above Ans: c
29. The switch board instruments (a) Should be mounted in vertical position (b) Should be mounted in horizontal position (c) Either (a) or (b) (d) neither (a) nor (b) Ans: a 30. The function of shunt in an ammeter is to (a) By pass the current (b) Increase the sensitivity of the ammeter (c) Increase the resistance of ammeter (d) None of the above Ans: a 31. The multiplier and the meter coil in a voltmeter are in(a) series (b) Parallel (c) series-parallel (d) none of the above Ans: a 32. A moving iron instrument can be used for (a) D.C. only (b) A.C. only (c) both D.C. and A.C. Ans: c 33. The scale of a rectifier instrument is (a) linear (b) non-linear (c) either (a) or (b) (d) neither (a) nor (b) Ans: a 34. For measuring current at high frequency we should use (a) moving iron instrument (b) electrostatic instrument (c) thermocouple instrument (d) none of the above Ans: c 35. The resistance in the circuit of the moving coil of a dynamometer wattmeter should be (a) almost zero (b) low (c) high (d) none of the above Ans: c 36. A dynamometer wattmeter can be used for (a) both D.C. and A.C. (b) D.C. only (c) A.C. only (d) any of the above Ans: a 37. An induction wattmeter can be used for (a) both D.C. and A.C. (6) D.C. only (c) A.C. only (d) any of the above Ans: b 38. The pressure coil of a wattmeter should be connected on the supply side of the current coil when (a) load impedance is high (b) load impedance is low (c) supply voltage is low (d) none of the above Ans: a 39. In a low power factor wattmeter the pressure coil is connected (a) to the supply side of the current coil (b) to the load side of the current coil (c) in any of the two meters at connection (d) none of the above Ans: b
40. In a low power factor wattmeter the compensating coil is connected (a) in series with current coil (b) in parallel with current coil (c) in series with pressure coil (d) in parallel with pressure coil Ans: c 41. In a 3-phase power measurement by two wattmeter method, both the watt meters had identical readings. The power factor of the load was (a) unity (6) 0.8 lagging (c) 0.8 leading (d) zero Ans: a 42. In a 3-phase power measurement by two wattmeter method the reading of one of the wattmeter was zero. The power factor of the load must be (a) unity (b) 0.5 (c) 0.3 (d) zero Ans: b 43. The adjustment of position of shading bands, in an energy meter is done to provide (a) friction compensation (b) creep compensation (c) braking torque (d) none of the above Ans: a 44. An ohmmeter is a (a) moving iron instrument (b) moving coil instrument (c) dynamometer instrument (d) none of the above Ans: b 45. When a capacitor was connected to the terminal of ohmmeter, the pointer indicated a low resistance initially and then slowly came to infinity position. This shows that capacitor is (a) short-circuited (b) all right (c) faulty Ans: b 46. For measuring a very high resistance we should use (a) Kelvin's double bridge (b) Wheat stone bridge (c) Meggar (d) None of the above Ans: c 47. The electrical power to a meggar is provided by (a) battery (b) permanent magnet D.C. generator (c) AC. Generator (d) any of the above Ans: b 48. In a meggar controlling torque is provided by (a) spring (b) gravity (c) coil (d) eddy current Ans: c 49. The operating voltage of a meggar is about (a) 6 V (b) 12 V (c) 40 V (d) 100 V Ans: d
50. Murray loop test can be used for location of (a) ground fault on a cable (b) short circuit fault on a cable (c) both the ground fault and the short-circuit fault (d) none of the above Ans: c 51. Which of the following devices should be used for accurate measurement of low D.C. voltage ? (a) Small range moving coil voltmeter (b) D.C. potentiometer (c) Small range thermocouple voltmeter (d) None of the above Ans: b 52. It is required to measure the true open circuit e.m.f. of a battery. The best device is (a) D.C. voltmeter (b) Ammeter and a known resistance (c) D.C. potentiometer (d) None of the above Ans: c 53. A voltage of about 200 V can be measured (a) directly by a D.C. potentiometer (b) a D.C. potentiometer in conjunction with a volt ratio box (c) a D.C. potentiometer in conjunction with a known resistance (d) none of the above Ans: b 54. A direct current can be measured by (a) a D.C. potentiometer directly (b) a D.C. potentiometer in conjunction with a standard resistance (c) a D.C. potentiometer in conjunction with a volt ratio box (d) none of the above Ans: b 55. To measure a resistance with the help of a potentiometer it is (a) necessary to standardise the potentiometer (b) not necessary to standardise the potentiometer (c) necessary to use a volt ratio box in conjunction with the potentiometer(d) none of the above Ans: b 56. A phase shifting transformer is used in conjunction with (a) D.C. potentiometer (b) Drysdale potentiometer (c) A.C. co-ordinate potentiometer (d) Crompton potentiometer Ans: b
57. Basically a potentiometer is a device for (a) comparing two voltages (b) measuring a current (c) comparing two currents (d) measuring a voltage (e) none of the above Ans: a 58. In order to achieve high accuracy, the slide wire of a potentiometer should be (a) as long as possible (b) as short as possible (c) neither too small not too large (d) very thick Ans: a 59. To measure an A. C. voltage by using an A.C. potentiometer, it is desirable that the supply for the potentiometer in taken (a) from a source which is not the same as the unknown voltage (b) from a battery (c) from the same source as the unknown voltage (d) any of the above Ans: c 60. The stator of phase shifting transformer for use in conjunction with an A.C. potentiometer usually has a (a) single-phase winding (b) two-phase winding (c) three-phase winding (d) any of the above Ans: b 61. In an AC. co-ordinate potentiometer, the currents in the phase and quadrature potentiometer are adjusted to be (a) out of phase by 90° (b) out of phase by 60° (c) out of phase by 30° (d) out of phase by 0° (e) out of phase by 180° Ans: a 62. A universal RLC bridge uses (a) Maxwell bridge configuration for measurement of inductance and De Santas bridge for measurement of capacitance (b) Maxwell Wein bridge for measurement of inductance and modified De Santy's bridge for measurement of capacitance (c) Maxwell Wein bridge for measurement of inductance and Wein bridge for measurement of capacitance (d) Any of the above.Ans: b 63. For measurements on high voltage capacitors, the suitable bridge is (a) Wein bridge (b) Modified De Santy's bridge (c) Schering bridge (d) Any of the above (e) None of the above Ans: c
64. In an Anderson bridge, the unknown inductance is measured in terms of (a) known inductance and resistance (b) known capacitance and resistance (c) known resistance (d) known inductance Ans: b 65. Wagner earthing device is used to eliminate errors due to (a) electrostatic coupling (b) electromagnetic coupling (c) both (a) and (b) (d) none of the above Ans: a 66. For measurement of mutual inductance we can use (a) Anderson bridge (b) Maxwell's bridge (c) Heaviside bridge (d) Any of the above Ans: c 67. For measurement of inductance having high value, we should use (a) Maxwell's bridge (b) Maxwell Wein bridge (c) Hay's bridge (d) Any of the above Ans: c 68. If the current in a capacitor leads the voltage by 80°, the loss angle of the capacitor is (a) 10° (b) 80° (c) 120° (d) 170° Ans: a 69. In a Schering bridge the potential of the detector above earth potential is (a) a few volts only (b) 1 kV (c) 5 kV (d) 10 kV Ans: a 70. To avoid the effect of stray magnetic field in A.C. bridges we can use (a) Magnetic screening (b) Wagner earthing device (c) Wave filters (d) any of the above Ans: a 71. If an inductance is connected in one arm of bridge and resistances in the remaining three arms (a) the bridge can always be balanced (b) the bridge cannot be balanced (c) the bridge can be balanced if the resistances have some specific values Ans: b
72. A power factor meter has (a) one current circuit and two pres¬sure circuits (b) one current circuit and one pressure circuit (c) two current circuits and one pres¬sure circuit (d) none of the above Ans: a 73. The two pressure coils of a single phase power factor meter have (a) the same dimensions and the same number of turns (b) the same dimension but different number of turns (c) the same number of turns but different dimensions (d) none of the above Ans: a 74. In a single phase power factor meter the phase difference between the currents in the two pressure coils is (a) exactly 0° (b) approximately 0° (c) exactly 90° (d) approximately 90° Ans: c 75. In a dynamometer 3-phase power factor meter, the planes of the two moving coils are at (a) 0° (b) 60° (c) 90° (d) 120° Ans: d 76. In a vibrating reed frequency meter the natural frequencies of two adjacent reeds have a difference of (a) 0.1 Hz (b) 0.25 Hz (c) 0.5 Hz (d) 1.5 Hz Ans: c 77. In a Weston frequency meter, the magnetic axes of the two fixed coils are (a) parallel (b) perpendicular (c) inclined at 60° (d) inclined at 120° Ans: b 78. A Weston frequency meter is (a) moving coil instrument (b) moving iron instrument (c) dynamometer instrument (d) none of the above Ans: b 79. A Weston synchronoscope is a (a) moving coil instrument (b) moving iron instrument (c) dynamometer instrument (d) none of the above Ans: c 80. In a Weston synchronoscope, the fixed coils are connected across (a) bus-bars (b) incoming alternator (c) a lamp (d) none of the above Ans: b
81. In Weston synchronoscope the moving coil is connected across (a) bus-bars (b) incoming alternator (c) fixed coils (d) any of the above Ans: a 82. The power factor of a single phase load can be calculated if the instruments available are (a) one voltmeter and one ammeter (b) one voltmeter, one ammetqr and one wattmeter (c) one voltmeter, one ammeter and one energy meter (d) any of the above Ans: b 83. The desirable static characteristics of a measuring system are (a) accuracy and reproducibility (b) accuracy, sensitivity and reproducibility (c) drift and dead zone (d) static error Ans: b 84. The ratio of maximum displacement deviation to full scale deviation of the instrument is called (a) static sensitivity (b) dynamic deviation (c) linearity (d) precision or accuracy Ans: c 85. Systematic errors are (a) instrumental errors (b) environmental errors (c) observational errors (d) all of the above Ans: d 86. Standard resistor is made from (a) Platinum (b) maganin (c) silver (d) nichrome Ans: b 87. Commonly used standard capacitor is (a) spherical type (b) concentric cylindrical type (c) electrostatic type (d) multilayer parallel plate type Ans: b 88. Operating torques in analogue instruments are (a) Deflecting and control (b) Deflecting and damping (c) Deflecting, control and damping (d) vibration and balancing Ans: c 89. Commonly used instruments in power system measurement are (a) Induction (b) moving coil or iron (c) Rectifier (d) electrostatic Ans: a
90. Damping of the Ballistic galvanometer is made small to (a) Get first deflection large (b) Make the system oscillatory (c) Make the system critically damped (d) Get minimum overshoot Ans: a 91. If an instrument has cramped scale for larger values, then it follows (a) Square law (b) Logarithmic law (c) Uniform law (d) none of the above Ans: b 92. Volt box is a component to (a) extend voltage range (b) measure voltage (c) compare voltage in a box (d) none of the above Ans: a 93. E.m.f. of a Weston cell is accurately measured by (a) Electrostatic voltmeter (b) Hot wire voltmeter (c) Isothermal voltmeter (d) electrodynamic voltmeter Ans: a 94. The gravity controlled instrument has crowded scale because current is proportional to (a) balancing weight (b) deflection angle (c) sine of deflection angle Ans: c 95. A sensitive galvanometer produces large deflection for a (a) small value of current (b) large value of current (c) large value of power (d) large value of voitage (e) none of the above Ans: a 96. A multirangq instrument has (a) multiple shunt or series resistances inside the meter (b) multicoii arrangement (c) variable turns of coil (d) multi range meters inside the measurement system (e) any of the above Ans: a 97. The rectifier instrument is not free from (a) temperature error (b) wave shape error (c) frequency error (d) all of the above Ans: c
98. Alternating current is measured by (a) induction ammeter (b) permanent magnet type ammeter (c) electrostatic ammeter (d) moving iron repulsion type voltmeter Ans: a 99. Most sensitive galvanometer is (a) elastic galvanometer (b) vibration galvanometer (c) Duddlb galvanometer (d) spot ballistic galvanometer Ans: d 100. Instrument transformers are (a) potential transformers (b) current transformers (c) both (a) and (b) (d) power transformers Ans: c 101. An instrument transformer is used to extend the range of (a) induction instrument (b) electrostatic instrument (c) moving coil instrument (d) any of the above Ans: a 102. Wattmeter cannot be designed on the principle of (a) electrostatic instrument (b) thermocouple instrument (c) moving iron instrument (d) electrodynamic instrument Ans: c 103. In an energymeter braking torque is produced to (a) safe guard it against creep(b) brake the instrument (c) bring energy meter to stand still (d) maintain steady speed and equal to driving torque Ans: d 104. Various adjustments in an energy meter include (a) light load or friction (b) lag and creep (c) overload and voltage compensation (d) temperature compensation (e) all of the above Ans: e
105. The power of a n-phase circuit can be measured by using a minimum of (a) (n - 1) wattmeter elements (b) n wattmeter elements (c) (n + 1) wattmeter elements (d) 2n wattmeter elements Ans: a 106. Two holes in the disc of energymeter are drilled at the opposite sides of the spindle to (a) improve its ventilation (b) eliminate creeping at no load (c) increase its deflecting torque (d) increase its braking tcrque Ans: b 107. Which of the following is measured by using a vector voltmeter? (a) Amplifier gain and phase shift (b) Filler transfer functions (c) Complex insersion loss (d) All of the above Ans: d 108. The principle on which vector voltmeter is based is (a) that it works on the principle of complex variation (b) that it measures the response of linear ramp voltage (c) same as digital meter (d) that it measures the amplitude of a single at two points and at the same time measures their phase difference Ans: d 109. To measure radio frequency, the suitable frequency meter is (a) Weston frequency meter (b) reed vibrator frequency meter (c) hetrodyne frequency meter (d) electrical resonance frequency meter Ans: c
D.C. Generators 1. Laminations of core are generally made of (a) case iron (b) carbon (c) silicon steel (d) stainless steel Ans: c 2. Which of the following could be lamina-proximately the thickness of lamina-tions of a D.C. machine ? (a) 0.005 mm (b) 0.05 mm (c) 0.5 m (d) 5 m Ans: c 3. The armature of D.C. generator is laminated to (a) reduce the bulk (b) provide the bulk (c) insulate the core (d) reduce eddy current loss Ans: d 4. The resistance of armature winding depends on (a) length of conductor (b) cross-sectional area of the conductor (c) number of conductors (d) all of the above Ans: d 5. The field coils of D.C. generator are usually made of (a) mica (b) copper (c) cast iron (d) carbon Ans: b 6. The commutator segments are connected to the armature conductors by means FOLLOWERSof (a) copper lugs (b) resistance wires (c) insulation pads (d) brazing Ans: a 7. In a commutator
(a) copper is harder than mica (b) mica and copper are equally hard (c) mica is harder than copper (d) none of the above Ans: c 8. In D.C. generators the pole shoes are fastened to the pole core by (a) rivets (b) counter sunk screws (c) brazing (d) welding Ans: b 9. According to Fleming's right-hand rule for finding the direction of induced e.m.f., when middle finger points in the direction of induced e.m.f., forefinger will point in the direction of (a) motion of conductor (b) lines of force (c) either of the above (d) none of the above Ans: b 10. Fleming's right-hand rule regarding direction of induced e.m.f., correlates (a) magnetic flux, direction of current flow and resultant force (b) magnetic flux, direction of motion and the direction of e.m.f. induced (c) magnetic field strength, induced voltage and current (d) magnetic flux, direction of force and direction of motion of conductor Ans: b 11. While applying Fleming's right-hand rule to And the direction of induced e.m.f., the thumb points towards (a) direction of induced e.m.f. (b) direction of flux (c) direction of motion of the conductor if forefinger points in the direction of generated e.m.f. (d) direction of motion of conductor, if forefinger points along the lines of flux Ans: d 12. The bearings used to support the rotor shafts are generally (a) ball bearings (b) bush bearings (c) magnetic bearmgs (d) needle bearings Ans: a 13. In D.C. generators, the cause of rapid brush wear may be
(a) severe sparking (b) rough commutator surface (c) imperfect contact (d) any of the above Ans: d 14. In lap winding, the number of brushes is always (a) double the number of poles (b) same as the number of poles (c) half the number of poles (d) two Ans: b 15. For a D.C. generator when the number of poles and the number of armature conductors is fixed, then which winding will give the higher e.m.f. ? (a) Lap winding (b) Wave winding (c) Either of (a) and (b) above (d) Depends on other features of design Ans: b 16. In a four-pole D.C. machine (a) all the four poles are north poles (b) alternate poles are north and south (c) all the four poles are south poles (d) two north poles follow two south poles Ans: b 17. Copper brushes in D.C. machine are used (a) where low voltage and high currents are involved (b) where high voltage and small cur-rents are involved (c) in both of the above cases (d) in none of the above cases Ans: a 18. A separately excited generator as compared to a self-excited generator (a) is amenable to better voltage con-trol (b) is more stable (c) has exciting current independent of load current (d) has all above features Ans: d 19. In case of D.C. machines, mechanical losses are primary function of (a) current (b) voltage (c) speed
(d) none of above Ans: c 20. Iron losses in a D.C. machine are independent of variations in (a) speed (b) load (c) voltage (d) speed and voltage Ans: b 21. In D.C. generators, current to the external circuit from armature is given through (a) commutator (b) solid connection (c) slip rings (d) none of above Ans: a 23. Brushes of D.C. machines are made of (a) carbon (b) soft copper (c) hard copper (d) all of above Ans: a 24. If B is the flux density, I the length of conductor and v the velocity of conductor, then induced e.m.f. is given by (a)Blv (b)Blv2 (c)Bl2v (d)Bl2v2 Ans: a 25. In case of a 4-pole D.C. generator provided with a two layer lap winding with sixteen coils, the pole pitch will be (a) 4 (b) 8 (c) 16 (d) 32 Ans: b 26. The material for commutator brushes is generally (a) mica (b) copper (c) cast iron
(d) carbon Ans: d 27. The insulating material used between the commutator segments is normally (a) graphite (b) paper (c) mica (d) insulating varnish Ans: c 28. In D.C. generators, the brushes on commutator remain in contact with conductors which (a) lie under south pole (b) lie under north pole (c) lie under interpolar region (d) are farthest from the poles Ans: c 29. If brushes of a D.C. generator are moved in order to bring these brushes in magnetic neutral axis, there will be (a) demagnetisation only (b) cross magnetisation as well as magnetisation (c) crossmagnetisation as well as demagnetising (d) cross magnetisation only Ans: c 30. Armature reaction of an unsaturated D.C. machine is (a) crossmagnetising (b) demagnetising (c) magnetising (d) none of above Ans: a 31. D.C. generators are connected to the busbars or disconnected from them only under the floating condition (a) to avoid sudden loading of the primemover (b) to avoid mechanicaljerk to the shaft (c) to avoid burning of switch contacts (d) all above Ans: d 32. Eddy currents are induced in the pole shoes of a D.C. machine due to (a) oscillating magnetic field (b) pulsating magnetic flux (c) relative rotation between field and armature
(d) all above Ans: c 33. In a D.C. machine, short-circuited field coil will result in (a) odour of barning insulation (b) unbalanced magnetic pull producing vibrations (c) reduction of generated voltage for which excitation has to be increased to maintain the voltage (d) all above Ans: 34. Equilizer rings are required in case armature is (a) wave wound (b) lap wound (c) delta wound (d) duplex wound Ans: b 35. Welding generator will have (a) lap winding (b) wave winding (c) delta winding (d) duplex wave winding Ans: a 36. In case of D.C. machine winding, number of commutator segments is equal to (a) number of armature coils (b) number of armature coil sides (c) number of armature conductors (d) number of armature turns Ans: a 37. For a D.C. machines laboratory following type of D.C. supply will be suitable (a) rotary converter (b) mercury are rectifier (c) induction motor D.C. generator set (d) synchronous motor D.C. generator set Ans: c 38. The function of pole shoes in the case of D.C. machine is (a) to reduce the reluctance of the magnetic path (b) to spread out the flux to achieve uniform flux density (c) to support the field coil (d) to discharge all the above functionsAns: d 39. In the case of lap winding resultant pitch is
(a) multiplication of front and back pitches (b) division of front pitch by back pitch (c) sum of front and back pitches (d) difference of front and back pitches Ans: d 40. A D.C. welding generator has (a) lap winding (b) wave moving (c) duplex winding (d) any of the above Ans: a 41. Which of the following statement about D.C. generators is false ? (a) Compensating winding in a D.C. machine helps in commutation (b) In a D. C. generator interpoles winding is connected in series with the armature winding (c) Back pitch and front pitch are both odd and approximately equal to the pole pitch (d) Equilizing bus bars are used with parallel running of D.C. shunt generators Ans: d 42. The demagnetising component of armature reaction in a D.C. generator (a) reduces generator e.m.f. (b) increases armature speed (c) reduces interpoles flux density (d) results in sparking trouble Ans: a 43. Magnetic field in a D.C. generator is produced by (a) electromagnets (b) permanent magnets (c) both (a) and (b) (d) none of the above Ans: a 44. The number of brushes in a commutator depends on (a) speed of armature (b) type of winding (c) voltage (d) amount of current to be collected Ans: d 45. Compensating windings are used in D.C. generators (a) mainly to reduce the eddy currents by providing local short-circuits (b) to provide path for the circulation of cooling air (c) to neutralise the cross-magnetising effect of the armature reaction
(d) none of the above Ans: c 46. Which of the following components of a D.C, generator plays vital role for providing direct current of a D.C. generator ? (a) Dummy coils (b) Commutator (c) Eye bolt (d) Equilizer rings Ans: b 47. In a D.C. generator the ripples in the direct e.m.f. generated are reduced by (a) using conductor of annealed copper (b) using commutator with large number of segments (c) using carbon brushes of superior quality (d) using equiliser rings Ans: c 48. In D.C. generators, lap winding is used for (a) high voltage, high current (b) low voltage, high current (c) high voltage, low current (d) low voltage, low current Ans: b 49. Two generators A and B have 6-poles each. Generator A has wave wound armature while generator B has lap wound armature. The ratio of the induced e.m.f. is generator A and B will be (a) 2 : 3 (b) 3 : 1 (c) 3 : 2 (d) 1 : 3 Ans: b 50. The voltage drop for which of the following types of brush can be expected to be least ? (a) Graphite brushes (b) Carbon brushes (c) Metal graphite brushes (d) None of the above Ans: c
51. The e.m.f. generated by a shunt wound D.C. generator isE. Now while pole flux remains constant, if the speed of the generator is doubled, the e.m.f. generated will be (a) E/2 (b) 2E (c) slightly less than E (d) E Ans: b 52. In a D.C. generator the actual flux distribution depends upon (a) size of air gap (b) shape of the pole shoe (c) clearance between tips of the ad¬jacent pole shoes (d) all of the above Ans: 53. The armature core of a D.C. generator is usually made of (a) silicon steel (b) copper (c) non-ferrous material (d) cast-iron Ans: a 9.63. Satisfactory commutation of D.C. machines requires (a) brushes should be of proper grade and size (b) brushes should smoothly run in the holders (c) smooth, concentric commutator properly undercut (d) all of the above Ans: d 54. Open circuited armature coil of a D.C. machine is (a) identified by the scarring of the commutator segment to which open circuited coil is connected (b) indicated by a spark completely around the commutator (c) both (a) and (b) (d) none of the above Ans: c 55. In a D.C. machine, fractional pitch winding is used (a) to increase the generated voltage (b) to reduce sparking (c) to save the copper because of shorter end connections (d) due to (b) and (c) above Ans:
56. For the parallel operation of two or more D.C. compound generators, we should ensure that (a) voltage of the incoming generator should be same as that of bus bar (b) polarity of incoming generator should be same as that of bus bar (c) all the series fields should be run in parallel by means of equilizer connection (d) series fields of all generators should be either on positive side or negative side of the armature (e) all conditions mentioned above should be satisfied Ans: d 57. D.C. series generator is used (a) to supply traction load (b) to supply industrial load at constant voltage (c) voltage at the toad end of the feeder (d) for none of the above purpose Ans: c 58. Following D.C. generator will be in a position to build up without any residual magnetism in the poles (a) series generator (b) shunt generator (c) compound generator (d) self-excited generator Ans: d 59. Interpole flux should be sufficient to (a) neutralise the commutating self induced e.m.f. (b) neutralise the armature reaction flux (c) neutralise both the armature reaction flux as well as commutating e.m.f. induced in the coil (d) perform none of the above functions Ans: c 60. D.C. generator generally preferred for charging automobile batteries is (a) series generator (b) shunt generator (c) long shunt compound generator (d) any of'the above Ans: c 61. In a D.C. generator the number of mechanical degrees and electrical degrees will be the same when(a) r.p.m. is more than 300
(b) r.p.m. is less than 300 (c) number of poles is 4 (d) number of poles is 2 Ans: d 62. Permeance is the reciprocal of (a) flux density (b) reluctance (c) ampere-turns (d) resistance Ans: b 63. In D.C. generators the polarity of the interpoles (a) is the same as that of the main pole ahead (b) is the same as that of the immediately preceding pole (c) is opposite to that of the main pole ahead (d) is neutral as these poles do not play part in generating e.m.f. Ans: a 64. The e.m.f. generated in a D.C. generator is directly proportional to (a) flux/pole (b) speed of armature (c) number of poles (d) all of the above Ans: b 65. In a D.C. generator the magnetic neutral axis coincides with the geometrical neutral axis, when (a) there is no load on|he generator (b) the generator runs on full load (c) the generator runs on overload (d) the generator runs on designed speed Ans: a 66. In a D.C. generator in order to reduce sparking at brushes, the self-induced e.m.f. in the coil is neutralised by all of the following except (a) interpoles (b) dummy coils (c) compensating winding (d) shifting of axis of brushes Ans: b 67. In D.C. generators on no-load, the air gap flux distribution in space is (a) sinusoidal
(b) triangular (c) pulsating (d) flat topped Ans: d 68. A shunt generator running at 1000 r.p.m. has generated e.m.f. as 200 V. If the speed increases to 1200 r.p.m., the generated e.m.f. will be nearly (a) 150 V (b) 175 V (c) 240 V (d) 290 V Ans: c69. The purpose of providing dummy coils in a generator is (a) to reduce eddy current losses (b) to enhance flux density (c) to amplify voltage (d) to provide mechanical balance for the rotor Ans: d 70. In a shunt generator the voltage build up is generally restricted by (a) speed limitation (b) armature heating (c) insulation restrictions (d) saturation of iron Ans: 71. If a D.C. generator fails to build up the probable cause could not be (a) imperfect brush contact (b) field resistance less than the critical resistance (c) no residual magnetism in the generator (d) faulty shunt connections tending to reduce the residual magnetism Ans: b 72. Flashing the field of D.C. generator means (a) neutralising residual magnetism (b) creating residual magnetism by a D.C. source (c) making the magnetic losses of forces parallel (d) increasing flux density by adding extra turns of windings on poles Ans: b 73. The e.m.f. induced in the armature of a shunt generator is 600 V. The armature resistance is 0.1 ohm. If the armature current is 200 A, the terminal voltage will be (a) 640 V (b) 620 V (c) 600 V
(d) 580 V Ans: d 74. In a D.C. generator the critical resistance refers to the resistance of (a) brushes (b) field (c) armature (d) load Ans: b 75. To achieve sparkless commutation brushes of a D.C. generator are rockedm ahead so as to bring them (a) just ahead of magnetic neutral axis (b) in magnetic neutral axis (c) just behind the magnetic neutral axis Ans: a 76. Armature coil is short circuited by brushes when it lies (a) along neutral axis (b) along field axis (c) in any of the above positions (d) in none of the above positions Ans: a 77. A cumulatively compounded long shunt generator when operating as a motor would be(a) cumulatively compounded long shunt (b) differentially compounded long shunt (c) cumulatively compounded short shunt (d) differentially compounded short shunt Ans: b 78. To avoid formation of grooves in the commutator of a D.C. machine (a) the brushes of opposite polarity should track each other (b) the brushes of same polarity should track each other (c) brush position has no effect on the commutator grooving Ans: a 79. The following constitute short-circuit in the armature winding. (a) Insulation failure between two com-mutator bars (6) Insulation failure between two turns of a coil (c) Two of more turns of the same coil getting grounded (d) All of the above Ans: d 80. The rapid wear of brushes takes place due to (a) abrasion from dust
(b) excessive spring pressure (c) rough commutator bars (d) high mica insulation between com-mutation bars (e) all of the above factors Ans: e 81. Number of tappings for each equilizer ring is equal to (a) number of pole pairs (b) number of poles (c) number of parallel paths (d) number of commutator segments Ans: a 82. A D.C. generator can be considered as (a) rectifier (b) primemover (c) rotating amplifier (d) power pump Ans: c 83. In any rotating machine that part which houses the conductors and in which e.m.f. induced is to be utilised is called (a) rotor (b) stator (c) field (d) armature Ans: d 84. In a D.C. machine stray loss is the sum of (a) total copper loss and mechanical loss (b) armature copper loss and iron loss (c) shunt field copper loss and mechanical loss (d) iron loss and mechanical loss Ans: d 85. Lap winding is composed of (a) any even number of conductors(b) any odd number of conductors (c) that even number which is exact multiple of poles + 2 (d) that even number which is exact multiple of poles Ans: a 86. In a D.C. generator in case the resistance of the field winding is increased, then output voltage will (a) increase
(b) decrease (c) remain unaffected (d) fluctuate heavily Ans: b 87. An exciter for a turbo generator is a (a) separately excited generator (b) shunt generator (c) series generator (d) compound generator Ans: b 88. In case of a flat compounded generator (a) voltage generated is less than the rated voltage (b) generated voltage is proportional to the load on the generator (c) voltage remains constant irrespec¬tive of the load (d) speed varies in proportion to the load on the generator Ans: c 89. Which of the following generator will have negligible terminal voltage while running on noload ? (a) Series generator (b) Shunt generator (c) Compound generator (d) Separately excited generator Ans: a 90. Which of the following D.C. generators will be in a position to build up without any residual magnetism in the poles ? (a) Series generator (b) Shunt generator (c) Compound generator (d) None of the above Ans: d 91. In over compounded generator, full load terminal voltage is (a) almost zero (b) less than noload terminal voltage (c) more than noload terminal voltage (d) equal to no-load terminal voltage Ans: c 92. In a level compounded D.C. generator, full load terminal voltage is (a) negligibly low (b) equal to no-load terminal voltage
(c) more than no-load terminal voltage (d) less than no-load terminal voltage Ans: b 93. The terminal voltage of a D.C. shunt generator drops on load because of all of thefollowing reasons except (a) armature reaction (b) armature resistance drop (c) field weakening due to armature reaction and armature (d) commutation Ans: d 94. In a D.C. generator (a) external resistance = internal char-acteristic - armature reaction (b) internal characteristic = magnetisation characteristic - ohmic drop (c) external characteristic = magnetisation characteristic - ohmic drop - armature reaction (d) magnetisation characteristic = external characteristic Ans: c 95. A sinusoidal voltage of 5 Hz is applied to the field of a shunt generator. The armature voltage wave (a) will be zero (b) will be of 5 Hz (c) willbeof5xiVHz (d) will be of v Hz 5 Ans: b 96. A 220 V D.C. generator is run at full speed without any excitation. The open circuit voltage will be (a) zero (b) about 2 V (c) about 50 V (d) 220 V Ans: b 97. In a separately excited generator supplying rated load the armature reaction , (a) is always present (b) is always absent (c) may be sometimes present (d) none of the above Ans: a
98. If residual magnetism is present in a D.C. generator, the induced e.m.f. at zero speed will be (a) zero (b) small (c) the same as rated voltage (d) high Ans: a 99. Armature reaction in a generator results in (a) demagnetisation of leading pole tip and magnetisation of trailing pole tip (b) demagnetisation of trailing pole tip and magnetisation of leading pole tip (c) damagnetising the centre of all poles (d) magnetising the centre of all poles Ans: a 100. Following energized winding of a D.C. machine should not be opened as it would produce high inductive voltage which may be dangerous to personnel and may cause its own insulation failure. (a) Series field (b) Compensating field (c) Inter pole field(d) Shunt field Ans: d 101. Wave winding is composed of (a) any even number of conductors (b) any odd number of conductors (c) that even number which is exact multiple of poles + 2 (d) that even number which is exact multiple of poles Ans: c 102. The critical resistance of the D.C. generator is the resistance of (a) field (b) brushes (c) armature (d) load Ans: a 103. When two D.C. series generators are running in parallel, an equilizer bar is used (a) to increase the speed and hence generated e.m.f. (b) to increase the series flux (c) so that two similar machines will pass approximately equal currents to the load (d) to reduce the combined effect of ar-mature reaction of both machines
Ans: c 104. Which of the following generating machine will offer constant voltage on all loads ? (a) Self-excited generator (b) Separately excited generator (c) Level compounded generator . (d) All of the above Ans: c 105. Which of the following generators will be preferred if they are required to be run in parallel ? (a) Shunt generators (b) Series generators (c) Compound generators (d) None of the above Ans: a 106. Two generators are running in parallel. One of the generators may run as motor for which of the following reasons ? (a) The direction of that generator is reversed (b) The speed of that generator is increased (c) The field of that generator is weakened (d) That generator takes large share of loads Ans: d 107. A D.C. generator works on the principle of (a) Lenz's law (b) Ohm's law (c) Faraday's law of electromagnetic induction (d) none of the above Ans: c 108. A series generator can self-excite (a) only if the load current is zero (b) only if the load current is not zero (c) irrespective of the value of load current(d) none of the above Ans: b 109. A shunt generator can self-excite (a) only if the resistance of the field circuit is less than critical value (b) only if the resistance of the field circuit is greater than critical value (c) irrespective of the value of the resis-tance in the field circuit Ans: a
110. The terminal voltage of a series generator is 150 V when the load current is 5 A. If the load current is increased to 10 A, the terminal voltage will be (a) 150 V (b) less than 150 V (c) greater than 150 V (d) none of the above Ans: c 111. The open circuit voltage of a compound generator is 250 V. At full load the terminal voltage (a) will be less than 250 V (b) will always be 250 V (c) may be greater or less than 250 V (d) none of the above Ans: c 112. Two D.C. shunt generators, each with armature resistance of 0.02 ohm and field resistance of 50 ohm run in parallel and supply a total current of 1000 amperes to the load circuit. If their e.m.fs. are 270 V and 265 V, their bus bar voltage will be (a) 270 V (b) 267.5 V (c) 265 V (d) 257.4 V Ans: b 113. The essential condition for parallel operation of two D.C. generators is that they have ' (a) same kW rating (b) the same operation r.p.m. (c) the same drooping voltage charac-teristics (d) same percentage regulation Ans: c 114. When two D.C. generators are running in parallel an equilizer bar is used (a) to increase the series flux (b) to increase the generated e.m.f. (c) to reduce the combined effect of ar-mature reaction of both the machines (d) so that the two identical machines will pass approximately equal currents to the load Ans: d 115. With a D.C. generator which of the following regulation is preferred ?
(a) 100% regulation (b) infinite regulation (c) 50% regulation (d) 1% regulation Ans: d 116. Which generator would you prefer for feeding long D.C. transmission lines ? (a) Series generator (b) Shunt generator(c) Over compound generator (d) Flat compound generator Ans: c 117. In a D.C. generator the critical resistance can be increased by (a) increasing its field resistance (b) decreasing its field resistance (c) increasing its speed (d) decreasing its speed Ans: c 118. The number of armature parallel paths in a two-pole D.C. generator having duplex lap winding is (a) 2 (b) 4 (c) 6 (d) 8 Ans: b 119. For both lap and wave windings, there are as many commutator bars as the number of (a) slots (b) armature conductors (c) winding elements (d) poles Ans: c 120. The series field of a short-shunt D.C. generator is excited by (a) external current (b) armature current (c) shunt current (d) load current Ans: d 121. As a result of armature reaction, the reduction in the total mutual air gap flux in a D.C. generator is approximately
(a) 40 percent (b) 25 percent (c) 10 percent (d) 5 percent Ans: d 122. Shunt generators are most suited for stable parallel operation because of their (a) rising voltage characteristics (b) identical voltage characteristics (c) drooping voltage characteristics (d) linear voltage characteristics Ans: c 123. The main factor which leads to unstable parallel operation of flat and over compounded generators is (a) their rising voltage characteristics (b) unequal number of turns in their series field windings (c) unequal speed regulation of their primemovers (d) unequal series field resistances Ans: a 124. If a self excited D.C. generator after being installed, fails to build up on its first trial run, the first thing to do is to(a) reverse the field connections (b) increase the field resistance (c) increase the speed of primemover (d) check armature insulation resis¬tance Ans: a
D.C Motors 1. No-load speed of which of the following motor will be highest ? (a) Shunt motor (b) Series motor (c) Cumulative compound motor (d) Differentiate compound motor Ans: b 2. The direction of rotation of a D.C. series motor can be changed by (a) interchanging supply terminals (b) interchanging field terminals (c) either of (a) and (b) above (d) None of the above Ans: b 3. Which of the following application requires high starting torque ?
(a) Lathe machine (b) Centrifugal pump (c) Locomotive (d) Air blower Ans: c 4. If a D.C. motor is to be selected for conveyors, which rriotor would be preferred ? (a) Series motor (b) Shunt motor (c) Differentially compound motor (d) Cumulative compound motor Ans: a 5. Which D.C. motor will be preferred for machine tools ? (a) Series motor (b) Shunt motor (c) Cumulative compound motor (d) Differential compound motor Ans: b 6. Differentially compound D.C. motors can find applications requiring (a) high starting torque (b) low starting torque (c) variable speed FOLLOWERS(d) frequent on-off cycles Ans: b 7. Which D.C. motor is preferred for elevators ? (a) Shunt motor (b) Series motor (c) Differential compound motor (d) Cumulative compound motor Ans: d 8. According to Fleming's left-hand rule, when the forefinger points in the direction of the field or flux, the middle finger will point in the direction of (a) current in the conductor aovtaat of conductor (c) resultant force on conductor (d) none of the above Ans: a 9. If the field of a D.C. shunt motor gets opened while motor is running (a) the speed of motor will be reduced % (b) the armature current will reduce (c) the motor will attain dangerously high speed 1 (d) the motor will continue to nuvat constant speed
Ans: c 10. Starters are used with D.C. motors because (a) these motors have high starting torque (b) these motors are not self-starting (c) back e.m.f. of these motors is zero initially (d) to restrict armature current as there is no back e.m.f. while starting Ans: d 11. In D.C. shunt motors as load is reduced (a) the speed will increase abruptly (b) the speed will increase in proportion to reduction in load (c) the speed will remain almost/constant (d) the speed will reduce Ans: c 12. A D.C. series motor is that which (a) has its field winding consisting of thick wire and less turns (b) has a poor torque (c) can be started easily without load (d) has almost constant speed Ans: a 13. For starting a D.C. motor a starter is required because (a) it limits the speed of the motor (b) it limits the starting current to a safe value (c) it starts the motor (d) none of the above Ans: b 14. The type of D.C. motor used for shears and punches is (a) shunt motor (b) series motor (c) differential compoutid D.C. motor (d) cumulative compound D.C. motor Ans: d 15. If a D.C. motor is connected across the A.C. supply it will (a) run at normal speed (b) not run (c) run at lower speed (d) burn due to heat produced in the field winding by .eddy currents Ans: d 16. To get the speed of D.C, motor below the normal without wastage of electrical energy is used.
(a) Ward Leonard control (b) rheostatic control (c) any of the above method (d) none of the above method Ans: a 17. When two D.C. series motors are connected in parallel, the resultant speed is (a) more than the normal speed (b) loss than the normal speed (c) normal speed (d) zero Ans: c 18. The speed of a D.C. shunt motor more than its full-load speed can be obtained by (a) decreasing the field current (b) increasing the field current (c) decreasing the armature current (d) increasing the armature current Ans: a 19. In a D.C. shunt motor, speed is (a) independent of armature current (b) directly proportional to the armature current (c) proportional to the square of the current (d) inversely proportional to the armature current Ans: a 20. A direct on line starter is used: for starting motors (a) iip to 5 H.P. (b) up to 10 H.P. (c) up to 15 H.P. (d) up to 20 H.P. Ans: a 21. What will happen if the back e.m.f. of a D.C. motor vanishes suddenly? (a) The motor will stop (b) The motor will continue to run (c) The armature may burn (d) The motor will run noisy Ans: c 22. In case of D.C. shunt motors the speed is dependent on back e.m.f. only because (a) back e.m.f. is equal to armature drop (b) armature drop is negligible (c) flux is proportional to armature current (d) flux is practically constant in D:C. shunt motors
Ans: d 23. In a D.C. shunt motor, under the conditions of maximum power, the current in the armature will be (a) almost negligible (b) rated full-load current (c) less than full-load current (d) more than full-load current Ans: d 24. These days D.C. motors are widely used in (a) pumping sets (b) air compressors (c) electric traction (d) machine shops Ans: c 25. By looking at which part of the motor, it can be easily confirmed that a particular motor is D.C. motor? (a) Frame (b) Shaft (c) Commutator (d) Stator Ans: c 26. In which of the following applications D.C. series motor is invariably tried? (a) Starter for a car (b) Drive for a water pump (c) Fan motor (d) Motor operation in A.C. or D.C. Ans: a 27. In D.C. machines fractional pitch winding is used (a) to improve cooling (b) to reduce copper losses (c) to increase the generated e.m.f. (d) to reduce the sparking Ans: d 28. A three point starter is considered suitable for (a) shunt motors (b) shunt as well as compound motors (c) shunt, compound and series motors (d) all D.C. motors Ans: b
29. In case-the conditions for maximum power for a D.C. motor are established, the efficiency of the motor will be (a) 100% (b) around 90% (c) anywhere between 75% and 90% (d) less than 50% Ans: d 30. The ratio of starting torque to full-load torque is least in case of (a) series motors (b) shunt motors (c) compound motors (d) none of the above Ans: b 32. In D.C. motor which of the following can sustain the maximum temperature rise? (a) Slip rings (b) Commutator (c) Field winding (d) Armature winding Ans: c 33. Which of the following law/rule can he used to determine the direction of rotation of D.C. motor ? (a) Lenz's law (b) Faraday's law (c) Coloumb's law (d) Fleming's left-hand rule Ans: d 34. Which of the following load normally needs starting torque more than the rated torque? (a) Blowers (b) Conveyors (c) Air compressors (d) Centrifugal pumps Ans: b 35. The starting resistance of a D.C. motor is generally (a) low (b) around 500 Q (c) 1000 Q (d) infinitely large Ans: a
36. The speed of a D.C. series motor is (a) proportional to the armature current (b) proportional to the square of the armature current (c) proportional to field current (d) inversely proportional to the armature current Ans: d 37. In a D.C. series motor, if the armature current is reduced by 50%, the torque of the motor will be equal to (a) 100% of the previous value (b) 50% of the previous value (c) 25% of the previous value (d) 10% of the previous value (e) none of the above Ans: c 38. The current drawn by the armature of D.C. motor is directly proportional to (a) the torque required (b) the speed of the motor (c) the voltage across the terminals (d) none of the above Ans: a 39. The power mentioned on the name plate of an electric motor indicates (a) the power drawn in kW (b) the power drawn in kVA (c) the gross power(d) the output power available at the shaft Ans: d 40. Which D.C. motor has got maximum self loading property? (a) Series motor (b) Shunt motor (c) Cumulatively compounded 'motor (d) Differentially compounded motor Ans: d 41. Which D.C. motor will be suitable alongwith flywheel for intermittent light and heavy loads? (a) Series motor (b) Shunt motor (c) Cumulatively compounded motor (d) Differentially compounded motor Ans: c
42. If a D.C. shunt motor is working at no load and if shunt field circuit suddenly opens (a) nothing will happen to th£ motor (b) this will make armature to take heavy current, possibly burning it (c) this will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses (d) motor will run at very slow speed Ans: c 43. D.C. series motors are used (a) where load is constant (b) where load changes frequently (c) where constant operating speed is needed (d) in none of the above situations. Ans: d 44. For the same H.P. rating and full load speed, following motor has poor starting torque (a) shunt (b) series (c) differentially compounded (d) cumulativelyc'ompounded Ans: c 45. In case of conductively compensated D.C. series motors, the compensating winding is provided (a) as separately wound unit (6) in parallel with armature winding (c) in series with armature winding (d) in parallel with field winding Ans: c 46. Sparking at the commutator of a D.C. motor may result in (a) damage to commutator segments (b) damage to commutator insulation (c) increased power consumption (d) all of the above Ans: d 47. Which of the following motor is preferred for operation in highly explosive atmosphere ? (a) Series motor (b) Shunt motor (c) Air motor(d) Battery operated motor Ans: c
48. If the supply voltage for a D.C. motor is increased, which of the following will decrease ? (a) Starting torque (b) Operating speed (c) Full-load current (d) All of the above Ans: c 49. Which one of the following is not the function of pole shoes in a D.C. machine ? (a) To reduce eddy current loss (b) To support the field coils (c) To spread out flux for better unifor-mity (d) To reduce the reluctance of the mag-netic path Ans: a 50. The mechanical power developed by a shunt motor will be maximum when the ratio of back e.m.f. to applied voltage is (a) 4.0 (b) 2.0 (c) 1.0 (d) 0.5 Ans: d 51. The condition for maximum power in case of D.C. motor is (a) back e.m.f. = 2 x supply voltage (b) back e.m.f. = | x supply voltage (c) supply voltage = | x back e.m.f. (d) supply voltage = back e.m.f. Ans: b 52. For which of the following applications a D.C. motor is preferred over an A.C. motor ? (a) Low speed operation (b) High speed operation (c) Variable speed operation (d) Fixed speed operation Ans: c 53. In D.C. machines the residual magnetism is of the order of (a) 2 to 3 per cent (6) 10 to 15 per cent (c) 20 to 25 per cent (d) 50 to 75 per cent Ans: a
54. Which D.C. motor is generally preferred for cranes and hoists ? (a) Series motor (b) Shunt motor (c) Cumulatively compounded motor (d) Differentially compounded motor Ans: a 55. Three point starter can be used for (a) series motor only (b) shunt motor only (c) compound motor only (d) both shunt and compound motorAns: d 56. Sparking, is discouraged in a D.C. motor because (a) it increases the input power con-sumption (b) commutator gets damaged (c) both (a) and (b) (d) none of the above Ans: b 57. Speed control by Ward Leonard method gives uniform speed variation (a) in one direction (b) in both directions (c) below normal speed only (d) above normal speed only. Ans: b 58. Flywheel is used with D.C. compound motor to reduce the peak demand by the motor, compound motor will have to be (a) level compounded (b) under compounded (c) cumulatively compounded (d) differentially compounded Ans: c 59. Following motor is used where high starting torque and wide speed range control is required. (a) Single phase capacitor start (b) Induction motor (c) Synchronous motor (d) D.C. motor (e) None of the above
Ans: d 60. In a differentially compounded D.C. motor, if shunt field suddenly opens (a) the motor will first stop and then run in opposite direction as series motor (b) the motor will work as series motor and run at slow speed in the same direction (c) the motor will work as series motor and run at high speed in the same direction (d) the motor will not work and come to stop Ans: a 61. Which of the following motor has the poorest speed regulation ? (a) Shunt motor (b) Series motor (c) Differential compound motor (d) Cumulative compound motor Ans: b 62. Buses, trains, trolleys, hoists, cranes require high starting torque and therefore make use of (a) D.C. series motor (b) D.C. shunt motor (c) induction motor (d) all of above motors Ans: a 63. As -the load is increased the speed of D.C. shunt motor will (a) reduce slightly (b) increase slightly(c) increase proportionately (d) remains unchanged Ans: a 64. The armature torque of the D.C. shunt motor is proportional to (a) field flux only (b) armature current only (c) both (a) and (b) (d) none of the above Ans: b 65. Which of the following method of speed control of D.C. machine will offer minimum efficiency ? (a) Voltage control method (b) Field control method (c) Armature control method (d) All above methods Ans: c 66. Usually wide and sensitive speed control is desired in case of (a) centrifugal pumps
(b) elevators (c) steel rolling mills (d) colliery winders Ans: d 67. The speed of a motor falls from 1100 r.p.m. at no-load to 1050 r.p.m. at rated load. The speed regulation of the motor is (a) 2.36% (6) 4.76% (c) 6.77% (d) 8.84% Ans: b 68. The armature voltage control of D.C. motor provides (a) constant torque drive (b) constant voltage drive (c) constant current drive (d) none of the above Ans: a 69. As there is no back e.m.f. at the instant of starting a D.C. motor, in order to prevent a heavy current from flowing though the armature circuit (a) a resistance is connected in series with armature (b) a resistance is connected parallel to the armature (c) armature is temporarily open circuited (d) a high value resistor is connected across the field winding Ans: a 70. The speed of a D.C. shunt motor can be increased by (a) increasing the resistance in armature circuit (b) increasing the resistance in field circuit (c) reducing the resistance in the field circuit (d) reducing the resistance in the armature circuit Ans: b 71. If I2 be the armature current, then speed of a D.C. shunt motor is (a) independent of Ia(b) proportional to la (c) varies as (Ia) (d) varies as la Ans: a 72. In case the back e.m.f. and the speed of a D.C. motor are doubled, the torque developed by the motor will (a) remain unchanged
(6) reduce to one-fourth value (c) increase four folds (d) be doubled Ans: a 73. At the instant of starting when a D.C. motor is put on supply, it behaves like (a) a highly resistive circuit (6) a low resistance circuit (c) a capacitive circuit (d) none of the above Ans: b 74. The speed of a D.C. motor can be varied by varying (a) field current (b) applied voltage (c) resistance in series with armature (d) any of the above Ans: d 75. Which one of the following is not necessarily the advantage of D.C. motors over A.C. motors ? (a) Low cost (b) Wide speed range (c) Stability (d) High starting torque. Ans: a 76. For a D.C. shunt motor if the excitation is changed (a) torque will remain constant (b) torque will change but power will remain constant (c) torque and power both will change (d) torque, power and speed, all will change Ans: b 77. Which motor has the poorest speed control? (a) Differentially compounded motor (b) Cumulatively compounded motor (c) Shunt motor (d) Series motor Ans: d 78. The plugging gives the (a) zero torque braking (b) smallest torque braking (c) highest torque braking
(d) none of the above Ans: c 79. The armature voltage control of D.C. motor provides (a) constant voltage drive(b) constant current drive (c) constant torque drive (d) none of the above Ans: c 80. If a D.C. motor designed for 40°C ambient temperature is to be used for 50°C ambient temperature, then the motor (a) of lower H.P. should be selected (6) of higher H.P. should be selected (c) can be used for 50°C ambient temperature also (d) is to be derated by a factor recom-mended by manufacturer and select the next higher H.P. motor Ans: d 81. If the terminals of armature of D.C. motor are interchanged, this action will offer following kind of braking (o) regenerative (b) plugging (c) dynamic braking (d) none of the above (e) any of the above Ans: b 82. Which of the following motors one will choose to drive the rotary compressor ? (a) D.C. shunt motor (b) D.C. series motor (c) Universal motor (d) Synchronous motor Ans: d 83. If the speed of a D.C. shunt motor is increased, the back e.m.f. of the motor will (a) increase (b) decrease (c) remain same (d) become zero Ans: a 84. Why are the D.C. motors preferred for traction applications ? (a) Torque and speed are inversely proportional to armature current
(b) Torque is proportional to armature current (c) Torque is proportional to square root of armature current (d) The speed is inversely proportional to the torque and the torque is proportional to square of armature current Ans: d 85. Which of the following motors is usually used in house-hold refrigerators ? (a) D.C. shunt motor (b) D.C. series motor (c) Single phase induction motor (split phase start or induction run motor) (d) Reluctance motor (e) Synchronous motor Ans: c 86. Which of the following motors is most suitable for signalling devices and many kinds of timers ? (a) D.C. shunt motor (b) D.C. series motor (c) Induction motor(d) Reluctance motor Ans: d 87. Which motor should not be started on no-load ? (a) Series motor (b) Shunt motor (c) Cumulatively compounded motor (d) Differentially compounded motor. Ans: a 88. Ward-Leonard control is basically a (a) voltage control method (b) field divertor method (c) field control method (d) armature resistance control method Ans: a 89. For constant torque drive which speed control method is preferred ? (a) Field control (b) Armature voltage control (c) Shunt armature control (d) Mechanical loading system Ans: b 90. In Ward-Leonard control the lower limit of speed is imposed by (a) residual magnetism of the generator (b) core losses of motor
(c) mechanical losses of motor and gen¬erator together (d) all of the above Ans: a 91. The main disadvantage of the Ward-Leonard control method is (a) high initial cost (b) high maintenance cost (c) low efficiency at Hght loads (d) all of the above Ans: d 92. Regenerative method of braking is based on that (a) back e.m.f. is less than the applied voltage (b) back e.m.f. is equal to the applied voltage (c) back e.m.f. of rotor is more than the applied voltage (d) none of the above Ans: b 93. The hysteresis loss in a D.C. machine least depends on (a) Frequency of magnetic reversals (b) Maximum value of flux density (c) Volume and grade of iron (d) Rate of flow of ventilating air Ans: d 94. In a D.C. generator all of the following could be the effects of iron losses except (a) Loss of efficiency (b) Excessive heating of core (c) Increase in terminal voltage (d) Rise in temperature of ventilating air Ans: c95. The losses occurring in a D.C. generator are given below. Which loss is likely to have highest proportion at rated load of the generator ? (a) hysteresis loss (b) field copper loss (c) armature copper loss (d) eddy current loss Ans: c 96. Which of the following loss in a D.C. generator varies significantly with the load current ? (a) Field copper loss (b) Windage loss (c) Armature copper loss (d) None of the above
Ans: c 97. Torque developed by a D.C. motor depends upon (a) magnetic field (b) active length of the conductor (c) current flow through the conductors (d) number of conductors (e) radius of armature (f) all above factors Ans: f 98. D.C. shunt motors are used for driving (a) trains (b) cranes (c) hoists (d) machine tools Ans: d 99. In a manual shunt motor starter (a) over load relay is connected in series and no volt relay in parallel with the load (6) over load relay is connected in paral¬lel and no volt relay in series with the load (c) over load relay and no volt relay are both connected in series with the load (d) over load relay and no volt relay are both connected in parallel with the load Ans: a 100. Which of the following steps is likely to result in reduction of hysteresis loss in a D.C. generator ? (a) Providing laminations in armature core (b) Providing laminations in stator (c) Using non-magnetic material for frame (d) Using material of low hysteresis co-efficient for armature core material Ans: d 101. Which of the following loss in a D.C. generator is dissipated in the form of heat? (a) Mechanical loss (b) Core loss (c) Copper loss (d) All of the above Ans: d 102. Which of the following losses are significantly reduced by laminating the core of a D.C. generator ? (a) Hysteresis losses (b) Eddy current losses (c) Copper losses
(d) Windage losses Ans: b 103. The total losses in a well designed D.C. generator of 10 kW will be nearly (a) 100 W (b) 500 W (c) 1000 W (d) 1500 W Ans: b 104. The condition for maximum efficiency for a D.C. generator is (a) eddy current losses = stray losses (b) hysteresis losses = eddy current losses (c) copper losses = 0 (d) variable losses = constant losses Ans: d 105. D.C. generators are normally designed for maximum efficiency around (a) full-load (b) rated r.p.m. (c) rated voltage (d) all of the above Ans: a 106. In a D.C. generator, the iron losses mainly take place in (a) yoke (b) commutator (c) armature conductors (d) armature rotor Ans: d 107. D.C. generators are installed near the load centres to reduce (a) iron losses (b) line losses (c) sparking (d) corona losses Ans: b 108. The purpose of retardation test on D.C. shunt machines is to find out (a) stray losses (b) eddy current losses (c) field copper losses (d) windage losses Ans: a 109. Which of the following tests will be suitable for testing two similar D.C. series motors of
large capacity ? (a) Swinburne's test (b) Hopkinson's test (c) Field test (d) Brake test Ans: c 110. Hopkinson's test on D.C. machines is conducted at (a) no-load (b) part load (c) full-load(d) overload Ans: c 111. During rheostat braking of D.C. series motors (a) motor is run as a generator (b) motor is reversed in direction (c) motor is run at reduced speed Ans: a 112. For which types of D.C. motor, dynamic braking is generally used ? (a) Shunt motors (b) Series motors (c) Compound motors (d) All of the above Ans: d 113. Which method of braking is generally used in elevators ? (a) Plugging (b) Regenerative braking (c) Rheostatic braking (d) None of the above Ans: a 114. In variable speed motor (a) a stronger commutating field is needed at low speed than at high speed (b) a weaker commutating field is needed at low speed than at high speed (c) same commutating field is needed at low speed than at high speed (d) none of the above is correct Ans: b 115. When the armature of a D.C. motor rotates, e.m.f. induced is (a) self-induced e.m.f. (b) mutually induced e.m.f. (c) back e.m.f. (d) none of the above Ans: c
116. Where D.C. motor of H.P. 12 or more requires frequent starting, stopping, reversing and speed control (a) drum type controller is used (b) three point starter is used (c) four point starter is used (d) all above can be used Ans: a 117. If a D.C. shunt motor is working at full load and if shunt field circuit suddenly opens (a) this will make armature to take heavy current, possibly burning it (6) this will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses (c) nothing will happen to motor (d) motor will come to stop Ans: a 118. D.C. motor is to drive a load which has certain minimum value for most of the time and some peak value for short duration. We will select the (a) series motor (b) shunt motor(c) compound motor (d) any of the above Ans: a 119. D.C. motor is to a drive a load which is almost nil for certain part of the load cycle and peak value for short duration. We will select this (a) series motor (b) shunt motor (c) compound motor (d) any of the above Ans: c 120. Which D.C. motor has got maximum self relieving property ? (a) Series motor (6) Shunt motor (c) Cumulatively compounded motor (d) Differentially compounded motor Ans: a 121. In the D.C. motor the iron losses occur in (a) the field
(b) the armature (c) the brushes (d) the commutator Ans: b 122. The speed of a D.C. shunt motor is required to be more than full load speed. This is possible by (a) reducing the field current (b) decreasing the armature current (c) increasing the armature current (d) increasing the excitation current (e) none of the above methods Ans: a 123. One D.C. motor drives another D.C. motor. The second D.C. motor when excited and driven (a) runs as a generator (b) does not run as a generator (c) also runs as a motor comes to stop after sometime Ans: a
