Utilization of Electrical energy

ELECTRICAL ENGINEERING 

Some important mcq 

( UEE, illumination) 

1.Luminous flux is

   (a) the rate of energy radiation in the                form  of light waves. 

   (b) the part of light energy. radiated by              Sun  that is received on

   (c)measured in lux

2. Glare is caused due to

(a) excessive luminance

(b) excessive lighting contrast in the field of vision 

(c) either (a) or (b)

3. Unit of illumination is

(a) lumen

 (c) lux.

(b) lambert 

(d) steradians.

4. The illumination at a surface due to a      source of light placed at a distance d'       from the surface varies as 

   (a) 1/d²

   (b) l/d. 

   (c) d

   (d) d³

5.The illumination at various points             on    a horizontal surface illu-                        minated by     the same source                     varies as

 (a)   cos(θ)

 (b) cos(θ²)

 (c) cos(θ³)

 d) 1/cos(θ)

 6. Carbon arc lamps are commonly                  used  in

(a) cinema projectors.

 (b) domestic lighting

 (c) factory lighting

 (d) street lighting

7. For two filaments of same material         operating at the same tem perature,         the diameter and current through             filament are related by

       (a) diameter directly proportional to            current. 

   (b) diameter proportional to (current²)

   (c) diameter proportional to (current)⅔

   (d) none of these.

8.The melting point of tungsten is

(a) 3,400°C.

 (b) 2,800°C.

 (C) 2,600°C.

(d) 2,400C. 

9. The vacuum inside an incandescent              lamp is of the order of 

  (a) 10‐2 mm Hg.

 (b) 10‐⁴mmHg. 

  (c) 10‐⁷mm Hg.

(d) 10 ‐⁸mmHg.

1o. The rate of evaporation of Upon                  tungsten filament in a lamp                          depends  Upon  

  (a) exhaust tube diameter. 

  (b) glass shell diameter. 

   (e) vapour pressure inside. 

  (d) none of the above

11. Heat from the lamp filament is                 transmitted to the surrounding                   mainly through

 (a) circulation 

  (b) conduction

  (c) convection. 

   (d) radiation 

12. Which of the following material is            most commonly used for the                      filaments  in incandscent lamps ?

      (a) Tungsten 

      (b) Tantalum

     (c) Osmium 

     (d) Silver

13. A zero watt lamp consumes power of 

(a) zero watt.

 (b) 5-10 W.

(c) about 15 W. 

(d) about 25 W.

 14. The safe operating temperature of a        tungsten filament

(a) 1,000°C 

(b) 3,000°C. 

(c) 2,000°C: 

(d) 3,500°C

15. The output of a tungsten filament                 depends on 

     (a) size of the shell. 

      (b) size of the lamp

     (c) temperature of filament 

     (d) all of the above 

16. What percentage of the input energy         is radiated by filament lamps 

       (5) 60-70 per cent 

        (b) 40-50 per cent

       (c) 25 - 30 per cent.

        (d) 10-15 per cent.

 18. An electric bulb, when broken,                   produces bang It is on account of 

   (a) vacuum inside the bulb.

   (b) pressure inside is equal to that                      outside

   (c) pressure of air in the bulb 

     (d) none of the above. 

19. In an incandescent lamp, bird cage            filament is usually used in Vacuum            bulb so as to

    (a) increase the life span of the filament 

    (b) give uniform radiations

    (c) reduce the oxidation phenomenon 

    (d) reduce the convection loSSes.

20. Filament lamp at starting will take                 current

   (a) equal to its full running current 

   (b) more than its full running current

   (c) less than its full running current.

     (d) none of these 

21. Most affected parameter of a                      filament   lamp due to variation in            operating     voltage is 

    (a) life.

    (b) light output. 

    (c)luminous  efficiency 

   (d) wattage.

22. Which gas is sometimes used in                   filament lamps

(a) Nitrogen.

 (b) Argon

 (c) Curbon dioxide.

 (d) Krypton

23. Which of the following vapour/gas             will give yellow colour in a filamen             lamp ? 

     (a) Helium. 

    (b) Mercury. 

    (c) Magnesium. 

    (d) Sodium.

24. Magnesium vapour in a filament                  lamp    gives 

(a) green colour light.

 (by pink colour light 

(c) blue colour light. 

(d) white colour light.

25. The gas used in a gas-filled filament             lamp is

(a) helium

 (b) oxygen 

(c) nitrogen. 

(d) ozone. 

26. In filament lamps, coiled coil                         filaments are used in

(a) coloured lamps 

(b) gas-filled lamps:

(c) low wastage lamps. 

(d) higher wattage lamps. 

27. In electric discharge lamps, light is               produced by

 (a) magnetic effect of current.

 (b) heating effect of current. 

 (c) cathode ray emission

 (d) ionisation in a gas or vapour

 28. In electric discharge lamps for                     stabilization of are

(a) a choke is connected in series with the          supply

 (b) a variable resistance is connected in            series with the circuit 

(c) a condenser is connected across the            supply

Ac machine

Ac machine  , some  important mcq  

( 2018 EVEN,  polytechnic  5th sem)

1. The short-circuit characteristics of      an alternator is

      (a) Always linear

      (b) Always non-linea

     (0) Either (a) or (b)

     (d) None of the above 

2. 6-pole, 50 HZ 3-phase induction motor       is running at 950 rpm and has rotor           Cu-loss of 5 kw. Its rotor input is

    (a) 100 kw

       

     (b) 10 kw

    (c) 95 kw 

     (d) 5.3 kw

3. Alternator can be excited by

(a) A.C.

(b) None of these

(c) D.C.

(d) Both (a) and (b)

4. No. of slips-ring in a 3-phase                       synchronous motor will be

    (a) 0

    (b) 1

    (c) 2

     (d) 4

5.The power factor of an alternator is          determined by its 

   (b) Load

   (b)  Prime mover

    (c) load 

    (d) excitation 

6. A4-pole, 1200 rpm alternator will          generate emf at  

(a) 50 Hz
 (b) 40 Hz
 (c)  60 Hz
(d) 25 Hz

7. In an alternator the armature flux       helps the main field flux when the      load power factor is

 (a) Unity

 (b) zero lagging

 (c) 0.8 lagging 

(d) Zero leading

8. In an alternator damper winding are       used to

 (a) Reduce eddy current loss

(b) Prevent hunting

(c) Reduce armature reaction 

(d) None of these

9.The maximum possible speed at                 which  alternator can be driven to             generate 60 Hz and 4000 volts is

(a) 3600 rpm

(b) 3000 rpm

(c) 4000 rpm 

(d) 1500 rpm

10. In a 3-phase synchronous motor, the       magnitude of field  flux 

(a) Remains constant at all loads 

(b) Varies with load 

(c) Varies with speed 

(d) Varies with power factor

 11.When a synchronous motor is                    running at synchronous speed, the            damper winding produces 

 (a) Damping torque

 (6) Eddy current torque

(c) Torque adding the developed torque

(d) No torque

12. A 3-phase, 4 pole , 50 Hz induction              motor is    running at 1425 rpm                    while supplying full load. Its slip  is

      (a) 5%

       (b) 4% 

       (c) 3%

      (d) 10%

13. Rotating magnetic field is produced           in 

(a) 3 phase  induction  motor 

(b) dc series  motor 

(c) Ac series  motor 

(d) none of these

15 .The power factor of an induction               motor at full load  is around 

(a) Unity 

(b) 0.85 lagging

(c) 0.5 leading 

(d) 0.85 Leading 

15.A ceiling fan uses

(c) Cupacitor start motor

 (d ) Capacitor start capacitor run motor

(d) None of these

16. Stator of an induction motor is made         of 

(a) Carbon 

(b) Wood

(c) Silicon steel laminations

 (d) None of these 

17. The motor used in electric toys

(a) Capacitor start motor

 (c) Shaded pole motor

(c) shaded pole motor 

(d)  none of above 

18 .The short circuit characteristic of an        alternator is

(a) always  linear 

(b) Always  non linear 

(c) Either  A ans B 

(d) none  of  the  above 

19. Alternator are rated  in

(a) MW

(b) KVAR

(c) KWH 

(d)KWA

20.No of slips rings  in a 3 phase    synchronous  motor  will be 

(a) 0 

(b) 1 

(c) 2

(d) 4

Utilization of Electrical energy

         Some  important  questions 

(20 . Mcq for Electrical engineering              students ,  ILLUMINATION)

1. The filament of a GLS lamp is made      of

(a) aluminium. (c) carbon

(b) tungsten.     (d) copper

2.Which of the following is not the            GLS lamp of the standard rating ?

(a) 15 W  (b) 40 W  (c) 75 W  (d) 100 W. 

3. The luminous efficiency of GLS               lamps is normally in the range                of....lumens/watt

       (a) 100 to 150 

        (b) 75 to 100

         (c) 50 to 75

         (d) 10 to 18

4. Nitrogen or argon is filled in GLS           lamps so as to

 (a) retard evaporation of tungsten                       filament.

(b) improve efficiency

 c) change the colour of the light

(d) reduce the glare.

5. In case of frosted GLS lamps,                  frosting of shell is done by 

   (a) acid etching .

   (b) ammonia

    (c) ozone

   (d) salt water

6. In case of GLS lamps the increase         in   supply voltage reduces

  (a) power consumption 

  (b) lumens output

  (c) life: 

(d) efficiency

7.Sodium vapour lamp needs an               ionisation voltage of about 

(a) 5 V. 

(b) 20 V. 

(C) 50 V. 

(d) 100 V

8. The ignition voltage for a sodium           lamp is about

(a) 100-125 V 

(c) 300-400 V

(b) 200-240 V 

(d) 400-600 V

9. When a sodium vapour lamp is               switched on initially the colour is

  (a) red.

  (b) pink. 

  (c) yellow. 

  (d) blue.

10. The colour of light given out by a           sodium vapour discharge lamp is

(a) pink

 (b) bluish green  

(c) yellow. 

(d) blue. 

11.An auto transformer used with             sodium vapour lamp should have

(a) high step-up ratio

 (b) high leakage reactance.

 (c) high step-down resistance.

(d) high efficiency

12.Leak transformer in a sodium                vapour lamp initially provides

     (b) low voltage

     (a) high current

      (c) high voltage,

13. In a sodium vapour discharge                 lamp the neon gas 

(a) changes the colour of light,

(b) prevents Vapourization of filament,

 (c) acts as a shield around the filament,

(d) assists in developing enough heat to               vapourize the sodium 

Q

14.The capacitor is used in auto-                 transformer circuit of a sodium             vapour lamp in order to

(a) regulate discharge voltage

(b) improve the circuit power factor.

(c) control lamp illuminution level. 

(d) protect the lamp against overvoltage,

15.The sodium vapour lamp (a) is               only suitable for ac and so needs          choke control

(a) is only suitable for ac and so needs                choke  control 

(b) needs capacitor in its auto-transformer        circuit to improve the power factor              which is very low (about 0.3 lagging).

(C) comes up to its rated   output in                     approximately

(d) all of the above.

16. The luminous efficiency of a                  sodium vapour lamp is....lumens           per watt

 (a) 40-50

 (b) 50-100

 (c) 120-200 

 (d) 10-12

17. Phosphor zinc silicate produces            light of 

(a) pink colour.

(b) red colour.

(c) green colour

(d) yellow colour,

18. A mercury vapour lamp gives                light o

(a) pink colour 

(b) yellow colour 

(c) greenish-blue colour 

(d) red colour

19. High pressure mercury vapour              lamps 

(a) similar in construction to sodium                  vapour lamps:

(b) need 4 or 5 minutes to attain full                   brilliancy

 (c) are generally used for general                         industrial lighting

        yards, work areas, shoping centres etc.

 (d) all of the above

20.In high pressure mercury vapour          lamps

 (a) the main electrodes are made of                      tungsten wire in from of helix

(b) the choke is provided to limit the                 current to a safe value.

(e) in addition to two main electrodes a             starting (auxiliary) elec trode is                     connected through a high resistance

(d) all of the above.

Synchronous machine

  SOME IMPORTANT MCQ FOR  ELECTRICAL STUDENTS 

(20 mcq, synchronous machine) 

1. Alternator operates  on the 

  principle of 

(a) electromagnetic induction 

(b) self induction. 

(c) mutual  induction 

(d) self or mutual  induction 

2.The armature bof an alternator 

(a) is a stationary member 

(b) is revolving  member 

(c)  is the frame  

(d) consisting of the winding  into which            current is induced 

3. In morden  alternator, the rotating      part  is 

(a) field  system 

(b) armature 

(c) armature  as well as field system

(d) none of the above 

4.The current from the stator of an         alternator is taken  out the external     load circuit  through 

(a) slip rings   

(b) commentator segments  

(c) solid  connections 

(d) carbon  brushes 

5.An alternator  is . 

(a) a polyphase synchronous machine  

     operated with dc exciter

(b) a polyphase synchronous machine                operated with ac exciter

(c) a three phase  induction machine with           prime mover.

(d) any ac generator 

6. Which  type of alternator is used in       hydroelectric power stations ?

(a) Non salient pole alternator 

(b)Turbo generator 

(c) salient pole alternator 

(d) stream  turbine  alternator 

7. In a synchronous machine the,                stator frame is made of

(a) stainless steel 

(b) CRGOS

(c) cast iron 

(d) cast steel 

8. The stator core of a synchronous          machine is built up of   .................          laminations 

(a) stainless steel 

(b) silicone steel 

(c) cast iron  

(d) cast steel 

9. The slip rings employed in a 3                phase synchronous machine are            insulated for

(a) output  rated  voltage 

(b) low voltage 

(c) very  low  voltage 

(d) very high  voltage 

10. Hydro-generators are generally            employed to run at 

(a) 500

(b) 1,000

(c) 1,500

(d) 3,000

11. The salient pole rotors have 

(a) two or four projecting poles carrying            the field  coils 

(b) a large number of projecting poles                carrying the field coils 

(c) thick steel laminations riveted together       and fixed to the rotor by a dova-tail                joint 

(d) pole faces usually  provided with slots          for damper winding 

(e) all of the above  except  (a) 

12. Large  diameter  of salient pole            field  structure,  the pole  shoes              cover about... of pole pitch 

(a) it occupies  much  less space  

(b) it saves lot of copper in stator winding 

(c) it reduces weight of the motor 

(d) number  of conductors held  in large           circumference of rotor  is very large             and so they need  not be  long 

13. The stator of modern  alternator          are wound for...... phase group 

(a) 180⁰

(b) 120⁰

(c) 60⁰

(d) 240⁰

14. For a two layer  winding  the                  number  of stator slots  is equal            to the number  of 

(a) poles  

(b) conductor 

(c) coils  side

(d) coils 

15. The armature reaction effect in a        synchronous machine depends on

(a) load current  

(b) power  factor  of  the  load 

(c) speed of  machine  

(d) both  a and b 

16. A leading power factor load on an alternator implies that it's voltage regulation shall be

(a ) positive

(b) negative 

(c) zero 

(d) any of these 

17. A pony  motor is basically a 

(a) small  induction motor 

(d) dc series motor 

(c) dc shunt  motor 

(d) double  winding ac/dc motor 

18. When a synchronous motor is                 running at synchronous     speed          ,damper winding produces

(a) damping  torque 

(b) eddy current torque 

(c) torque  aiding the developed torque 

(d) no torque 

19. While  starting  synchronous                   motor its field winding should be 

(a) kept open 

(b) short circuited 

(c) connected to a  dc source 

(d) none  of the above 

20. which of the  following  motor is           not a synchronous motor ?

(b) Hysteresis 

(b) Repulsion 

(c) inductors 

(d) Reluctance 

Utilization of Electrical Energy

Some Important MCQ for Electrical Students

1. The basic elements of an electric         drive are 

(a) electric motor and the transmission              system .

(b) electric motor, the transmission and                  control system .

(c)  the transmission and control  system.

(d)  electric motor  and conversion equipment. 

2. Electric drive is becoming more and             more popular because 

(a)  it simple, clean, compact and reliable. 

(b)  it provides  easy  and smooth control,                 flexibility in layout ,easy starting and                   facility for remote control 

(c)  it is cheaper in initial   as well  as in                     maintenance  cost

(d)  all of the above 

  3. The main  drawback of electric  drive           is    that

(a)   it is  cumbersome  drive  

(b)   it is costlier in initial  as well as in    

         maintenance cost 

(c)  Electrical  power  supply  failure makes             the drive  standstill 

(d)  all of the above  

4. An existing  workshop  is  to be                    changed  over  from  an engine  drive to      an electric  drive  . The  type  of drive          likely  to be adopted  

(a) individual  drive  

(b) group  drive   

(c) multi-motor drive  

(d) any of the  above  

5. The  type  of drive used for a paper      mill requiring  constant  speed              operation  and flexibility  of                     control  is  

(a) group  drive 

(b) multi-motor 

(c) individual  drive  or multimulti-motor 

(d) individual  drive 

6. Introduction  of automation in production  of processes  has become  possible  only  because  of  use of 

(a) an electric  drive  

(b) group  drive  

(c) individual  drive or multi-motor drive 

(d) individual drive 

7. The selection of an electric  motor         is governed  by 

(a) nature of  load  to be handled 

(b) environment  conditions 

(c) nature  of electric  supply  available 

(d) all of the  above 

8. Dc motor are still preferred  for             use in

(a) Electrical  excavator, steel  mills  and            cranes 

(b) lathe and machine  tools  

(c) flour  mills  and jaw crushers 

(d) paper  industry 

9. The least  significant  electrical               characteristic  in selection  of                 electric  motor  flour  mills  is 

(a) starting  characteristics 

(b) breaking 

(C) running  characteristics  

(d) efficiency 

10. The least significant feature                     while  selecting  a motor  for                    centrifugal  pumps  is 

(a) speed  control 

(b) power  rating  of motor 

(c) operation  speed 

(d) starting  characteristic 

11. A typical  active  load  

(a) hoist  

(b) blower 

( c) pump 

( d) lathe 

12. An elevator  drive  is required  to       operate  in 

(a) one quadrant  

(b) two quadrant  

(c) three  quadrant 

(d) four quadrant 

13. Load  torque  constant  at all                  speeds is represented  by a 

(a) fan 

(b) compressor 

(c) centrifugal  pump  load  

14. The load  for which  the motor               always  starts  on load  is  

(a) fan motor  

(b) conveyor  motor  

(c) flour  mill motor 

(d) all of  the  above 

15.Belt conveyor  affer ...... starting           torque 

(a) high  

(b) medium 

(c) low 

(d) zero 

16. The travelling   speed of a crane             varies  from  

(a) 20 to 25m/s. 

(b) 10 to  20 m/s. 

(c) 1.0 to 2.5 m/s. 

(d) 0.2 to 1.0 m/s.

17. The diameter  of the motor  shaft            for an electric  motor  depends                upon  

(a) speed  only 

(b) power output 

(c) speed and power  output  

(d) speed , power  output  and  power                   factor 

18. When an electric  train  is moving         down  hill , the dc motor  will be            operate as a dc 

(a) series  motor  

(b) series  generator 

(c) shunt  motor 

(d) shunt  generator 

19. A dc series motor  is used for an             overhauling  load. It can work                stable  if 

(a) the armature is shunted  by a resistor 

(b) the field  winding  is reversed 

(c)  a resistor  is put in series  with the                  machine 

(d) a divertor is put across  the  field 

20.which motor should  not be used           for centrifugal  pump 

(a) series  motor