MCQ 

1)with the increases in field excitation of a dc generator , its generated emf

a) remain constant 

b) increases 

c) decreases 

d) increase up to a limit and then remain almost constant 


ANS:  increase up to a limit and then remain almost constant 

2) in a dc generator , lap winding is used for 


a) low current and low voltage ratting 

b) high current and low voltage ratting

c) high current and high voltage ratting 

d) low current and high voltage ratting


ANS:   high current and low voltage ratting


 3)in a dc generator , wave  winding is used for 


a) low current and low voltage ratting 

b) high current and low voltage ratting

c) high current and high voltage ratting 

d) low current and high voltage ratting

ANS :low current and high voltage ratting

4) the field coils of a DC generator are usually made of 


a) copper 

b) mica 

c) carbon 

d) cast iron


ANS: copper

5) which material is used for core construction of dc machine 


a) silicon steel 

b) carbon steel

c) nickel steel

d) all of the above 

ANS: silicon steel

6) commutators are used in dc machine to convert 


a) AC to DC 

b) high voltage DC to low voltage DC 

c) DC to AC 

d) all of the above 

ANS:  AC to DC 


7) in a generator , the electricity produced in a armature is 


a) DC 

b) AC

c) both a and b

d) none of the above


ANS: AC


8)DC generator works on the principle of production 


a) static induced emf 

b) dynamically induced emf 

c) both a and b 

d) none of the above 

ANS :  dynamically induced emf 


 10) generator works on the principle of production 


a) static induced emf 

b) dynamically induced emf 

c) both a and b 

d) none of the above 

ANS :  both a and b 

11)which machine are used for battery charging 

a) dc shunt  generator

b) dc series generator

c) compounded dc generator 

d) all of the above 


ANS :dc shunt generator

12) magnetic field in a dc generator is normally produced by


a) electromagnets 

b)permanent magnets 

c) both a and b 

none of the above 

ANS:  electromagnets 


13) in a dc machine , the eddy current losses occurs in 

a) field pole 

b) yoke 

c) commutating poles 

d) armature


ANS: armature 

14) armature reaction in dc generators will result in 

a) short circuit 

b) open circuit 

c) increase in slip

d)reduction in generated emf 


ANS: reduction in generated emf 


15) for the parallel operation , the generator normally preferred are


a) series generator 

b) shunt generator

c) compound generator 

d) all of the above


ANS: shunt generator  

16) the power factor of an alternator depends on the

a) speed of rotor 

b) core losses 

c) armature losses 

d) load

ANS : load

17) in an alternator voltage drop occurs in 


a) armature resistance , leakage reactance , armature reaction and earth connection

b)   armature resistance , leakage reactance , armature reaction 

c) armature resistance , leakage reactance 

d)  armature resistance 

ANS :  armature resistance , leakage reactance , armature reaction 

18) salient pole are generally used on

 a) low and medium speed prime movers 

b) medium speed prime movers only

c)  low speed prime movers only

d)  high speed prime movers only


ANS: low and  medium speed prime movers only

19) the frequency of voltage generated in an alternator depends on the 


a) number of pole 

b) rotative speed 

c) number of pole and rotative speed 

d) number of pole , rotative speed and type of winding


ANS :  number of pole and rotative speed 

20) the magnitude of various voltage drops that occur in an alternator , depends on


a) load current 

b) power factor X load current 

c) power factor of the load 

d) none of the above 

ANS ; load current 

21) the speed of alternator increase 


a) the frequency   increase 

b) the frequency decrease 

c) the frequency remain constant but power factor decrease 

d) none of the above


ANS: the frequency increase

22) the advantage of using short pitched winding in an alternator is that is 


a) suppresses the harmonics in generated emf 

b) reduced the total voltage around the armature coil 

c) saves the copper used winding 

d) improves cooling by better circulation of air 


ANS:  reduced the total voltage around the armature coil

23)the starting torque of  3 phase induction motor can be increased by increasing 


a) the rotor reactance 

b) the stator reactance 

c) the rotor resistance 

d) the stator resistance 


ANS: the rotor resistance  

24) the maximum torque in a 3 - phase induction motor occurs at a slip


a) R2/X2

b) X2/R2

c) R2²/X2

d) X2²/R2²

ANS: R2/X2

25) for the high starting torque , the three phase induction motor  is 

a) slip ring type

b) squirrel cage type 

c) deep bar squirrel cage type 

d) all of the above


ANS: slip ring type

26) the starting torque of a single  phase induction motor is 


a) low 

b) high 

c) zero 

d) none of the above 

ANS: zero

27) frequency of rotor current in induction motor is 
a) equal to supply frequency 

b) slip times supply frequency 

c) greater than supply frequency 

d) all of the above 

ANS :slip times supply frequency 

28) rotor copper loss of three phase induction motor is equal to the 


a) rotational loss 

b) stator loss

c) friction loss

d) slip time rotor input power 

ANS:  slip time rotor input power


29) the stator core of the induction motor is  made of 


a) laminated cast iron 

b) mild steel 

c) silicon steel stamping 

d) soft wood 


ANS:  silicon steel stamping

30) the effect of increasing the length of the air gap in an induction motor will increase 


a) power factor 

b) magnetizing current 

c) air gap flux 

d) speed

ANS:  magnetizing current 

31) the speed of induction motor 


a) decrease too much with the increase of load 

b) increase with increase load 

c)  decrease slightly with the increase of load

d) remain constant with the increasing of load 


ANS:  decrease slightly with the increase of load

32) the slip speed of an induction motor depends upon


a) supply voltage 

b) mechanical load 

c) eddy current 

d) armature current 


ANS: mechanical load 

33) if an induction machine is run at above synchronous speed , it is acts as 


a) at synchronous motor 

b) an induction generator 

c) an induction motor 

d) all of the above 


ANS:  an induction generator 

34) in a transformer operation , which quantity remain same

a) voltage

b) current

c) frequency

d) all of the above


ANS: frequency

35) magnetizing impedance of a transformer  is determined by

a) short circuit test 

b) open circuit test 

c) both a and b 

d) none of the above 

ANS: open circuit test 

36)the short circuit test of a transformer  gives information about  

a) core losses of the transformer 

b) copper losses of the transformer 

c) winding circuit impedance 

d) none of these 

ANS: copper losses of transformer 

37)the open circuit test of a transformer gives the information about  

a) core losses of the transformer 

b) copper losses of the transformer 

c) exciting current 

d) none of these 

ANS: core losses of the transformer 

38)in a step down transformer which one following statements is true 

a) number of secondary turns is less than primary turns  

b) number of secondary turns is more than primary turns

 c) secondary  power  is more than primary power

d)  secondary current  is less than primary current

ANS: number of secondary turns is less than primary turns

39) the leakage flux in a transformer depends upon the value of 

a)load current 

b)supply frequency 

c) mutual flux 

d)none of these 

ANS: load current 

40)core of transformer is laminated to reduce 

a) hysteresis loss

b) eddy current losses

c) copper losses

d) all of the above

ANS: eddy current losses

41) in a transformer , humming sound occurs due to 

a) oil

b) insulation 

c) magnetostriction

d) none of these 

ANS: magnetostriction

42) auto transformer is used in transmission  and distribution 

a) when operator is not available

b) when iron losses are not reduced 

c) when the transformer ratio is small

d) all of the above

ANS: when the transformer ratio is small

43) all day efficiency of a transformer is


a) equal to its power efficiency

b) less than its power efficiency

c)more than its power efficiency 

d) none of the above 

 ANS: less than its power efficiency

44) hysteresis losses  are directly proportional to the 

 a) square of frequency and flux density to the power 1.6

 b)frequency and flux density to the power 1.6

 c)square of frequency and flux density to the power square

 d) frequency and flux density to the power 

ANS: frequency and flux density to the power 1.6

45) eddy current losses  are directly proportional to the 

 a) square of frequency and flux density to the power 1.6

 b)frequency and flux density to the power 1.6

 c)square of frequency and flux density to the power square

 d) frequency and flux density to the power

 ANS: square of frequency and flux density to the power square

46) when the transformer is loaded , the secondary terminal voltage drop . that means load power factor is 

a) lagging 

b) leading

c) unity

d) zero


  ANS: lagging

47)which following losses remain  constant during  normal operation of transformer

a)core losses 

b)copper losses

c) stray losses

d) none of the above

ANS: core losses

48) principle of statically induced EMF is applied  in 

a)generator

b) motor

c)transformer

d) all of the above

ANS: transformer

49) if a load on secondary side of a transformer  increase , the current on the primary side 

a) remain constant 

b) increase 

c) decrease

d) none of these


 ANS: increase

50) select the correct  statement:

a)emf per turn of both the winding are equal.

b) emf per turn in HV winding is more than the emf per turn in LV winding

c) emf per turn in HV winding is  less than the emf per turn in LV winding

d)none of the above


ANS: emf per turn of both the winding are equal.

51) which one of the following is not a condition of parallel operation of transformer

a) polarity of the transformers should be same

b) terminal voltage of the transformers should be same

c) percentage impedance of the transformers should be same 

d) KVA ratting of transformers should be same



ANS:  KVA ratting of transformers should be same

52) small transformer below 25 KVA can be easily cooled by

a) air natural cooling

b) forced air cooling

c) oil natural cooling

d) oil forced cooling


ANS:  air natural cooling

53) in air  forced cooling . the fan are

a) always on

b)on when temperature increase from permissible limit

c) on when temperature decrease from permissible limit

d)on during the day time



 ANS: on when temperature increase from permissible limit

54) In a transformer power transfer  from primary winding to secondary winding by the

a) cooling oil

b) air

c) flux

d) all of the above 


ANS:FLUX

55) which winding in a transformer  has more number of turns 

a) low voltage side

b) high voltage side 

c) primary winding 

d) secondary winding


ANS:  high voltage side 

56) which winding in a transformer  has less number of turns 

a) low voltage side

b) high voltage side 

c) primary winding 

d) secondary winding

ANS: low voltage side

57) which winding in a step down transformer  has more number of turns 

a) either primary winding or secondary winding

b) primary winding 

c) secondary winding

d) all of the above 


ANS : PRIMARY WINDING

58)  which winding in a step up transformer  has more number of turns 

a) either primary winding or secondary winding

b) primary winding 

c) secondary winding

d) all of the above


ANS: secondary winding 

59)A common method of  cooling a transformer is

a)natural air cooling method 

b) air  blast  cooling 

c) oil cooling

d) all of the above


ANS: oil cooling

60) in a transformer the tapping are generally  provided on

a) low voltage side

b) high voltage side 

c) primary winding 

d) secondary winding

ANS: low voltage side

61) the transformer ratting are usually expressed in term of

a) KW

b) KVA

c) voltage

d) ohms


ANS : KVA

62)  which material to used Construction of transformer  core

a) copper

b) silicon steel

c) aluminium 

d) all of the above


ANS : Silicon steel

63)  which material to used Construction of transformer  winding

a) copper

b) silicon steel

c) aluminium 

d) all of the above

ANS : Copper

64) the thickness  of lamination used in a transformer usually

a) 0.4mm to 0.5 mm

b) 4 mm to 5 mm

c) 5mm to 10 mm

d) 10 mm to 20 mm

ANS : 0.4 mm to 0.5 mm

65) the maximum efficiency of distribution transformer is

a) at  full load

b) at no load

c) at 50% full load

d) at 90% full load

ANS: at 50% full load