2017 JULY  WIREMAN THEORY SEMESTER - IV

1. In a transformer the energy is conveyed from primary to secondary
a) Through cooling coil

b) Through air

c) By the flux

d) None of these

Answer:- c) By the flux

2. A transformer core is laminated to
a) Reduce Hysteresis Loss
c) Reduce Copper Losses

b) Reduce Eddy Current Losses
d) Reduce All Above Losses

Answer:- b) Reduce Eddy Current Losses

3. The path of a magnetic flux in a transformer should have_

a) High resistance

b) High reluctance

c) Low resistance

d) Low reluctance

Answer:- d) Low reluctance

4. The dielectric strength of transformer oil is expected to be___.

a) lkV b) 33 kV c) 100 kV d) 330 kV

Answer:- b) 33 kV

5. The purpose of providing an iron core in a transformer is to

a) Provide support to windings

b) Reduce hysteresis loss

c) Decrease the reluctance of the magnetic path

d) Reduce eddy current losses

Answer:- c) Decrease the reluctance of the magnetic path

6. Which of the following is not a part of transformer installation?

a) Conservator b) Breather c) Buchholz relay     d) Exciter

Answer:- d) Exciter

7. While conducting short-circuit test on a transformer the following side is short circuited,
a) High voltage side

b) Low voltage side 

c) Primary side       

d) Secondary side

Answer:- b) Low voltage side 

8. Which winding in a transformer has more number of turns?

a) Low voltage winding

b) High voltage winding

c) Primary winding

d) Secondary winding

Answer:- b) High voltage winding

9. Efficiency of a power transformer is of the order of__.

a) 100 per cent

b) 98 per cent

c) 50 per cent

d) 25 per cent

Answer:- b) 98 per cent

10. A common method of cooling a power transformer is____

a) Natural air cooling

b) Air blast cooling

c) Oil cooling

d) None of these

Answer:- c) Oil cooling

11. In the transformer the function of a conservator is to__.

a) Provide fresh air for cooling the transformer

b) Supply cooling oil to transformer in time of need

c) Protect the transformer from damage when oil expends due to heating

d) None of the above

Answer:- c) Protect the transformer from damage when oil expends due to heating

12. No-load current of a transformer has__

a) Has high magnitude and low power factor

b) Has high magnitude and high power factor

c) Has small magnitude and high power factor

d) Has small magnitude and low power factor

Answer:- d) Has small magnitude and low power factor

13. The power transformer is a constant_.

a) Voltage device     

b) Current device     

c) Power device      

d) Main flux device

Answer:- d) Main flux device

14. Two transformers operating in parallel will share the load depending upon their
a) Leakage reactance b) Per unit impedance

c) Efficiencies d) Ratings

Answer:- b) Per unit impedance

15. In a transformer the tappings are generally provided on

a) Primary side        b) Secondary side     c) Low voltage side   d) High voltage side

Answer:- c) Low voltage side  

16. The chemical used in breather for transformer should have the quality of _

a) Ionizing air

b) Absorbing moisture

c) Cleansing the transformer oil

d) Cooling the transformer oil

Answer:- b) Absorbing moisture

17. The transformer ratings are usually expressed in terms of
a) Volts

b) Amperes

c) kW

d) kVA

Answer:- d) kVA

18. Material used for construction of transformer core is usually__.

a) Wood

b) Copper

c) Aluminium

d) Silicon steel

Answer:- d) Silicon steel

19. The function of conservator in a transformer is_.

a) To project against'internal fault

b) To reduce copper as well as core losses

c) To cool the transformer oil

d) To take care of the expansion and contraction of transformer oil due to variation of
temperature of surroundings

Answer:- d) To take care of the expansion and contraction of transformer oil due to variation of
temperature of surroundings

20. Buchholz's relay gives warning and protection against_

a) Electrical fault inside the transformer itself

b) Electrical fault outside the transformer in outgoing feeder

c) For both outside and inside faults

d) None of the above

Answer:- a) Electrical fault inside the transformer itself

21. The value of flux involved m the e.m.f. equation of a transformer is ….
a) Average value     

b) r.m.s value

c) Maximum value.

d) Instantaneous value

Answer:- c) Maximum value.

22. Silicon steel used in laminations mainly reduces_____.

a) Hysteresis loss     

b) Eddy current losses

c) Copper losses      

d) All of these

Answer:- a) Hysteresis loss     

23. Which of the following is the main advantage of an auto-transformer over a two winding
transformer?

a) Hysteresis losses are reduced

b) Saving in winding material

c) Copper losses are negligible

d) Eddy losses are totally eliminated

Answer:- b) Saving in winding material

24. Two transformers are connected in parallel. These transformers do not have equal
percentage impedance. This is likely to result in_.

a) Short-circuiting of the secondaries

b) Power factor of one of the transformers is leading while that of the other lagging

c) Transformers having higher copper losses will have negligible core losses

d) Loading of the transformers not in proportion to their kVA ratings

Answer:- d) Loading of the transformers not in proportion to their kVA ratings

25. Open circuit test on transformers is conducted to determine

a) Hysteresis losses   b) Copper losses       c) Core losses d) Eddy current losses

Answer:- c) Core losses

26. Short circuit test on transformers is conducted to determine .

a) Hysteresis losses   b) Copper losses       c) Core losses d) Eddy current losses

Answer:- b) Copper losses

27. The size of a transformer core will depend on

a) Frequency b) Area of the core

c) Flux density of the core material d) Both (a) & (b)

Answer:- d) Both (a) & (b)

28. Which of the following parts of a transformer is visible from outside?

a) Bushings b) Core c) Primary winding   d) Secondary winding

Answer:- a) Bushings

29. Auto-transformer makes effective saving on copper and copper losses, when its
transformation ratio is___

a) Approximately equal to one b) Less than one

c) Great than one d) None of these

Answer:- a) Approximately equal to one

30. Part of the transformer which is most subject to damage from overheating is _
a) Iron core b) Copper winding   

c) Winding insulation

d) Frame or

Answer:- c) Winding insulation

31. In a thermal power plant cooling towers are used to_____

a) Condense low pressure steam

b) Cool condensed steam

c) Cool water used in condenser for condensing steam

d) Cool feed water of boiler

Answer:- c) Cool water used in condenser for condensing steam

32. Advantage of hydro-electric power station is___________-

a) Low operating cost b) Free from pollution problems

c) No fuel transportation problems d) All of these

Answer:- d) All of these

33. Which power plant normally operates at high speeds?

a) Diesel engine plant b) Petrol engine plant

c) Steam turbine plant

d) Hydroelectric power plant

Answer:- c) Steam turbine plant

34. By which of the following systems electric power may be transmitted?
a) Overhead system b) Underground system

c) Both (a) & (b) d) None of these

Answer:- c) Both (a) & (b)

35. Overhead system can be designed for operation up to
a) 11 kV

b)33kV

c)  66kV

d) 400 kV

Answer:- c)  66kV

36. Which of the following materials is not used for transmission and distribution of electrical
power? |

a) Copper b) Aluminium c) Steel d) Tungsten

Answer:- d) Tungsten

37. Galvanised steel wire is generally used as__.

a) Stay wire b) Earth wire

c) Structural components

d) All of these

Answer:- d) All of  these

38. The usual spans with R.C.C, poles are___.

a) 40—50 meters      h) 60—100 meters   

c) 80—100 meters   

d) 300—500 meters

Answer:- c) 80—100 meters

39. The operating voltage of super tension cables is up to_.

a) 3.3 kV b) 6.6 kV c) 11 kV d) 33 kV

Answer:- d) 33 kV

40. The operating voltage of extra high tension cables is upto__.

a) 6.6 kV b) 11 kV c) 33 kV d) 66 kV

Answer:- d) 66 kV

 41. Which of the following methods is used for laying of underground cables?

a) Direct laying       b) Draw-in-system    c) Solid system        d) All of these

Answer:- d) All of these

42. High voltage transmission lines use__.

a) Suspension insulators b) Pin insulators

c) Both (a) & (b) d) None of these

Answer:- a) Suspension insulators

43. Overhead lines generally use__,

a) Copper conductors b) All aluminium conductors

c) A.C.S.R. conductors d) None of these

Answer:- c) A.C.S.R. conductors

44. The material commonly used for sheaths of underground cables is_

a) Lead

b) Rubber c) Copper d) Iron

Answer:- a) Lead

45. A feeder, in a transmission system, feeds power to___.

a) Distributors        b) Generating stations c) Service mains     d) Ail of these

Answer:- a) Distributors

46. Which circuit breaker is generally used in railway traction?

a) SF6 circuit breaker

b) Air break circuit breaker

c) Vacuum circuit breaker d) Minimum oil circuit breaker

Answer:- b) Air break circuit breaker

47. A relay used for protection of motors against overload is_.

a) Impedance relay b) Electromagnetic attraction type

c) Thermal relay

d) Buchholz's relay

Answer:- c) Thermal relay

48. A circuit breaker will normally operate_____.

a) When the switch is put on b) When the line is to be checked

c) When the power is to be supplied d) Whenever fault in the line occurs

Answer:- d) Whenever fault in the line occurs

49. Which relay is used for feeders?

a) MHO relay b) Translay relay

c) Merz price protection d) Buchholz relay

Answer:- b) Translay relay

50. Buchholz relay is operated by

a) Eddy current relay

c) Electro-magnetic induction

b) Gas pressure

d) Electro-static induction

 Answer:- b) Gas pressure