Wireman theory sem 4 july 2017

17/B/C/S-4/4/EPAPER -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

A transformer core is laminated to_.
a) Reduce Hysteresis Loss b) Reduce Eddy Current Losses
c) Reduce Copper Losses d) Reduce All Above Losses

The path of a magnetic flux in a transformer should have_
a) High resistance b) High reluctance
c) Low resistance d) Low reluctance

The dielectric strength of transformer oil is expected to be___.
a) IkV b) 33 kV c) 100 kV d) 330 kV

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

Which of the following is not a part of transformer installation?
a) Conservator        b) Breather c) Buchholz relay     d) Exciter

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

Which winding in a transformer has more number of turns?
a) Low voltage winding b) High voltage winding
c) Primary winding d) Secondary winding

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

A common method of cooling a power transformer is___
a) Natural air cooling b) Air blast cooling
c) Oil cooling d) None of these

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

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

The power transformer is a constant_.
a) Voltage device     b) Current device     c) Power device       d) Main flux device

Two transformers operating in parallel will share the load depending upon their
a) Leakage reactance b) Per unit impedance
c) Efficiencies d) Ratings

In a transformer the tappings are generally provided on
a) Primary side        b) Secondary side     c) Low voltage side   d) High voltage side

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

The transformer ratings are usually expressed in terms of.................
a) Volts b) Amperes c) kW d)kVA

.Material used for construction of transformer core is usually__.
a) Wood b) Copper c) Aluminium d) Silicon steel

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

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

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

Silicon steel used in laminations mainly reduces______.
a) Hysteresis loss     b) Eddy current lossesc) Copper losses       d) All of these

Which of the following is the main advantage of an auto-transformer over a two winding
a) Hysteresis losses are reduced b) Saving in winding material
c) Copper losses are negligible d) Eddy losses are totally eliminated

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

Open circuit test on transformers is conducted to determine
a) Hysteresis losses   b) Copper losses      c) Core losses d) Eddy current losses

Short circuit test on transformers is conducted to determine.

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

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)

Which of the following parts of a transformer is visible from outstde?
a) Bushings b) Core c) Primary winding   d) Secondary winding

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

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

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

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

Which power plant normally operates at high speeds?
a) Diesel engine plant b) Petrol engine plant
c) Steam turbine plant
d) Hydroelectric power plant

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

Overhead system can be designed for operation up to _
a) 11 kV b)33kV c)66kV d) 400 kV

Which of the following materials is not used for transmission and distribution of electrical
power? j
a) Copper b) Aluminium c) Steel d) Tungsten

Galvanised steel wire is generally used as_____.
a) Stay wire b) Earth wire
c) Structural components d) All of these

The usual spans with R.C.C. poles are___.
a) 40—50 meters     b) 60—100 meters    c) 80—100 meters    d) 300—500 meters

The operating voltage of super tension cables is up to_.
a)3.3kV b)6.6kV c)llkV" d)33kV

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

The operating voltage of extra high tension cables is upto__.
a) 6.6 kV b) 11 kV c) 33 kV d) 66 kV

High voltage transmission lines use______.
a) Suspension insulators b) Pin insulators
c) Both (a) & (b) d) None of these

High voltage transmission lines use______.
a) Suspension insulators b) Pin insulators
c) Both (a) & (b) d) None of these

Overhead lines generally use
a) Copper conductors
c) A.CS.R. conductors
b) All aluminium conductors
d)None of these

The material commonly used for sheaths of underground cables is_
a) Lead b) Rubber c) Copper d) Iron

A feeder, in a transmission system, feeds power to___.
a) Distributors b) Generating stations c) Service mains     d) All of these

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

A relay used for protection of motors against overload is_.
a) Impedance relay b) Electromagnetic attraction type
c) Thermal relay d) Buchholz's relay

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

Which relay is used for feeders?
a) MHO relay b) Translay relay
c) Merz price protection d) Buchholz relay

Buchholz relay is operated by_.
a) Eddy current relay b) Gas pressure
c) Electro-magnetic induction d) Electro-static induction

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