Electrical Engineering · Question Bank

Transformers

258 questions · page 10 of 13. Answer in your head first, then check the solution.

📘 EE Mock Board Exam
TypeAll 258Problem solving 148Objective 110
DifficultyAll 258Easy 171Medium 71Hard 16
#181📘 EE Pocket Reviewer RojasEasy
What is the purpose of putting the transformer windings under oil?
ATo lubricate and cool the windings
BTo insulate and lubricate the windings
CTo insulate and cool the windings
DTo insulate, cool and lubricate the windings
#182📘 EE Pocket Reviewer RojasEasy
Which of the following is true about a transformer?
AThe per unit resistance, reactance and impedance are the same, whether its referred to primary or secondary side
BIf the power factor is leading the regulation of a good transformer is higher than when it has a lagging power factor
CThe efficiency of a transformer is maximum when it is underload and operating at unity pf
DA good transformer must have regulation as high as possible
#183📘 EE Pocket Reviewer RojasEasy
Which one dictates the primary current in a CT?
AThe core of the transformer
BThe load current
CThe secondary burden
DAll of these
#184📘 EE Pocket Reviewer RojasEasy
The no load input power of a transformer is practically equal to which of the following?
ACopper loss at no load
BFriction and windage loss
CStray power loss
DIron loss
#185📘 EE Pocket Reviewer RojasEasy
What principle is used in transformer?
AStatic induction
BDynamic induction
CSelf induction
DMutual induction
#186📘 EE Pocket Reviewer RojasEasy
What is the purpose of connecting sometimes a “reactor” in series to a transformer?
ATo deliver more kVA
BTo control the fault current
CTo correct its operating power factor
DTo improve its voltage regulation
#187📘 EE Pocket Reviewer RojasEasy
In the transformer equivalent circuit, the core loss is represented by which of the following circuit elements?
AA series resistance
BA series inductance
CA shunt resistance
DA shunt inductance
#188📘 EE Pocket Reviewer RojasEasy
What is the reason why a transformer is an efficient device?
AIt is a static device
BIt uses both inductive and capacitive coupling
CIts winding has less resistance
DIts friction and windage loss is small
#189📘 EE Pocket Reviewer RojasEasy
The increased in the kVA capacity produced by connecting a two winding transformer as an autotransformer is due to which of the following?
AIncreased in the secondary voltage
BIncreased in the transformer efficiency
CIncreased in turns ratio
DEstablishment of a conductive link between primary and secondary
#190📘 EE Pocket Reviewer RojasEasy
What is the purpose of stampings in transformers?
ATo reduce the hysteresis loss
BTo reduce the eddy current loss
CTo reduce the copper loss
DAll of these
#191📘 EE Pocket Reviewer RojasEasy
The cores of transformers is normally made from which of the following materials?
ASilicon steel
BSeasoned wood
CAnnealed copper
DAluminum
#192📘 EE Pocket Reviewer RojasEasy
Which of the following is true about the primary and secondary induced emfs in a transformer?
AThey are always equal in magnitude
BThey are always anti-phase with each other
CThey are always in-phase with each other
DThey are always dependent on the load connected on the secondary side
#193📘 EE Pocket Reviewer RojasEasy
What is the purpose of a tap changing transformer?
ATo supply low voltage for instruments
BTo step up the voltage
CTo step down the voltage
DTo step up as well as step down the voltage
#194📘 EE Pocket Reviewer RojasEasy
Which one is an essential feature of an autotransformer?
AIt uses only one winding
BIt is more suited for single-phase supply
CIt is completely automatic in its operation
DIt is particularly suited for situations where the voltage transformation ratio exceeds unity
#195📘 EE Pocket Reviewer RojasEasy
The core of a transformer must posses which of the following characteristics?
ALow permeability and high hysteresis
BLow permeability and low hysteresis
CHigh permeability and low hysteresis
DHigh permeability and high hysteresis
#196📘 EE Pocket Reviewer RojasEasy
At what condition will the efficiency of a transformer be maximum?
AResistance of both windings are equal
BCopper loss is equal to core loss
CPer unit impedance of both windings are equal
DLoad served is a unity pf load
#197📘 EE Pocket Reviewer RojasEasy
Which of the following cannot be done by a transformer?
AIncrease the output power
BIncrease the output impedance
CIncrease the output voltage
DIncrease the output current
#198📘 EE Pocket Reviewer RojasEasy
What is the cause of the humming sound in a transformer?
ATransformer winding
BTransformer oil
CMagnetostriction
DSize of transformer tanks
#199📘 EE Pocket Reviewer RojasEasy
The all-day efficiency of a transformer is ____ commercial efficiency of the same transformer.
AEqual to
BLess than the
CGreater than the
DEither less than or greater than the
#200📘 EE Pocket Reviewer RojasEasy
Which loss will decrease when the load of transformer will decrease?
ACopper loss
BEddy current loss
CHysteresis loss
DAll of these

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