Electrical Engineering · Question Bank

Transformers

258 questions · page 13 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
#241📘 EE Pocket Reviewer RojasEasy
What is common to the two windings in a transformer?
AMagnetic circuit
BNumber of turns
CElectric current
DVoltage induced
#242📘 EE Pocket Reviewer RojasEasy
During the short circuit test, the iron loss of a transformer is negligible. Why?
AThe entire input power is just enough to meet the copper losses
BThe iron losses becomes totally saturated
CSupply frequency is held constant
DThe flux produced is only a small fraction of the normal flux
#243📘 EE Pocket Reviewer RojasEasy
Which one is a reason why dust particles should never be allowed to accumulate on the windings and core on a dry-type transformer?
AIt will tend to corrode the metal surface
BIt will reduce dissipation of heat
CIt will absorb oil and grease
DIt may short circuit the windings
#244📘 EE Pocket Reviewer RojasEasy
In an autotransformer, how does the primary and secondary windings coupled?
AMagnetically coupled only
BElectrically coupled only
CBoth magnetically and electrically coupled
DNo coupling necessary
#245📘 EE Pocket Reviewer RojasEasy
What will happen to the eddy current loss of a transformer when its load is increased?
AIt will increase
BIt will decrease
CIt will remain the same
DNone of these
#246📘 EE Pocket Reviewer RojasEasy
Which of the following can be altered by a transformer?
AFrequency
BPower
CDemand factor
DVoltage
#247📘 EE Pocket Reviewer RojasEasy
What is the most common method of cooling a power transformer?
ANatural air cooling
BForced-air cooling
COil cooling
DSpecial gas cooling
#248📘 EE Pocket Reviewer RojasEasy
The core of a transformer are made from laminations of which of the following metal sheets?
ALow carbon steel
BSilicon steel
CChrome steel
DMedium carbon steel
#249📘 EE Pocket Reviewer RojasEasy
What is the reason why the transformer cores are laminated?
ATo simplify its construction
BTo minimize eddy current loss
CTo reduce the cost
DTo reduce the hysteresis loss
#250📘 EE Pocket Reviewer RojasEasy
Which one is considered a main advantage of an autotransformer over a conventional two winding transformer?
AContinuously varying voltage is available
BConsiderable saving in the winding materials
CCopper losses are considerably reduced
DBoth A and B
#251📘 EE Pocket Reviewer RojasEasy
Which of the following can be determined with the open circuit test in a transformer?
AFull load copper loss
BIron loss
CFull load efficiency
DEquivalent winding resistance
#252📘 EE Pocket Reviewer RojasEasy
The savings in copper achieved by converting a two-winding transformer into an autotransformer is determined from which of the following?
AVoltage transformation ratio
BLoad connected on the secondary
CSize of the transformer core
DType of material used as the core
#253📘 EE Pocket Reviewer RojasEasy
Which one is the biggest advantage of T-T connection over the V-V connection for 3-phase power transformation?
AIt provides a set of balanced voltages under load
BIt provides a true 3-phase, 4-wire system
CIt provides a higher ratio of utilization
DIt provides more voltages
#254📘 EE Pocket Reviewer RojasEasy
Which of the following is a determining factor for the reactance of the transformer?
ALeakage flux
BMutual flux
CSize of the core
DPermeability of the core
#255📘 EE Pocket Reviewer RojasEasy
What is the reason why the secondary of a current transformer is short-circuited before the meter is removed?
ATo protect the primary circuit
BFor safety purposes of the electricians
CTo avoid core saturation and high voltage induction
DAll of these
#256📘 EE Pocket Reviewer RojasEasy
In a transformer, what is reason why the leakage flux of each winding is proportional to the current in that winding?
AThe leakage paths do not saturate
BThe two windings are electrically isolated
CThe mutual flux is confined in the core
DOhm's law applies to magnetic circuits
#257📘 EE Pocket Reviewer RojasEasy
What is the reason why transformers have good all day efficiency?
AIts copper loss is low
BIts core loss is low
CIts copper and core losses are both low
DIt is only loaded few hours in a given day
#258📘 EE Pocket Reviewer RojasEasy
What is the effect of leakage flux in a transformer?
AIt will increase the copper loss
BIt will cause voltage drop in the windings
CIt will increase the eddy current loss
DIt will cause the life of the core to shorten

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