Transformers MCQs : This section focuses on the "Basics" of Transformers. These Multiple Choice Questions (MCQs) should be practiced to improve the Transformers skills required for various interviews (campus interview, walk-in interview, company interview), placement, entrance exam and other competitive examinations.
A _________ is a passive electrical device that transfers electrical energy from one electrical circuit to another, or multiple circuits.
A. voltage regulation
D. phase conversion
Explanation: A transformer is a passive electrical device that transfers electrical energy from one electrical circuit to another, or multiple circuits
Transformers are most commonly used for ?
A. increasing low AC voltages at high current
B. decreasing high AC voltages at low current
C. increasing high AC voltages at low current
D. Both A and B
Explanation: Transformers are most commonly used for increasing low AC voltages at high current (a step-up transformer) or decreasing high AC voltages at low current (a step-down transformer) in electric power applications, and for coupling the stages of signal-processing circuits.
Transformers can also be used for isolation?
C. Can be true or false
D. Can not say
Explanation: True, Transformers can also be used for isolation, where the voltage in equals the voltage out, with separate coils not electrically bonded to one another.
The first constant-potential transformer invented in?
Explanation: The invention of the first constant-potential transformer in 1885
Transformer losses arise from?
A. Winding joule losses
B. Stray losses
C. Eddy current losses
D. All of the above
Explanation: Transformer losses arise from : Winding joule losses, Stray losses , Eddy current losses.
In a transformer the resistance between its primary and secondary is ______________
B. Very small
D. Can not say
Explanation: Since the primary and secondary windings are not connected to each other, one can say there exists the resistance of infinite ohms. These windings are connected to each other magnetically not electrically
An ideal transformer will have maximum efficiency at a load such that _____________
A. copper loss = iron loss
B. copper loss < iron loss
C. copper loss > iron loss
D. Can not say
Explanation: Maximum efficiency of a transformer is defined at the that values when, copper losses become completely equal to the iron losses. In all other cases the efficiency will be lower than the maximum value
What is the no-load current drawn by transformer?
A. 0.2 to 0.5 per cent
B. 2 to 5 per cent
C. 12 to 15 per cent
D. 20 to 30 per cent
Explanation: The no load current is about 2-5% of the full load current and it accounts for the losses in a transformer. These no-load losses include core(iron/fixed) losses, which contains eddy current losses & hysteresis losses and the copper(I2*R) losses due to the no Load current.
A transformer oil used in an electrical transformer must be free from ________
Explanation: Transformer oil serves the purpose of cooling and it also acts as an insulator between primary and secondary winding, thus it must be free from moisture else it will conduct electric current through it, leading to failure of a transformer.
Which of the following is not an Applications of transformers?
A. transformer used for impedance matching
B. transformer used for isolate four circuits electrically
C. used to increase or decrease the alternating voltages in electric power applications
D. transformer used in voltmeter, ammeters, protective relay
Explanation: The transformer used for isolate two circuits electrically.