Transformers Exam Questions and
Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant
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1. What is the primary function of a transformer?
A. Convert AC to DC
B. Increase electrical resistance
C. Transfer electrical energy between circuits through electromagnetic
induction
D. Store electrical energy
Rationale: A transformer transfers electrical energy from one circuit to
another through electromagnetic induction without direct electrical
contact. It can step voltage up or down while maintaining the same
frequency.
2. A transformer operates on the principle of:
A. Electrostatic attraction
B. Chemical reaction
C. Electromagnetic induction
D. Thermal conduction
,Rationale: Transformers work according to Faraday's Law of
Electromagnetic Induction. A changing magnetic field in the primary
winding induces a voltage in the secondary winding.
3. Which type of current is required for normal transformer
operation?
A. Direct current (DC) only
B. Alternating current (AC)
C. Pulsating DC only
D. Static electricity
Rationale: A transformer requires alternating current because the
continuously changing magnetic field produced by AC induces voltage in
the secondary winding. Steady DC produces no changing magnetic field
after initial energization.
4. What is the laminated iron core used for in a transformer?
A. Increase resistance
B. Reduce voltage
C. Minimize eddy current losses while providing a magnetic path
D. Increase current flow
Rationale: Laminating the core into thin insulated sheets significantly
reduces eddy current losses while maintaining an efficient path for
magnetic flux.
5. In an ideal transformer, the input power is:
,A. Greater than output power
B. Less than output power
C. Equal to output power
D. Always zero
Rationale: An ideal transformer has no losses, meaning input power
equals output power. Real transformers have minor losses due to copper
resistance, core losses, and leakage flux.
6. A transformer with more turns on the secondary than the primary
is called a:
A. Isolation transformer
B. Step-up transformer
C. Step-down transformer
D. Current transformer
Rationale: A step-up transformer increases voltage because the
secondary winding contains more turns than the primary winding.
7. A transformer with fewer turns on the secondary than the primary
is known as a:
A. Isolation transformer
B. Instrument transformer
C. Step-down transformer
D. Distribution reactor
Rationale: A step-down transformer reduces voltage because the
secondary winding has fewer turns than the primary winding.
, 8. The transformer turns ratio is determined by comparing:
A. Resistance values
B. Number of turns in the primary and secondary windings
C. Core thickness
D. Wire insulation
Rationale: Voltage transformation is directly proportional to the ratio of
turns between the primary and secondary windings.
9. If the primary voltage is 240 V and the turns ratio is 2:1, the
secondary voltage is:
A. 480 V
B. 120 V
C. 240 V
D. 60 V
Rationale: With a 2:1 turns ratio, the secondary has half as many turns
as the primary, resulting in half the voltage: 240 ÷ 2 = 120 V.
10. Transformer efficiency is generally highest when:
A. No load is connected
B. It is overloaded
C. Operating near its rated load
D. Operating at half frequency
Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant
Download Pdf.
1. What is the primary function of a transformer?
A. Convert AC to DC
B. Increase electrical resistance
C. Transfer electrical energy between circuits through electromagnetic
induction
D. Store electrical energy
Rationale: A transformer transfers electrical energy from one circuit to
another through electromagnetic induction without direct electrical
contact. It can step voltage up or down while maintaining the same
frequency.
2. A transformer operates on the principle of:
A. Electrostatic attraction
B. Chemical reaction
C. Electromagnetic induction
D. Thermal conduction
,Rationale: Transformers work according to Faraday's Law of
Electromagnetic Induction. A changing magnetic field in the primary
winding induces a voltage in the secondary winding.
3. Which type of current is required for normal transformer
operation?
A. Direct current (DC) only
B. Alternating current (AC)
C. Pulsating DC only
D. Static electricity
Rationale: A transformer requires alternating current because the
continuously changing magnetic field produced by AC induces voltage in
the secondary winding. Steady DC produces no changing magnetic field
after initial energization.
4. What is the laminated iron core used for in a transformer?
A. Increase resistance
B. Reduce voltage
C. Minimize eddy current losses while providing a magnetic path
D. Increase current flow
Rationale: Laminating the core into thin insulated sheets significantly
reduces eddy current losses while maintaining an efficient path for
magnetic flux.
5. In an ideal transformer, the input power is:
,A. Greater than output power
B. Less than output power
C. Equal to output power
D. Always zero
Rationale: An ideal transformer has no losses, meaning input power
equals output power. Real transformers have minor losses due to copper
resistance, core losses, and leakage flux.
6. A transformer with more turns on the secondary than the primary
is called a:
A. Isolation transformer
B. Step-up transformer
C. Step-down transformer
D. Current transformer
Rationale: A step-up transformer increases voltage because the
secondary winding contains more turns than the primary winding.
7. A transformer with fewer turns on the secondary than the primary
is known as a:
A. Isolation transformer
B. Instrument transformer
C. Step-down transformer
D. Distribution reactor
Rationale: A step-down transformer reduces voltage because the
secondary winding has fewer turns than the primary winding.
, 8. The transformer turns ratio is determined by comparing:
A. Resistance values
B. Number of turns in the primary and secondary windings
C. Core thickness
D. Wire insulation
Rationale: Voltage transformation is directly proportional to the ratio of
turns between the primary and secondary windings.
9. If the primary voltage is 240 V and the turns ratio is 2:1, the
secondary voltage is:
A. 480 V
B. 120 V
C. 240 V
D. 60 V
Rationale: With a 2:1 turns ratio, the secondary has half as many turns
as the primary, resulting in half the voltage: 240 ÷ 2 = 120 V.
10. Transformer efficiency is generally highest when:
A. No load is connected
B. It is overloaded
C. Operating near its rated load
D. Operating at half frequency
