Transformer MCQs – Set 2: Here is a new set of 25 questions, this set includes transformer construction, turns ratio, losses, equivalent circuits, tests, impedance, three-phase transformers, connections, and applications.
Join EEE Made Easy Whatsapp Channel
25 Transformer MCQs – Set 2
Read: Best Books for Transformer Design and Electrical Machine Design
1. Which winding of a transformer is connected to the AC supply?
A) Secondary winding
B) Primary winding
C) Tertiary winding
D) Auxiliary winding
Correct Answer: B) Primary winding
2. In a transformer, electrical energy is transferred from primary to secondary mainly through:
A) Mechanical coupling
B) Magnetic field
C) Electrostatic field only
D) Heat energy
Correct Answer: B) Magnetic field
3. In a step-down transformer, which quantity decreases?
A) Voltage
B) Frequency
C) Core flux
D) Number of primary turns
Correct Answer: A) Voltage
4. If the number of secondary turns is less than the number of primary turns, the transformer is:
A) Step-up
B) Step-down
C) Isolation
D) Current transformer
Correct Answer: B) Step-down
5. The turns ratio of a transformer is related to:
A) Voltage ratio
B) Frequency ratio
C) Power factor only
D) Efficiency only
Correct Answer: A) Voltage ratio
6. For an ideal transformer, if the primary voltage is increased while the turns ratio remains constant, the secondary voltage will:
A) Decrease
B) Increase
C) Remain zero
D) Remain unchanged
Correct Answer: B) Increase
7. In an ideal transformer, which of the following is assumed to be zero?
A) Mutual flux
B) Copper and core losses
C) Secondary voltage
D) Primary current
Correct Answer: B) Copper and core losses
8. The no-load current of a practical transformer is generally:
A) Very large
B) Zero
C) Small compared with full-load current
D) Equal to full-load current
Correct Answer: C) Small compared with full-load current
9. The no-load current of a transformer is required mainly to:
A) Produce the required magnetic flux and supply core losses
B) Produce mechanical rotation
C) Increase frequency
D) Reduce secondary voltage
Correct Answer: A) Produce the required magnetic flux and supply core losses
10. Which loss is approximately constant from no-load to full-load?
A) Copper loss
B) Core loss
C) Load loss
D) loss
Correct Answer: B) Core loss
11. Copper loss in a transformer varies approximately with:
A) Voltage
B) Frequency
C) Square of load current
D) Square of voltage
Correct Answer: C) Square of load current
12. Hysteresis loss in a transformer occurs because of:
A) Resistance of windings
B) Repeated magnetization and demagnetization of the core
C) Mechanical friction
D) Leakage current in insulation
Correct Answer: B) Repeated magnetization and demagnetization of the core
13. Which material property helps reduce hysteresis loss in transformer cores?
A) High hysteresis
B) Low magnetic permeability
C) Low hysteresis
D) High electrical resistance only
Correct Answer: C) Low hysteresis
14. Transformer oil is commonly used for:
A) Increasing frequency
B) Cooling and insulation
C) Increasing copper resistance
D) Reducing the turns ratio
Correct Answer: B) Cooling and insulation
15. The conservator tank in an oil-filled transformer primarily provides space for:
A) Copper windings
B) Expansion and contraction of transformer oil
C) Increasing magnetic flux
D) Reducing frequency
Correct Answer: B) Expansion and contraction of transformer oil
16. A Buchholz relay is generally used for protection of:
A) Small dry-type transformers
B) Oil-immersed transformers with a conservator
C) DC motors
D) Transmission lines only
Correct Answer: B) Oil-immersed transformers with a conservator
17. The equivalent circuit of a practical transformer includes resistance and:
A) Reactance
B) Capacitance only
C) Mechanical load
D) Rectifier
Correct Answer: A) Reactance
18. Leakage flux in a transformer produces:
A) Leakage reactance
B) Mechanical torque
C) Frequency increase
D) Zero impedance
Correct Answer: A) Leakage reactance
19. When referring an impedance from one side of a transformer to the other, the impedance is multiplied by:
A) Turns ratio
B) Square of the turns ratio
C) Square root of turns ratio
D) Frequency ratio
Correct Answer: B) Square of the turns ratio
20. A transformer has 500 primary turns and 100 secondary turns. If the primary voltage is 1000 V, the ideal secondary voltage is:
A) 100 V
B) 200 V
C) 500 V
D) 2000 V
Correct Answer: B) 200 V
Calculation:
21. In a transformer, if the secondary voltage is reduced by a step-down action, the secondary current ideally:
A) Also decreases
B) Increases
C) Becomes zero
D) Remains exactly the same
Correct Answer: B) Increases
22. Which three-phase transformer connection provides a neutral point on the star-connected side?
A) Delta–Delta
B) Star–Star without neutral
C) Star–Delta
D) Delta–Delta only
Correct Answer: C) Star–Delta
23. Which transformer connection is commonly used when a neutral is required on the secondary side of a three-phase distribution system?
A) Delta–Star
B) Delta–Delta
C) Delta–Delta with no neutral
D) Delta–Delta only
Correct Answer: A) Delta–Star
24. The main purpose of a tap changer in a transformer is to:
A) Change the operating frequency
B) Adjust the transformer voltage ratio
C) Eliminate all copper losses
D) Convert AC to DC
Correct Answer: B) Adjust the transformer voltage ratio
25. An isolation transformer generally has a voltage ratio of approximately:
A) 10:1
B) 5:1
C) 1:1
D) 1:10
Correct Answer: C) 1:1
Quick Answer Key – Set 2
| Q.No. | Answer | Q.No. | Answer | Q.No. | Answer |
|---|---|---|---|---|---|
| 1 | B | 10 | B | 19 | B |
| 2 | B | 11 | C | 20 | B |
| 3 | A | 12 | B | 21 | B |
| 4 | B | 13 | C | 22 | C |
| 5 | A | 14 | B | 23 | A |
| 6 | B | 15 | B | 24 | B |
| 7 | B | 16 | B | 25 | C |
| 8 | C | 17 | A | ||
| 9 | A | 18 | A |
Join EEE Made Easy Whatsapp Channel
Read More on Transformer
- Best Books for Transformer Design and Electrical Machine Design
- Transformers MCQ questions set 1
- Transformers MCQ Questions- Set 2
- Transformer MCQ Questions Set 3
- Efficiency of Transformer|Equation & Example
- Losses in a Transformer
- [Solved]Transformer Voltage Regulation Problem
- LVDT|Linear Variable Differential Transformer
- Autotransformer|Application of Autotransformer
- Transformers Electrical Engineering Interview Questions
- Why Transformers Hum: 7 Shocking Causes and Expert Solutions You Need to Know
- Single-phase transformer Connections Series & parallel
- Hysterisis and Eddy current losses
- Special Transformers
- Static Electrification in transformers
- Magnetostriction and its ill effects