Here are 20 MCQs based on UNIT III: SINGLE PHASE TRANSFORMERS, focused on Understand and Apply levels of Bloom’s Taxonomy.
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⚡ UNIT III – SINGLE PHASE TRANSFORMERS
MCQs Based on Understand & Apply Levels
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🔷 Section A: Transformer Basics & EMF Equation
1. Which of the following is the basic working principle of a transformer?
A) Electrostatic induction
B) Magnetic repulsion
C) Electromagnetic induction
D) Thermionic emission
Answer: C) Electromagnetic induction
2. The EMF equation of a transformer is given by:
A) E = B × L × v
B) E = 4.44 × f × N × Î¦
C) E = I × R
D) E = N × V
Answer: B) E = 4.44 × f × N × Î¦
3. If a transformer has a turns ratio of 1:2, then the transformer is:
A) Step-up transformer
B) Step-down transformer
C) Isolation transformer
D) Auto transformer
Answer: A) Step-up transformer
4. Transformer ratings are usually expressed in:
A) kW
B) Amps
C) kVA
D) HP
Answer: C) kVA
5. Which of the following applications requires a step-down transformer?
A) Transmission lines
B) Power stations
C) Home appliances
D) Solar power plants
Answer: C) Home appliances
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🔷 Section B: Phasor Diagrams & Ideal Transformer
6. In an ideal transformer, which of the following is zero?
A) Core flux
B) Copper loss
C) Induced EMF
D) Magnetizing current
Answer: B) Copper loss
7. In a no-load phasor diagram, the no-load current lags the applied voltage by:
A) 0°
B) 90°
C) 180°
D) Nearly 90°
Answer: D) Nearly 90°
8. At lagging power factor load, the load current in the phasor diagram will:
A) Lead the voltage
B) Lag the voltage
C) Be in phase
D) None of these
Answer: B) Lag the voltage
9. The equivalent circuit of a transformer helps to determine:
A) Cooling rate
B) Core shape
C) Voltage regulation and efficiency
D) Flux leakage
Answer: C) Voltage regulation and efficiency
10. Which element of equivalent circuit represents the iron losses?
A) Series resistance
B) Leakage reactance
C) Parallel resistance
D) Magnetizing reactance
Answer: C) Parallel resistance
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🔷 Section C: Voltage Regulation & Efficiency
11. Voltage regulation of a transformer is defined as:
A) Ratio of primary to secondary voltage
B) Change in secondary voltage from no-load to full-load
C) Change in current from full-load to no-load
D) Power factor variation
Answer: B) Change in secondary voltage from no-load to full-load
12. A transformer is said to be more efficient when:
A) Core loss > Copper loss
B) Copper loss > Core loss
C) Core loss = Copper loss
D) Losses are not minimized
Answer: C) Core loss = Copper loss
13. What is all-day efficiency concerned with?
A) Peak load performance
B) Constant load performance
C) Energy consumed over a 24-hour period
D) Cooling capacity
Answer: C) Energy consumed over a 24-hour period
14. If a transformer has full-load efficiency of 98%, the losses are:
A) 2% of output
B) 2% of input
C) 2% of kVA
D) 2% of voltage
Answer: B) 2% of input
15. To find condition for maximum efficiency, we equate:
A) Voltage and current
B) Core loss and copper loss
C) Primary and secondary voltage
D) Iron loss and load power
Answer: B) Core loss and copper loss
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🔷 Section D: Parallel Operation & Auto Transformer
16. For parallel operation, the transformers must have:
A) Equal weight
B) Same polarity and voltage ratio
C) Same size
D) Different impedance
Answer: B) Same polarity and voltage ratio
17. One major advantage of parallel operation is:
A) More noise
B) Load sharing
C) Higher losses
D) Increased copper usage
Answer: B) Load sharing
18. An auto transformer differs from a two-winding transformer by having:
A) No magnetic core
B) One winding common to both primary and secondary
C) Two isolated windings
D) No current transformation
Answer: B) One winding common to both primary and secondary
19. Which of the following is a disadvantage of an auto transformer?
A) More weight
B) More copper
C) Lack of electrical isolation
D) Less efficiency
Answer: C) Lack of electrical isolation
20. Which type of transformer is more efficient for the same rating?
A) T
wo-winding transformer
B) Auto transformer
C) Isolation transformer
D) Pulse transformer
Answer: B) Auto transformer
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