1. What will happen if the transformers working in parallel are not connected with regard to polarity?
A. The power factor of the two transformers will be different from the power factor of common load
B. Incorrect polarity will result in dead short circuit
C. The transformers will not share load in proportion to their kVA ratings
D. none of the above
Answer: B
2. Transformer breaths in when
A. load on it increases
B. load on it decreases
C. load remains constant
D. none of the above
Answer: B
3. Material used for construction of transformer core is usually
A. wood
B. copper
C. aluminium
D. silicon steel
Answer: D
4. Natural oil cooling is used for transformers up to a rating of
A. 3000 kVA
B. 1000 kVA
C. 500 kVA
D. 250 kVA
Answer: A
5. The maximum load that a power transformer can carry is limited by its
A. temperature rise
B. dielectric strength of oil
C. voltage ratio
D. copper loss
Answer: C
6. Which of the following is the most likely source of harmonics in a transformer?
A. poor insulation
B. Overload
C. loose connections
D. Core saturation
Answer: D
7. The leakage flux in a transformer depends upon
A. load current
B. load current and voltage
C. load current, voltage and frequency
D. load current, voltage, frequency and power factor
Answer: A
8. The noise produced by a transformer is termed as
A. zoom
B. hum
C. ringing
D. buzz
Answer: B
9. A no-load test is performed on a transformer to determine
A. core loss
B. copper loss
C. efficiency
D. magnetizing current
E. magnetizing current and loss
Answer: E
10. Which of the following parts of a transformer is visible from outside?
A. Bushings
B. Core
C. Primary winding
D. Secondary winding
Answer: A
11. The magnetizing current of a transformer is usually small because it has
A. small air gap
B. large leakage flux
C. laminated silicon steel core
D. fewer rotating parts
Answer: Option A
12. Which of the following insulating materials can withstand the highest temperature safely?
A. Cellulose
B. Asbestos
C. Mica
D. Glass fibre
Answer: C
13. In case of 3-phase induction motors, plugging means
A. pulling the motor directly on line without a starter
B. locking of rotor due to harmonics
C. starting the motor on load which is more than the rated load
D. interchanging two supply phases for quick stopping
Answer: D
14. The main reason for generation of harmonics in a transformer could be
A. fluctuating load
B. poor insulation
C. mechanical vibrations
D. saturation of core
Answer: D
15. When secondary of a current transformer is open-circuited its iron core will be
A. hot because of heavy iron losses taking place in it due to high flux density
B. hot because primary will carry heavy current
C. cool as there is no secondary current
D. none of above will happen
Answer: A
16. Spacers are provided between adjacent coils
A. to provide free passage to the cooling oil
B. to insulate the coils from each other
C. both (A) and (B)
D. none of the above
Answer: A
17. A shell-type transformer has
A. high eddy current losses
B. reduced magnetic leakage
C. negligibly hysteresis losses
D. none of the above
Answer: B
18. In Ns is the synchronous speed and s the slip, then actual running speed of an induction motor will be
A. Ns
B. s.N.
C. (l-s)Ns
D. (Ns-l)s
Answer: C
19. Distribution transformers are generally designed for maximum efficiency around
A. 90% load
B. Zero load
C. 25% load
D. 50% load
Answer: D
20. Power transformers are generally designed to have maximum efficiency around
A. no-load
B. half-load
C. near full-load
D. 10% overload
Answer: C
21. Which of the following statements regarding an idel single-phase transformer having a turn ratio of 1 : 2 and drawing a current of 10 A from 200 V A.C. supply is incorrect?
A. Its secondary current is 5 A
B. Its secondary voltage is 400 V
C. Its rating is 2 kVA
D. Its secondary current is 20 A
Answer: D
22. The maximum efficiency of a distribution transformer is
A. at no load
B. at 50% full load
C. at 80% full load
D. at full load
Answer: B
23. Which of the following protection is normally not provided on small distribution transformers?
A. Overfluxing protection
B. Buchholz relay
C. Overcurrent protection
D. All of the above
Answer: B
24. Insertion of resistance in the rotcir of an induction motor to develop a given torque
A. decreases the rotor current
B. increases the rotor current
C. rotor current becomes zero
D. rotor current rernains same
Answer: D
25. The efficiency of a transformer will be maximum when
A. copper losses = hysteresis losses
B. hysteresis losses = eddy current losses
C. eddy current losses = copper losses
D. copper losses = iron losses
Answer: D
26. The transformer ratings are usually expressed in terms of
A. volts
B. amperes
C. kW
D. kVA
Answer: D
27. Harmonics in transformer result in
A. increased core losses
B. increased I2R losses
C. magnetic interference with communication circuits
D. all of the above
Answer: D
28. The efficiency of a transformer, under heavy loads, is comparatively low because
A. copper loss becomes high in proportion to the output
B. iron loss is increased considerably
C. voltage drop both in primary and secondary becomes large
D. secondary output is much less as compared to primary input
Answer: A
29. In a power or distribution transformer about 10 per cent end turns are heavily insulated
A. to withstand the high voltage drop due to line surge produced by the shunting capacitance of the end turns
B. to absorb the line surge voltage and save the winding of transformer from damage
C. to reflect the line surge and save the winding of a transformer from damage
D. none of the above
Answer: A
30. Which winding in a transformer has more number of turns?
A. Low voltage winding
B. High voltage winding
C. Primary winding
D. Secondary winding
Answer: B
For More Transformer MCQs (Set of 400 Most Asked MCQs)
For More Transmission & Distribution MCQS
For More Switchgear and Protection MCQS
For More Basic Electrical MCQs
For More Cell &Battery MCQS