Transformer Objective Type Question Answers

1. A transformer will work on 

(i) a.c. only
(ii) d.c. only
(iii) a.c. as well as d.c
(iv) none of the above

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2. The primary and secondary of a transformer are ……… coupled.

(i) electrically
(ii) magnetically
(iii) electrically and magnetically
(iv) none of the above

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3. A transformer is an efficient device because it  

(i) is a static device
(ii) uses inductive coupling
(iii) uses capacitive coupling
(iv) uses electric coupling

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4. A transformer transfers electrical energy from primary to secondary usually with a change in 

(i) frequency
(ii) power
(iii) voltage
(iv) time period

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5. The voltage per turn of the primary of a transformer is  …….. the voltage per turn of the secondary.

(i) more than
(ii) less than
(iii) the same as
(iv) none of the above

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6. The winding of the transformer with greater number of turns will be  

(i) high-voltage winding
(ii) low-voltage winding
(iii) either high or low voltage windiny
(iv) none of the above

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7. A transformer does not posses  ……… changing property.

(i) impedance
(ii) voltage
(iii) current
(iv) power

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8. The iron-core is used to ……….. of the transformer.

(i) increase the weight
(ii) provide tight magnetic coupling
(iii) reduce core losses
(iv) none of the above

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9. If a transformer core has air gaps, then

(i) reluctanue of magnetic path is decreased
(ii) hysteresis loss is decreased
(iii) magnetising current is greatly increased
(iv) eddy current is increased

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10. The maximum flux produced in the core of a transformer is ………

(i) directly proportional to supply frequency
(ii) inversely proportional to supply frequency
(iii) inversely proportional to primary voltage
(iv) none of the above

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11. The flux in the core of a single-phase transformer is 

(i) purely alternating one
(ii) purely rotating one
(iii) partly alternating and partly rotating
(iv) none of the above

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12. A transformer is so designed that primary and secondary have 

(i) high leakage reactance
(ii) large resistance
(iii) tight magnetic coupling
(iv) good electric coupling

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 13. When the primary of a transformer is connected to a d.c. supply  

(i) primary draws small current
(ii) primary leakage reactance is increased
(iii) core losses are increased
(iv) primary may bum out

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14. An ideal transformer is one which

(i) has no losses and leakage reactance
(ii) does not work
(iii) has same number of primary and secondary turns
(iv) none of the above

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15. A low-voltage outdoor lighting system uses a transformer that steps 120 V down to 24 V for safety. The equivalent resistance of all low-voltage lamps is 9.6 Ω. What is the current in the secondary coil ? Assume the transformer is ideal and there are no losses in the line.

(i) 2 A
(ii) 2.5 A
(iii) 4.5 A
(iv) 1.5 A

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16. In the above question, what is the current in the primary coil ?

(i) 1.5A
(ii) 4.5A
(iii) 2.5 A
(iv) 0.5 A

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17. In Q. 15, how much power is used ?

(i) 30 W
(ii) 20 W
(iii) 60 W
(iv) 40 W

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transformer objective type questions
Figure 1

18. Fig. 1 shows a practical transformer on no-load. The no-load current Io

(i) is in phase with V1
(ii) lags V1 by 90°
(iii) lags V1 by an angle less than 90°
(iv) leads V1 by 90°

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19. The no-load primary current Io Fig. 1 is 

(i) wholly reactive
(ii) wholly active
(iii) partly active and partly reactive
(iv) none of the above

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20. The no-load primary current Io is about  ……… of full-load primary current.

(i) 3 – 5%
(ii) 15 – 30%
(iii) 30 – 40%
(iv) above 40%

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