In this page, you can solve transformer MCQ or multiple-choice questions. You can also analyse your answers at the same time by clicking Answer tab.
1. Which of the following would refer to an ideal transformer?
- Winding resistances are negligible.
- Leakage-fluxes are included.
- Core losses are negligible.
- Magnetization characteristic is linear.
- i, ii and iii only
- i, iii and iv only
- i, ii and iv only
- ii, iii and iv only
2. An ideal transformer is having 150 turns primary and 750 turns secondary. The primary coil is connected to a 240 V, 50 Hz source. The secondary winding supplies a load of 4 A at lagging power factor of 0.8. What is the power supplied by the transformer to the load?
- 4200 W
- 3840 W
- 2100 W
- 1920 W
3. A 1000V/400V power transtormer has a nominal short-circuit voltage VSC = 40%. Which one of the following statements is correct?
- A voltage of 400 V appears across the short-circuited secondary terminals.
- A voltage of 16V appears across the short-circuited secondary terminals.
- When the secondary terminals are short-circuited, the rated current flows at the primary side at a primary voltage of 400V.
- The primary voltage drops to 400 V, when the secondary terminals are short-circuited.
4. Eddy current losses in transformer cores and be reduced by the use of
- Solid cores
- Laminated cores
Select the correct answer using the codes given below
- ii and iii only
- i and ii only
- i, ii and iii
- i and iii only
5. A transformer may have negative voltage regulation if the load power factor (p.f.) is
- Leading for some values of p.f.
- Unity p.f.
- Lagging but not zero p.f.
- Only zero p.f. lag
6. A 2400/240 V, 200 kVA, single-phase transformer has a core loss of 1.8 kW at rated voltage. Its equivalent resistance is 1.1%. Then the transfer efficiency at 0.9 power factor and on full load is
7. In a power transformer, the core loss is 50 W at 40 Hz, and 100 W at 60 Hz, under the condition of same maximum flux density in both cases. The core loss at 50 Hz will be
- 73 W
- 64 W
- 91 W
- 82 W
8. The regulation of a transformer in which ohmic loss is 1% of the output and reactance drop is 5% of the voltage, when operating at 0.8 power factor lagging is
9. Consider the following losses for short circuit test on a transformer:
- Copper loss
- Copper and iron losses
- Eddy current and hysteresis losses
- Friction and windage losses
- ii only
- i only
- ii, iii and iv
- iii only
10. A 4kVA transformer has iron-loss of 200 W and full load copper loss of 200 W. The maximum efficiency at unity power factor will be
11. The percentage resistance and reactance of a transformer are 2% and 4% respectively. The approximate regulation on full load at 0.8 pf lag is
12. In a normal operation of 400 V, 50 Hz transformer, the total iron loss is 2500 W. When the supply voltage and frequency are reduced to 200 V and 25 Hz respectively, the corresponding loss is 850 W. The eddy-current loss at normal voltage
- 800 W
- 400 W
- 1600 W
- 200 W
13. A 250 kVA, 11000 V/400 V and 50 Hz single-phase transformer has 80 turns on the secondary, what is the maximum value of flux?
- 2475 mWb
- 0.2 mWVb
- 22.5 mWb
- 55.2 mWb
14. A 2000/200 V, 50 Hz single-phase transformer has an exciting current of 0.5 A and a core-loss of 600 W. When H.V. side is energized by the rated voltage and frequency, the magnetizing current is
- 0.1 A
- 0.2 A
- 0.3 A
- 0.4 A
15. In the core-type two winding transformer, the low voltage winding is placed adjacent to the steel core, in order to
- facilitate dissipation of heat during the operation of the transformer
- minimize the amount of insulation required.
- reduce the chances of axial displacement with respect to the high voltage winding placed outside.
- reduce the mutual radial stress between the two windings.
16. If the percentage impedance of the two transformers working in parallel are different then
- transformers will be overheated
- power factors of both the transformers will be same
- parallel operation will not be possible
- parallel operation will still be possible
17. The voltage regulation of a transformer having 2% resistance and 5% reactance, at full load, 0.8 pf lagging is
18. In a transformer the core loss is 100 Watt at 40 Hz and 72 Watt at 37 Hz, then eddy current and hysteresis losses at 50 Hz respectively are
- 25 Watt and 105 Watt
- 20 Watt and 100 Watt
- 100 Watt and 32 Watt
- 32 Watt and 100 Watt
19. In a transformer, if the iron losses and copper losses are 40.5 kW and 50 kW respectively, then at what fraction of load will be efficiency be maximum?
20. A 100 VA, 120/12 V transformer is to be connected so as to form a step-up transformer. A primary voltage of 120 V is applied to the transformer. What is the secondary voltage of the transformer?
- 1.2 V
- 132 V
- 120 V