Practice Test: Question Set - 16
1. Which of the following statements regarding an idle 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
2. No-load on a transformer is carried out to determine
- (A) Copper loss
- (B) Magnetizing current
- (C) Magnetizing current and loss
- (D) Efficiency of the transformer
3. In the transformer following winding has got more cross-sectional area
- (A) Low voltage winding
- (B) High voltage winding
- (C) Primary winding
- (D) Secondary winding
4. Efficiency of a power transformer is of the order of
- (A) 100 percent
- (B) 98 percent
- (C) 50 percent
- (D) 25 percent
5. 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
6. No-load current of a transformer has
- (A) Has high magnitude and low power factor
- (B) Has high magnitude and high power factor
- (C) Has small magnitude and high power factor
- (D) Has small magnitude and low power factor
7. The chemical used in breather for transformer should have the quality of
- (A) Ionizing air
- (B) Absorbing moisture
- (C) Cleansing the transformer oil
- (D) Cooling the transformer oil
8. The function of conservator in a transformer is
- (A) To project against internal fault
- (B) To reduce copper as well as core losses
- (C) To cool the transformer oil
- (D) To take care of the expansion and contraction of
transformer oil due to variation of temperature of surroundings
9. 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
10. Harmonics in transformer result in
- (A) Increased core losses
- (B) Increased I2R losses
- (C) Magnetic interference with communication
circuits
- (D) All of the above
11. Power transformers are generally designed to have maximum efficiency around
- (A) No-load
- (B) Half-load
- (C) Near full-load
- (D) 10% overload
12. An ideal transformer will have maximum efficiency at a load such that
- (A) Copper loss = iron loss
- (B) Copper loss < iron loss
- (C) Copper loss > iron loss
- (D) None of the above
13. Which type of winding is used in 3 phase shell-type transformer?
- (A) Circular type
- (B) Sandwich type
- (C) Cylindrical type
- (D) Rectangular type
14. A shell-type transformer has
- (A) High eddy current losses
- (B) Reduced magnetic leakage
- (C) Negligibly hysteresis losses
- (D) None of the above
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