Practice Test: Question Set - 03
1. Which of the following is the main advantage of an autotransformer over a two winding transformer?
- (A) Hysteresis losses are reduced
- (B) Saving in winding material
- (C) Copper losses are negligible
- (D) Eddy losses are totally eliminated
2. Helical coils can be used on
- (A) Low voltage side of high kVA transformers
- (B) High frequency transformers
- (C) High voltage side of small capacity transformers
- (D) High voltage side of high kVA rating transformers
3. A transformer with a 110 V primary has a 15:1 turns ratio. The load resistance, RL, is 120 Ω. What is the approximate voltage across the load?
- (A) 7.3 V
- (B) 73 V
- (C) 88 V
- (D) 880 V
4. A transformer changes ac to dc.
- (A) True
- (B) False
5. When a 200 Ω load resistor is connected across the secondary winding of a transformer with a turns ratio of 4, the source "sees" a reflective load of
- (A) 50 Ω
- (B) 12.5 Ω
- (C) 800 Ω
- (D) 0 Ω
6. If the supply frequency to the transformer is increased, the iron loss will
- (A) Not change
- (B) Decrease
- (C) Increase
- (D) Any of the above
7. Short circuit test on transformers is conducted to determine
- (A) Hysteresis losses
- (B) Copper losses
- (C) Core losses
- (D) Eddy current losses
8. The primary is the winding connected to the source, and the secondary is the winding connected to the load.
- (A) True
- (B) False
9. What is the coefficient of coupling for a transformer in which 4% of the total flux generated in the primary does not pass through the secondary?
- (A) 0.4
- (B) 4
- (C) 9.6
- (D) 0.96
10. Natural air coo ling is generally restricted for transformers up to
- (A) 1.5 MVA
- (B) 5 MVA
- (C) 15 MVA
- (D) 50 MVA
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