Electrical Machines Quiz (Transformer)

1. What kVA rating is required for a transformer that must handle a maximum load current of 8 A with a        secondary voltage of 2 kV?
A. 4 kVA
B. 0.25 kVA
C. 16 kVA
D. 8 kVA

2. The turns ratio required to match an 80  source to a 320  load is
A. 80 B. 20
C. 4 D. 2

3. When the turns ratio of a transformer is 20 and the primary ac voltage is 12 V, the secondary voltage is
A. 12 V
B. 120 V
C. 240 V
D. 2,400 V

4. If a transformer has 50 turns in the primary winding and 10 turns in the secondary winding, what is the reflective resistance if the secondary load resistance is 250 ?
A. 250
B. 25
C. 6,250
D. 62,500

5. A certain transformer has 400 turns in the primary winding and 2,000 turns in the secondary winding. The turns ratio is
A. 0.2 
B. 0.4
C. 5 
D. 25

6. The primary winding of a transformer has 110 V ac across it. What is the secondary voltage if the turns ratio is 8?
A. 8.8 V
B. 88 V
C. 880 V
D. 8,800 V

7. To step 110 V ac down to 20 V ac, the turns ratio must be
A. 5.5 
B. 18
C. 0.18 
D. 0.018

8. The mutual inductance when k = 0.65, L1 = 2 H, and L2 = 5 H is
A. 2 mH
B. 2 H
C. 4 H
D. 8 H

9. If 25 W of power are applied to the primary of an ideal transformer with a turns ratio of 10, the power delivered to the secondary load is
A. 25 W
B. 0 W
C. 250 W
D. 2.5 W

10. A transformer with a 110 V primary has a 15:1 turns ratio. The load resistance, RL, is 120 . What is the approximate voltage across the load?
A. 7.3 V
B. 73 V
C. 88 V
D. 880 V

Answers:
1. c
2. d
3. c
4. c
5. c
6. c
7. c
8. b
9. a
10. a

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