QUIZ OF DAY-TRANSFORMER BASIC NUMERICAL QUESTIONS AND ANSWERS

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
Answer: Option C

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

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
Answer: Option C

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 ohm?
A.
250 ohm
B.
25 ohm
C.
6,250 ohm
D.
62,500 ohm
Answer: Option C

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
Answer: Option C

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
Answer: Option C

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
Answer: Option C

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

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
Answer: Option A

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

11. 
How many primary volts must be
applied to a transformer with a turns ratio of 0.1 to obtain a secondary
voltage of 9 V?
A.
9 V
B.
90 V
C.
900 V
D.
0.9 V
Answer: Option B

12. 
In a certain loaded transformer,
the secondary voltage is one-fourth the primary voltage. The secondary
current is
A.
one-fourth the primary current
B.
four times the primary current
C.
equal to the primary current
D.
one-fourth the primary current
and equal to the primary current
Answer: Option B

13. 
A certain transformer has a turns
ratio of 1 and a 0.85 coefficient of coupling. When 2 V ac is applied to the
primary, the secondary voltage is
A.
1.7 V
B.
0.85 V
C.
1 V
D.
0 V
Answer: Option A

14. 
The primary coil of a transformer
is connected to a 60 V ac source. The secondary coil is connected to a 330 ohm  load. The turns ratio is 3:1.
What is the secondary voltage?
A.
2 V
B.
20 V
C.
180 V
D.
18 V
Answer: Option B

15. 
The primary winding of a power
transformer should always be
A.
open
B.
shorted
C.
switched
D.
fused
Answer: Option D

16. 
A certain amplifier has 600 ohm internal resistance looking
from its output. In order to provide maximum power to a 4 ohm speaker, what turns ratio must
be used in the coupling transformer?
A.
8
B.
0.8
C.
0.08
D.
80
Answer: Option C

17.A transformer
A.
changes ac to dc
B.
changes dc to ac
C.
steps up or down dc voltages
D.
steps up or down ac voltages
Answer: Option D

18. 
The primary of a transformer is
connected to a 6 V battery. The turns ratio is 1:3 and the secondary load, RL,
is 100 ohm. The voltage across the load
is
A.
0 V
B.
6 V
C.
18 V
D.
2 V
Answer: Option A

19. 
To step 120 V ac up to 900 V ac,
the turns ratio must be
A.
75
B.
750
C.
7.5
D.
0.13
Answer: Option C

20. 
When a 200 ohm 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 ohm
B.
12.5 ohm
C.
800 ohm
D.
0 ohm
Answer: Option B

21. 
In a certain transformer, the
input power to the primary is 120 W. If 8.5 W are lost to the winding
resistance, what is the output power to the load, neglecting any other
issues?
A.
0 W
B.
14.1 W
C.
111.5 W
D.
1,020 W
Answer: Option C

22. 
When a 6 V battery is connected
across the primary of a transformer with a turns ratio of 8, the secondary
voltage is
A.
0 V
B.
6 V
C.
48 V
D.
0.75 V
Answer: Option A

23. 
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
Answer: Option D

24. 
A transformer has a 1:6 turns
ratio and a secondary coil load resistance of 470 ohm. The load resistance as seen
by the source is
A.
1.3 ohm
B.
7.8 ohm
C.
78 ohm
D.
13 ohm
Answer: Option D

QUIZ OF DAY-11/06/2017 GK & CURRENT AFFAIRS
GENERAL KNOWLEDGE QUIZ-34 (IMPORTANT OLD GK FOR VIZAG MT EXAM )

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