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i need help with penn foster exams 006806 wiring havac circuits 086011

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i need help with penn foster exams
006806 wiring havac circuits
086011 transformers
006807 advanced electrical work
006037 wiring electrical circuits
Submitted: 5 years ago.
Category: Homework
Expert:  akch2002 replied 5 years ago.
how many questions are there in each exam?
Customer: replied 5 years ago.


Examination Number

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Questions 1 to 20: Select the best answer to each question.
* All questions require an answer ( 1 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 )
* 1. What is the efficiency of a transformer that has an input of 600 VA and an output to a load of 580 VA?
A. 20 VA
B. 180 VA
C. 83.8%
D. 96.6%
2. The secondary line-to-line voltage of a three-phase Y-Y-connected transformer bank is 115 VAC. What would be the secondary line to neutral voltage?
A. 199.2 V
B. 66.4 V
C. 84.2 V
D. 50 V
* 3. Most of the transformers that you'll find in your plant are either single-phase or
A. zero-phase.
B. two-phase.
C. three-phase.
D. four-phase.
* 4. An inductor whose reactance can be varied by supplying current through a separate DC winding is called
A. a reactance tube.
B. a current transformer.
C. an autotransformer.
D. a saturable reactor.
* 5. If the turns ratio of a transformer is 4 : 1 and the incoming voltage is 120 VAC, what is the secondary voltage?
A. 30 VAC
B. 120 VAC
C. 240 VAC
D. 480 VAC
* 6. If the primary in a transformer has more turns than the secondary, the secondary has
A. lower current.
B. lower voltage.
C. higher power.
D. lower ampere-turns.
* 7. What type of transformer is used to prevent electrical noise from passing from the primary winding to the secondary winding?
A. Dry-type transformer
B. Oil-filled transformer
C. Shielded transformer
D. Delta transformer
* 8. You'll work at times with a transformer that has one winding connected in series with the other to form the equivalent of a single winding. This is called
A. a distribution transformer.
B. an electronic transformer.
C. a specialty transformer.
D. an autotransformer.
* 9. If the power in the primary circuit of a 4 : 1 transformer is 12 watts, what will be the power in the secondary of this transformer?
A. 3 watts
B. 4 watts
C. 12 watts
D. 48 watts
* 10. What would be the power in the secondary of a transformer that has a voltage of 48 VAC and a current of 2.2 A?
A. 52.8 watts
B. 105.6 watts
C. 121.8 watts
D. 212.6 watts
* 11. What is the kVA rating of a transformer that has a secondary winding that's delivering 10 amps at 480 VAC?
A. 4.8 kVA
B. 48 kVA
C. 480 kVA
D. 4800 kVA
* 12. A basic transformer consists of two separate conductive coils wrapped around a(n) _____ core.
A. copper
B. oiled paper
C. iron
D. plastic
* 13. Three single-phase transformers, each having a secondary phase current of 10 A, are Delta-Delta-connected. The value of the secondary line current is
A. 1.73 A.
B. 17.3 A.
C. 57.8 A.
D. 578 A.
* 14. The primary current drawn by the transformer shown below will be
A. 2 A.
B. 5 A.
C. 10 A.
D. 50 A.


* 15. What special installation or maintenance requirements are needed for askarel-insulated transformers?
A. Cooling water must be supplied to the transformer core.
B. The transformer must be installed in a vault if the voltage exceeds 35,000 VAC.
C. The oil must be changed at least once a year.
D. The radiator must be installed where air can circulate and the fins must remain clean.
* 16. Typical potential transformers are used for
A. allowing the connection of low-voltage measuring instruments to high-voltage lines.
B. biasing control circuits in high-voltage circuits.
C. powering lighting systems from high-voltage feed lines.
D. powering current-sensitive relays in control circuits.
* 17. Why are high-quality transformers wound with large diameter wire?
A. To lower the hysteresis losses
B. To lower the I2R losses
C. To lower the eddy current losses
D. To lower the magnetic leakage losses
* 18. If 120 VAC is applied to a transformer with a turns ratio of 6 : 1, what type of transformer is present and what is the output voltage of the secondary?
A. Step up, 720 VAC
B. Step up, 600 VAC
C. Step down, 20 VAC
D. Step down, 60 VAC
* 19. When a load is suddenly connected to a transformer, the secondary voltage will be reduced. This drop in voltage is called transformer
A. seduction.
B. regulation.
C. excitation.
D. conductance.
* 20. What type of device is used on a distribution transformer to protect the transformer from voltage spikes?
A. A fuse
B. A pressure vent
C. A surge diverter
D. A ground shield
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Expert:  akch2002 replied 5 years ago.
Thanks. I have got the questions and will try to upload the answers today.
Expert:  akch2002 replied 5 years ago.

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