# ELECTRICIAN`S MATE Quiz 07:

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1. When a transformer transfers electrical energy, what elements are either increased or decreased by the transformer?

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Frequency, voltage, and current

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Voltage and frequency only

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Frequency and current only

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Current and voltage only
Current and voltage only
2. When you use vectors to analyze ac circuits, what rotation direction represents (a) positive and (b) negative polarity?

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(a) Counterclockwise (b) left

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(a) Counterclockwise (b) clockwise

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(a) Right (b) left

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(a) Right (b) clockwise
•  (a) Counterclockwise (b) clockwise
3. In each winding of a transformer, the total induced voltage has what relationship to the number of turns in that winding?

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Reciprocal

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Subtractive

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Proportional

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Proportional
4. At which of the following points will a generator’s output voltage increase?

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When the rotating field strength increases

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Both 1 and 2 above

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When the rotor speed decreases
When the rotating field strength increases
5. When the phase current in a balanced deltaconnected generator is 20 amperes, what is the line current?

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20.0 A

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34.6 A

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6.6 A

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10.0 A
20.0 A
6. A generator is operating at 450 volts ac, 60 hertz, supplying a load of 1,000 amperes and 306,000 watts. What is the power factor?

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0.80

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0.75

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1.24

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0.68
0.68
7. When dealing with the load rating of ac generators, what factor must be accounted for?

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The weight of the field windings

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The type of voltage regulator used

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The speed of the generator

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The internal heat the generator can withstand
The internal heat the generator can withstand
8. When the phase voltage is 100 volts in a deltaconnected ac generator, what is the line or load voltage?

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100.0 V

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173.0 V

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200.0 V

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70.7 V
100.0 V
9. In transformers, electrical energy is transferred from one circuit to another through which of the following actions?

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Hysteresis coupling

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Resistive-capacitive coupling

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Electromagnetic induction
Electromagnetic induction
10. The rotary force used to provide the rotating action in generators may be supplied by which of the following prime movers?

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An electric motor

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A turbine

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An internal combustion engine

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Each of the above
Each of the above
11. In a transformer, what winding is designated as the primary?

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The one that delivers energy to the load

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The one that receives energy from an ac source

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The one with the lowest voltage

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The one with the highest voltage
The one that delivers energy to the load
12. A transformer’s efficiency is stated as a ratio of what factor of the transformer’s input to output?

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Line loss

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Phase current

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Voltage

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Power
Power
13. The line voltage of a wye-connected stator with a balanced load isn’t twice the phase voltage for what reason?

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The phase voltages are out of phase with each other

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The loads seen by the generator are usually inductive

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The line currents are unequal

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The load across each line is different
The phase voltages are out of phase with each other
14. In a transformer, the low-voltage winding is placed next to the core instead of the highvoltage winding for what reason?

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To reduce Ir drop

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To reduce hysteresis loss

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To reduce leakage flux

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To reduce insulation requirements
To reduce insulation requirements
15. The most practical method to control voltage of an ac generator is to regulate the generator’s speed.

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True

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False
False
16. AC generator sets may be divided into what two classes?

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Low-speed, engine-driven and high-speed, turbine-driven

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High-speed, turbine-driven and high-speed, engine-driven

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Low-speed, engine-driven and low-speed, turbine-driven

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Low-speed, turbine-driven and high-speed, engine-driven
Low-speed, engine-driven and high-speed, turbine-driven
17. What function is provided by ac generator exciters?

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DC to the field windings

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AC to the stationary armature

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AC to the stationary field windings
AC to the stationary armature
18. You can reduce eddy current losses in the core of a transformer by installing which of the following components?

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Subdivided windings

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Thin, insulated lamination

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Heat-treated core material

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Grain-oriented material
Thin, insulated lamination
19. A decrease in general terminal voltage caused by an inductive load is partly the result of which of the following actions?

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Increased armature mmf produced by increased field flux

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Reduced dc field flux caused by the opposing action of the armature mmf

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Increased dc field flux caused by the aiding action of the armature mmf

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Reduced current through the armature conductors
Reduced current through the armature conductors
20. Which of the following statements defines the term power factor?

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The product of the voltage and the current of the system

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The difference between the voltage and the current

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It is set at 0.08 lagging

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The expression of the losses within the electrical distribution system
The expression of the losses within the electrical distribution system
21. Because of damage caused by heat, you should NOT operate a transformer rated at 400 hertz at which of the following frequencies?

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340

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370

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450

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420
370
22. What is the magnitude of the voltage across any two phases?

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Equal to the voltage across a single phase

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Equal to the sum of the voltage across all three phases

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Larger than the voltage across a single phase

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Smaller than the voltage across a single Phase
Larger than the voltage across a single phase
23. In a purely capacitive circuit, what is the relationship between voltage and current?

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Voltage and current are in phase

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Current lags voltage

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Voltage and current are in phase
24. The output frequency of an ac generator varies directly with which of the following generator characteristics?

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The number of poles on the rotor

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The speed of rotation of the rotor

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Both 1 and 2 above

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The frequency of the field current
Both 1 and 2 above
25. The rotary force from the prime mover is transmitted to the ac generator by which of the following components?

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Rotor drive shaft

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Stator

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AC generator armature

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Exciter field
Rotor drive shaft
 Author: david11090 ID: 232214 Card Set: ELECTRICIAN`S MATE Quiz 07: Updated: 2013-09-01 05:46:22 Tags: ELECTRICIAN`S MATE Quiz 07 Folders: Description: ELECTRICIAN`S MATE Quiz 07: Show Answers: