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AC Theory

Instructions:

Answer 50 questions in 30 minutes.
If you are not ready to take this test, you can study here.
Match each statement with the correct term.
Don't refresh. All questions and answers are randomly picked and ordered every time you load a test.

This is a study tool. The 3 wrong answers for each question are randomly chosen from answers to other questions. So, you might find at times the answers obvious, but you will see it re-enforces your understanding as you take the test each time.

1. If you use a clamp-on ammeter or tong tester around all three-phase wires of an energized three- phase circuit simultaneously...
15 feet off the ground.
The current will read zero.
It provides good speed control.
1 amp.

2. How can you tell if a victim receiving mouth-to-mouth resuscitation is getting air into the lungs?
277 volts.
Clamp-on ammeter.
The chest should rise or inflate.
15 feet off the ground.

3. High voltage is used to transmit power over long distances...
5:1
Second-degree burn.
Because less current flowing at high voltage causes less line loss per kilowatt.
Isolation transformer.

4. Where should grounding resistors be located?
At the source transformer.
5:1
Current that changes constantly in magnitude and periodically in direction.
An electromagnet.

5. A transformer with 10 turns on the primary coil and 100 turns on the secondary is classified as...
The current will read zero.
A step-up transformer.
They must be installed at least 7 feet above the ground.
Disconnect the frame-grounding conductor.

6. The purpose of a zig-zag transformer is to...
Draw less current.
Because 440-volt power draws less current so cables and control circuit wiring can be smaller.
12 to 15 times a minute.
Derive a neutral for grounding purposes.

7. A current transformer has a ratio of 350:5. If the phase current is 70 amperes - what would be the secondary current?
Continuous.
1 amp.
The motor rotation is reversed.
100 turns.

8. If the conductors of a balanced - three-phase circuit pass through a current transformer - how many amps will flow in the transformer?
A device used to store electrical energy.
Derive a neutral for grounding purposes.
H terminals.
Zero amps.

9. Surface transformer installations - unless constructed to eliminate shock hazards - must be installed at least...
The sum of the two capacitors.
15 feet off the ground.
A.C.
They must be installed at least 7 feet above the ground.

10. What is the first step to be followed in aiding a victim of electrical shock?
Second-degree burn.
Transformer
Cut around clothing that has adhered to the burned area.
Check to make sure that the victim is not still in contact with the electricity.

11. How do you change the direction of a 3-phase AC motor?
The current will read zero.
Reverse any two-phase leads.
Reduce high AC current to lower values and provide isolation between high voltage circuits and metering.
5:1.

12. Which of the following does a squirrel cage induction motor have?
Nearly constant.
15 feet off the ground.
Stator windings.
Potential transformer.

13. The transformer used only to measure voltage is a...
Because less current flowing at high voltage causes less line loss per kilowatt.
At the source transformer.
Lower current and higher voltage
Potential transformer.

14. If 2000 watts is read in the primary of a single-phase transformer - What is the wattage in the secondary? (Assuming no losses.)
2000 watts
Inductance.
100 volts.
An electromagnet.

15. The primary leads of a single-phase transformer should be connected to the...
Draw less current.
H terminals.
Inductance.
A step-up transformer.

16. The combined capacitance of two capacitors in parallel is...
Potential transformer.
480 volts.
The sum of the two capacitors.
At the source transformer.

17. A transformer has 1 -600 turns in the primary and 400 turns in the secondary. The primary voltage is 2 -400 volts. What is the secondary voltage?
60 cycles per second (60 Hertz).
A.C.
Draw less current.
600 volts.

18. A transformer with 3000 turns in the primary winding has a primary voltage of 4 -800 volts and a secondary voltage of 240 volts. How many turns are in the secondary winding?
150 turns.
Clamp-on ammeter.
5:1
Transformer

19. To protect against over-current in a three-phase circuit over-current protection must be provided for...
1 amp.
At least two phases
An electromagnet.
15 feet off the ground.

20. The following motor leads are brought out of a 3-phase motor (T1 - T2 - T3 - T4 - T5 - T6). This motor is probably for...
Two speeds
The motor rotation is reversed.
Lower current and higher voltage.
3 -979 Volts.

21. Define alternating current...
At the source transformer.
5:1
No.6 AWG.
Current changing constantly in magnitude and periodically in direction.

22. A transformer with a 1:1 ratio is usually a (an)...
Carotid pulse - which is located in the neck next to the Adam's apple.
A device used to store electrical energy.
Isolation transformer.
60 cycles per second (60 Hertz).

23. The property of an electrical circuit that opposes any change in voltage is called...
Check to make sure that the victim is not still in contact with the electricity.
Capacitance.
Provides single-phase power to smaller loads such as lights - heaters - etc.
At the source transformer.

24. If a voltmeter is connected between a phase lead and the ground of a three-phase 480-volt system - the meter will read...
They must be installed at least 7 feet above the ground.
The current will read zero.
An electrical shock hazard may exist.
277 volts.

25. Find the turns ratio of a single-phase transformer with the following values: Primary power of 10 KW - secondary current of 200 amps - and primary voltage of 250 volts.
Derive a neutral for grounding purposes.
Capacitance.
5:1.
X.

26. AC voltage is raised or lowered by means of...
Current changing constantly in magnitude and periodically in direction.
Kilovolt ampere (KVA).
Transformers.
Second-degree burn.

27. What is the danger when working around capacitors?
Provides single-phase power to smaller loads such as lights - heaters - etc.
Grounded phase and ground fault devices were not operating.
An electrical shock hazard may exist.
The motor rotation is reversed.

28. What should the duty rating of a grounding resistor be?
Continuous.
Capacitance.
Because less current flowing at high voltage causes less line loss per kilowatt.
Derive a neutral for grounding purposes.

29. Operating coils - motors - transformers - relays and solenoids depend upon...
The current will read zero.
Electro-magnetism for their operation.
An electromagnet.
H terminals.

30. Which of the following is not needed when using an ohmmeter to determine if a motor is grounded?
Disconnect the frame-grounding conductor.
200 volts AC.
12 to 15 times a minute.
Because 440-volt power draws less current so cables and control circuit wiring can be smaller.

31. If 13 -200 volts are measured from phase-to-phase across a wye-connected secondary - What is the phase-to-ground voltage?
Cut around clothing that has adhered to the burned area.
2000 watts
7 -630 volts.
Current changing constantly in magnitude and periodically in direction.

32. Why is 440-volt - three-phase power more commonly used in mining than 220-volt - three-phase power?
Nearly constant.
Because 440-volt power draws less current so cables and control circuit wiring can be smaller.
5:1
600 volts.

33. When troubleshooting a circuit with a bank of capacitors - what precautions must be taken?
The capacitors should be discharged.
Inductance.
Current changing constantly in magnitude and periodically in direction.
Stator windings.

34. Not true about AC power?
60 cycles per second (60 Hertz).
No.6 AWG.
It provides good speed control.
100 volts.

35. A burn causing a blister is classified as a...
1 amp.
Squirrel-cage rotor.
Second-degree burn.
60 cycles per second (60 Hertz).

36. Current in an AC circuit may be measured by...
Inductance.
60 cycles per second (60 Hertz).
Clamp-on ammeter.
Short-circuited after power has been removed.

37. Should a ground fault occur - what device can be installed to limit the current in the neutral of a three-phase AC system?
Reverse any two-phase leads.
Stator windings.
Provides single-phase power to smaller loads such as lights - heaters - etc.
A grounding resistor.

38. All transformers step voltage up or down by...
Inductance.
Larger than that found in the primary winding.
3 -979 Volts.
277 volts.

39. When connecting 3 single-phase transformers into a three-phase system - which of the following is NOT required for the single-phase transformers.
The motor rotation is reversed.
They should be made by the same manufacturer.
X.
1 amp.

40. What happens to a motor that is connected to a three-phase cable when two of the cable's leads are reversed?
Short-circuited after power has been removed.
The motor rotation is reversed.
Provides single-phase power to smaller loads such as lights - heaters - etc.
Full-load - three-phase voltage.

41. Alternating current may be defined as...
An electromagnet.
Stator windings.
600 volts.
Current that changes constantly in magnitude and periodically in direction.

42. If a voltmeter were placed between two phase leads of a three-phase 480-volt system - the meter would read...
Potential transformer.
480 volts.
An electrical shock hazard may exist.
Carotid pulse - which is located in the neck next to the Adam's apple.

43. If current were flowing through a grounding resistor in a 440-volt - resistance-grounded system - this would probably be because...
Nearly constant.
15 feet off the ground.
Grounded phase and ground fault devices were not operating.
Second-degree burn.

44. The main function of CT's and PT's on a main substation is to...
Allow for metering voltage and Current.
Circuit Breaker.
Current changing constantly in magnitude and periodically in direction.
The sum of the two capacitors.

45. A 3-phase - 2 speed - constant torque motor is running at fast speed. The motor windings are connected wye for fast speed. Motor leads T4 - T5 and T6 are connected to the line leads. Motor leads T1 - T2 and T3 should be...
480 volts.
Electro-magnetism for their operation.
Two speeds
Tied together

46. The current on the primary side of a step-down transformer with a 4:1 ratio will be...
Four times less than that of the secondary.
The chest should rise or inflate.
At least two phases
Inductance.

47. What is a capacitor?
480 volts.
A device used to store electrical energy.
Reduce high AC current to lower values and provide isolation between high voltage circuits and metering.
Inductance.

48. Not a symptom of electrical shock?.
Full-load - three-phase voltage.
Hyperventilation.
Electro-magnetism for their operation.
The capacitors should be discharged.

49. A solenoid coil is...
An electromagnet.
Lower current and higher voltage
Check to make sure that the victim is not still in contact with the electricity.
Zero amps.

50. The load to which the secondary winding of a current transformer was connected has opened. The secondary leads should be...
Allow for metering voltage and Current.
Transformer
Short-circuited after power has been removed.
Disconnect the frame-grounding conductor.

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AC Theory

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Adobe Photoshop CS 5 Keyboard Shortcuts

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After Effects Keyboard Shortcuts

Agile Development

Agile Scrum Methodology

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