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AC Theory

Instructions:

Answer 50 questions in 15 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. The speed of an alternating current - squirrel-cage induction motor is...
Zero amps.
Nearly constant.
An electrical shock hazard may exist.
100 volts.

2. What value of voltage will be measured from phase-to-phase - in a wye-connected secondary - if 2 -300 volts is measured from phase-to-ground?
1 amp.
The capacitors should be discharged.
3 -979 Volts.
At the source transformer.

3. Three-phase AC underground cables must be provided with overcurrent protection using a...
Larger than that found in the primary winding.
Circuit Breaker.
1 amp.
An electromagnet.

4. Using a 10:1 ratio transformer - the terminals on the secondary side or lower voltage side would be marked...
Reverse any two-phase leads.
X.
Allow for metering voltage and Current.
15 feet off the ground.

5. Operating coils - motors - transformers - relays and solenoids depend upon...
Transformer
Electro-magnetism for their operation.
60 Hertz
7 -630 volts.

6. Not a symptom of electrical shock?.
No.6 AWG.
Hyperventilation.
Derive a neutral for grounding purposes.
At least two phases

7. The transformer used only to measure voltage is a...
The sum of the two capacitors.
Potential transformer.
Electro-magnetism for their operation.
60 Hertz

8. The minimum allowable size for trailing cables for mobile haulage equipment powered by alternating current is...
Squirrel-cage induction motor.
H terminals.
No.6 AWG.
The chest should rise or inflate.

9. When troubleshooting a circuit with a bank of capacitors - what precautions must be taken?
Zero amps.
The capacitors should be discharged.
Short-circuited after power has been removed.
60 cycles per second (60 Hertz).

10. A transformer with 1 -500 turns in the primary winding has a primary voltage of 2 -400 volts and a secondary voltage of 120 volts. How many turns are in the secondary winding?
75 turns.
Second-degree burn.
No.6 AWG.
Squirrel-cage induction motor.

11. A transformer with a 1:1 ratio is usually a (an)...
Tied together
200 volts AC.
A step-up transformer.
Isolation transformer.

12. Define alternating current...
Current changing constantly in magnitude and periodically in direction.
They should be made by the same manufacturer.
480 volts.
H terminals.

13. The neutral ground-bed electrical power system of an underground mine should be separated from the lightning arrestor grounds by at least...
25 feet.
The chest should rise or inflate.
A grounding resistor.
60 cycles per second (60 Hertz).

14. How should clothing be removed from a burn?
Inductance.
Alternating current.
Cut around clothing that has adhered to the burned area.
75 turns.

15. AC voltage is raised or lowered by means of...
1 amp.
Continuous.
Transformers.
Clamp-on ammeter.

16. The load to which the secondary winding of a current transformer was connected has opened. The secondary leads should be...
Short-circuited after power has been removed.
Because 440-volt power draws less current so cables and control circuit wiring can be smaller.
Disconnect the frame-grounding conductor.
Draw less current.

17. The combined capacitance of two capacitors in parallel is...
100 turns.
They must be installed at least 7 feet above the ground.
75 turns.
The sum of the two capacitors.

18. The most reliable method to use to determine whether or not the heart has stopped is by checking the...

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19. If a voltmeter were placed between two phase leads of a three-phase 480-volt system - the meter would read...
480 volts.
It provides good speed control.
Lower current and higher voltage
Squirrel-cage rotor.

20. When connecting 3 single-phase transformers into a three-phase system - which of the following is NOT required for the single-phase transformers.
They should be made by the same manufacturer.
Lower current and higher voltage.
Potential transformer.
A grounding resistor.

21. Current in an AC circuit may be measured by...
Kilovolt ampere (KVA).
Clamp-on ammeter.
Larger than that found in the primary winding.
3 -979 Volts.

22. Not true about AC power?
It provides good speed control.
Derive a neutral for grounding purposes.
The capacitors should be discharged.
Grounded phase and ground fault devices were not operating.

23. 460 volts AC is required to operate two motors - one connected in single-phase and the other connected in three-phase. The three-phase motor will...
The chest should rise or inflate.
12 to 15 times a minute.
Draw less current.
Continuous.

24. What happens to a motor that is connected to a three-phase cable when two of the cable's leads are reversed?
Allow for metering voltage and Current.
The motor rotation is reversed.
Nearly constant.
Derive a neutral for grounding purposes.

25. What is the first step to be followed in aiding a victim of electrical shock?
Nearly constant.
200 volts AC.
800 volts.
Check to make sure that the victim is not still in contact with the electricity.

26. The primary leads of a single-phase transformer should be connected to the...
Draw less current.
75 turns.
H terminals.
The chest should rise or inflate.

27. The size of a transformer is measured in...
Kilovolt ampere (KVA).
Isolation transformer.
5:1
75 turns.

28. 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.
An electromagnet.
Potential transformer.
Provides single-phase power to smaller loads such as lights - heaters - etc.

29. High voltage is used to transmit power over long distances...
Current changing constantly in magnitude and periodically in direction.
Disconnect the frame-grounding conductor.
The current will read zero.
Because less current flowing at high voltage causes less line loss per kilowatt.

30. The standard frequency of power supplied by the power company is...
60 cycles per second (60 Hertz).
5:1
A device used to store electrical energy.
Second-degree burn.

31. At what rate should mouth-to-mouth resuscitation be applied?
A device used to store electrical energy.
12 to 15 times a minute.
5:1
Grounded phase and ground fault devices were not operating.

32. If 13 -200 volts are measured from phase-to-phase across a wye-connected secondary - What is the phase-to-ground voltage?
7 -630 volts.
15 feet off the ground.
Transformer
Four times less than that of the secondary.

33. Compared to the secondary of a loaded - step-down transformer - the primary has...
The capacitors should be discharged.
Lower current and higher voltage.
Allow for metering voltage and Current.
2000 watts

34. A solenoid coil is...
An electromagnet.
Shunted and taped
Draw less current.
A.C.

35. A transformer with 10 turns on the primary coil and 100 turns on the secondary is classified as...
A step-up transformer.
The motor rotation is reversed.
A device used to store electrical energy.
Disconnect the frame-grounding conductor.

36. 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?
Cut around clothing that has adhered to the burned area.
600 volts.
Because 440-volt power draws less current so cables and control circuit wiring can be smaller.
Alternating current.

37. If a voltmeter is connected between a phase lead and the ground of a three-phase 480-volt system - the meter will read...
Grounded phase and ground fault devices were not operating.
60 Hertz
Check to make sure that the victim is not still in contact with the electricity.
277 volts.

38. A control power transformer...
A grounding resistor.
H terminals.
Provides single-phase power to smaller loads such as lights - heaters - etc.
Full-load - three-phase voltage.

39. Under fault conditions - the grounding resistor in a high voltage circuit limits the voltage drop in the grounding circuit external to the resistor to not more than...
Larger than that found in the primary winding.
They should be made by the same manufacturer.
100 volts.
75 turns.

40. Surface transformer installations - unless constructed to eliminate shock hazards - must be installed at least...
15 feet off the ground.
The sum of the two capacitors.
75 turns.
60 Hertz

41. The property of an electric circuit that opposes any change in current is called...
Stator windings.
A.C.
A device used to store electrical energy.
Inductance.

42. A current transformer has a ratio of 350:5. If the phase current is 70 amperes - what would be the secondary current?
1 amp.
2000 watts
60 cycles per second (60 Hertz).
75 turns.

43. How can you tell if a victim receiving mouth-to-mouth resuscitation is getting air into the lungs?
Continuous.
A.C.
The chest should rise or inflate.
The motor rotation is reversed.

44. Not an acceptable method for the installations of surface transformers?
A device used to store electrical energy.
The sum of the two capacitors.
They must be installed at least 7 feet above the ground.
A grounding resistor.

45. Which of the following is not needed when using an ohmmeter to determine if a motor is grounded?
Disconnect the frame-grounding conductor.
3 -979 Volts.
Larger than that found in the primary winding.
Shunted and taped

46. The primary function of a power transformer is to provide...
Full-load - three-phase voltage.
They must be installed at least 7 feet above the ground.
Cut around clothing that has adhered to the burned area.
2000 watts

47. The secondary windings on a 10:1 step-down transformer will have a wire size...
Larger than that found in the primary winding.
Capacitance.
Draw less current.
Clamp-on ammeter.

48. The main function of CT's and PT's on a main substation is to...
75 turns.
3 -979 Volts.
At the source transformer.
Allow for metering voltage and Current.

49. If the conductors of a balanced - three-phase circuit pass through a current transformer - how many amps will flow in the transformer?
Zero amps.
Squirrel-cage induction motor.
H terminals.
Circuit Breaker.

50. A transformer has a primary voltage of 2 -800 volts and a secondary reading of 140 volts. If there are 2000 turns on the primary - how many turns are on the secondary?
100 turns.
A step-up transformer.
Squirrel-cage induction motor.
Inductance.