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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 transformer used only to measure voltage is a...
Potential transformer.
Shunted and taped
Because 440-volt power draws less current so cables and control circuit wiring can be smaller.
It provides good speed control.

2. At what rate should mouth-to-mouth resuscitation be applied?
12 to 15 times a minute.
Nearly constant.
Stator windings.
Lower current and higher voltage.

3. The standard frequency of power supplied by the power company is...
Carotid pulse - which is located in the neck next to the Adam's apple.
Current that changes constantly in magnitude and periodically in direction.
Hyperventilation.
60 cycles per second (60 Hertz).

4. What is the first step to be followed in aiding a victim of electrical shock?
Check to make sure that the victim is not still in contact with the electricity.
Nearly constant.
480 volts.
Larger than that found in the primary winding.

5. How should clothing be removed from a burn?
Cut around clothing that has adhered to the burned area.
The current will read zero.
100 volts.
Disconnect the frame-grounding conductor.

6. Compared to the secondary of a loaded - step-down transformer - the primary has...
The current will read zero.
Carotid pulse - which is located in the neck next to the Adam's apple.
Circuit Breaker.
Lower current and higher voltage.

7. Using a 10:1 ratio transformer - the terminals on the secondary side or lower voltage side would be marked...
600 volts.
The motor rotation is reversed.
25 feet.
X.

8. A transformer with a 1:1 ratio is usually a (an)...
Isolation transformer.
2000 watts
Kilovolt ampere (KVA).
480 volts.

9. The primary leads of a single-phase transformer should be connected to the...
The current will read zero.
H terminals.
At the source transformer.
60 cycles per second (60 Hertz).

10. The standard frequency of alternating current used at a mine is...
5:1
X.
60 Hertz
No.6 AWG.

11. What type motor is a wound-rotor induction motor?
100 turns.
A.C.
X.
The chest should rise or inflate.

12. Current that changes periodically in direction is...
Potential transformer.
75 turns.
277 volts.
Alternating current.

13. The primary function of a power transformer is to provide...
Transformer
5:1.
Full-load - three-phase voltage.
An electromagnet.

14. The main function of CT's and PT's on a main substation is to...
A device used to store electrical energy.
The sum of the two capacitors.
Allow for metering voltage and Current.
Inductance.

15. 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...
Draw less current.
Allow for metering voltage and Current.
The capacitors should be discharged.
Transformer

16. The property of an electric circuit that opposes any change in current is called...
Inductance.
60 Hertz
Circuit Breaker.
Two speeds

17. What is the danger when working around capacitors?
The capacitors should be discharged.
Grounded phase and ground fault devices were not operating.
3 -979 Volts.
An electrical shock hazard may exist.

18. If 13 -200 volts are measured from phase-to-phase across a wye-connected secondary - What is the phase-to-ground voltage?
Stator windings.
Squirrel-cage induction motor.
7 -630 volts.
Reverse any two-phase leads.

19. The current on the primary side of a step-down transformer with a 4:1 ratio will be...
The current will read zero.
Four times less than that of the secondary.
25 feet.
600 volts.

20. When connecting 3 single-phase transformers into a three-phase system - which of the following is NOT required for the single-phase transformers.
3 -979 Volts.
They should be made by the same manufacturer.
Squirrel-cage induction motor.
Because less current flowing at high voltage causes less line loss per kilowatt.

21. AC voltage is raised or lowered by means of...
Reverse its rotation.
Transformers.
Second-degree burn.
15 feet off the ground.

22. Not an acceptable method for the installations of surface transformers?
Second-degree burn.
Lower current and higher voltage
They must be installed at least 7 feet above the ground.
Reverse any two-phase leads.

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

24. What should the duty rating of a grounding resistor be?
25 feet.
Current changing constantly in magnitude and periodically in direction.
Continuous.
Because less current flowing at high voltage causes less line loss per kilowatt.

25. Which of the following does a squirrel cage induction motor have?
100 turns.
5:1.
Stator windings.
200 volts AC.

26. The neutral ground-bed electrical power system of an underground mine should be separated from the lightning arrestor grounds by at least...
25 feet.
H terminals.
100 volts.
Two speeds

27. A transformer with 10 turns on the primary coil and 100 turns on the secondary is classified as...
200 volts AC.
Carotid pulse - which is located in the neck next to the Adam's apple.
Stator windings.
A step-up transformer.

28. A solenoid coil is...
480 volts.
An electromagnet.
Electro-magnetism for their operation.
25 feet.

29. Compared to the secondary of a loaded - step-down transformer - the primary has...
Lower current and higher voltage
H terminals.
75 turns.
5:1.

30. 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?
An electromagnet.
Because 440-volt power draws less current so cables and control circuit wiring can be smaller.
A step-up transformer.
600 volts.

31. Not a symptom of electrical shock?.
A step-up transformer.
Reduce high AC current to lower values and provide isolation between high voltage circuits and metering.
Hyperventilation.
No.6 AWG.

32. High voltage is used to transmit power over long distances...
Because less current flowing at high voltage causes less line loss per kilowatt.
Second-degree burn.
Allow for metering voltage and Current.
They should be made by the same manufacturer.

33. What position of a selector switch using a voltmeter would you select to check a 120-volt AC circuit to obtain the most accurate reading?
277 volts.
They must be installed at least 7 feet above the ground.
5:1.
200 volts AC.

34. What happens to a motor that is connected to a three-phase cable when two of the cable's leads are reversed?
Continuous.
The motor rotation is reversed.
100 volts.
Inductance.

35. All transformers step voltage up or down by...
Two speeds
Inductance.
Check to make sure that the victim is not still in contact with the electricity.
Shunted and taped

36. A wound-rotor induction motor has all the following EXCEPT...
Because less current flowing at high voltage causes less line loss per kilowatt.
Squirrel-cage rotor.
75 turns.
Four times less than that of the secondary.

37. If current were flowing through a grounding resistor in a 440-volt - resistance-grounded system - this would probably be because...
Reverse its rotation.
They should be made by the same manufacturer.
Grounded phase and ground fault devices were not operating.
Kilovolt ampere (KVA).

38. A current transformer has a ratio of 350:5. If the phase current is 70 amperes - what would be the secondary current?
1 amp.
Continuous.
12 to 15 times a minute.
277 volts.

39. Define alternating current...
Reduce high AC current to lower values and provide isolation between high voltage circuits and metering.
277 volts.
Kilovolt ampere (KVA).
Current changing constantly in magnitude and periodically in direction.

40. The following motor leads are brought out of a 3-phase motor (T1 - T2 - T3 - T4 - T5 - T6). This motor is probably for...
Current that changes constantly in magnitude and periodically in direction.
The capacitors should be discharged.
Two speeds
Continuous.

41. Surface transformer installations - unless constructed to eliminate shock hazards - must be installed at least...
Electro-magnetism for their operation.
15 feet off the ground.
At least two phases
Hyperventilation.

42. The purpose of a zig-zag transformer is to...
A.C.
Derive a neutral for grounding purposes.
Squirrel-cage induction motor.
Circuit Breaker.

43. A transformer has a primary voltage of 2 -400 volts and a secondary reading of 120 volts. If there are 1 -500 turns on the primary - how many turns are on the secondary?
Inductance.
They should be made by the same manufacturer.
75 turns.
Isolation transformer.

44. How can you tell if a victim receiving mouth-to-mouth resuscitation is getting air into the lungs?
A device used to store electrical energy.
No.6 AWG.
The chest should rise or inflate.
They should be made by the same manufacturer.

45. Three-phase AC underground cables must be provided with overcurrent protection using a...
25 feet.
Cut around clothing that has adhered to the burned area.
Circuit Breaker.
75 turns.

46. 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?
An electrical shock hazard may exist.
3 -979 Volts.
5:1.
100 turns.

47. If any two-phase wires are reversed on a three-phase motor - the motor will...
Alternating current.
At least two phases
100 turns.
Reverse its rotation.

48. The speed of an alternating current - squirrel-cage induction motor is...
7 -630 volts.
Zero amps.
60 Hertz
Nearly constant.

49. 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.
Full-load - three-phase voltage.
They should be made by the same manufacturer.
5:1.
The motor rotation is reversed.

50. The minimum allowable size for trailing cables for mobile haulage equipment powered by alternating current is...
Zero amps.
A.C.
Inductance.
No.6 AWG.