Test your basic knowledge |

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. 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.
Grounded phase and ground fault devices were not operating.
5:1
No.6 AWG.

2. Not an acceptable method for the installations of surface transformers?
They must be installed at least 7 feet above the ground.
Electro-magnetism for their operation.
12 to 15 times a minute.
Reverse any two-phase leads.

3. Should a ground fault occur - what device can be installed to limit the current in the neutral of a three-phase AC system?
Second-degree burn.
They should be made by the same manufacturer.
A grounding resistor.
Because less current flowing at high voltage causes less line loss per kilowatt.

4. 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.
Inductance.
Potential transformer.
Stator windings.

5. Not a symptom of electrical shock?.
Tied together
Hyperventilation.
3 -979 Volts.
An electromagnet.

6. A transformer with 10 turns on the primary coil and 100 turns on the secondary is classified as...
100 turns.
Shunted and taped
Tied together
A step-up transformer.

7. If 2000 watts is read in the primary of a single-phase transformer - What is the wattage in the secondary? (Assuming no losses.)
They must be installed at least 7 feet above the ground.
Reverse its rotation.
A grounding resistor.
2000 watts

8. A transformer with a 1:1 ratio is usually a (an)...
Isolation transformer.
5:1.
Inductance.
The motor rotation is reversed.

9. At what rate should mouth-to-mouth resuscitation be applied?
Lower current and higher voltage
12 to 15 times a minute.
The sum of the two capacitors.
The motor rotation is reversed.

10. Define alternating current...
Current changing constantly in magnitude and periodically in direction.
Isolation transformer.
Larger than that found in the primary winding.
At the source transformer.

11. 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...
Transformers.
60 cycles per second (60 Hertz).
Because less current flowing at high voltage causes less line loss per kilowatt.
Draw less current.

12. Compared to the secondary of a loaded - step-down transformer - the primary has...
Lower current and higher voltage.
1 amp.
The motor rotation is reversed.
480 volts.

13. Surface transformer installations - unless constructed to eliminate shock hazards - must be installed at least...
An electromagnet.
The capacitors should be discharged.
The sum of the two capacitors.
15 feet off the ground.

14. The neutral ground-bed electrical power system of an underground mine should be separated from the lightning arrestor grounds by at least...
Potential transformer.
Four times less than that of the secondary.
Short-circuited after power has been removed.
25 feet.

15. The main function of CT's and PT's on a main substation is to...
800 volts.
Isolation transformer.
Allow for metering voltage and Current.
12 to 15 times a minute.

16. The standard frequency of alternating current used at a mine is...
Lower current and higher voltage.
Short-circuited after power has been removed.
12 to 15 times a minute.
60 Hertz

17. Where should grounding resistors be located?
It provides good speed control.
At the source transformer.
2000 watts
Tied together

18. Current transformers - or CT's - are used to...
Hyperventilation.
75 turns.
H terminals.
Reduce high AC current to lower values and provide isolation between high voltage circuits and metering.

19. Current in an AC circuit may be measured by...
Clamp-on ammeter.
12 to 15 times a minute.
Reverse any two-phase leads.
Shunted and taped

20. A transformer has 2000 turns in the primary and 500 turns in the secondary. The primary voltage is 3 -200 volts. What is the secondary voltage?
Inductance.
800 volts.
Cut around clothing that has adhered to the burned area.
Draw less current.

21. The load to which the secondary winding of a current transformer was connected has opened. The secondary leads should be...
Kilovolt ampere (KVA).
They must be installed at least 7 feet above the ground.
A device used to store electrical energy.
Short-circuited after power has been removed.

22. The purpose of a zig-zag transformer is to...
A step-up transformer.
Electro-magnetism for their operation.
Derive a neutral for grounding purposes.
Carotid pulse - which is located in the neck next to the Adam's apple.

23. 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?
Reduce high AC current to lower values and provide isolation between high voltage circuits and metering.
60 cycles per second (60 Hertz).
H terminals.
3 -979 Volts.

24. If any two-phase wires are reversed on a three-phase motor - the motor will...
Reverse its rotation.
Continuous.
It provides good speed control.
Grounded phase and ground fault devices were not operating.

25. 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...
Clamp-on ammeter.
Two speeds
100 volts.
5:1

26. The transformer used only to measure voltage is a...
The sum of the two capacitors.
A device used to store electrical energy.
A step-up transformer.
Potential transformer.

27. What is the danger when working around capacitors?
Carotid pulse - which is located in the neck next to the Adam's apple.
An electrical shock hazard may exist.
2000 watts
At the source transformer.

28. What is a capacitor?
Inductance.
Circuit Breaker.
A device used to store electrical energy.
Because 440-volt power draws less current so cables and control circuit wiring can be smaller.

29. If the conductors of a balanced - three-phase circuit pass through a current transformer - how many amps will flow in the transformer?
60 cycles per second (60 Hertz).
Zero amps.
800 volts.
Draw less current.

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

31. If current were flowing through a grounding resistor in a 440-volt - resistance-grounded system - this would probably be because...
Grounded phase and ground fault devices were not operating.
They must be installed at least 7 feet above the ground.
Isolation transformer.
Tied together

32. 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?
Two speeds
277 volts.
The sum of the two capacitors.
600 volts.

33. Three-phase AC underground cables must be provided with overcurrent protection using a...
Circuit Breaker.
Provides single-phase power to smaller loads such as lights - heaters - etc.
At least two phases
Grounded phase and ground fault devices were not operating.

34. 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?
Electro-magnetism for their operation.
Allow for metering voltage and Current.
75 turns.
Lower current and higher voltage.

35. To protect against over-current in a three-phase circuit over-current protection must be provided for...
It provides good speed control.
At least two phases
5:1.
800 volts.

36. What type of 3-phase AC motor is used most often around a mine?
Kilovolt ampere (KVA).
Inductance.
A step-up transformer.
Squirrel-cage induction motor.

37. The speed of an alternating current - squirrel-cage induction motor is...
It provides good speed control.
Nearly constant.
2000 watts
75 turns.

38. When connecting 3 single-phase transformers into a three-phase system - which of the following is NOT required for the single-phase transformers.
Check to make sure that the victim is not still in contact with the electricity.
100 volts.
60 Hertz
They should be made by the same manufacturer.

39. High voltage is used to transmit power over long distances...
Hyperventilation.
Lower current and higher voltage
Because less current flowing at high voltage causes less line loss per kilowatt.
100 turns.

40. How can you tell if a victim receiving mouth-to-mouth resuscitation is getting air into the lungs?
Provides single-phase power to smaller loads such as lights - heaters - etc.
The chest should rise or inflate.
A grounding resistor.
15 feet off the ground.

41. When not connected to a load - the secondary leads of a current transformer should be...
Shunted and taped
100 volts.
75 turns.
Transformers.

42. The following motor leads are brought out of a 3-phase motor (T1 - T2 - T3 - T4 - T5 - T6). This motor is probably for...
600 volts.
Alternating current.
Two speeds
7 -630 volts.

43. When troubleshooting a circuit with a bank of capacitors - what precautions must be taken?
Reverse its rotation.
The capacitors should be discharged.
Inductance.
Because 440-volt power draws less current so cables and control circuit wiring can be smaller.

44. Operating coils - motors - transformers - relays and solenoids depend upon...
Electro-magnetism for their operation.
At the source transformer.
Derive a neutral for grounding purposes.
The chest should rise or inflate.

45. 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?
A device used to store electrical energy.
A grounding resistor.
They should be made by the same manufacturer.
200 volts AC.

46. What happens to a motor that is connected to a three-phase cable when two of the cable's leads are reversed?
3 -979 Volts.
200 volts AC.
The motor rotation is reversed.
Second-degree burn.

47. Which of the following does a squirrel cage induction motor have?
Stator windings.
X.
Transformer
Draw less current.

48. How should clothing be removed from a burn?
Cut around clothing that has adhered to the burned area.
5:1.
Because less current flowing at high voltage causes less line loss per kilowatt.
Transformers.

49. What type motor is a wound-rotor induction motor?
A.C.
Alternating current.
Derive a neutral for grounding purposes.
5:1

50. Using a 10:1 ratio transformer - the terminals on the secondary side or lower voltage side would be marked...
Alternating current.
X.
Second-degree burn.
No.6 AWG.