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. If 13 -200 volts are measured from phase-to-phase across a wye-connected secondary - What is the phase-to-ground voltage?
Transformers.
Reverse any two-phase leads.
7 -630 volts.
Reverse its rotation.

2. The load to which the secondary winding of a current transformer was connected has opened. The secondary leads should be...
Grounded phase and ground fault devices were not operating.
277 volts.
Short-circuited after power has been removed.
Isolation transformer.

3. If you use a clamp-on ammeter or tong tester around all three-phase wires of an energized three- phase circuit simultaneously...
Because 440-volt power draws less current so cables and control circuit wiring can be smaller.
Full-load - three-phase voltage.
Draw less current.
The current will read zero.

4. Which of the following does a squirrel cage induction motor have?
Provides single-phase power to smaller loads such as lights - heaters - etc.
Full-load - three-phase voltage.
Stator windings.
Allow for metering voltage and Current.

5. A wound-rotor induction motor has all the following EXCEPT...
Stator windings.
Cut around clothing that has adhered to the burned area.
Squirrel-cage rotor.
Tied together

6. Alternating current may be defined as...
Current that changes constantly in magnitude and periodically in direction.
Current changing constantly in magnitude and periodically in direction.
Tied together
They must be installed at least 7 feet above the ground.

7. Compared to the secondary of a loaded - step-down transformer - the primary has...
Lower current and higher voltage
Clamp-on ammeter.
An electrical shock hazard may exist.
Circuit Breaker.

8. If the conductors of a balanced - three-phase circuit pass through a current transformer - how many amps will flow in the transformer?
Cut around clothing that has adhered to the burned area.
Disconnect the frame-grounding conductor.
The capacitors should be discharged.
Zero amps.

9. The neutral ground-bed electrical power system of an underground mine should be separated from the lightning arrestor grounds by at least...
25 feet.
Disconnect the frame-grounding conductor.
Tied together
Cut around clothing that has adhered to the burned area.

10. 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?
No.6 AWG.
Current changing constantly in magnitude and periodically in direction.
60 Hertz
800 volts.

11. The speed of an alternating current - squirrel-cage induction motor is...
H terminals.
Because less current flowing at high voltage causes less line loss per kilowatt.
X.
Nearly constant.

12. 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...
12 to 15 times a minute.
Tied together
7 -630 volts.
480 volts.

13. The property of an electrical circuit that opposes any change in voltage is called...
Circuit Breaker.
Capacitance.
2000 watts
480 volts.

14. What should the duty rating of a grounding resistor be?
Carotid pulse - which is located in the neck next to the Adam's apple.
Continuous.
75 turns.
H terminals.

15. Not true about AC power?
100 turns.
Kilovolt ampere (KVA).
It provides good speed control.
2000 watts

16. 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?
Squirrel-cage induction motor.
600 volts.
Lower current and higher voltage.
Short-circuited after power has been removed.

17. 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.
800 volts.
A grounding resistor.
An electromagnet.

18. The combined capacitance of two capacitors in parallel is...
60 cycles per second (60 Hertz).
The capacitors should be discharged.
150 turns.
The sum of the two capacitors.

19. Operating coils - motors - transformers - relays and solenoids depend upon...
The motor rotation is reversed.
Potential transformer.
Electro-magnetism for their operation.
3 -979 Volts.

20. Not an acceptable method for the installations of surface transformers?
At least two phases
60 Hertz
They must be installed at least 7 feet above the ground.
Hyperventilation.

21. All transformers step voltage up or down by...
7 -630 volts.
200 volts AC.
Disconnect the frame-grounding conductor.
Inductance.

22. What happens to a motor that is connected to a three-phase cable when two of the cable's leads are reversed?
Inductance.
A device used to store electrical energy.
Four times less than that of the secondary.
The motor rotation is reversed.

23. The secondary windings on a 10:1 step-down transformer will have a wire size...
Capacitance.
They must be installed at least 7 feet above the ground.
Larger than that found in the primary winding.
An electromagnet.

24. What is the first step to be followed in aiding a victim of electrical shock?
Reverse its rotation.
277 volts.
Lower current and higher voltage.
Check to make sure that the victim is not still in contact with the electricity.

25. A transformer with 10 turns on the primary coil and 100 turns on the secondary is classified as...
They should be made by the same manufacturer.
Carotid pulse - which is located in the neck next to the Adam's apple.
A step-up transformer.
Reverse any two-phase leads.

26. How should clothing be removed from a burn?
Draw less current.
At the source transformer.
Cut around clothing that has adhered to the burned area.
Transformer

27. When troubleshooting a circuit with a bank of capacitors - what precautions must be taken?
No.6 AWG.
The capacitors should be discharged.
Derive a neutral for grounding purposes.
100 turns.

28. 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?
Reverse any two-phase leads.
It provides good speed control.
75 turns.
Allow for metering voltage and Current.

29. 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?
Stator windings.
Cut around clothing that has adhered to the burned area.
Tied together
100 turns.

30. Which of the following is not needed when using an ohmmeter to determine if a motor is grounded?
Disconnect the frame-grounding conductor.
H terminals.
Circuit Breaker.
Isolation transformer.

31. The purpose of a zig-zag transformer is to...
Derive a neutral for grounding purposes.
The chest should rise or inflate.
200 volts AC.
H terminals.

32. What steps up or steps down AC voltage?
100 turns.
Squirrel-cage rotor.
Allow for metering voltage and Current.
Transformer

33. Current that changes periodically in direction is...
X.
Alternating current.
Hyperventilation.
Shunted and taped

34. 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...
Because less current flowing at high voltage causes less line loss per kilowatt.
150 turns.
Stator windings.
100 volts.

35. If current were flowing through a grounding resistor in a 440-volt - resistance-grounded system - this would probably be because...
Tied together
Grounded phase and ground fault devices were not operating.
At least two phases
The chest should rise or inflate.

36. Surface transformer installations - unless constructed to eliminate shock hazards - must be installed at least...
15 feet off the ground.
Tied together
The chest should rise or inflate.
X.

37. A solenoid coil is...
Transformer
3 -979 Volts.
Current changing constantly in magnitude and periodically in direction.
An electromagnet.

38. Three-phase AC underground cables must be provided with overcurrent protection using a...
60 cycles per second (60 Hertz).
Circuit Breaker.
Reverse its rotation.
5:1

39. The size of a transformer is measured in...
The capacitors should be discharged.
They must be installed at least 7 feet above the ground.
Kilovolt ampere (KVA).
Disconnect the frame-grounding conductor.

40. At what rate should mouth-to-mouth resuscitation be applied?
12 to 15 times a minute.
5:1.
No.6 AWG.
They must be installed at least 7 feet above the ground.

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

42. 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.
Second-degree burn.
Draw less current.
Check to make sure that the victim is not still in contact with the electricity.

43. To protect against over-current in a three-phase circuit over-current protection must be provided for...
Carotid pulse - which is located in the neck next to the Adam's apple.
Capacitance.
At least two phases
Transformers.

44. Compared to the secondary of a loaded - step-down transformer - the primary has...
Current changing constantly in magnitude and periodically in direction.
7 -630 volts.
Lower current and higher voltage.
Stator windings.

45. What type motor is a wound-rotor induction motor?
At least two phases
Second-degree burn.
15 feet off the ground.
A.C.

46. 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?
Because 440-volt power draws less current so cables and control circuit wiring can be smaller.
600 volts.
Current that changes constantly in magnitude and periodically in direction.
75 turns.

47. Find the turns ratio of a single-phase transformer with the following values: Primary power of 5KW - secondary current of 100 amps - and primary voltage of 250 volts.
Reverse its rotation.
Short-circuited after power has been removed.
A grounding resistor.
5:1

48. 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?
3 -979 Volts.
150 turns.
A.C.
Carotid pulse - which is located in the neck next to the Adam's apple.

49. What type of 3-phase AC motor is used most often around a mine?
Draw less current.
1 amp.
Squirrel-cage induction motor.
Current changing constantly in magnitude and periodically in direction.

50. Should a ground fault occur - what device can be installed to limit the current in the neutral of a three-phase AC system?
X.
The motor rotation is reversed.
A grounding resistor.
Inductance.

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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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