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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. At what rate should mouth-to-mouth resuscitation be applied?
12 to 15 times a minute.
75 turns.
150 turns.
Hyperventilation.

2. Two 10-hp induction motors are operating on 460 volts AC. One motor is connected by single- phase; the other is connected in three-phase. The three-phase will...
277 volts.
Draw less current.
15 feet off the ground.
Grounded phase and ground fault devices were not operating.

3. The primary function of a power transformer is to provide...
Full-load - three-phase voltage.
75 turns.
Inductance.
Because less current flowing at high voltage causes less line loss per kilowatt.

4. 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?
75 turns.
X.
Second-degree burn.
15 feet off the ground.

5. 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?
Grounded phase and ground fault devices were not operating.
800 volts.
Transformer
Carotid pulse - which is located in the neck next to the Adam's apple.

6. A burn causing a blister is classified as a...
Second-degree burn.
60 Hertz
A.C.
Squirrel-cage rotor.

7. 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?
An electrical shock hazard may exist.
Continuous.
200 volts AC.
It provides good speed control.

8. A solenoid coil is...
An electromagnet.
75 turns.
Shunted and taped
Circuit Breaker.

9. A transformer with a 1:1 ratio is usually a (an)...
Second-degree burn.
An electrical shock hazard may exist.
Isolation transformer.
Reverse its rotation.

10. 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.
Disconnect the frame-grounding conductor.
Allow for metering voltage and Current.
They must be installed at least 7 feet above the ground.
5:1

11. Compared to the secondary of a loaded - step-down transformer - the primary has...
Lower current and higher voltage
12 to 15 times a minute.
5:1.
Reduce high AC current to lower values and provide isolation between high voltage circuits and metering.

12. Three-phase AC underground cables must be provided with overcurrent protection using a...
Because less current flowing at high voltage causes less line loss per kilowatt.
2000 watts
Circuit Breaker.
Electro-magnetism for their operation.

13. What should the duty rating of a grounding resistor be?
Continuous.
Reverse any two-phase leads.
277 volts.
15 feet off the ground.

14. What type motor is a wound-rotor induction motor?
Draw less current.
Nearly constant.
Check to make sure that the victim is not still in contact with the electricity.
A.C.

15. If a voltmeter is connected between a phase lead and the ground of a three-phase 480-volt system - the meter will read...
Inductance.
Electro-magnetism for their operation.
277 volts.
Nearly constant.

16. 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...
75 turns.
A.C.
277 volts.
Tied together

17. The speed of an alternating current - squirrel-cage induction motor is...
Larger than that found in the primary winding.
Squirrel-cage rotor.
Second-degree burn.
Nearly constant.

18. What is the danger when working around capacitors?
An electromagnet.
An electrical shock hazard may exist.
Zero amps.
Reverse any two-phase leads.

19. What is a capacitor?
Squirrel-cage induction motor.
Full-load - three-phase voltage.
A device used to store electrical energy.
2000 watts

20. When troubleshooting a circuit with a bank of capacitors - what precautions must be taken?
The capacitors should be discharged.
Second-degree burn.
Squirrel-cage rotor.
Draw less current.

21. How can you tell if a victim receiving mouth-to-mouth resuscitation is getting air into the lungs?
Because 440-volt power draws less current so cables and control circuit wiring can be smaller.
The chest should rise or inflate.
An electromagnet.
No.6 AWG.

22. The secondary windings on a 10:1 step-down transformer will have a wire size...
X.
Larger than that found in the primary winding.
Transformer
Current that changes constantly in magnitude and periodically in direction.

23. When connecting 3 single-phase transformers into a three-phase system - which of the following is NOT required for the single-phase transformers.
Larger than that found in the primary winding.
Cut around clothing that has adhered to the burned area.
They should be made by the same manufacturer.
Carotid pulse - which is located in the neck next to the Adam's apple.

24. The minimum allowable size for trailing cables for mobile haulage equipment powered by alternating current is...
12 to 15 times a minute.
277 volts.
2000 watts
No.6 AWG.

25. What is the first step to be followed in aiding a victim of electrical shock?
Draw less current.
The sum of the two capacitors.
Disconnect the frame-grounding conductor.
Check to make sure that the victim is not still in contact with the electricity.

26. Using a 10:1 ratio transformer - the terminals on the secondary side or lower voltage side would be marked...
X.
Allow for metering voltage and Current.
15 feet off the ground.
Squirrel-cage rotor.

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

28. The transformer used only to measure voltage is a...
200 volts AC.
Short-circuited after power has been removed.
They should be made by the same manufacturer.
Potential transformer.

29. Not true about AC power?
Isolation transformer.
It provides good speed control.
60 cycles per second (60 Hertz).
Grounded phase and ground fault devices were not operating.

30. 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?
Cut around clothing that has adhered to the burned area.
Tied together
100 turns.
An electromagnet.

31. All transformers step voltage up or down by...
Shunted and taped
Squirrel-cage rotor.
Electro-magnetism for their operation.
Inductance.

32. The combined capacitance of two capacitors in parallel is...
Nearly constant.
Kilovolt ampere (KVA).
The sum of the two capacitors.
A.C.

33. 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.
They should be made by the same manufacturer.
X.
Carotid pulse - which is located in the neck next to the Adam's apple.
5:1.

34. Not a symptom of electrical shock?.
An electrical shock hazard may exist.
Hyperventilation.
Current that changes constantly in magnitude and periodically in direction.
100 turns.

35. Where should grounding resistors be located?
The sum of the two capacitors.
At the source transformer.
Lower current and higher voltage.
Disconnect the frame-grounding conductor.

36. If current were flowing through a grounding resistor in a 440-volt - resistance-grounded system - this would probably be because...
At the source transformer.
Zero amps.
Grounded phase and ground fault devices were not operating.
2000 watts

37. High voltage is used to transmit power over long distances...
Because less current flowing at high voltage causes less line loss per kilowatt.
Draw less current.
Draw less current.
A.C.

38. The standard frequency of alternating current used at a mine is...
60 Hertz
Electro-magnetism for their operation.
They must be installed at least 7 feet above the ground.
The sum of the two capacitors.

39. Current transformers - or CT's - are used to...
Current that changes constantly in magnitude and periodically in direction.
An electrical shock hazard may exist.
Reduce high AC current to lower values and provide isolation between high voltage circuits and metering.
It provides good speed control.

40. Which of the following is not needed when using an ohmmeter to determine if a motor is grounded?
Nearly constant.
Disconnect the frame-grounding conductor.
Potential transformer.
At the source transformer.

41. 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?
15 feet off the ground.
150 turns.
Potential transformer.
No.6 AWG.

42. A control power transformer...
Provides single-phase power to smaller loads such as lights - heaters - etc.
Electro-magnetism for their operation.
Zero amps.
Continuous.

43. Surface transformer installations - unless constructed to eliminate shock hazards - must be installed at least...
480 volts.
15 feet off the ground.
A grounding resistor.
An electrical shock hazard may exist.

44. The current on the primary side of a step-down transformer with a 4:1 ratio will be...
Draw less current.
Electro-magnetism for their operation.
An electromagnet.
Four times less than that of the secondary.

45. The property of an electric circuit that opposes any change in current is called...
No.6 AWG.
Inductance.
Disconnect the frame-grounding conductor.
It provides good speed control.

46. 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.
It provides good speed control.
Capacitance.
3 -979 Volts.

47. 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.
Circuit Breaker.
Lower current and higher voltage
The sum of the two capacitors.

48. The standard frequency of power supplied by the power company is...
60 cycles per second (60 Hertz).
2000 watts
X.
It provides good speed control.

49. The property of an electrical circuit that opposes any change in voltage is called...
3 -979 Volts.
Squirrel-cage rotor.
The sum of the two capacitors.
Capacitance.

50. 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?
600 volts.
Disconnect the frame-grounding conductor.
Draw less current.
3 -979 Volts.