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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. Not an acceptable method for the installations of surface transformers?
They must be installed at least 7 feet above the ground.
They should be made by the same manufacturer.
100 turns.
Transformer

2. What type motor is a wound-rotor induction motor?
Allow for metering voltage and Current.
100 volts.
Transformer
A.C.

3. When troubleshooting a circuit with a bank of capacitors - what precautions must be taken?
3 -979 Volts.
The capacitors should be discharged.
Inductance.
60 cycles per second (60 Hertz).

4. A burn causing a blister is classified as a...
60 cycles per second (60 Hertz).
75 turns.
H terminals.
Second-degree burn.

5. When connecting 3 single-phase transformers into a three-phase system - which of the following is NOT required for the single-phase transformers.
200 volts AC.
60 cycles per second (60 Hertz).
They should be made by the same manufacturer.
At least two phases

6. All transformers step voltage up or down by...
X.
It provides good speed control.
Second-degree burn.
Inductance.

7. 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.
2000 watts
5:1
Nearly constant.
25 feet.

8. The secondary windings on a 10:1 step-down transformer will have a wire size...
Larger than that found in the primary winding.
Tied together
5:1
Four times less than that of the secondary.

9. When not connected to a load - the secondary leads of a current transformer should be...
Circuit Breaker.
Squirrel-cage induction motor.
Shunted and taped
Electro-magnetism for their operation.

10. The property of an electrical circuit that opposes any change in voltage is called...
277 volts.
2000 watts
Capacitance.
Reverse any two-phase leads.

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

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12. 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.
60 Hertz
X.
25 feet.

13. 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?
A device used to store electrical energy.
Current changing constantly in magnitude and periodically in direction.
800 volts.
Four times less than that of the secondary.

14. 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.
5:1.
Full-load - three-phase voltage.
60 Hertz
Transformers.

15. A wound-rotor induction motor has all the following EXCEPT...
Squirrel-cage rotor.
600 volts.
Hyperventilation.
Full-load - three-phase voltage.

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?
A grounding resistor.
600 volts.
100 turns.
150 turns.

17. How can you tell if a victim receiving mouth-to-mouth resuscitation is getting air into the lungs?
At the source transformer.
Inductance.
The chest should rise or inflate.
Reverse its rotation.

18. The following motor leads are brought out of a 3-phase motor (T1 - T2 - T3 - T4 - T5 - T6). This motor is probably for...
Disconnect the frame-grounding conductor.
Kilovolt ampere (KVA).
Two speeds
Transformer

19. The combined capacitance of two capacitors in parallel is...
Isolation transformer.
The sum of the two capacitors.
They must be installed at least 7 feet above the ground.
Inductance.

20. The minimum allowable size for trailing cables for mobile haulage equipment powered by alternating current is...
3 -979 Volts.
277 volts.
No.6 AWG.
The current will read zero.

21. 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.
A step-up transformer.
X.
An electrical shock hazard may exist.

22. What type of 3-phase AC motor is used most often around a mine?
They must be installed at least 7 feet above the ground.
Squirrel-cage induction motor.
60 Hertz
A.C.

23. What steps up or steps down AC voltage?
150 turns.
277 volts.
Disconnect the frame-grounding conductor.
Transformer

24. If a voltmeter is connected between a phase lead and the ground of a three-phase 480-volt system - the meter will read...
277 volts.
Stator windings.
100 turns.
75 turns.

25. 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?
150 turns.
Because 440-volt power draws less current so cables and control circuit wiring can be smaller.
Short-circuited after power has been removed.
Current that changes constantly in magnitude and periodically in direction.

26. The size of a transformer is measured in...
Tied together
5:1
2000 watts
Kilovolt ampere (KVA).

27. Using a 10:1 ratio transformer - the terminals on the secondary side or lower voltage side would be marked...
Tied together
100 turns.
Check to make sure that the victim is not still in contact with the electricity.
X.

28. The neutral ground-bed electrical power system of an underground mine should be separated from the lightning arrestor grounds by at least...
Second-degree burn.
Allow for metering voltage and Current.
It provides good speed control.
25 feet.

29. If 2000 watts is read in the primary of a single-phase transformer - What is the wattage in the secondary? (Assuming no losses.)
Four times less than that of the secondary.
An electrical shock hazard may exist.
277 volts.
2000 watts

30. Not a symptom of electrical shock?.
Two speeds
Disconnect the frame-grounding conductor.
The current will read zero.
Hyperventilation.

31. The standard frequency of power supplied by the power company is...
H terminals.
60 cycles per second (60 Hertz).
An electrical shock hazard may exist.
Disconnect the frame-grounding conductor.

32. Compared to the secondary of a loaded - step-down transformer - the primary has...
A step-up transformer.
Nearly constant.
Lower current and higher voltage
Inductance.

33. A solenoid coil is...
480 volts.
An electromagnet.
Cut around clothing that has adhered to the burned area.
Clamp-on ammeter.

34. The property of an electric circuit that opposes any change in current is called...
Reverse any two-phase leads.
The motor rotation is reversed.
100 volts.
Inductance.

35. Current in an AC circuit may be measured by...
Disconnect the frame-grounding conductor.
Because less current flowing at high voltage causes less line loss per kilowatt.
An electromagnet.
Clamp-on ammeter.

36. What is the danger when working around capacitors?
Two speeds
At the source transformer.
An electrical shock hazard may exist.
Current that changes constantly in magnitude and periodically in direction.

37. Which of the following is not needed when using an ohmmeter to determine if a motor is grounded?
The chest should rise or inflate.
At the source transformer.
At least two phases
Disconnect the frame-grounding conductor.

38. The load to which the secondary winding of a current transformer was connected has opened. The secondary leads should be...
A.C.
Short-circuited after power has been removed.
Cut around clothing that has adhered to the burned area.
Derive a neutral for grounding purposes.

39. The primary function of a power transformer is to provide...
The chest should rise or inflate.
The sum of the two capacitors.
Inductance.
Full-load - three-phase voltage.

40. The transformer used only to measure voltage is a...
5:1.
An electrical shock hazard may exist.
Potential transformer.
200 volts AC.

41. A transformer with a 1:1 ratio is usually a (an)...
An electromagnet.
No.6 AWG.
Transformers.
Isolation transformer.

42. The speed of an alternating current - squirrel-cage induction motor is...
Nearly constant.
Lower current and higher voltage.
Inductance.
Draw less current.

43. What happens to a motor that is connected to a three-phase cable when two of the cable's leads are reversed?
The motor rotation is reversed.
100 volts.
Isolation transformer.
75 turns.

44. Not true about AC power?
The motor rotation is reversed.
480 volts.
It provides good speed control.
Second-degree burn.

45. Operating coils - motors - transformers - relays and solenoids depend upon...
Derive a neutral for grounding purposes.
Electro-magnetism for their operation.
Hyperventilation.
Current that changes constantly in magnitude and periodically in direction.

46. A transformer with 10 turns on the primary coil and 100 turns on the secondary is classified as...
60 cycles per second (60 Hertz).
A step-up transformer.
Reverse its rotation.
100 volts.

47. What is a capacitor?
Clamp-on ammeter.
A step-up transformer.
At least two phases
A device used to store electrical energy.

48. AC voltage is raised or lowered by means of...
Clamp-on ammeter.
No.6 AWG.
Transformers.
200 volts AC.

49. The purpose of a zig-zag transformer is to...
150 turns.
Derive a neutral for grounding purposes.
Squirrel-cage rotor.
Cut around clothing that has adhered to the burned area.

50. Which of the following does a squirrel cage induction motor have?
Stator windings.
Full-load - three-phase voltage.
Hyperventilation.
Current that changes constantly in magnitude and periodically in direction.