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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.
X.
Larger than that found in the primary winding.

2. 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.
They must be installed at least 7 feet above the ground.
7 -630 volts.
Stator windings.

3. A transformer with a 1:1 ratio is usually a (an)...
Lower current and higher voltage
Isolation transformer.
Alternating current.
15 feet off the ground.

4. What should the duty rating of a grounding resistor be?
Cut around clothing that has adhered to the burned area.
Squirrel-cage induction motor.
Inductance.
Continuous.

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

6. What steps up or steps down AC voltage?
150 turns.
Transformer
Reduce high AC current to lower values and provide isolation between high voltage circuits and metering.
75 turns.

7. Not a symptom of electrical shock?.
Hyperventilation.
100 turns.
Reverse any two-phase leads.
Current that changes constantly in magnitude and periodically in direction.

8. The size of a transformer is measured in...
200 volts AC.
Kilovolt ampere (KVA).
Carotid pulse - which is located in the neck next to the Adam's apple.
The sum of the two capacitors.

9. What is a capacitor?
75 turns.
A grounding resistor.
A step-up transformer.
A device used to store electrical energy.

10. 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?
200 volts AC.
480 volts.
At least two phases
An electrical shock hazard may exist.

11. 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.
A grounding resistor.
The sum of the two capacitors.
5:1
They must be installed at least 7 feet above the ground.

12. 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?
800 volts.
Shunted and taped
200 volts AC.
Current changing constantly in magnitude and periodically in direction.

13. 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?
The chest should rise or inflate.
277 volts.
100 turns.
Disconnect the frame-grounding conductor.

14. To protect against over-current in a three-phase circuit over-current protection must be provided for...
The chest should rise or inflate.
Draw less current.
An electrical shock hazard may exist.
At least two phases

15. 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.
The current will read zero.
A device used to store electrical energy.
They should be made by the same manufacturer.

16. The property of an electrical circuit that opposes any change in voltage is called...
It provides good speed control.
X.
A grounding resistor.
Capacitance.

17. 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...
Isolation transformer.
Draw less current.
Current that changes constantly in magnitude and periodically in direction.
The chest should rise or inflate.

18. Compared to the secondary of a loaded - step-down transformer - the primary has...
800 volts.
Lower current and higher voltage.
7 -630 volts.
5:1.

19. Not an acceptable method for the installations of surface transformers?
Electro-magnetism for their operation.
They must be installed at least 7 feet above the ground.
Nearly constant.
Kilovolt ampere (KVA).

20. A current transformer has a ratio of 350:5. If the phase current is 70 amperes - what would be the secondary current?
The capacitors should be discharged.
277 volts.
1 amp.
H terminals.

21. Compared to the secondary of a loaded - step-down transformer - the primary has...
Lower current and higher voltage
Allow for metering voltage and Current.
Two speeds
A grounding resistor.

22. What type motor is a wound-rotor induction motor?
100 volts.
Transformer
600 volts.
A.C.

23. How can you tell if a victim receiving mouth-to-mouth resuscitation is getting air into the lungs?
200 volts AC.
The chest should rise or inflate.
Reverse its rotation.
7 -630 volts.

24. Define alternating current...
Carotid pulse - which is located in the neck next to the Adam's apple.
60 cycles per second (60 Hertz).
Disconnect the frame-grounding conductor.
Current changing constantly in magnitude and periodically in direction.

25. Current in an AC circuit may be measured by...
Clamp-on ammeter.
A device used to store electrical energy.
Four times less than that of the secondary.
Hyperventilation.

26. Surface transformer installations - unless constructed to eliminate shock hazards - must be installed at least...
100 turns.
15 feet off the ground.
Electro-magnetism for their operation.
They should be made by the same manufacturer.

27. 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...
Two speeds
100 volts.
Squirrel-cage induction motor.
The current will read zero.

28. A transformer with 10 turns on the primary coil and 100 turns on the secondary is classified as...
A step-up transformer.
60 Hertz
Circuit Breaker.
The motor rotation is reversed.

29. The speed of an alternating current - squirrel-cage induction motor is...
A step-up transformer.
Nearly constant.
25 feet.
277 volts.

30. The transformer used only to measure voltage is a...
100 volts.
Nearly constant.
Stator windings.
Potential transformer.

31. The minimum allowable size for trailing cables for mobile haulage equipment powered by alternating current is...
Derive a neutral for grounding purposes.
480 volts.
X.
No.6 AWG.

32. The load to which the secondary winding of a current transformer was connected has opened. The secondary leads should be...
Cut around clothing that has adhered to the burned area.
Short-circuited after power has been removed.
The current will read zero.
3 -979 Volts.

33. Using a 10:1 ratio transformer - the terminals on the secondary side or lower voltage side would be marked...
Four times less than that of the secondary.
The sum of the two capacitors.
The motor rotation is reversed.
X.

34. 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?
Hyperventilation.
150 turns.
Lower current and higher voltage
1 amp.

35. Operating coils - motors - transformers - relays and solenoids depend upon...
Full-load - three-phase voltage.
Electro-magnetism for their operation.
Reverse its rotation.
The motor rotation is reversed.

36. Current that changes periodically in direction is...
Alternating current.
Grounded phase and ground fault devices were not operating.
3 -979 Volts.
A.C.

37. AC voltage is raised or lowered by means of...
Nearly constant.
Tied together
Transformers.
100 turns.

38. High voltage is used to transmit power over long distances...
Inductance.
Tied together
Because less current flowing at high voltage causes less line loss per kilowatt.
Derive a neutral for grounding purposes.

39. Not true about AC power?
Kilovolt ampere (KVA).
Squirrel-cage rotor.
2000 watts
It provides good speed control.

40. The property of an electric circuit that opposes any change in current is called...
Transformer
600 volts.
The motor rotation is reversed.
Inductance.

41. If current were flowing through a grounding resistor in a 440-volt - resistance-grounded system - this would probably be because...
Alternating current.
100 volts.
Grounded phase and ground fault devices were not operating.
Disconnect the frame-grounding conductor.

42. The standard frequency of power supplied by the power company is...
5:1.
480 volts.
Continuous.
60 cycles per second (60 Hertz).

43. 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.
Short-circuited after power has been removed.
Allow for metering voltage and Current.
Tied together

44. If the conductors of a balanced - three-phase circuit pass through a current transformer - how many amps will flow in the transformer?
60 Hertz
A grounding resistor.
They must be installed at least 7 feet above the ground.
Zero amps.

45. What is the first step to be followed in aiding a victim of electrical shock?
Disconnect the frame-grounding conductor.
Lower current and higher voltage
They must be installed at least 7 feet above the ground.
Check to make sure that the victim is not still in contact with the electricity.

46. Alternating current may be defined as...
7 -630 volts.
A.C.
Current that changes constantly in magnitude and periodically in direction.
Disconnect the frame-grounding conductor.

47. If any two-phase wires are reversed on a three-phase motor - the motor will...
An electromagnet.
5:1
Reverse its rotation.
200 volts AC.

48. The standard frequency of alternating current used at a mine is...
60 Hertz
277 volts.
5:1
Draw less current.

49. A solenoid coil is...
An electromagnet.
Cut around clothing that has adhered to the burned area.
Hyperventilation.
Disconnect the frame-grounding conductor.

50. The secondary windings on a 10:1 step-down transformer will have a wire size...
5:1
1 amp.
Current changing constantly in magnitude and periodically in direction.
Larger than that found in the primary winding.