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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. Using a 10:1 ratio transformer - the terminals on the secondary side or lower voltage side would be marked...
X.
Stator windings.
Continuous.
600 volts.

2. 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?
Capacitance.
Carotid pulse - which is located in the neck next to the Adam's apple.
At least two phases
75 turns.

3. The property of an electric circuit that opposes any change in current is called...
Inductance.
5:1
Disconnect the frame-grounding conductor.
The current will read zero.

4. Operating coils - motors - transformers - relays and solenoids depend upon...
Electro-magnetism for their operation.
They should be made by the same manufacturer.
Clamp-on ammeter.
The sum of the two capacitors.

5. If any two-phase wires are reversed on a three-phase motor - the motor will...
Reverse its rotation.
Inductance.
No.6 AWG.
75 turns.

6. All transformers step voltage up or down by...
12 to 15 times a minute.
Kilovolt ampere (KVA).
Inductance.
A.C.

7. Should a ground fault occur - what device can be installed to limit the current in the neutral of a three-phase AC system?
A grounding resistor.
Continuous.
Second-degree burn.
Cut around clothing that has adhered to the burned area.

8. A current transformer has a ratio of 350:5. If the phase current is 70 amperes - what would be the secondary current?
150 turns.
1 amp.
The chest should rise or inflate.
Nearly constant.

9. Which of the following is not needed when using an ohmmeter to determine if a motor is grounded?
A.C.
Because less current flowing at high voltage causes less line loss per kilowatt.
75 turns.
Disconnect the frame-grounding conductor.

10. Not a symptom of electrical shock?.
100 turns.
Hyperventilation.
Short-circuited after power has been removed.
Isolation transformer.

11. Which of the following does a squirrel cage induction motor have?
Potential transformer.
A.C.
Continuous.
Stator windings.

12. The secondary windings on a 10:1 step-down transformer will have a wire size...
200 volts AC.
Larger than that found in the primary winding.
At the source transformer.
Stator windings.

13. If you use a clamp-on ammeter or tong tester around all three-phase wires of an energized three- phase circuit simultaneously...
Tied together
The current will read zero.
Kilovolt ampere (KVA).
Capacitance.

14. What type motor is a wound-rotor induction motor?
150 turns.
A.C.
Allow for metering voltage and Current.
Electro-magnetism for their operation.

15. What should the duty rating of a grounding resistor be?
Continuous.
They should be made by the same manufacturer.
Transformers.
Grounded phase and ground fault devices were not operating.

16. The primary function of a power transformer is to provide...
Lower current and higher voltage
Short-circuited after power has been removed.
Continuous.
Full-load - three-phase voltage.

17. At what rate should mouth-to-mouth resuscitation be applied?
12 to 15 times a minute.
Disconnect the frame-grounding conductor.
Transformer
Hyperventilation.

18. AC voltage is raised or lowered by means of...
Lower current and higher voltage.
3 -979 Volts.
Current that changes constantly in magnitude and periodically in direction.
Transformers.

19. If current were flowing through a grounding resistor in a 440-volt - resistance-grounded system - this would probably be because...
Second-degree burn.
Grounded phase and ground fault devices were not operating.
A grounding resistor.
Lower current and higher voltage

20. Current in an AC circuit may be measured by...
Clamp-on ammeter.
800 volts.
Kilovolt ampere (KVA).
Four times less than that of the secondary.

21. When connecting 3 single-phase transformers into a three-phase system - which of the following is NOT required for the single-phase transformers.
The capacitors should be discharged.
They should be made by the same manufacturer.
Derive a neutral for grounding purposes.
15 feet off the ground.

22. Current that changes periodically in direction is...
Alternating current.
Second-degree burn.
Inductance.
Reverse its rotation.

23. What is the danger when working around capacitors?
Derive a neutral for grounding purposes.
Second-degree burn.
Grounded phase and ground fault devices were not operating.
An electrical shock hazard may exist.

24. 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?
600 volts.
60 Hertz
Potential transformer.
Electro-magnetism for their operation.

25. 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.
5:1
Because less current flowing at high voltage causes less line loss per kilowatt.
Continuous.

26. What is a capacitor?
Two speeds
A device used to store electrical energy.
75 turns.
800 volts.

27. A transformer with a 1:1 ratio is usually a (an)...
An electromagnet.
Allow for metering voltage and Current.
Reverse its rotation.
Isolation transformer.

28. 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.
Short-circuited after power has been removed.
The chest should rise or inflate.
Inductance.
5:1

29. Compared to the secondary of a loaded - step-down transformer - the primary has...
Capacitance.
Lower current and higher voltage
No.6 AWG.
Second-degree burn.

30. The standard frequency of power supplied by the power company is...
Stator windings.
60 cycles per second (60 Hertz).
Carotid pulse - which is located in the neck next to the Adam's apple.
Transformers.

31. When not connected to a load - the secondary leads of a current transformer should be...
12 to 15 times a minute.
They should be made by the same manufacturer.
Shunted and taped
Draw less current.

32. To protect against over-current in a three-phase circuit over-current protection must be provided for...
A.C.
5:1.
At least two phases
They should be made by the same manufacturer.

33. If the conductors of a balanced - three-phase circuit pass through a current transformer - how many amps will flow in the transformer?
Transformers.
Zero amps.
An electrical shock hazard may exist.
12 to 15 times a minute.

34. 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?
An electromagnet.
The current will read zero.
Draw less current.
800 volts.

35. The transformer used only to measure voltage is a...
Grounded phase and ground fault devices were not operating.
Potential transformer.
3 -979 Volts.
A.C.

36. A wound-rotor induction motor has all the following EXCEPT...
Four times less than that of the secondary.
Draw less current.
It provides good speed control.
Squirrel-cage rotor.

37. 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.
Second-degree burn.
H terminals.
480 volts.

38. How can you tell if a victim receiving mouth-to-mouth resuscitation is getting air into the lungs?
12 to 15 times a minute.
Reverse its rotation.
Capacitance.
The chest should rise or inflate.

39. What happens to a motor that is connected to a three-phase cable when two of the cable's leads are reversed?
5:1
They should be made by the same manufacturer.
The motor rotation is reversed.
They must be installed at least 7 feet above the ground.

40. The purpose of a zig-zag transformer is to...
It provides good speed control.
Derive a neutral for grounding purposes.
800 volts.
Reverse its rotation.

41. 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.
Isolation transformer.
Derive a neutral for grounding purposes.
Reverse any two-phase leads.

42. How do you change the direction of a 3-phase AC motor?
Two speeds
Reverse any two-phase leads.
100 volts.
Current changing constantly in magnitude and periodically in direction.

43. 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?
60 Hertz
Because less current flowing at high voltage causes less line loss per kilowatt.
Inductance.
100 turns.

44. The minimum allowable size for trailing cables for mobile haulage equipment powered by alternating current is...
Transformer
No.6 AWG.
Reduce high AC current to lower values and provide isolation between high voltage circuits and metering.
Disconnect the frame-grounding conductor.

45. If a voltmeter is connected between a phase lead and the ground of a three-phase 480-volt system - the meter will read...
Squirrel-cage induction motor.
Lower current and higher voltage.
277 volts.
Transformer

46. The current on the primary side of a step-down transformer with a 4:1 ratio will be...
60 Hertz
Derive a neutral for grounding purposes.
Four times less than that of the secondary.
H terminals.

47. If a voltmeter were placed between two phase leads of a three-phase 480-volt system - the meter would read...
At least two phases
480 volts.
Electro-magnetism for their operation.
They must be installed at least 7 feet above the ground.

48. Compared to the secondary of a loaded - step-down transformer - the primary has...
Nearly constant.
800 volts.
Squirrel-cage induction motor.
Lower current and higher voltage.

49. If 2000 watts is read in the primary of a single-phase transformer - What is the wattage in the secondary? (Assuming no losses.)
Larger than that found in the primary winding.
2000 watts
Isolation transformer.
150 turns.

50. Three-phase AC underground cables must be provided with overcurrent protection using a...
Circuit Breaker.
200 volts AC.
The capacitors should be discharged.
Zero amps.