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DC Theory

Instructions:

Answer 50 questions in 15 minutes.
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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. What is the opposition to flow of electric current?
Current that flows in only one direction.
Attract each other.
Resistance.
A counter-EMF.

2. The armature of a direct current motor - when running - generates...
Ohms.
In series.
A counter-EMF.
15 minutes.

3. What voltage would be required to force 10 amps through a 20-ohm resistor?
No.4 AWG.
200 volts
Hydrogen.
100 ohms

4. You have three 12-volt batteries. How should you connect them in order to supply 36 volts?
Wattmeter.
In series.
There is a hazard of blowing the contents back into your face - 'explosive reaction'.
60 ohms.

5. The unit of measurement of power is...
Watts.
Stays the same.
There is a hazard of blowing the contents back into your face - 'explosive reaction'.
Treat for physical shock.

6. Voltage is measured with a...
Amperes.
Distance.
Voltmeter.
No.4 AWG.

7. Define resistance...
Flush thoroughly with water.
A. Total resistance is less than the smallest resistor.
The opposition to flow of electrons in a circuit.
In series.

8. The instrument used to check the electrolyte of a battery is a...
37.3 kilowatts
Decrease.
Hydrometer.
Current.

9. The best insulator against the lines of magnetic force is...
Distance.
Ammeter.
Current that flows in one direction only.
200 volts

10. Voltage in a parallel circuit...
After charging
Current that flows in one direction only.
E=IR.
Stays the same.

11. Define direct current...
No.4 AWG.
4.8 ohms
A. Total resistance is less than the smallest resistor.
Current that flows in one direction only.

12. What is the total resistance of three 16-ohm resistors connected in series?
48 ohms.
Voltmeter.
4.8 ohms
Attract each other.

13. A triac is?
In series.
Heat
A bi-directional device that can pass current in either direction.
A counter-EMF.

14. Current is measured with a (an)...
Hydrogen.
It must prevent internal explosions.
Decrease.
Ammeter.

15. What is the flow of electrons in a conductor?
Current that flows in one direction only.
E=IR.
Current.
Clean water.

16. Which of the following motors CANNOT be run without a load?
Attract each other.
Series-wound.
Watts.
48 ohms.

17. Not a requirement of an explosion-proof enclosure?
1.260 to 1.280.
Watts.
It must prevent internal explosions.
Ohms.

18. What is the equivalent resistance of two 8-ohm resistors connected in parallel?
Hydrometer.
4.0 ohms.
Soft iron.
Current.

19. In a parallel circuit...
No.4 AWG.
A. Total resistance is less than the smallest resistor.
Voltmeter.
Current.

20. The unit of measurement of current is...
Amperes.
60 ohms.
Current.
Ohmmeter.

21. Define direct current...
Compound-wound and shunt-wound.
Current that flows in only one direction.
8 ohms.
Clean water.

22. You have three 9-volt batteries. How should you connect them in order to supply 27 volts?
In series.
Distance.
It must prevent ignition of surrounding methane atmosphere.
Treat for physical shock.

23. The combined resistance of two resistors in parallel is...
Current that flows in one direction only.
48 volts
Less than the resistance of either resistor.
Stays the same.

24. Unlike poles of a magnet will...
Better speed control on motors.
Attract each other.
Less than the resistance of either resistor.
15 minutes.

25. What is the equivalent resistance of an 8-ohm and a 12-ohm resistor connected in parallel?
4.8 ohms
37.3 kilowatts
Current that flows in one direction only.
Watts.

26. What is the total voltage of four 9-volt batteries connected in a series?
Ohms.
Resistance.
36 volts.
Clean water.

27. Which current flows in only one direction?
75 volts.
200 volts
Direct current.
Treat for physical shock.

28. What is the total voltage of two 6-volt batteries connected in parallel?
Decrease.
6 volts.
Until the victim receives medical attention.
1.260 to 1.280.

29. What is the total voltage of four 12-volt batteries connected in series?
Direct current.
In parallel.
48 volts
The opposition to flow of electrons in a circuit.

30. The specific gravity of the electrolyte of a fully charged battery should be...
Burns will appear only at the point where contact is made to the energized circuit.
A wire wound resistor.
Stays the same.
1.260 to 1.280.

31. The explosive gas that is generated when a battery is charging is...
Hydrogen.
500 volts.
Current.
Stays the same.

32. What is the unit of electromotive force or electric pressure?
Resistance.
Voltage.
A bi-directional device that can pass current in either direction.
Current that flows in only one direction.

33. If the victim of an electrical shock has been burned while in contact with electricity - the first treatment you should apply - if the victim's heart and respiratory system are still functioning - is to...
Current
400 ampere-hours.
Treat for physical shock.
Power.

34. Not true about electrical shocks?
In parallel.
Burns will appear only at the point where contact is made to the energized circuit.
A. Total resistance is less than the smallest resistor.
Soft iron.

35. What is the rate that work is done or heat is dissipated?
Higher current with voltage remaining the same.
Ohms.
Power.
Current that flows in only one direction.

36. A battery capable of producing 20 amperes steadily for 20 hours at 80 degrees Fahrenheit would have an ampere-hour rating of...
A bi-directional device that can pass current in either direction.
37.3 kilowatts
400 ampere-hours.
In parallel.

37. The first step in treating a chemical burn - such as one caused by battery acid - is to...
Ohms.
A. Total resistance is less than the smallest resistor.
Flush thoroughly with water.
Attract each other.

38. The minimum allowable size of trailing cable on DC-powered mobile haulage equipment is...
Current that flows in one direction only.
1.260 to 1.280.
No.4 AWG.
Clean water.

39. The dangerously explosive gas emitted by charging a lead-acid storage battery is...
Hydrogen.
500 volts.
Current that flows in one direction only.
Attract each other.

40. Define current...
Heat
Voltage.
A counter-EMF.
The movement of electrons in a circuit.

41. What is the equivalent resistance of two 16-ohm resistors connected in parallel?
Less than the resistance of either resistor.
8 ohms.
Voltmeter.
4.0 ohms.

42. What voltage would be required to force 10 amps through a 50-ohm resistor?
6 volts.
Until the victim receives medical attention.
1.260 to 1.280.
500 volts.

43. How must two 12-volt batteries be connected in order to increase the current capacity?
Series-wound.
In parallel.
No.4 AWG.
Heat

44. Resistance is measured with a...
Clean water.
In series.
Less than the resistance of either resistor.
Ohmmeter.

45. The advantage of DC over AC is that DC offers...
Repel each other.
48 ohms.
Better speed control on motors.
A counter-EMF.

46. How long should treatment for shock be continued?
A. Total resistance is less than the smallest resistor.
Hydrometer.
Until the victim receives medical attention.
There is a hazard of blowing the contents back into your face - 'explosive reaction'.

47. The most common reason that solid state devices fail is...
Heat
Higher current with voltage remaining the same.
Repel each other.
A bi-directional device that can pass current in either direction.

48. What voltage is required to force 5 amps through a 15-ohm resistor?
Stays the same.
15 minutes.
No.4 AWG.
75 volts.

49. Power is measured with a...
It must prevent internal explosions.
In series.
Wattmeter.
Watts.

50. Trailing cable on DC-powered mobile haulage equipment must be at least...
No.4 AWG.
Voltmeter.
Flush the burn the clean water.
Direct current.

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DC Theory

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