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DC 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. The armature of a direct current motor - when running - generates...
Repel each other.
A bi-directional device that can pass current in either direction.
A counter-EMF.
100 ohms

2. Storage battery charging stations must be provided with what kind of current protection?
200 volts
Ammeter.
Reverse.
6 volts.

3. Not a requirement of an explosion-proof enclosure?
Direct current.
It must prevent internal explosions.
Voltage.
36 volts.

4. Which of the following motors are considered to be constant or nearly constant speed?
Compound-wound and shunt-wound.
Reverse.
37.3 kilowatts
The movement of electrons in a circuit.

5. What is Ohm's Law?
E=IR.
Voltage.
Hydrogen.
Distance.

6. The first step in treating a chemical burn - such as one caused by battery acid - is to...
A bi-directional device that can pass current in either direction.
Flush thoroughly with water.
Amperes.
The opposition to flow of electrons in a circuit.

7. The most common reason that solid state devices fail is...
A bi-directional device that can pass current in either direction.
Wattmeter.
Heat
96 volts.

8. Like poles of a magnet will...
Repel each other.
96 volts.
1.260 to 1.280.
A counter-EMF.

9. What is the opposition to flow of electric current?
100 ohms
The movement of electrons in a circuit.
Resistance.
A counter-EMF.

10. What should be used in treating an eye injury caused by battery acid?
Clean water.
Treat for physical shock.
Soft iron.
15 minutes.

11. Which of the following motors CANNOT be run without a load?
After charging
Resistance.
Attract each other.
Series-wound.

12. Define direct current...
Until the victim receives medical attention.
500 volts.
Current that flows in one direction only.
Watts.

13. Which current flows in only one direction?
Direct current.
Power.
Resistance.
Current.

14. In a parallel circuit...
Hydrogen.
Distance.
After charging
A. Total resistance is less than the smallest resistor.

15. Batteries connected in parallel provide...
Higher current with voltage remaining the same.
Resistance.
Stays the same.
Flush thoroughly with water.

16. Which of the following stays the same in all parts of a series circuit?
Ventilation.
Stays the same.
Current
No.4 AWG.

17. What is the total resistance of three 16-ohm resistors connected in series?
Distance.
Current
746 watts.
48 ohms.

18. Voltage in a parallel circuit...
The opposition to flow of electrons in a circuit.
Amperes.
Stays the same.
500 volts.

19. When should water be added to a battery?
No.4 AWG.
Decrease.
Hydrogen.
After charging

20. 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...
Treat for physical shock.
Clean water.
4.8 ohms
A counter-EMF.

21. What is the total voltage of four 9-volt batteries connected in a series?
36 volts.
Wattmeter.
Higher current with voltage remaining the same.
Watts.

22. What is the total voltage of four 12-volt batteries connected in series?
400 ampere-hours.
Distance.
48 volts
A counter-EMF.

23. What is the total resistance of four 25-ohm resistors connected in series?
8 ohms.
100 ohms
Better speed control on motors.
Direct current.

24. The explosive gas that is generated when a battery is charging is...
Hydrogen.
Hydrometer.
The movement of electrons in a circuit.
36 volts.

25. A triac is?
Voltmeter.
A bi-directional device that can pass current in either direction.
Treat for physical shock.
Current.

26. Unlike poles of a magnet will...
Stays the same.
Attract each other.
Amperes.
Treat for physical shock.

27. Not an electro-magnet?
Soft iron.
A wire wound resistor.
60 ohms.
6 volts.

28. The minimum allowable size of trailing cable on DC-powered mobile haulage equipment is...
No.4 AWG.
746 watts.
Wattmeter.
Soft iron.

29. What is the equivalent resistance of two 16-ohm resistors connected in parallel?
A wire wound resistor.
Better speed control on motors.
8 ohms.
Repel each other.

30. Current in a series circuit...
Hydrogen.
Higher current with voltage remaining the same.
Watts.
Stays the same.

31. Define resistance...
The opposition to flow of electrons in a circuit.
No.4 AWG.
It must prevent internal explosions.
A bi-directional device that can pass current in either direction.

32. What is the equivalent resistance of two 8-ohm resistors connected in parallel?
It must prevent internal explosions.
Treat for physical shock.
Clean water.
4.0 ohms.

33. You have three 12-volt batteries. How should you connect them in order to supply 36 volts?
36 volts.
In series.
Power.
6 volts.

34. What must be provided at underground battery charging stations?
Ventilation.
100 ohms
Ammeter.
Distance.

35. What voltage is required to force 5 amps through a 15-ohm resistor?
Burns will appear only at the point where contact is made to the energized circuit.
In series.
Voltage.
75 volts.

36. The unit of measurement of power is...
Decrease.
6 volts.
Current
Watts.

37. If the cross-sectional area of a conductor is increased - its resistance will...
Stays the same.
E=IR.
Decrease.
4.8 ohms

38. The instrument used to check the electrolyte of a battery is a...
746 watts.
Hydrogen.
Current that flows in one direction only.
Hydrometer.

39. The best insulator against the lines of magnetic force is...
746 watts.
Distance.
Hydrometer.
6 volts.

40. What voltage would be required to force 10 amps through a 20-ohm resistor?
200 volts
37.3 kilowatts
In series.
36 volts.

41. What is the total resistance of four 15-ohm resistors connected in series?
Ohmmeter.
Clean water.
60 ohms.
Hydrometer.

42. Voltage is measured with a...
Series-wound.
The opposition to flow of electrons in a circuit.
Voltmeter.
746 watts.

43. Power is measured with a...
Wattmeter.
Better speed control on motors.
6 volts.
Voltage.

44. Chemical burns caused by battery acid should be washed with clean water for at least...
Repel each other.
15 minutes.
Current
Watts.

45. Resistance is measured with a...
Burns will appear only at the point where contact is made to the energized circuit.
Ohmmeter.
Repel each other.
Compound-wound and shunt-wound.

46. What is the unit of electromotive force or electric pressure?
Voltage.
75 volts.
36 volts.
After charging

47. The dangerously explosive gas emitted by charging a lead-acid storage battery is...
15 minutes.
A bi-directional device that can pass current in either direction.
Hydrogen.
A wire wound resistor.

48. The specific gravity of the electrolyte of a fully charged battery should be...
It must prevent ignition of surrounding methane atmosphere.
In series.
1.260 to 1.280.
Voltmeter.

49. The core of an electro-magnet should be made of...
500 volts.
Soft iron.
Current that flows in one direction only.
Amperes.

50. Current is measured with a (an)...
Ammeter.
Hydrometer.
200 volts
Decrease.