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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. A triac is?
Attract each other.
Current that flows in one direction only.
Stays the same.
A bi-directional device that can pass current in either direction.

2. Define resistance...
Flush the burn the clean water.
37.3 kilowatts
It must prevent internal explosions.
The opposition to flow of electrons in a circuit.

3. The longer the conductor - the greater the...
It must prevent internal explosions.
60 ohms.
Repel each other.
Resistance.

4. Trailing cable on DC-powered mobile haulage equipment must be at least...
Reverse.
Better speed control on motors.
Hydrogen.
No.4 AWG.

5. What is the hazard of pouring water into battery acid 'electrolyte'?

6. What is the rate that work is done or heat is dissipated?
100 ohms
Power.
No.4 AWG.
60 ohms.

7. What voltage would be required to force 10 amps through a 20-ohm resistor?
Resistance.
6 volts.
200 volts
48 ohms.

8. Resistors are rated in ohms and...
Distance.
Watts.
Compound-wound and shunt-wound.
Clean water.

9. The combined resistance of two resistors in parallel is...
Watts.
Less than the resistance of either resistor.
There is a hazard of blowing the contents back into your face - 'explosive reaction'.
Watts.

10. Power is measured with a...
60 ohms.
Wattmeter.
Reverse.
48 volts

11. The unit of measurement of power is...
Watts.
Resistance.
Distance.
6 volts.

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

13. What is the equivalent resistance of two 8-ohm resistors connected in parallel?
Current that flows in one direction only.
4.0 ohms.
Amperes.
36 volts.

14. Chemical burns caused by battery acid should be washed with clean water for at least...
Watts.
15 minutes.
No.4 AWG.
Current

15. 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...
A. Total resistance is less than the smallest resistor.
48 ohms.
Reverse.
Treat for physical shock.

16. The explosive gas that is generated when a battery is charging is...
Treat for physical shock.
Hydrogen.
Wattmeter.
4.8 ohms

17. Unlike poles of a magnet will...
Attract each other.
Stays the same.
Burns will appear only at the point where contact is made to the energized circuit.
Ohmmeter.

18. Not a requirement of an explosion-proof enclosure?
48 ohms.
E=IR.
It must prevent internal explosions.
Repel each other.

19. How must two 12-volt batteries be connected in order to increase the current capacity?
Voltage.
Watts.
100 ohms
In parallel.

20. The most common reason that solid state devices fail is...
Amperes.
Heat
Compound-wound and shunt-wound.
In series.

21. If the cross-sectional area of a conductor is increased - its resistance will...
Decrease.
Hydrometer.
Amperes.
Ammeter.

22. What is the total resistance of four 25-ohm resistors connected in series?
E=IR.
Resistance.
100 ohms
Attract each other.

23. Not an electro-magnet?
Power.
Repel each other.
Current
A wire wound resistor.

24. The unit of measurement of current is...
8 ohms.
15 minutes.
Amperes.
It must prevent ignition of surrounding methane atmosphere.

25. What is the equivalent resistance of an 8-ohm and a 12-ohm resistor connected in parallel?
Current
It must prevent internal explosions.
Hydrogen.
4.8 ohms

26. What is the flow of electrons in a conductor?
Hydrometer.
Current.
96 volts.
Decrease.

27. What is the total voltage of two 6-volt batteries connected in parallel?
37.3 kilowatts
6 volts.
The movement of electrons in a circuit.
Higher current with voltage remaining the same.

28. Which current flows in only one direction?
Series-wound.
Direct current.
Watts.
No.4 AWG.

29. Define current...
Treat for physical shock.
Reverse.
The movement of electrons in a circuit.
Stays the same.

30. What is the first step in treating a chemical burn of the eye?
400 ampere-hours.
Flush the burn the clean water.
100 ohms
There is a hazard of blowing the contents back into your face - 'explosive reaction'.

31. Current in a series circuit...
Distance.
6 volts.
Stays the same.
Ammeter.

32. What must be provided at underground battery charging stations?
Decrease.
400 ampere-hours.
Better speed control on motors.
Ventilation.

33. Which of the following stays the same in all parts of a series circuit?
Hydrogen.
Distance.
Current
The movement of electrons in a circuit.

34. What should be used in treating an eye injury caused by battery acid?
In series.
Clean water.
48 volts
Voltage.

35. Which of the following motors CANNOT be run without a load?
Series-wound.
Direct current.
There is a hazard of blowing the contents back into your face - 'explosive reaction'.
Soft iron.

36. The advantage of DC over AC is that DC offers...
Better speed control on motors.
Distance.
48 volts
Wattmeter.

37. Define direct current...
4.8 ohms
Until the victim receives medical attention.
Current that flows in one direction only.
200 volts

38. The instrument used to check the electrolyte of a battery is a...
After charging
Ammeter.
Hydrometer.
Current that flows in only one direction.

39. What is the total voltage of four 9-volt batteries connected in a series?
A. Total resistance is less than the smallest resistor.
36 volts.
Stays the same.
Ventilation.

40. What is the equivalent resistance of two 16-ohm resistors connected in parallel?
A counter-EMF.
8 ohms.
Hydrometer.
48 ohms.

41. The specific gravity of the electrolyte of a fully charged battery should be...
400 ampere-hours.
Repel each other.
1.260 to 1.280.
Watts.

42. What is the total resistance of three 16-ohm resistors connected in series?
E=IR.
The movement of electrons in a circuit.
Current that flows in one direction only.
48 ohms.

43. The unit of measurement of resistance is?
60 ohms.
Current
Ohms.
It must prevent internal explosions.

44. Which of the following motors are considered to be constant or nearly constant speed?
It must prevent internal explosions.
No.4 AWG.
Compound-wound and shunt-wound.
400 ampere-hours.

45. What is Ohm's Law?
15 minutes.
No.4 AWG.
E=IR.
Wattmeter.

46. A battery capable of producing 20 amperes steadily for 20 hours at 80 degrees Fahrenheit would have an ampere-hour rating of...
Burns will appear only at the point where contact is made to the energized circuit.
400 ampere-hours.
No.4 AWG.
In parallel.

47. Resistance is measured with a...
37.3 kilowatts
Less than the resistance of either resistor.
Ohmmeter.
Attract each other.

48. The core of an electro-magnet should be made of...
Soft iron.
Decrease.
400 ampere-hours.
75 volts.

49. How long should treatment for shock be continued?
Wattmeter.
Until the victim receives medical attention.
Direct current.
75 volts.

50. Storage battery charging stations must be provided with what kind of current protection?
Reverse.
500 volts.
Higher current with voltage remaining the same.
Stays the same.