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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 minimum allowable size of trailing cable on DC-powered mobile haulage equipment is...
Power.
Hydrogen.
No.4 AWG.
400 ampere-hours.

2. Not an electro-magnet?
A wire wound resistor.
Hydrogen.
Burns will appear only at the point where contact is made to the energized circuit.
8 ohms.

3. If the cross-sectional area of a conductor is increased - its resistance will...
8 ohms.
746 watts.
Repel each other.
Decrease.

4. In a parallel circuit...
A. Total resistance is less than the smallest resistor.
Less than the resistance of either resistor.
Resistance.
Clean water.

5. What is the total resistance of four 25-ohm resistors connected in series?
100 ohms
400 ampere-hours.
Repel each other.
Attract each other.

6. What voltage is required to force 5 amps through a 15-ohm resistor?
75 volts.
Hydrogen.
E=IR.
Burns will appear only at the point where contact is made to the energized circuit.

7. Resistors are rated in ohms and...
Watts.
96 volts.
Wattmeter.
Ohmmeter.

8. What is the rate that work is done or heat is dissipated?
Current that flows in only one direction.
Until the victim receives medical attention.
Power.
Voltage.

9. What is the equivalent resistance of an 8-ohm and a 12-ohm resistor connected in parallel?
4.8 ohms
Ohmmeter.
8 ohms.
Watts.

10. The advantage of DC over AC is that DC offers...
In parallel.
Better speed control on motors.
Hydrometer.
Flush the burn the clean water.

11. What voltage would be required to force 10 amps through a 50-ohm resistor?
Repel each other.
100 ohms
Flush the burn the clean water.
500 volts.

12. The combined resistance of two resistors in parallel is...
48 ohms.
4.8 ohms
Less than the resistance of either resistor.
Hydrometer.

13. What is the equivalent resistance of two 16-ohm resistors connected in parallel?
It must prevent internal explosions.
8 ohms.
75 volts.
After charging

14. Voltage is measured with a...
The opposition to flow of electrons in a circuit.
Hydrogen.
Stays the same.
Voltmeter.

15. The explosive gas that is generated when a battery is charging is...
Amperes.
Clean water.
Hydrogen.
Ohmmeter.

16. Define direct current...
Direct current.
Ammeter.
Current that flows in only one direction.
In series.

17. Which of the following is a requirement of an explosion-proof enclosure?
It must prevent ignition of surrounding methane atmosphere.
There is a hazard of blowing the contents back into your face - 'explosive reaction'.
Voltage.
6 volts.

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

19. Which of the following motors CANNOT be run without a load?
Burns will appear only at the point where contact is made to the energized circuit.
Series-wound.
746 watts.
96 volts.

20. Like poles of a magnet will...
Current
Higher current with voltage remaining the same.
Repel each other.
Clean water.

21. What is the total voltage of eight 12-volt batteries connected in series?
In parallel.
A. Total resistance is less than the smallest resistor.
Ammeter.
96 volts.

22. Define resistance...
A counter-EMF.
The opposition to flow of electrons in a circuit.
Flush the burn the clean water.
Repel each other.

23. 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...
48 volts
A counter-EMF.
Distance.
Treat for physical shock.

24. The unit of measurement of resistance is?
A. Total resistance is less than the smallest resistor.
75 volts.
Ohms.
In series.

25. Which of the following stays the same in all parts of a series circuit?
500 volts.
Current
Current that flows in one direction only.
Until the victim receives medical attention.

26. What is the opposition to flow of electric current?
15 minutes.
Clean water.
Resistance.
Amperes.

27. Chemical burns caused by battery acid should be washed with clean water for at least...
Flush the burn the clean water.
100 ohms
15 minutes.
Ohmmeter.

28. You have three 12-volt batteries. How should you connect them in order to supply 36 volts?
Flush the burn the clean water.
In series.
Hydrogen.
Ventilation.

29. The first step in treating a chemical burn - such as one caused by battery acid - is to...
In parallel.
Hydrometer.
After charging
Flush thoroughly with water.

30. How long should treatment for shock be continued?
Ventilation.
Until the victim receives medical attention.
A counter-EMF.
100 ohms

31. A battery capable of producing 20 amperes steadily for 20 hours at 80 degrees Fahrenheit would have an ampere-hour rating of...
400 ampere-hours.
1.260 to 1.280.
200 volts
Ammeter.

32. What is the total voltage of four 9-volt batteries connected in a series?
Stays the same.
Hydrogen.
36 volts.
No.4 AWG.

33. How many watts are in one horsepower?
Higher current with voltage remaining the same.
746 watts.
No.4 AWG.
A bi-directional device that can pass current in either direction.

34. The core of an electro-magnet should be made of...
Soft iron.
Series-wound.
A wire wound resistor.
6 volts.

35. What is Ohm's Law?
Voltmeter.
Ammeter.
E=IR.
Amperes.

36. The most common reason that solid state devices fail is...
60 ohms.
A counter-EMF.
Heat
E=IR.

37. Not true about electrical shocks?
Burns will appear only at the point where contact is made to the energized circuit.
Repel each other.
Ammeter.
15 minutes.

38. The specific gravity of the electrolyte of a fully charged battery should be...
48 ohms.
Ammeter.
Heat
1.260 to 1.280.

39. The instrument used to check the electrolyte of a battery is a...
Hydrometer.
48 ohms.
Stays the same.
Watts.

40. What is the unit of electromotive force or electric pressure?
Current
Flush the burn the clean water.
Voltage.
Decrease.

41. What is the total voltage of two 6-volt batteries connected in parallel?
6 volts.
400 ampere-hours.
The movement of electrons in a circuit.
746 watts.

42. Power is measured with a...
Series-wound.
Heat
4.8 ohms
Wattmeter.

43. Unlike poles of a magnet will...
There is a hazard of blowing the contents back into your face - 'explosive reaction'.
Reverse.
Attract each other.
In series.

44. What should be used in treating an eye injury caused by battery acid?
400 ampere-hours.
Distance.
Clean water.
Series-wound.

45. What is the total resistance of three 16-ohm resistors connected in series?
48 ohms.
A counter-EMF.
Stays the same.
Resistance.

46. The unit of measurement of current is...
Amperes.
Clean water.
In series.
Soft iron.

47. The unit of measurement of power is...
Watts.
Stays the same.
48 ohms.
It must prevent internal explosions.

48. Not a requirement of an explosion-proof enclosure?
A wire wound resistor.
E=IR.
It must prevent internal explosions.
After charging

49. Which current flows in only one direction?
Voltmeter.
Flush thoroughly with water.
Direct current.
37.3 kilowatts

50. A triac is?
A bi-directional device that can pass current in either direction.
Better speed control on motors.
Soft iron.
Heat