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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. Power is measured with a...
8 ohms.
4.8 ohms
Wattmeter.
Stays the same.

2. Which of the following motors are considered to be constant or nearly constant speed?
Hydrometer.
A bi-directional device that can pass current in either direction.
Compound-wound and shunt-wound.
Soft iron.

3. Define direct current...
75 volts.
Ohmmeter.
Current that flows in one direction only.
Stays the same.

4. The first step in treating a chemical burn - such as one caused by battery acid - is to...
Flush thoroughly with water.
Stays the same.
Current that flows in only one direction.
Compound-wound and shunt-wound.

5. What voltage would be required to force 10 amps through a 20-ohm resistor?
E=IR.
No.4 AWG.
Better speed control on motors.
200 volts

6. A battery capable of producing 20 amperes steadily for 20 hours at 80 degrees Fahrenheit would have an ampere-hour rating of...
96 volts.
400 ampere-hours.
It must prevent internal explosions.
75 volts.

7. What is the unit of electromotive force or electric pressure?
Voltage.
Better speed control on motors.
Amperes.
Power.

8. The dangerously explosive gas emitted by charging a lead-acid storage battery is...
Hydrogen.
It must prevent internal explosions.
Ohms.
100 ohms

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

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10. Which of the following stays the same in all parts of a series circuit?
Current
Ohms.
A wire wound resistor.
Series-wound.

11. What voltage would be required to force 10 amps through a 50-ohm resistor?
200 volts
500 volts.
E=IR.
Decrease.

12. What is the total voltage of two 6-volt batteries connected in parallel?
6 volts.
In parallel.
Hydrogen.
60 ohms.

13. In a parallel circuit...
Reverse.
There is a hazard of blowing the contents back into your face - 'explosive reaction'.
Less than the resistance of either resistor.
A. Total resistance is less than the smallest resistor.

14. Voltage in a parallel circuit...
48 volts
Hydrometer.
Treat for physical shock.
Stays the same.

15. Like poles of a magnet will...
96 volts.
Repel each other.
Direct current.
Until the victim receives medical attention.

16. Batteries connected in parallel provide...
Current that flows in one direction only.
Ohmmeter.
In series.
Higher current with voltage remaining the same.

17. Not a requirement of an explosion-proof enclosure?
It must prevent internal explosions.
Power.
Higher current with voltage remaining the same.
1.260 to 1.280.

18. The most common reason that solid state devices fail is...
37.3 kilowatts
Current that flows in only one direction.
Heat
In series.

19. What is the opposition to flow of electric current?
Resistance.
Ohmmeter.
Flush the burn the clean water.
Until the victim receives medical attention.

20. Which of the following motors CANNOT be run without a load?
Series-wound.
60 ohms.
48 volts
After charging

21. How many watts are in one horsepower?
Watts.
746 watts.
Hydrogen.
Direct current.

22. The best insulator against the lines of magnetic force is...
Distance.
Compound-wound and shunt-wound.
Stays the same.
48 volts

23. What voltage is required to force 5 amps through a 15-ohm resistor?
E=IR.
15 minutes.
Watts.
75 volts.

24. 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...
Voltage.
Treat for physical shock.
It must prevent ignition of surrounding methane atmosphere.
75 volts.

25. You have three 9-volt batteries. How should you connect them in order to supply 27 volts?
746 watts.
In series.
There is a hazard of blowing the contents back into your face - 'explosive reaction'.
After charging

26. How must two 12-volt batteries be connected in order to increase the current capacity?
36 volts.
In parallel.
A counter-EMF.
It must prevent internal explosions.

27. The combined resistance of two resistors in parallel is...
48 volts
In parallel.
Amperes.
Less than the resistance of either resistor.

28. What is the total voltage of four 9-volt batteries connected in a series?
It must prevent internal explosions.
36 volts.
E=IR.
8 ohms.

29. Trailing cable on DC-powered mobile haulage equipment must be at least...
4.8 ohms
No.4 AWG.
Distance.
Series-wound.

30. The armature of a direct current motor - when running - generates...
96 volts.
A counter-EMF.
A bi-directional device that can pass current in either direction.
1.260 to 1.280.

31. What is the total resistance of three 16-ohm resistors connected in series?
No.4 AWG.
Current that flows in only one direction.
Attract each other.
48 ohms.

32. When should water be added to a battery?
Heat
37.3 kilowatts
After charging
Watts.

33. The explosive gas that is generated when a battery is charging is...
Burns will appear only at the point where contact is made to the energized circuit.
1.260 to 1.280.
Until the victim receives medical attention.
Hydrogen.

34. The unit of measurement of power is...
Watts.
Distance.
Higher current with voltage remaining the same.
Treat for physical shock.

35. The instrument used to check the electrolyte of a battery is a...
Reverse.
Amperes.
200 volts
Hydrometer.

36. Chemical burns caused by battery acid should be washed with clean water for at least...
15 minutes.
Watts.
Flush thoroughly with water.
Treat for physical shock.

37. What is the total resistance of four 15-ohm resistors connected in series?
100 ohms
After charging
60 ohms.
Voltage.

38. What is the total resistance of four 25-ohm resistors connected in series?
Resistance.
100 ohms
E=IR.
Less than the resistance of either resistor.

39. You have three 12-volt batteries. How should you connect them in order to supply 36 volts?
In series.
A bi-directional device that can pass current in either direction.
746 watts.
4.8 ohms

40. Which current flows in only one direction?
There is a hazard of blowing the contents back into your face - 'explosive reaction'.
Stays the same.
36 volts.
Direct current.

41. How many kilowatts are used to develop 50 horsepower?
Burns will appear only at the point where contact is made to the energized circuit.
37.3 kilowatts
A. Total resistance is less than the smallest resistor.
15 minutes.

42. Define resistance...
Less than the resistance of either resistor.
36 volts.
The opposition to flow of electrons in a circuit.
It must prevent ignition of surrounding methane atmosphere.

43. Voltage is measured with a...
Decrease.
Stays the same.
Until the victim receives medical attention.
Voltmeter.

44. The unit of measurement of current is...
4.0 ohms.
Amperes.
Watts.
75 volts.

45. Define direct current...
Current that flows in only one direction.
Ventilation.
Power.
Reverse.

46. What is the equivalent resistance of two 16-ohm resistors connected in parallel?
Watts.
8 ohms.
A bi-directional device that can pass current in either direction.
Ohms.

47. Storage battery charging stations must be provided with what kind of current protection?
Resistance.
15 minutes.
Reverse.
Soft iron.

48. What is the equivalent resistance of an 8-ohm and a 12-ohm resistor connected in parallel?
No.4 AWG.
4.8 ohms
37.3 kilowatts
Repel each other.

49. Unlike poles of a magnet will...
Attract each other.
Hydrogen.
75 volts.
Voltage.

50. What is the rate that work is done or heat is dissipated?
Power.
Hydrogen.
60 ohms.
Repel each other.