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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. What is the total resistance of four 15-ohm resistors connected in series?
Decrease.
It must prevent internal explosions.
Burns will appear only at the point where contact is made to the energized circuit.
60 ohms.

2. The dangerously explosive gas emitted by charging a lead-acid storage battery is...
In series.
Hydrogen.
Watts.
A. Total resistance is less than the smallest resistor.

3. What is the opposition to flow of electric current?
96 volts.
Treat for physical shock.
Series-wound.
Resistance.

4. Define resistance...
No.4 AWG.
Compound-wound and shunt-wound.
Attract each other.
The opposition to flow of electrons in a circuit.

5. What voltage is required to force 5 amps through a 15-ohm resistor?
75 volts.
Attract each other.
Soft iron.
Current

6. The core of an electro-magnet should be made of...
Higher current with voltage remaining the same.
Soft iron.
Stays the same.
Heat

7. When should water be added to a battery?
After charging
60 ohms.
In series.
Stays the same.

8. Current is measured with a (an)...
Until the victim receives medical attention.
Burns will appear only at the point where contact is made to the energized circuit.
Ammeter.
Treat for physical shock.

9. Which of the following motors are considered to be constant or nearly constant speed?
Decrease.
500 volts.
Reverse.
Compound-wound and shunt-wound.

10. Voltage in a parallel circuit...
500 volts.
36 volts.
6 volts.
Stays the same.

11. What is the total voltage of four 9-volt batteries connected in a series?
In series.
48 ohms.
36 volts.
Attract each other.

12. 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.
The opposition to flow of electrons in a circuit.
36 volts.
Decrease.

13. What is the total resistance of three 16-ohm resistors connected in series?
Decrease.
Current
48 ohms.
A. Total resistance is less than the smallest resistor.

14. Trailing cable on DC-powered mobile haulage equipment must be at least...
No.4 AWG.
Direct current.
Hydrogen.
Compound-wound and shunt-wound.

15. What is the total voltage of four 12-volt batteries connected in series?
E=IR.
In series.
Clean water.
48 volts

16. Which current flows in only one direction?
Stays the same.
Ventilation.
Direct current.
Soft iron.

17. The combined resistance of two resistors in parallel is...
746 watts.
After charging
A. Total resistance is less than the smallest resistor.
Less than the resistance of either resistor.

18. Define direct current...
746 watts.
Current that flows in only one direction.
Soft iron.
Current

19. What is the flow of electrons in a conductor?
Current.
In parallel.
A bi-directional device that can pass current in either direction.
It must prevent internal explosions.

20. Chemical burns caused by battery acid should be washed with clean water for at least...
It must prevent ignition of surrounding methane atmosphere.
Voltage.
15 minutes.
8 ohms.

21. What voltage would be required to force 10 amps through a 20-ohm resistor?
6 volts.
Hydrogen.
200 volts
60 ohms.

22. You have three 9-volt batteries. How should you connect them in order to supply 27 volts?
Watts.
4.0 ohms.
In series.
37.3 kilowatts

23. What is the total voltage of two 6-volt batteries connected in parallel?
8 ohms.
Amperes.
Burns will appear only at the point where contact is made to the energized circuit.
6 volts.

24. The first step in treating a chemical burn - such as one caused by battery acid - is to...
Less than the resistance of either resistor.
Flush thoroughly with water.
100 ohms
Heat

25. What is the total resistance of four 25-ohm resistors connected in series?
100 ohms
4.8 ohms
Stays the same.
Ohms.

26. The explosive gas that is generated when a battery is charging is...
Compound-wound and shunt-wound.
Hydrogen.
A. Total resistance is less than the smallest resistor.
Watts.

27. The best insulator against the lines of magnetic force is...
No.4 AWG.
Distance.
500 volts.
Flush thoroughly with water.

28. The longer the conductor - the greater the...
The movement of electrons in a circuit.
No.4 AWG.
No.4 AWG.
Resistance.

29. Unlike poles of a magnet will...
48 volts
Ammeter.
Attract each other.
Burns will appear only at the point where contact is made to the energized circuit.

30. If the cross-sectional area of a conductor is increased - its resistance will...
No.4 AWG.
Decrease.
48 volts
Distance.

31. The instrument used to check the electrolyte of a battery is a...
Distance.
A. Total resistance is less than the smallest resistor.
Hydrometer.
Hydrogen.

32. Power is measured with a...
Current that flows in only one direction.
A wire wound resistor.
Wattmeter.
Hydrogen.

33. What is the first step in treating a chemical burn of the eye?
No.4 AWG.
Less than the resistance of either resistor.
No.4 AWG.
Flush the burn the clean water.

34. How long should treatment for shock be continued?
In series.
Ohms.
Compound-wound and shunt-wound.
Until the victim receives medical attention.

35. Which of the following is a requirement of an explosion-proof enclosure?
37.3 kilowatts
It must prevent ignition of surrounding methane atmosphere.
4.8 ohms
60 ohms.

36. Resistors are rated in ohms and...
Watts.
In series.
Flush thoroughly with water.
96 volts.

37. Not a requirement of an explosion-proof enclosure?
Power.
It must prevent internal explosions.
Better speed control on motors.
Flush thoroughly with water.

38. What is the rate that work is done or heat is dissipated?
Power.
Flush the burn the clean water.
Better speed control on motors.
Voltage.

39. What is Ohm's Law?
After charging
96 volts.
E=IR.
Less than the resistance of either resistor.

40. The minimum allowable size of trailing cable on DC-powered mobile haulage equipment is...
Amperes.
Clean water.
Resistance.
No.4 AWG.

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

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42. In a parallel circuit...
8 ohms.
A. Total resistance is less than the smallest resistor.
Current.
Compound-wound and shunt-wound.

43. The armature of a direct current motor - when running - generates...
After charging
Attract each other.
A counter-EMF.
There is a hazard of blowing the contents back into your face - 'explosive reaction'.

44. The specific gravity of the electrolyte of a fully charged battery should be...
Ventilation.
Wattmeter.
1.260 to 1.280.
96 volts.

45. Like poles of a magnet will...
8 ohms.
Repel each other.
Amperes.
Watts.

46. A battery capable of producing 20 amperes steadily for 20 hours at 80 degrees Fahrenheit would have an ampere-hour rating of...
Less than the resistance of either resistor.
The movement of electrons in a circuit.
400 ampere-hours.
200 volts

47. Current in a series circuit...
Watts.
It must prevent ignition of surrounding methane atmosphere.
15 minutes.
Stays the same.

48. Resistance is measured with a...
It must prevent internal explosions.
Ohmmeter.
Repel each other.
4.8 ohms

49. How many watts are in one horsepower?
Ammeter.
36 volts.
8 ohms.
746 watts.

50. How many kilowatts are used to develop 50 horsepower?
Better speed control on motors.
Higher current with voltage remaining the same.
A counter-EMF.
37.3 kilowatts