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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. Which of the following motors CANNOT be run without a load?
Series-wound.
4.8 ohms
It must prevent internal explosions.
Current that flows in one direction only.

2. Which of the following is a requirement of an explosion-proof enclosure?
Ammeter.
Compound-wound and shunt-wound.
Current.
It must prevent ignition of surrounding methane atmosphere.

3. Not a requirement of an explosion-proof enclosure?
Heat
Power.
Stays the same.
It must prevent internal explosions.

4. Not true about electrical shocks?
Current
Burns will appear only at the point where contact is made to the energized circuit.
It must prevent internal explosions.
It must prevent ignition of surrounding methane atmosphere.

5. Trailing cable on DC-powered mobile haulage equipment must be at least...
No.4 AWG.
Series-wound.
Flush the burn the clean water.
The movement of electrons in a circuit.

6. Chemical burns caused by battery acid should be washed with clean water for at least...
48 ohms.
15 minutes.
Flush thoroughly with water.
500 volts.

7. What is the total resistance of three 16-ohm resistors connected in series?
Stays the same.
48 ohms.
E=IR.
100 ohms

8. In a parallel circuit...
A. Total resistance is less than the smallest resistor.
8 ohms.
Stays the same.
Amperes.

9. What is the first step in treating a chemical burn of the eye?
48 volts
In series.
Flush the burn the clean water.
Hydrometer.

10. The instrument used to check the electrolyte of a battery is a...
96 volts.
Hydrometer.
In series.
In series.

11. The first step in treating a chemical burn - such as one caused by battery acid - is to...
36 volts.
E=IR.
Distance.
Flush thoroughly with water.

12. What should be used in treating an eye injury caused by battery acid?
Amperes.
Clean water.
E=IR.
Heat

13. What is Ohm's Law?
Wattmeter.
Power.
Hydrogen.
E=IR.

14. You have three 9-volt batteries. How should you connect them in order to supply 27 volts?
E=IR.
In series.
200 volts
75 volts.

15. What is the total voltage of two 6-volt batteries connected in parallel?
The movement of electrons in a circuit.
No.4 AWG.
Current.
6 volts.

16. Voltage in a parallel circuit...
96 volts.
Stays the same.
60 ohms.
Watts.

17. 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.
Distance.
Resistance.

18. Like poles of a magnet will...
48 ohms.
A bi-directional device that can pass current in either direction.
Repel each other.
100 ohms

19. Not an electro-magnet?
A wire wound resistor.
The movement of electrons in a circuit.
Power.
Better speed control on motors.

20. When should water be added to a battery?
Amperes.
Hydrogen.
There is a hazard of blowing the contents back into your face - 'explosive reaction'.
After charging

21. Resistors are rated in ohms and...
Ammeter.
Resistance.
36 volts.
Watts.

22. The most common reason that solid state devices fail is...
Heat
100 ohms
Flush the burn the clean water.
No.4 AWG.

23. The dangerously explosive gas emitted by charging a lead-acid storage battery is...
No.4 AWG.
Stays the same.
Hydrogen.
Clean water.

24. The longer the conductor - the greater the...
Watts.
Heat
Flush thoroughly with water.
Resistance.

25. Which of the following motors are considered to be constant or nearly constant speed?
Wattmeter.
Compound-wound and shunt-wound.
36 volts.
Current that flows in only one direction.

26. What is the equivalent resistance of two 16-ohm resistors connected in parallel?
In series.
746 watts.
It must prevent ignition of surrounding methane atmosphere.
8 ohms.

27. What must be provided at underground battery charging stations?
Ventilation.
Heat
After charging
In series.

28. The unit of measurement of current is...
Flush the burn the clean water.
Amperes.
100 ohms
Ammeter.

29. Voltage is measured with a...
It must prevent ignition of surrounding methane atmosphere.
Direct current.
Higher current with voltage remaining the same.
Voltmeter.

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

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31. Define direct current...
Distance.
Current that flows in one direction only.
The movement of electrons in a circuit.
Ohmmeter.

32. Current in a series circuit...
Stays the same.
15 minutes.
Current that flows in only one direction.
In series.

33. What is the opposition to flow of electric current?
Better speed control on motors.
Voltmeter.
Until the victim receives medical attention.
Resistance.

34. How many watts are in one horsepower?
746 watts.
Wattmeter.
4.0 ohms.
Distance.

35. Resistance is measured with a...
Stays the same.
After charging
Ohmmeter.
Series-wound.

36. The combined resistance of two resistors in parallel is...
Decrease.
Ohmmeter.
Soft iron.
Less than the resistance of either resistor.

37. What voltage would be required to force 10 amps through a 20-ohm resistor?
48 volts
Until the victim receives medical attention.
Watts.
200 volts

38. What is the equivalent resistance of two 8-ohm resistors connected in parallel?
Current that flows in only one direction.
It must prevent internal explosions.
Burns will appear only at the point where contact is made to the energized circuit.
4.0 ohms.

39. Power is measured with a...
Heat
500 volts.
Wattmeter.
Resistance.

40. The advantage of DC over AC is that DC offers...
Better speed control on motors.
48 volts
Hydrogen.
Soft iron.

41. How long should treatment for shock be continued?
48 volts
Until the victim receives medical attention.
Direct current.
Ammeter.

42. The core of an electro-magnet should be made of...
60 ohms.
Until the victim receives medical attention.
Soft iron.
In series.

43. The specific gravity of the electrolyte of a fully charged battery should be...
36 volts.
1.260 to 1.280.
Attract each other.
Current that flows in one direction only.

44. What is the unit of electromotive force or electric pressure?
Stays the same.
A wire wound resistor.
Heat
Voltage.

45. Unlike poles of a magnet will...
Attract each other.
200 volts
A counter-EMF.
A bi-directional device that can pass current in either direction.

46. Define current...
Power.
The movement of electrons in a circuit.
1.260 to 1.280.
There is a hazard of blowing the contents back into your face - 'explosive reaction'.

47. What is the total voltage of four 12-volt batteries connected in series?
48 volts
96 volts.
Repel each other.
Hydrogen.

48. Define direct current...
15 minutes.
Current that flows in only one direction.
200 volts
8 ohms.

49. What is the rate that work is done or heat is dissipated?
8 ohms.
Clean water.
Reverse.
Power.

50. The best insulator against the lines of magnetic force is...
Series-wound.
Repel each other.
Wattmeter.
Distance.