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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. Current in a series circuit...
Power.
Stays the same.
Direct current.
It must prevent internal explosions.

2. When should water be added to a battery?
Compound-wound and shunt-wound.
Hydrogen.
Treat for physical shock.
After charging

3. The minimum allowable size of trailing cable on DC-powered mobile haulage equipment is...
Amperes.
6 volts.
Current
No.4 AWG.

4. The longer the conductor - the greater the...
36 volts.
Ammeter.
Higher current with voltage remaining the same.
Resistance.

5. The core of an electro-magnet should be made of...
Voltage.
Hydrogen.
Soft iron.
Flush thoroughly with water.

6. Which of the following is a requirement of an explosion-proof enclosure?
In series.
It must prevent ignition of surrounding methane atmosphere.
It must prevent internal explosions.
500 volts.

7. You have three 9-volt batteries. How should you connect them in order to supply 27 volts?
In series.
Reverse.
The movement of electrons in a circuit.
A bi-directional device that can pass current in either direction.

8. The advantage of DC over AC is that DC offers...
Hydrometer.
1.260 to 1.280.
Better speed control on motors.
Current

9. Which current flows in only one direction?
Direct current.
200 volts
6 volts.
Flush the burn the clean water.

10. How must two 12-volt batteries be connected in order to increase the current capacity?
Watts.
In parallel.
The movement of electrons in a circuit.
100 ohms

11. In a parallel circuit...
Attract each other.
Voltage.
Less than the resistance of either resistor.
A. Total resistance is less than the smallest resistor.

12. Which of the following motors CANNOT be run without a load?
746 watts.
A bi-directional device that can pass current in either direction.
Series-wound.
Heat

13. Unlike poles of a magnet will...
Ammeter.
Attract each other.
Current that flows in only one direction.
Ohmmeter.

14. Not an electro-magnet?
No.4 AWG.
A wire wound resistor.
500 volts.
Hydrogen.

15. Like poles of a magnet will...
15 minutes.
Repel each other.
4.8 ohms
Power.

16. Current is measured with a (an)...
Ammeter.
Flush thoroughly with water.
8 ohms.
Burns will appear only at the point where contact is made to the energized circuit.

17. What is the opposition to flow of electric current?
Compound-wound and shunt-wound.
Hydrometer.
Resistance.
Better speed control on motors.

18. Define current...
Higher current with voltage remaining the same.
Series-wound.
Watts.
The movement of electrons in a circuit.

19. How many watts are in one horsepower?
8 ohms.
Direct current.
746 watts.
After charging

20. Batteries connected in parallel provide...
The opposition to flow of electrons in a circuit.
Higher current with voltage remaining the same.
Current that flows in only one direction.
In series.

21. You have three 12-volt batteries. How should you connect them in order to supply 36 volts?
In series.
After charging
36 volts.
746 watts.

22. What should be used in treating an eye injury caused by battery acid?
Burns will appear only at the point where contact is made to the energized circuit.
After charging
Clean water.
Hydrogen.

23. Storage battery charging stations must be provided with what kind of current protection?
It must prevent ignition of surrounding methane atmosphere.
Power.
Reverse.
Less than the resistance of either resistor.

24. If the cross-sectional area of a conductor is increased - its resistance will...
No.4 AWG.
Hydrogen.
E=IR.
Decrease.

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

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

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27. What is the total voltage of eight 12-volt batteries connected in series?
96 volts.
75 volts.
Current that flows in only one direction.
Ohms.

28. Not true about electrical shocks?
Reverse.
E=IR.
Ohms.
Burns will appear only at the point where contact is made to the energized circuit.

29. The armature of a direct current motor - when running - generates...
6 volts.
Flush the burn the clean water.
200 volts
A counter-EMF.

30. What is the total voltage of four 9-volt batteries connected in a series?
The opposition to flow of electrons in a circuit.
Decrease.
36 volts.
200 volts

31. What must be provided at underground battery charging stations?
Ventilation.
Attract each other.
Better speed control on motors.
No.4 AWG.

32. Define direct current...
Amperes.
Wattmeter.
Current that flows in one direction only.
Voltage.

33. Trailing cable on DC-powered mobile haulage equipment must be at least...
Better speed control on motors.
No.4 AWG.
Current that flows in only one direction.
Higher current with voltage remaining the same.

34. A triac is?
A bi-directional device that can pass current in either direction.
Flush the burn the clean water.
75 volts.
Stays the same.

35. What is the total resistance of four 15-ohm resistors connected in series?
Power.
746 watts.
100 ohms
60 ohms.

36. The explosive gas that is generated when a battery is charging is...
75 volts.
It must prevent ignition of surrounding methane atmosphere.
Hydrogen.
Current that flows in one direction only.

37. What voltage is required to force 5 amps through a 15-ohm resistor?
Ohmmeter.
4.8 ohms
100 ohms
75 volts.

38. What voltage would be required to force 10 amps through a 20-ohm resistor?
Current.
4.0 ohms.
It must prevent ignition of surrounding methane atmosphere.
200 volts

39. 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...
Stays the same.
Reverse.
Treat for physical shock.
48 volts

40. What is the rate that work is done or heat is dissipated?
Watts.
Power.
Series-wound.
8 ohms.

41. The unit of measurement of current is...
E=IR.
A counter-EMF.
Ammeter.
Amperes.

42. Define direct current...
Current that flows in only one direction.
Voltmeter.
Wattmeter.
4.0 ohms.

43. What is the equivalent resistance of an 8-ohm and a 12-ohm resistor connected in parallel?
Hydrometer.
8 ohms.
Attract each other.
4.8 ohms

44. The specific gravity of the electrolyte of a fully charged battery should be...
746 watts.
After charging
1.260 to 1.280.
400 ampere-hours.

45. Not a requirement of an explosion-proof enclosure?
Repel each other.
Current that flows in one direction only.
It must prevent internal explosions.
Hydrogen.

46. Voltage in a parallel circuit...
It must prevent internal explosions.
Clean water.
Stays the same.
Higher current with voltage remaining the same.

47. What is Ohm's Law?
Attract each other.
Direct current.
E=IR.
Resistance.

48. What is the equivalent resistance of two 16-ohm resistors connected in parallel?
Ohms.
Hydrogen.
Better speed control on motors.
8 ohms.

49. Voltage is measured with a...
Voltmeter.
75 volts.
746 watts.
4.8 ohms

50. Resistance is measured with a...
Ohmmeter.
1.260 to 1.280.
A wire wound resistor.
Reverse.