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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 first step in treating a chemical burn of the eye?
48 volts
There is a hazard of blowing the contents back into your face - 'explosive reaction'.
Flush the burn the clean water.
48 ohms.

2. What voltage would be required to force 10 amps through a 50-ohm resistor?
48 volts
In series.
500 volts.
Reverse.

3. Resistance is measured with a...
500 volts.
96 volts.
Ohmmeter.
Treat for physical shock.

4. Which of the following stays the same in all parts of a series circuit?
8 ohms.
Attract each other.
No.4 AWG.
Current

5. The core of an electro-magnet should be made of...
Ohms.
Soft iron.
6 volts.
Distance.

6. A triac is?
A bi-directional device that can pass current in either direction.
Stays the same.
After charging
Power.

7. The explosive gas that is generated when a battery is charging is...
Repel each other.
1.260 to 1.280.
Hydrogen.
Current that flows in one direction only.

8. The combined resistance of two resistors in parallel is...
Better speed control on motors.
Current that flows in only one direction.
Voltmeter.
Less than the resistance of either resistor.

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

10. The advantage of DC over AC is that DC offers...
Attract each other.
Watts.
Better speed control on motors.
Repel each other.

11. A battery capable of producing 20 amperes steadily for 20 hours at 80 degrees Fahrenheit would have an ampere-hour rating of...
75 volts.
Better speed control on motors.
4.8 ohms
400 ampere-hours.

12. Like poles of a magnet will...
A. Total resistance is less than the smallest resistor.
Series-wound.
E=IR.
Repel each other.

13. The specific gravity of the electrolyte of a fully charged battery should be...
1.260 to 1.280.
The movement of electrons in a circuit.
200 volts
Less than the resistance of either resistor.

14. What must be provided at underground battery charging stations?
Ventilation.
Current that flows in only one direction.
48 volts
There is a hazard of blowing the contents back into your face - 'explosive reaction'.

15. When should water be added to a battery?
After charging
It must prevent ignition of surrounding methane atmosphere.
Wattmeter.
8 ohms.

16. What is Ohm's Law?
746 watts.
E=IR.
Attract each other.
A bi-directional device that can pass current in either direction.

17. The instrument used to check the electrolyte of a battery is a...
36 volts.
Current.
Hydrometer.
No.4 AWG.

18. Define direct current...
Treat for physical shock.
Clean water.
After charging
Current that flows in only one direction.

19. What is the flow of electrons in a conductor?
In series.
Ohmmeter.
Current.
The movement of electrons in a circuit.

20. Not true about electrical shocks?
Resistance.
Soft iron.
Compound-wound and shunt-wound.
Burns will appear only at the point where contact is made to the energized circuit.

21. Current is measured with a (an)...
60 ohms.
Treat for physical shock.
After charging
Ammeter.

22. The best insulator against the lines of magnetic force is...
Current.
Distance.
Attract each other.
A bi-directional device that can pass current in either direction.

23. The unit of measurement of power is...
Current that flows in one direction only.
Watts.
8 ohms.
Soft iron.

24. Storage battery charging stations must be provided with what kind of current protection?
Direct current.
Reverse.
There is a hazard of blowing the contents back into your face - 'explosive reaction'.
Hydrogen.

25. Power is measured with a...
The opposition to flow of electrons in a circuit.
Compound-wound and shunt-wound.
In series.
Wattmeter.

26. Unlike poles of a magnet will...
Stays the same.
E=IR.
Hydrogen.
Attract each other.

27. Trailing cable on DC-powered mobile haulage equipment must be at least...
Less than the resistance of either resistor.
No.4 AWG.
200 volts
A counter-EMF.

28. Voltage in a parallel circuit...
Distance.
Reverse.
Stays the same.
Attract each other.

29. Which of the following motors are considered to be constant or nearly constant speed?
Compound-wound and shunt-wound.
8 ohms.
1.260 to 1.280.
60 ohms.

30. Not an electro-magnet?
96 volts.
200 volts
A wire wound resistor.
Ohms.

31. The first step in treating a chemical burn - such as one caused by battery acid - is to...
Current that flows in only one direction.
Flush thoroughly with water.
Series-wound.
Ammeter.

32. Not a requirement of an explosion-proof enclosure?
E=IR.
Ventilation.
It must prevent internal explosions.
No.4 AWG.

33. What is the total voltage of four 9-volt batteries connected in a series?
60 ohms.
36 volts.
The movement of electrons in a circuit.
There is a hazard of blowing the contents back into your face - 'explosive reaction'.

34. 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...
Current that flows in one direction only.
Higher current with voltage remaining the same.
Treat for physical shock.
6 volts.

35. Chemical burns caused by battery acid should be washed with clean water for at least...
Amperes.
Clean water.
15 minutes.
48 ohms.

36. What is the total voltage of eight 12-volt batteries connected in series?
Less than the resistance of either resistor.
96 volts.
Direct current.
The opposition to flow of electrons in a circuit.

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

38. What is the rate that work is done or heat is dissipated?
Power.
Ventilation.
Heat
Hydrogen.

39. What is the unit of electromotive force or electric pressure?
Decrease.
Voltage.
75 volts.
Treat for physical shock.

40. How must two 12-volt batteries be connected in order to increase the current capacity?
Current that flows in one direction only.
In parallel.
It must prevent ignition of surrounding methane atmosphere.
8 ohms.

41. The unit of measurement of resistance is?
96 volts.
Voltage.
A. Total resistance is less than the smallest resistor.
Ohms.

42. The longer the conductor - the greater the...
Less than the resistance of either resistor.
Resistance.
Series-wound.
Distance.

43. What is the total voltage of two 6-volt batteries connected in parallel?
6 volts.
Watts.
96 volts.
Stays the same.

44. The minimum allowable size of trailing cable on DC-powered mobile haulage equipment is...
Treat for physical shock.
No.4 AWG.
Voltage.
8 ohms.

45. Current in a series circuit...
Hydrogen.
Stays the same.
Soft iron.
Voltmeter.

46. The armature of a direct current motor - when running - generates...
Hydrometer.
There is a hazard of blowing the contents back into your face - 'explosive reaction'.
Flush the burn the clean water.
A counter-EMF.

47. What is the equivalent resistance of two 8-ohm resistors connected in parallel?
4.0 ohms.
Stays the same.
Voltmeter.
100 ohms

48. What is the opposition to flow of electric current?
Resistance.
746 watts.
It must prevent internal explosions.
Current

49. How many watts are in one horsepower?
Attract each other.
Direct current.
Hydrogen.
746 watts.

50. Batteries connected in parallel provide...
A wire wound resistor.
48 volts
Attract each other.
Higher current with voltage remaining the same.