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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. Define resistance...
Power.
The opposition to flow of electrons in a circuit.
Soft iron.
No.4 AWG.

2. Voltage is measured with a...
Current that flows in one direction only.
Voltmeter.
Burns will appear only at the point where contact is made to the energized circuit.
4.0 ohms.

3. What is the total resistance of four 25-ohm resistors connected in series?
It must prevent ignition of surrounding methane atmosphere.
100 ohms
The movement of electrons in a circuit.
Heat

4. The combined resistance of two resistors in parallel is...
Less than the resistance of either resistor.
Wattmeter.
Soft iron.
Higher current with voltage remaining the same.

5. Not true about electrical shocks?
Better speed control on motors.
Direct current.
Current
Burns will appear only at the point where contact is made to the energized circuit.

6. Storage battery charging stations must be provided with what kind of current protection?
6 volts.
Stays the same.
Current.
Reverse.

7. Define direct current...
E=IR.
Current that flows in one direction only.
500 volts.
Heat

8. The core of an electro-magnet should be made of...
Clean water.
60 ohms.
Soft iron.
Better speed control on motors.

9. The minimum allowable size of trailing cable on DC-powered mobile haulage equipment is...
No.4 AWG.
Stays the same.
400 ampere-hours.
8 ohms.

10. The explosive gas that is generated when a battery is charging is...
200 volts
Hydrogen.
Decrease.
A counter-EMF.

11. Unlike poles of a magnet will...
Attract each other.
4.8 ohms
8 ohms.
Reverse.

12. Which of the following is a requirement of an explosion-proof enclosure?
A wire wound resistor.
Voltmeter.
Stays the same.
It must prevent ignition of surrounding methane atmosphere.

13. What voltage would be required to force 10 amps through a 50-ohm resistor?
A bi-directional device that can pass current in either direction.
60 ohms.
500 volts.
Series-wound.

14. What is the total resistance of three 16-ohm resistors connected in series?
Clean water.
48 ohms.
There is a hazard of blowing the contents back into your face - 'explosive reaction'.
Decrease.

15. 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.
4.0 ohms.
After charging
Hydrogen.

16. Which of the following motors CANNOT be run without a load?
Series-wound.
1.260 to 1.280.
In series.
Soft iron.

17. What is the equivalent resistance of an 8-ohm and a 12-ohm resistor connected in parallel?
In parallel.
4.8 ohms
96 volts.
Hydrogen.

18. Batteries connected in parallel provide...
Higher current with voltage remaining the same.
746 watts.
There is a hazard of blowing the contents back into your face - 'explosive reaction'.
48 volts

19. Which of the following motors are considered to be constant or nearly constant speed?
Voltmeter.
Compound-wound and shunt-wound.
Flush thoroughly with water.
In series.

20. The specific gravity of the electrolyte of a fully charged battery should be...
Current.
1.260 to 1.280.
There is a hazard of blowing the contents back into your face - 'explosive reaction'.
36 volts.

21. What is the equivalent resistance of two 16-ohm resistors connected in parallel?
The movement of electrons in a circuit.
8 ohms.
After charging
It must prevent internal explosions.

22. The best insulator against the lines of magnetic force is...
Watts.
Attract each other.
Distance.
Amperes.

23. What must be provided at underground battery charging stations?
Ventilation.
Amperes.
200 volts
Stays the same.

24. What is the total voltage of eight 12-volt batteries connected in series?
Reverse.
60 ohms.
96 volts.
Higher current with voltage remaining the same.

25. The most common reason that solid state devices fail is...
48 ohms.
Repel each other.
Heat
Voltage.

26. The first step in treating a chemical burn - such as one caused by battery acid - is to...
It must prevent ignition of surrounding methane atmosphere.
Flush thoroughly with water.
37.3 kilowatts
Ohmmeter.

27. In a parallel circuit...
Repel each other.
Ventilation.
A. Total resistance is less than the smallest resistor.
15 minutes.

28. How must two 12-volt batteries be connected in order to increase the current capacity?
48 ohms.
Flush the burn the clean water.
In parallel.
Ohms.

29. The unit of measurement of resistance is?
500 volts.
Ohms.
48 ohms.
It must prevent ignition of surrounding methane atmosphere.

30. What is the total voltage of two 6-volt batteries connected in parallel?
60 ohms.
746 watts.
Current.
6 volts.

31. When should water be added to a battery?
Higher current with voltage remaining the same.
After charging
Reverse.
48 volts

32. Power is measured with a...
Amperes.
Distance.
Decrease.
Wattmeter.

33. Voltage in a parallel circuit...
In series.
Stays the same.
Direct current.
1.260 to 1.280.

34. The dangerously explosive gas emitted by charging a lead-acid storage battery is...
500 volts.
Hydrogen.
6 volts.
Power.

35. You have three 9-volt batteries. How should you connect them in order to supply 27 volts?
Decrease.
In series.
A wire wound resistor.
Resistance.

36. Resistors are rated in ohms and...
Less than the resistance of either resistor.
75 volts.
Watts.
Voltmeter.

37. What is the unit of electromotive force or electric pressure?
Ventilation.
Voltage.
500 volts.
Hydrogen.

38. Current in a series circuit...
Flush the burn the clean water.
Ventilation.
Stays the same.
Repel each other.

39. What is the total voltage of four 9-volt batteries connected in a series?
Higher current with voltage remaining the same.
36 volts.
Flush the burn the clean water.
Treat for physical shock.

40. The instrument used to check the electrolyte of a battery is a...
No.4 AWG.
There is a hazard of blowing the contents back into your face - 'explosive reaction'.
Soft iron.
Hydrometer.

41. What is the first step in treating a chemical burn of the eye?
400 ampere-hours.
Flush the burn the clean water.
746 watts.
Wattmeter.

42. The unit of measurement of power is...
Watts.
No.4 AWG.
Better speed control on motors.
746 watts.

43. What is the total voltage of four 12-volt batteries connected in series?
There is a hazard of blowing the contents back into your face - 'explosive reaction'.
E=IR.
48 volts
It must prevent internal explosions.

44. Which of the following stays the same in all parts of a series circuit?
Burns will appear only at the point where contact is made to the energized circuit.
Current
Distance.
36 volts.

45. How many watts are in one horsepower?
Watts.
Compound-wound and shunt-wound.
96 volts.
746 watts.

46. What should be used in treating an eye injury caused by battery acid?
Current.
Current
Clean water.
Decrease.

47. You have three 12-volt batteries. How should you connect them in order to supply 36 volts?
Watts.
In series.
A wire wound resistor.
Clean water.

48. A triac is?
A bi-directional device that can pass current in either direction.
Hydrometer.
Decrease.
Until the victim receives medical attention.

49. Define current...
Voltmeter.
In series.
Wattmeter.
The movement of electrons in a circuit.

50. What is Ohm's Law?
Voltage.
E=IR.
No.4 AWG.
Resistance.