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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. The armature of a direct current motor - when running - generates...
Stays the same.
E=IR.
A counter-EMF.
100 ohms

2. Which of the following stays the same in all parts of a series circuit?
Reverse.
36 volts.
Amperes.
Current

3. Which of the following motors are considered to be constant or nearly constant speed?
A counter-EMF.
Distance.
15 minutes.
Compound-wound and shunt-wound.

4. Trailing cable on DC-powered mobile haulage equipment must be at least...
Higher current with voltage remaining the same.
Stays the same.
No.4 AWG.
A wire wound resistor.

5. Define direct current...
In parallel.
Stays the same.
Current that flows in only one direction.
Ohms.

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

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7. What voltage would be required to force 10 amps through a 20-ohm resistor?
Flush thoroughly with water.
Soft iron.
200 volts
Stays the same.

8. What should be used in treating an eye injury caused by battery acid?
Hydrogen.
Clean water.
Attract each other.
Better speed control on motors.

9. The unit of measurement of resistance is?
In series.
Resistance.
Wattmeter.
Ohms.

10. Not a requirement of an explosion-proof enclosure?
75 volts.
It must prevent internal explosions.
Wattmeter.
Stays the same.

11. How long should treatment for shock be continued?
Until the victim receives medical attention.
Attract each other.
In series.
The opposition to flow of electrons in a circuit.

12. The unit of measurement of current is...
Resistance.
Burns will appear only at the point where contact is made to the energized circuit.
4.0 ohms.
Amperes.

13. The unit of measurement of power is...
It must prevent internal explosions.
Watts.
37.3 kilowatts
Less than the resistance of either resistor.

14. What is the flow of electrons in a conductor?
Resistance.
Decrease.
Current.
Watts.

15. The advantage of DC over AC is that DC offers...
Better speed control on motors.
Reverse.
Watts.
Resistance.

16. What is the equivalent resistance of two 8-ohm resistors connected in parallel?
4.0 ohms.
E=IR.
100 ohms
It must prevent internal explosions.

17. What is the unit of electromotive force or electric pressure?
37.3 kilowatts
Voltage.
Resistance.
Watts.

18. The instrument used to check the electrolyte of a battery is a...
Repel each other.
Burns will appear only at the point where contact is made to the energized circuit.
Hydrometer.
Current

19. What is the first step in treating a chemical burn of the eye?
Flush the burn the clean water.
200 volts
Decrease.
37.3 kilowatts

20. The core of an electro-magnet should be made of...
100 ohms
Soft iron.
8 ohms.
After charging

21. The combined resistance of two resistors in parallel is...
No.4 AWG.
Watts.
The movement of electrons in a circuit.
Less than the resistance of either resistor.

22. What is the total voltage of eight 12-volt batteries connected in series?
Burns will appear only at the point where contact is made to the energized circuit.
Voltmeter.
Higher current with voltage remaining the same.
96 volts.

23. Like poles of a magnet will...
Ammeter.
Repel each other.
Compound-wound and shunt-wound.
Stays the same.

24. Define resistance...
Resistance.
Resistance.
Voltage.
The opposition to flow of electrons in a circuit.

25. Which current flows in only one direction?
Direct current.
A bi-directional device that can pass current in either direction.
Attract each other.
After charging

26. Define current...
The movement of electrons in a circuit.
Better speed control on motors.
48 volts
Higher current with voltage remaining the same.

27. Current in a series circuit...
Flush the burn the clean water.
Ohmmeter.
Stays the same.
Until the victim receives medical attention.

28. The explosive gas that is generated when a battery is charging is...
Hydrogen.
Amperes.
15 minutes.
A wire wound resistor.

29. How many watts are in one horsepower?
746 watts.
75 volts.
Current.
Ventilation.

30. What is the total voltage of four 12-volt batteries connected in series?
Wattmeter.
Soft iron.
48 volts
Resistance.

31. When should water be added to a battery?
Current that flows in only one direction.
After charging
Heat
60 ohms.

32. What is the total resistance of three 16-ohm resistors connected in series?
Flush the burn the clean water.
48 ohms.
Burns will appear only at the point where contact is made to the energized circuit.
Until the victim receives medical attention.

33. The first step in treating a chemical burn - such as one caused by battery acid - is to...
It must prevent internal explosions.
A. Total resistance is less than the smallest resistor.
Flush thoroughly with water.
Current that flows in one direction only.

34. What is the total voltage of two 6-volt batteries connected in parallel?
Higher current with voltage remaining the same.
4.8 ohms
6 volts.
Amperes.

35. The most common reason that solid state devices fail is...
Stays the same.
The opposition to flow of electrons in a circuit.
Direct current.
Heat

36. You have three 9-volt batteries. How should you connect them in order to supply 27 volts?
A counter-EMF.
Current that flows in one direction only.
In series.
Watts.

37. Which of the following motors CANNOT be run without a load?
Series-wound.
Ammeter.
1.260 to 1.280.
4.8 ohms

38. Chemical burns caused by battery acid should be washed with clean water for at least...
96 volts.
Compound-wound and shunt-wound.
The movement of electrons in a circuit.
15 minutes.

39. How many kilowatts are used to develop 50 horsepower?
37.3 kilowatts
Burns will appear only at the point where contact is made to the energized circuit.
Resistance.
8 ohms.

40. Unlike poles of a magnet will...
Attract each other.
Until the victim receives medical attention.
Clean water.
Watts.

41. The specific gravity of the electrolyte of a fully charged battery should be...
Amperes.
96 volts.
400 ampere-hours.
1.260 to 1.280.

42. Power is measured with a...
Resistance.
Voltmeter.
Wattmeter.
It must prevent ignition of surrounding methane atmosphere.

43. What is Ohm's Law?
4.8 ohms
Soft iron.
Flush thoroughly with water.
E=IR.

44. Resistors are rated in ohms and...
Higher current with voltage remaining the same.
4.8 ohms
Watts.
Soft iron.

45. Voltage is measured with a...
Voltmeter.
Compound-wound and shunt-wound.
Current that flows in only one direction.
Soft iron.

46. Not an electro-magnet?
A wire wound resistor.
E=IR.
Soft iron.
Stays the same.

47. You have three 12-volt batteries. How should you connect them in order to supply 36 volts?
No.4 AWG.
In series.
500 volts.
60 ohms.

48. What is the total resistance of four 25-ohm resistors connected in series?
1.260 to 1.280.
100 ohms
In parallel.
48 ohms.

49. How must two 12-volt batteries be connected in order to increase the current capacity?
Current
Flush thoroughly with water.
In parallel.
Ohms.

50. What is the total resistance of four 15-ohm resistors connected in series?
Resistance.
Until the victim receives medical attention.
60 ohms.
Voltmeter.