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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 direct current...
Resistance.
Resistance.
Current that flows in one direction only.
Treat for physical shock.

2. If the cross-sectional area of a conductor is increased - its resistance will...
Voltage.
In parallel.
746 watts.
Decrease.

3. Current is measured with a (an)...
Ammeter.
A counter-EMF.
Decrease.
Stays the same.

4. What is the total voltage of four 9-volt batteries connected in a series?
Distance.
36 volts.
Resistance.
Attract each other.

5. The core of an electro-magnet should be made of...
Soft iron.
746 watts.
Hydrogen.
Current

6. What is the equivalent resistance of two 16-ohm resistors connected in parallel?
It must prevent internal explosions.
8 ohms.
Ammeter.
A bi-directional device that can pass current in either direction.

7. The minimum allowable size of trailing cable on DC-powered mobile haulage equipment is...
In series.
No.4 AWG.
Better speed control on motors.
The movement of electrons in a circuit.

8. What is the equivalent resistance of an 8-ohm and a 12-ohm resistor connected in parallel?
The movement of electrons in a circuit.
Better speed control on motors.
4.8 ohms
Resistance.

9. Batteries connected in parallel provide...
Higher current with voltage remaining the same.
Stays the same.
Distance.
Current

10. When should water be added to a battery?
After charging
Stays the same.
Resistance.
A counter-EMF.

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

12. Resistance is measured with a...
It must prevent ignition of surrounding methane atmosphere.
Ohmmeter.
Wattmeter.
8 ohms.

13. Power is measured with a...
Watts.
Flush thoroughly with water.
Distance.
Wattmeter.

14. The first step in treating a chemical burn - such as one caused by battery acid - is to...
15 minutes.
Direct current.
There is a hazard of blowing the contents back into your face - 'explosive reaction'.
Flush thoroughly with water.

15. You have three 12-volt batteries. How should you connect them in order to supply 36 volts?
A. Total resistance is less than the smallest resistor.
E=IR.
No.4 AWG.
In series.

16. How must two 12-volt batteries be connected in order to increase the current capacity?
Hydrometer.
In parallel.
Better speed control on motors.
200 volts

17. The unit of measurement of current is...
The opposition to flow of electrons in a circuit.
Soft iron.
Resistance.
Amperes.

18. Which of the following motors are considered to be constant or nearly constant speed?
Compound-wound and shunt-wound.
Ohmmeter.
There is a hazard of blowing the contents back into your face - 'explosive reaction'.
100 ohms

19. A triac is?
Burns will appear only at the point where contact is made to the energized circuit.
37.3 kilowatts
A bi-directional device that can pass current in either direction.
There is a hazard of blowing the contents back into your face - 'explosive reaction'.

20. The most common reason that solid state devices fail is...
48 ohms.
Heat
Ohms.
96 volts.

21. Which of the following stays the same in all parts of a series circuit?
Current
6 volts.
Current.
No.4 AWG.

22. What is the total resistance of four 25-ohm resistors connected in series?
Better speed control on motors.
Current that flows in only one direction.
100 ohms
6 volts.

23. The unit of measurement of resistance is?
Ventilation.
After charging
Ohms.
Resistance.

24. Define current...
The movement of electrons in a circuit.
There is a hazard of blowing the contents back into your face - 'explosive reaction'.
After charging
Flush thoroughly with water.

25. Not an electro-magnet?
37.3 kilowatts
E=IR.
A wire wound resistor.
6 volts.

26. The armature of a direct current motor - when running - generates...
Soft iron.
A counter-EMF.
It must prevent internal explosions.
It must prevent ignition of surrounding methane atmosphere.

27. What must be provided at underground battery charging stations?
Ventilation.
In parallel.
6 volts.
Attract each other.

28. The instrument used to check the electrolyte of a battery is a...
Watts.
The opposition to flow of electrons in a circuit.
Heat
Hydrometer.

29. You have three 9-volt batteries. How should you connect them in order to supply 27 volts?
In series.
A bi-directional device that can pass current in either direction.
Ohms.
Hydrogen.

30. Which current flows in only one direction?
Stays the same.
Hydrogen.
Soft iron.
Direct current.

31. Voltage is measured with a...
There is a hazard of blowing the contents back into your face - 'explosive reaction'.
Voltmeter.
Decrease.
Compound-wound and shunt-wound.

32. Unlike poles of a magnet will...
It must prevent internal explosions.
A wire wound resistor.
Watts.
Attract each other.

33. What should be used in treating an eye injury caused by battery acid?
Repel each other.
Clean water.
Ohmmeter.
Resistance.

34. What is the total voltage of two 6-volt batteries connected in parallel?
4.8 ohms
6 volts.
500 volts.
Less than the resistance of either resistor.

35. What is the total voltage of four 12-volt batteries connected in series?
37.3 kilowatts
48 volts
500 volts.
Less than the resistance of either resistor.

36. The explosive gas that is generated when a battery is charging is...
Hydrogen.
In series.
Resistance.
Distance.

37. In a parallel circuit...
Current
A. Total resistance is less than the smallest resistor.
Flush thoroughly with water.
Watts.

38. The advantage of DC over AC is that DC offers...
It must prevent internal explosions.
Voltage.
746 watts.
Better speed control on motors.

39. Which of the following is a requirement of an explosion-proof enclosure?
Watts.
Resistance.
It must prevent ignition of surrounding methane atmosphere.
4.0 ohms.

40. What is the unit of electromotive force or electric pressure?
Voltage.
Current
Treat for physical shock.
Watts.

41. Which of the following motors CANNOT be run without a load?
E=IR.
200 volts
Watts.
Series-wound.

42. What is the total resistance of four 15-ohm resistors connected in series?
60 ohms.
Until the victim receives medical attention.
No.4 AWG.
Repel each other.

43. 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...
It must prevent internal explosions.
200 volts
746 watts.
Treat for physical shock.

44. A battery capable of producing 20 amperes steadily for 20 hours at 80 degrees Fahrenheit would have an ampere-hour rating of...
37.3 kilowatts
8 ohms.
400 ampere-hours.
15 minutes.

45. The longer the conductor - the greater the...
Reverse.
Watts.
The movement of electrons in a circuit.
Resistance.

46. What is the total voltage of eight 12-volt batteries connected in series?
The opposition to flow of electrons in a circuit.
Stays the same.
96 volts.
Treat for physical shock.

47. Storage battery charging stations must be provided with what kind of current protection?
Reverse.
Resistance.
Flush the burn the clean water.
4.8 ohms

48. How long should treatment for shock be continued?
Until the victim receives medical attention.
Treat for physical shock.
Higher current with voltage remaining the same.
Resistance.

49. The specific gravity of the electrolyte of a fully charged battery should be...
Flush the burn the clean water.
1.260 to 1.280.
60 ohms.
746 watts.

50. Resistors are rated in ohms and...
Watts.
It must prevent internal explosions.
15 minutes.
Ohms.