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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 equivalent resistance of an 8-ohm and a 12-ohm resistor connected in parallel?
Watts.
400 ampere-hours.
Less than the resistance of either resistor.
4.8 ohms

2. What is the equivalent resistance of two 8-ohm resistors connected in parallel?
4.0 ohms.
Watts.
500 volts.
Stays the same.

3. A battery capable of producing 20 amperes steadily for 20 hours at 80 degrees Fahrenheit would have an ampere-hour rating of...
Until the victim receives medical attention.
Current that flows in one direction only.
Distance.
400 ampere-hours.

4. Define direct current...
Current that flows in one direction only.
Voltage.
Attract each other.
Hydrometer.

5. Resistance is measured with a...
48 volts
Resistance.
Watts.
Ohmmeter.

6. Which of the following is a requirement of an explosion-proof enclosure?
It must prevent ignition of surrounding methane atmosphere.
60 ohms.
Better speed control on motors.
Until the victim receives medical attention.

7. The combined resistance of two resistors in parallel is...
Direct current.
The movement of electrons in a circuit.
The opposition to flow of electrons in a circuit.
Less than the resistance of either resistor.

8. The longer the conductor - the greater the...
E=IR.
Resistance.
746 watts.
75 volts.

9. What is the total voltage of eight 12-volt batteries connected in series?
Amperes.
Hydrogen.
96 volts.
8 ohms.

10. Which of the following motors are considered to be constant or nearly constant speed?
Stays the same.
Soft iron.
Compound-wound and shunt-wound.
Ammeter.

11. Define direct current...
Current that flows in only one direction.
Resistance.
Hydrogen.
Series-wound.

12. How long should treatment for shock be continued?
Until the victim receives medical attention.
No.4 AWG.
Series-wound.
Current

13. The specific gravity of the electrolyte of a fully charged battery should be...
Watts.
1.260 to 1.280.
In series.
Until the victim receives medical attention.

14. Which of the following motors CANNOT be run without a load?
Series-wound.
Repel each other.
The movement of electrons in a circuit.
Treat for physical shock.

15. Power is measured with a...
Wattmeter.
100 ohms
48 ohms.
No.4 AWG.

16. The best insulator against the lines of magnetic force is...
Current.
60 ohms.
Attract each other.
Distance.

17. What is the total voltage of four 9-volt batteries connected in a series?
Decrease.
Current that flows in only one direction.
36 volts.
4.8 ohms

18. How many watts are in one horsepower?
4.0 ohms.
Amperes.
746 watts.
200 volts

19. When should water be added to a battery?
4.0 ohms.
After charging
A wire wound resistor.
E=IR.

20. The unit of measurement of current is...
Watts.
Soft iron.
Stays the same.
Amperes.

21. The advantage of DC over AC is that DC offers...
No.4 AWG.
37.3 kilowatts
Voltage.
Better speed control on motors.

22. Current is measured with a (an)...
Clean water.
Ammeter.
48 ohms.
100 ohms

23. What voltage would be required to force 10 amps through a 50-ohm resistor?
75 volts.
Watts.
8 ohms.
500 volts.

24. In a parallel circuit...
A. Total resistance is less than the smallest resistor.
Compound-wound and shunt-wound.
Less than the resistance of either resistor.
746 watts.

25. A triac is?
A wire wound resistor.
A bi-directional device that can pass current in either direction.
Heat
Resistance.

26. You have three 12-volt batteries. How should you connect them in order to supply 36 volts?
No.4 AWG.
In series.
Better speed control on motors.
Treat for physical shock.

27. What is the total voltage of two 6-volt batteries connected in parallel?
Series-wound.
15 minutes.
4.0 ohms.
6 volts.

28. What is the total resistance of three 16-ohm resistors connected in series?
Flush the burn the clean water.
48 ohms.
In series.
Repel each other.

29. What is the rate that work is done or heat is dissipated?
In series.
37.3 kilowatts
Power.
60 ohms.

30. Not true about electrical shocks?
Soft iron.
In series.
Treat for physical shock.
Burns will appear only at the point where contact is made to the energized circuit.

31. Current in a series circuit...
No.4 AWG.
60 ohms.
Stays the same.
75 volts.

32. Storage battery charging stations must be provided with what kind of current protection?
Power.
Hydrogen.
Current
Reverse.

33. Not an electro-magnet?
A wire wound resistor.
There is a hazard of blowing the contents back into your face - 'explosive reaction'.
Ventilation.
Hydrogen.

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...
Treat for physical shock.
The opposition to flow of electrons in a circuit.
Watts.
Repel each other.

35. Unlike poles of a magnet will...
Attract each other.
In series.
It must prevent internal explosions.
No.4 AWG.

36. The most common reason that solid state devices fail is...
A. Total resistance is less than the smallest resistor.
Power.
Soft iron.
Heat

37. The first step in treating a chemical burn - such as one caused by battery acid - is to...
A wire wound resistor.
Flush thoroughly with water.
Better speed control on motors.
Ammeter.

38. How must two 12-volt batteries be connected in order to increase the current capacity?
In parallel.
48 ohms.
37.3 kilowatts
Current that flows in only one direction.

39. Define current...
A wire wound resistor.
500 volts.
4.0 ohms.
The movement of electrons in a circuit.

40. The minimum allowable size of trailing cable on DC-powered mobile haulage equipment is...
Flush the burn the clean water.
A bi-directional device that can pass current in either direction.
746 watts.
No.4 AWG.

41. What is the flow of electrons in a conductor?
Decrease.
Ammeter.
Current.
Less than the resistance of either resistor.

42. Batteries connected in parallel provide...
Higher current with voltage remaining the same.
Repel each other.
A wire wound resistor.
8 ohms.

43. The unit of measurement of power is...
Distance.
Watts.
36 volts.
Stays the same.

44. What is the equivalent resistance of two 16-ohm resistors connected in parallel?
A wire wound resistor.
8 ohms.
Hydrogen.
The movement of electrons in a circuit.

45. Resistors are rated in ohms and...
After charging
Reverse.
Flush the burn the clean water.
Watts.

46. Which current flows in only one direction?
Direct current.
Higher current with voltage remaining the same.
Clean water.
Repel each other.

47. The core of an electro-magnet should be made of...
6 volts.
100 ohms
Soft iron.
E=IR.

48. If the cross-sectional area of a conductor is increased - its resistance will...
Voltmeter.
Hydrogen.
Decrease.
Better speed control on motors.

49. The instrument used to check the electrolyte of a battery is a...
Clean water.
200 volts
Hydrometer.
Until the victim receives medical attention.

50. Trailing cable on DC-powered mobile haulage equipment must be at least...
Compound-wound and shunt-wound.
Heat
A wire wound resistor.
No.4 AWG.