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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. Power is measured with a...
6 volts.
Wattmeter.
Series-wound.
746 watts.

2. What is the total resistance of four 15-ohm resistors connected in series?
60 ohms.
Resistance.
4.8 ohms
8 ohms.

3. Not an electro-magnet?
A wire wound resistor.
It must prevent ignition of surrounding methane atmosphere.
Better speed control on motors.
Hydrogen.

4. You have three 12-volt batteries. How should you connect them in order to supply 36 volts?
In series.
Hydrogen.
Current that flows in only one direction.
Treat for physical shock.

5. If the cross-sectional area of a conductor is increased - its resistance will...
Current that flows in only one direction.
Decrease.
Heat
There is a hazard of blowing the contents back into your face - 'explosive reaction'.

6. The dangerously explosive gas emitted by charging a lead-acid storage battery is...
Hydrometer.
Heat
Hydrogen.
Direct current.

7. Resistors are rated in ohms and...
Current.
E=IR.
Watts.
Flush thoroughly with water.

8. Define resistance...
Watts.
Hydrogen.
The opposition to flow of electrons in a circuit.
A. Total resistance is less than the smallest resistor.

9. What is the rate that work is done or heat is dissipated?
500 volts.
Power.
It must prevent internal explosions.
Watts.

10. Define direct current...
Current that flows in only one direction.
Better speed control on motors.
Resistance.
No.4 AWG.

11. The core of an electro-magnet should be made of...
After charging
Watts.
Burns will appear only at the point where contact is made to the energized circuit.
Soft iron.

12. A triac is?
Wattmeter.
A bi-directional device that can pass current in either direction.
It must prevent internal explosions.
746 watts.

13. How many kilowatts are used to develop 50 horsepower?
Resistance.
Higher current with voltage remaining the same.
36 volts.
37.3 kilowatts

14. Chemical burns caused by battery acid should be washed with clean water for at least...
15 minutes.
37.3 kilowatts
Watts.
96 volts.

15. The armature of a direct current motor - when running - generates...
A counter-EMF.
A. Total resistance is less than the smallest resistor.
Clean water.
A wire wound resistor.

16. What is the total voltage of two 6-volt batteries connected in parallel?
Resistance.
It must prevent internal explosions.
Ohmmeter.
6 volts.

17. What is the total voltage of four 12-volt batteries connected in series?
Current.
48 volts
There is a hazard of blowing the contents back into your face - 'explosive reaction'.
36 volts.

18. How must two 12-volt batteries be connected in order to increase the current capacity?
Decrease.
Stays the same.
A bi-directional device that can pass current in either direction.
In parallel.

19. Voltage in a parallel circuit...
Direct current.
Stays the same.
Hydrogen.
Current that flows in one direction only.

20. Current in a series circuit...
A counter-EMF.
48 volts
Current.
Stays the same.

21. What must be provided at underground battery charging stations?
Ohmmeter.
8 ohms.
Ventilation.
Attract each other.

22. Define current...
No.4 AWG.
It must prevent internal explosions.
Ohmmeter.
The movement of electrons in a circuit.

23. The unit of measurement of power is...
Reverse.
After charging
Voltage.
Watts.

24. The explosive gas that is generated when a battery is charging is...
Resistance.
Heat
A bi-directional device that can pass current in either direction.
Hydrogen.

25. Unlike poles of a magnet will...
Flush thoroughly with water.
Flush the burn the clean water.
Attract each other.
There is a hazard of blowing the contents back into your face - 'explosive reaction'.

26. How many watts are in one horsepower?
Watts.
746 watts.
Stays the same.
Current that flows in one direction only.

27. How long should treatment for shock be continued?
In series.
Until the victim receives medical attention.
Flush the burn the clean water.
Ohms.

28. Trailing cable on DC-powered mobile haulage equipment must be at least...
Direct current.
6 volts.
No.4 AWG.
In parallel.

29. What voltage would be required to force 10 amps through a 50-ohm resistor?
500 volts.
48 volts
37.3 kilowatts
E=IR.

30. What is the first step in treating a chemical burn of the eye?
100 ohms
Better speed control on motors.
Flush the burn the clean water.
Resistance.

31. What should be used in treating an eye injury caused by battery acid?
Power.
Series-wound.
Amperes.
Clean water.

32. Storage battery charging stations must be provided with what kind of current protection?
75 volts.
A. Total resistance is less than the smallest resistor.
Reverse.
15 minutes.

33. What is the equivalent resistance of two 16-ohm resistors connected in parallel?
400 ampere-hours.
8 ohms.
500 volts.
6 volts.

34. The advantage of DC over AC is that DC offers...
A. Total resistance is less than the smallest resistor.
1.260 to 1.280.
Better speed control on motors.
37.3 kilowatts

35. Current is measured with a (an)...
Distance.
Decrease.
Ammeter.
Stays the same.

36. Which of the following motors CANNOT be run without a load?
Series-wound.
Resistance.
Attract each other.
6 volts.

37. What is the total resistance of four 25-ohm resistors connected in series?
8 ohms.
There is a hazard of blowing the contents back into your face - 'explosive reaction'.
100 ohms
In parallel.

38. The first step in treating a chemical burn - such as one caused by battery acid - is to...
Flush thoroughly with water.
Watts.
Ventilation.
Resistance.

39. What is the total resistance of three 16-ohm resistors connected in series?
It must prevent ignition of surrounding methane atmosphere.
48 ohms.
500 volts.
Power.

40. Which of the following motors are considered to be constant or nearly constant speed?
Soft iron.
Hydrogen.
15 minutes.
Compound-wound and shunt-wound.

41. 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...
Ohms.
Flush thoroughly with water.
Attract each other.
Treat for physical shock.

42. A battery capable of producing 20 amperes steadily for 20 hours at 80 degrees Fahrenheit would have an ampere-hour rating of...
Attract each other.
400 ampere-hours.
Current that flows in only one direction.
Reverse.

43. What is the equivalent resistance of an 8-ohm and a 12-ohm resistor connected in parallel?
36 volts.
A. Total resistance is less than the smallest resistor.
A counter-EMF.
4.8 ohms

44. Which of the following is a requirement of an explosion-proof enclosure?
It must prevent ignition of surrounding methane atmosphere.
Treat for physical shock.
Current.
A wire wound resistor.

45. Not true about electrical shocks?
Burns will appear only at the point where contact is made to the energized circuit.
Current that flows in only one direction.
Reverse.
4.8 ohms

46. The minimum allowable size of trailing cable on DC-powered mobile haulage equipment is...
No.4 AWG.
Distance.
A. Total resistance is less than the smallest resistor.
Wattmeter.

47. What is the opposition to flow of electric current?
Power.
Current that flows in only one direction.
Resistance.
Distance.

48. What is the total voltage of eight 12-volt batteries connected in series?
Ohms.
Ohmmeter.
96 volts.
The movement of electrons in a circuit.

49. The unit of measurement of resistance is?
746 watts.
Watts.
Ohms.
8 ohms.

50. Which current flows in only one direction?
200 volts
Hydrometer.
Soft iron.
Direct current.