Test your basic knowledge |

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 two 8-ohm resistors connected in parallel?
4.0 ohms.
500 volts.
In series.
Hydrogen.

2. The explosive gas that is generated when a battery is charging is...
Until the victim receives medical attention.
100 ohms
Hydrogen.
8 ohms.

3. The advantage of DC over AC is that DC offers...
Hydrogen.
Current
Better speed control on motors.
500 volts.

4. Power is measured with a...
Better speed control on motors.
Voltage.
Wattmeter.
A. Total resistance is less than the smallest resistor.

5. What is the unit of electromotive force or electric pressure?
No.4 AWG.
Stays the same.
75 volts.
Voltage.

6. How long should treatment for shock be continued?
In series.
Until the victim receives medical attention.
48 ohms.
A bi-directional device that can pass current in either direction.

7. Resistance is measured with a...
Watts.
75 volts.
Ohmmeter.
It must prevent internal explosions.

8. The armature of a direct current motor - when running - generates...
Current that flows in one direction only.
Reverse.
No.4 AWG.
A counter-EMF.

9. What is the rate that work is done or heat is dissipated?
Ohms.
Series-wound.
Power.
Heat

10. A battery capable of producing 20 amperes steadily for 20 hours at 80 degrees Fahrenheit would have an ampere-hour rating of...
Power.
8 ohms.
400 ampere-hours.
Higher current with voltage remaining the same.

11. Voltage is measured with a...
4.0 ohms.
Voltmeter.
Flush the burn the clean water.
Decrease.

12. The core of an electro-magnet should be made of...
No.4 AWG.
Direct current.
Treat for physical shock.
Soft iron.

13. What is Ohm's Law?
4.0 ohms.
Soft iron.
8 ohms.
E=IR.

14. What is the first step in treating a chemical burn of the eye?
Power.
Reverse.
Flush the burn the clean water.
Ventilation.

15. The minimum allowable size of trailing cable on DC-powered mobile haulage equipment is...
Ammeter.
Stays the same.
No.4 AWG.
Current

16. What is the equivalent resistance of an 8-ohm and a 12-ohm resistor connected in parallel?
4.8 ohms
Current that flows in one direction only.
8 ohms.
Better speed control on motors.

17. Define direct current...
In series.
Current that flows in only one direction.
Burns will appear only at the point where contact is made to the energized circuit.
After charging

18. Not an electro-magnet?
A wire wound resistor.
Current that flows in only one direction.
Hydrogen.
Ohmmeter.

19. The best insulator against the lines of magnetic force is...
In series.
37.3 kilowatts
Resistance.
Distance.

20. Like poles of a magnet will...
Voltage.
It must prevent internal explosions.
48 ohms.
Repel each other.

21. What voltage would be required to force 10 amps through a 50-ohm resistor?
Current that flows in one direction only.
Resistance.
Reverse.
500 volts.

22. Which of the following stays the same in all parts of a series circuit?
Current
Voltmeter.
1.260 to 1.280.
Current that flows in only one direction.

23. What is the total resistance of four 25-ohm resistors connected in series?
96 volts.
100 ohms
Less than the resistance of either resistor.
36 volts.

24. How many kilowatts are used to develop 50 horsepower?
There is a hazard of blowing the contents back into your face - 'explosive reaction'.
Flush thoroughly with water.
37.3 kilowatts
A. Total resistance is less than the smallest resistor.

25. Define direct current...
Watts.
E=IR.
A. Total resistance is less than the smallest resistor.
Current that flows in one direction only.

26. The longer the conductor - the greater the...
Resistance.
Until the victim receives medical attention.
Ventilation.
Stays the same.

27. Not true about electrical shocks?
There is a hazard of blowing the contents back into your face - 'explosive reaction'.
Soft iron.
Burns will appear only at the point where contact is made to the energized circuit.
No.4 AWG.

28. Resistors are rated in ohms and...
Watts.
100 ohms
400 ampere-hours.
Resistance.

29. Not a requirement of an explosion-proof enclosure?
15 minutes.
The movement of electrons in a circuit.
Reverse.
It must prevent internal explosions.

30. 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...
1.260 to 1.280.
No.4 AWG.
Amperes.
Treat for physical shock.

31. You have three 9-volt batteries. How should you connect them in order to supply 27 volts?
In series.
Watts.
Flush the burn the clean water.
Higher current with voltage remaining the same.

32. Trailing cable on DC-powered mobile haulage equipment must be at least...
96 volts.
Treat for physical shock.
Watts.
No.4 AWG.

33. The unit of measurement of resistance is?
There is a hazard of blowing the contents back into your face - 'explosive reaction'.
Ohms.
Reverse.
It must prevent internal explosions.

34. The first step in treating a chemical burn - such as one caused by battery acid - is to...
Flush thoroughly with water.
36 volts.
Watts.
400 ampere-hours.

35. How must two 12-volt batteries be connected in order to increase the current capacity?
Hydrogen.
Clean water.
After charging
In parallel.

36. Current in a series circuit...
Stays the same.
Flush the burn the clean water.
Current that flows in only one direction.
48 ohms.

37. The most common reason that solid state devices fail is...
Heat
Hydrogen.
The movement of electrons in a circuit.
It must prevent internal explosions.

38. What is the total resistance of four 15-ohm resistors connected in series?
Stays the same.
Current
Flush thoroughly with water.
60 ohms.

39. Define resistance...
Current that flows in only one direction.
Voltage.
The opposition to flow of electrons in a circuit.
Flush thoroughly with water.

40. What voltage would be required to force 10 amps through a 20-ohm resistor?
500 volts.
No.4 AWG.
Current.
200 volts

41. The unit of measurement of power is...
Watts.
Amperes.
Voltage.
4.8 ohms

42. Which of the following motors CANNOT be run without a load?
Ammeter.
Decrease.
In series.
Series-wound.

43. What is the total voltage of four 9-volt batteries connected in a series?
36 volts.
75 volts.
In series.
Resistance.

44. What is the opposition to flow of electric current?
37.3 kilowatts
100 ohms
Resistance.
Power.

45. What is the total resistance of three 16-ohm resistors connected in series?
Less than the resistance of either resistor.
Voltmeter.
48 ohms.
E=IR.

46. What must be provided at underground battery charging stations?
In series.
Ohms.
Ventilation.
Hydrogen.

47. In a parallel circuit...
No.4 AWG.
Flush the burn the clean water.
A. Total resistance is less than the smallest resistor.
Compound-wound and shunt-wound.

48. What is the total voltage of four 12-volt batteries connected in series?
Decrease.
48 volts
Current that flows in one direction only.
8 ohms.

49. When should water be added to a battery?
Hydrogen.
After charging
The movement of electrons in a circuit.
100 ohms

50. The unit of measurement of current is...
Better speed control on motors.
Treat for physical shock.
The movement of electrons in a circuit.
Amperes.