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 voltage would be required to force 10 amps through a 20-ohm resistor?
200 volts
Wattmeter.
Resistance.
Stays the same.

2. The dangerously explosive gas emitted by charging a lead-acid storage battery is...
It must prevent internal explosions.
Heat
Wattmeter.
Hydrogen.

3. Resistors are rated in ohms and...
Power.
Watts.
Stays the same.
60 ohms.

4. Which of the following is a requirement of an explosion-proof enclosure?
It must prevent ignition of surrounding methane atmosphere.
Voltage.
Burns will appear only at the point where contact is made to the energized circuit.
Direct current.

5. How many kilowatts are used to develop 50 horsepower?
A counter-EMF.
37.3 kilowatts
Better speed control on motors.
No.4 AWG.

6. Define direct current...
Current.
4.8 ohms
A wire wound resistor.
Current that flows in one direction only.

7. The minimum allowable size of trailing cable on DC-powered mobile haulage equipment is...
Ammeter.
746 watts.
No.4 AWG.
Until the victim receives medical attention.

8. What is the equivalent resistance of an 8-ohm and a 12-ohm resistor connected in parallel?
Flush thoroughly with water.
4.8 ohms
It must prevent ignition of surrounding methane atmosphere.
4.0 ohms.

9. The combined resistance of two resistors in parallel is...
No.4 AWG.
Current.
Less than the resistance of either resistor.
Amperes.

10. Which of the following stays the same in all parts of a series circuit?
It must prevent internal explosions.
Current that flows in one direction only.
Amperes.
Current

11. How must two 12-volt batteries be connected in order to increase the current capacity?
No.4 AWG.
Burns will appear only at the point where contact is made to the energized circuit.
60 ohms.
In parallel.

12. Current in a series circuit...
Stays the same.
Amperes.
Reverse.
Resistance.

13. Not an electro-magnet?
A wire wound resistor.
Direct current.
Voltage.
Ohms.

14. What should be used in treating an eye injury caused by battery acid?
Clean water.
No.4 AWG.
Stays the same.
Current that flows in one direction only.

15. What voltage would be required to force 10 amps through a 50-ohm resistor?
500 volts.
After charging
Voltmeter.
No.4 AWG.

16. Current is measured with a (an)...
96 volts.
E=IR.
Ammeter.
Hydrometer.

17. Which of the following motors CANNOT be run without a load?
Series-wound.
Ventilation.
1.260 to 1.280.
15 minutes.

18. You have three 9-volt batteries. How should you connect them in order to supply 27 volts?
Resistance.
In series.
The opposition to flow of electrons in a circuit.
Repel each other.

19. What is the first step in treating a chemical burn of the eye?
96 volts.
Voltage.
Ventilation.
Flush the burn the clean water.

20. The specific gravity of the electrolyte of a fully charged battery should be...
A counter-EMF.
1.260 to 1.280.
Decrease.
Direct current.

21. What is the total voltage of four 12-volt batteries connected in series?
Higher current with voltage remaining the same.
Attract each other.
4.0 ohms.
48 volts

22. Not a requirement of an explosion-proof enclosure?
It must prevent internal explosions.
Heat
75 volts.
In series.

23. Not true about electrical shocks?
37.3 kilowatts
Burns will appear only at the point where contact is made to the energized circuit.
Voltage.
Heat

24. How many watts are in one horsepower?
In series.
Heat
746 watts.
Higher current with voltage remaining the same.

25. Power is measured with a...
Attract each other.
Wattmeter.
In series.
Hydrometer.

26. What is the total voltage of eight 12-volt batteries connected in series?
Distance.
96 volts.
500 volts.
The opposition to flow of electrons in a circuit.

27. What voltage is required to force 5 amps through a 15-ohm resistor?
Watts.
E=IR.
400 ampere-hours.
75 volts.

28. The explosive gas that is generated when a battery is charging is...
200 volts
Hydrogen.
48 volts
It must prevent ignition of surrounding methane atmosphere.

29. Define resistance...
37.3 kilowatts
The opposition to flow of electrons in a circuit.
Stays the same.
A bi-directional device that can pass current in either direction.

30. What is the total resistance of three 16-ohm resistors connected in series?
4.0 ohms.
Resistance.
Until the victim receives medical attention.
48 ohms.

31. The advantage of DC over AC is that DC offers...
Better speed control on motors.
Heat
In parallel.
Decrease.

32. What is the total resistance of four 25-ohm resistors connected in series?
60 ohms.
100 ohms
A wire wound resistor.
Voltage.

33. Chemical burns caused by battery acid should be washed with clean water for at least...
Current that flows in only one direction.
15 minutes.
Ohms.
Distance.

34. What is the total voltage of two 6-volt batteries connected in parallel?
Flush thoroughly with water.
6 volts.
The movement of electrons in a circuit.
Resistance.

35. The most common reason that solid state devices fail is...
In parallel.
In series.
Stays the same.
Heat

36. When should water be added to a battery?
Voltage.
After charging
Attract each other.
200 volts

37. Define current...
The opposition to flow of electrons in a circuit.
The movement of electrons in a circuit.
Higher current with voltage remaining the same.
Better speed control on motors.

38. Voltage is measured with a...
500 volts.
75 volts.
Voltmeter.
Power.

39. The unit of measurement of resistance is?
Ohms.
96 volts.
Current that flows in one direction only.
There is a hazard of blowing the contents back into your face - 'explosive reaction'.

40. The armature of a direct current motor - when running - generates...
15 minutes.
It must prevent ignition of surrounding methane atmosphere.
A counter-EMF.
A wire wound resistor.

41. If the cross-sectional area of a conductor is increased - its resistance will...
Decrease.
Amperes.
37.3 kilowatts
Higher current with voltage remaining the same.

42. A triac is?
E=IR.
A bi-directional device that can pass current in either direction.
Stays the same.
Power.

43. The unit of measurement of power is...
Watts.
Hydrogen.
8 ohms.
Stays the same.

44. Like poles of a magnet will...
In series.
Repel each other.
Resistance.
Flush the burn the clean water.

45. The longer the conductor - the greater the...
In parallel.
Resistance.
4.8 ohms
Power.

46. Resistance is measured with a...
Ventilation.
Ohmmeter.
Wattmeter.
1.260 to 1.280.

47. What is the opposition to flow of electric current?
746 watts.
Watts.
Resistance.
Ohmmeter.

48. In a parallel circuit...
1.260 to 1.280.
Distance.
Amperes.
A. Total resistance is less than the smallest resistor.

49. What is the total voltage of four 9-volt batteries connected in a series?
Hydrometer.
The movement of electrons in a circuit.
36 volts.
Series-wound.

50. The unit of measurement of current is...
4.8 ohms
A. Total resistance is less than the smallest resistor.
Resistance.
Amperes.