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. When should water be added to a battery?
A wire wound resistor.
After charging
Better speed control on motors.
Hydrometer.

2. What is the equivalent resistance of two 16-ohm resistors connected in parallel?
Direct current.
400 ampere-hours.
Resistance.
8 ohms.

3. Which current flows in only one direction?
Direct current.
The opposition to flow of electrons in a circuit.
Resistance.
Voltmeter.

4. Define current...
Less than the resistance of either resistor.
The movement of electrons in a circuit.
8 ohms.
60 ohms.

5. Not a requirement of an explosion-proof enclosure?
It must prevent internal explosions.
There is a hazard of blowing the contents back into your face - 'explosive reaction'.
Repel each other.
15 minutes.

6. What should be used in treating an eye injury caused by battery acid?
The movement of electrons in a circuit.
75 volts.
Clean water.
Current

7. Resistors are rated in ohms and...
Watts.
Hydrogen.
60 ohms.
8 ohms.

8. What is the rate that work is done or heat is dissipated?
Less than the resistance of either resistor.
Current that flows in one direction only.
Resistance.
Power.

9. What is the opposition to flow of electric current?
Resistance.
Current
Ohms.
Stays the same.

10. Which of the following stays the same in all parts of a series circuit?
Hydrogen.
Current that flows in only one direction.
Hydrogen.
Current

11. What is the total voltage of two 6-volt batteries connected in parallel?
Attract each other.
6 volts.
Current
Ohmmeter.

12. How many kilowatts are used to develop 50 horsepower?
36 volts.
37.3 kilowatts
Current.
8 ohms.

13. Current in a series circuit...
Current.
Until the victim receives medical attention.
Stays the same.
Resistance.

14. 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...
Attract each other.
Series-wound.
Treat for physical shock.
Voltage.

15. You have three 9-volt batteries. How should you connect them in order to supply 27 volts?
In series.
Ammeter.
75 volts.
Flush thoroughly with water.

16. What is the equivalent resistance of two 8-ohm resistors connected in parallel?
15 minutes.
In parallel.
Repel each other.
4.0 ohms.

17. The best insulator against the lines of magnetic force is...
Distance.
Ohmmeter.
Watts.
Treat for physical shock.

18. Voltage is measured with a...
Until the victim receives medical attention.
Ohmmeter.
4.8 ohms
Voltmeter.

19. You have three 12-volt batteries. How should you connect them in order to supply 36 volts?
Current that flows in only one direction.
Current that flows in one direction only.
In series.
48 volts

20. Not true about electrical shocks?
Flush the burn the clean water.
200 volts
Burns will appear only at the point where contact is made to the energized circuit.
Current that flows in only one direction.

21. What is Ohm's Law?
Flush the burn the clean water.
E=IR.
4.8 ohms
96 volts.

22. What is the total resistance of four 15-ohm resistors connected in series?
Direct current.
60 ohms.
96 volts.
Ohmmeter.

23. The minimum allowable size of trailing cable on DC-powered mobile haulage equipment is...
Current.
Stays the same.
Flush the burn the clean water.
No.4 AWG.

24. Not an electro-magnet?
Clean water.
Voltmeter.
A wire wound resistor.
Watts.

25. Define direct current...
400 ampere-hours.
Hydrogen.
8 ohms.
Current that flows in one direction only.

26. Current is measured with a (an)...
There is a hazard of blowing the contents back into your face - 'explosive reaction'.
After charging
Watts.
Ammeter.

27. The core of an electro-magnet should be made of...
Soft iron.
Burns will appear only at the point where contact is made to the energized circuit.
A wire wound resistor.
Hydrometer.

28. How long should treatment for shock be continued?
Until the victim receives medical attention.
In series.
Decrease.
After charging

29. The unit of measurement of current is...
Voltage.
Amperes.
Wattmeter.
Direct current.

30. If the cross-sectional area of a conductor is increased - its resistance will...
Compound-wound and shunt-wound.
1.260 to 1.280.
Decrease.
Until the victim receives medical attention.

31. Unlike poles of a magnet will...
In parallel.
Attract each other.
Hydrogen.
100 ohms

32. Which of the following motors CANNOT be run without a load?
Series-wound.
Distance.
There is a hazard of blowing the contents back into your face - 'explosive reaction'.
1.260 to 1.280.

33. The instrument used to check the electrolyte of a battery is a...
Hydrometer.
A bi-directional device that can pass current in either direction.
Wattmeter.
Watts.

34. Batteries connected in parallel provide...
Voltage.
Current that flows in one direction only.
A bi-directional device that can pass current in either direction.
Higher current with voltage remaining the same.

35. Which of the following motors are considered to be constant or nearly constant speed?
Amperes.
No.4 AWG.
Compound-wound and shunt-wound.
1.260 to 1.280.

36. Resistance is measured with a...
Wattmeter.
Ohmmeter.
Decrease.
Current.

37. The advantage of DC over AC is that DC offers...
Better speed control on motors.
A bi-directional device that can pass current in either direction.
Decrease.
200 volts

38. What voltage would be required to force 10 amps through a 50-ohm resistor?
Ohms.
Ammeter.
6 volts.
500 volts.

39. What is the first step in treating a chemical burn of the eye?
Stays the same.
Voltage.
4.8 ohms
Flush the burn the clean water.

40. Which of the following is a requirement of an explosion-proof enclosure?
After charging
It must prevent ignition of surrounding methane atmosphere.
In series.
Repel each other.

41. How many watts are in one horsepower?
No.4 AWG.
746 watts.
Flush thoroughly with water.
8 ohms.

42. What is the total resistance of four 25-ohm resistors connected in series?
100 ohms
Stays the same.
A wire wound resistor.
Flush thoroughly with water.

43. The specific gravity of the electrolyte of a fully charged battery should be...
200 volts
4.0 ohms.
100 ohms
1.260 to 1.280.

44. Define direct current...
Watts.
A counter-EMF.
Current that flows in only one direction.
Higher current with voltage remaining the same.

45. Like poles of a magnet will...
Repel each other.
Flush the burn the clean water.
Current
Distance.

46. The dangerously explosive gas emitted by charging a lead-acid storage battery is...
Hydrogen.
37.3 kilowatts
Current.
Heat

47. The longer the conductor - the greater the...
Resistance.
Attract each other.
4.0 ohms.
Compound-wound and shunt-wound.

48. The first step in treating a chemical burn - such as one caused by battery acid - is to...
After charging
A bi-directional device that can pass current in either direction.
Flush the burn the clean water.
Flush thoroughly with water.

49. Power is measured with a...
Distance.
Wattmeter.
4.0 ohms.
There is a hazard of blowing the contents back into your face - 'explosive reaction'.

50. What is the equivalent resistance of an 8-ohm and a 12-ohm resistor connected in parallel?
Until the victim receives medical attention.
4.8 ohms
No.4 AWG.
In parallel.