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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 total resistance of four 25-ohm resistors connected in series?
Voltmeter.
200 volts
Ohms.
100 ohms

2. What is the total voltage of four 12-volt batteries connected in series?
100 ohms
A bi-directional device that can pass current in either direction.
48 volts
36 volts.

3. Current is measured with a (an)...
Ammeter.
Higher current with voltage remaining the same.
Until the victim receives medical attention.
Treat for physical shock.

4. What is the flow of electrons in a conductor?
Hydrogen.
1.260 to 1.280.
75 volts.
Current.

5. You have three 12-volt batteries. How should you connect them in order to supply 36 volts?
After charging
No.4 AWG.
No.4 AWG.
In series.

6. Resistance is measured with a...
Ohmmeter.
A wire wound resistor.
Amperes.
Flush the burn the clean water.

7. What is the total resistance of three 16-ohm resistors connected in series?
Hydrogen.
48 ohms.
In series.
Voltmeter.

8. What is the unit of electromotive force or electric pressure?
Voltage.
A. Total resistance is less than the smallest resistor.
Less than the resistance of either resistor.
Distance.

9. What must be provided at underground battery charging stations?
Power.
400 ampere-hours.
Ventilation.
15 minutes.

10. What is the hazard of pouring water into battery acid 'electrolyte'?

11. The armature of a direct current motor - when running - generates...
A counter-EMF.
Ventilation.
4.8 ohms
Watts.

12. The instrument used to check the electrolyte of a battery is a...
Current that flows in one direction only.
A. Total resistance is less than the smallest resistor.
Hydrometer.
48 ohms.

13. Not true about electrical shocks?
Voltage.
200 volts
Burns will appear only at the point where contact is made to the energized circuit.
In series.

14. The specific gravity of the electrolyte of a fully charged battery should be...
Series-wound.
200 volts
Higher current with voltage remaining the same.
1.260 to 1.280.

15. The core of an electro-magnet should be made of...
Clean water.
Current that flows in only one direction.
Soft iron.
746 watts.

16. Resistors are rated in ohms and...
60 ohms.
Watts.
Series-wound.
Ammeter.

17. Trailing cable on DC-powered mobile haulage equipment must be at least...
Current
In series.
Hydrogen.
No.4 AWG.

18. The first step in treating a chemical burn - such as one caused by battery acid - is to...
Ohms.
Series-wound.
4.0 ohms.
Flush thoroughly with water.

19. What voltage is required to force 5 amps through a 15-ohm resistor?
Series-wound.
Clean water.
75 volts.
Voltage.

20. The combined resistance of two resistors in parallel is...
A wire wound resistor.
Power.
Clean water.
Less than the resistance of either resistor.

21. What should be used in treating an eye injury caused by battery acid?
6 volts.
Reverse.
Clean water.
200 volts

22. What voltage would be required to force 10 amps through a 20-ohm resistor?
200 volts
4.0 ohms.
A. Total resistance is less than the smallest resistor.
Current.

23. Which of the following motors CANNOT be run without a load?
Hydrogen.
Flush the burn the clean water.
Stays the same.
Series-wound.

24. Not an electro-magnet?
A wire wound resistor.
Watts.
Decrease.
In series.

25. Power is measured with a...
Wattmeter.
4.0 ohms.
It must prevent internal explosions.
Current.

26. The unit of measurement of resistance is?
Current that flows in one direction only.
Ohms.
15 minutes.
Until the victim receives medical attention.

27. Define direct current...
Hydrogen.
Amperes.
Current that flows in only one direction.
Repel each other.

28. The advantage of DC over AC is that DC offers...
After charging
Stays the same.
Better speed control on motors.
Current.

29. The dangerously explosive gas emitted by charging a lead-acid storage battery is...
Hydrogen.
Clean water.
6 volts.
E=IR.

30. How long should treatment for shock be continued?
Until the victim receives medical attention.
Voltmeter.
There is a hazard of blowing the contents back into your face - 'explosive reaction'.
746 watts.

31. 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...
A. Total resistance is less than the smallest resistor.
There is a hazard of blowing the contents back into your face - 'explosive reaction'.
75 volts.
Treat for physical shock.

32. Which current flows in only one direction?
In parallel.
Burns will appear only at the point where contact is made to the energized circuit.
Direct current.
Ammeter.

33. The unit of measurement of power is...
Watts.
Soft iron.
4.0 ohms.
Hydrometer.

34. The unit of measurement of current is...
Amperes.
Decrease.
Watts.
96 volts.

35. Current in a series circuit...
Stays the same.
Ventilation.
E=IR.
Clean water.

36. What voltage would be required to force 10 amps through a 50-ohm resistor?
It must prevent internal explosions.
Watts.
No.4 AWG.
500 volts.

37. How must two 12-volt batteries be connected in order to increase the current capacity?
Direct current.
Burns will appear only at the point where contact is made to the energized circuit.
In parallel.
Reverse.

38. Define direct current...
Ammeter.
Current that flows in one direction only.
Burns will appear only at the point where contact is made to the energized circuit.
Amperes.

39. What is the equivalent resistance of two 8-ohm resistors connected in parallel?
There is a hazard of blowing the contents back into your face - 'explosive reaction'.
4.0 ohms.
60 ohms.
Reverse.

40. You have three 9-volt batteries. How should you connect them in order to supply 27 volts?
In series.
4.8 ohms
Voltmeter.
Hydrometer.

41. What is the equivalent resistance of two 16-ohm resistors connected in parallel?
Ventilation.
8 ohms.
Treat for physical shock.
Heat

42. Voltage in a parallel circuit...
Ohmmeter.
Resistance.
96 volts.
Stays the same.

43. How many watts are in one horsepower?
Watts.
Current that flows in only one direction.
Resistance.
746 watts.

44. Which of the following motors are considered to be constant or nearly constant speed?
Clean water.
Repel each other.
In series.
Compound-wound and shunt-wound.

45. What is the total resistance of four 15-ohm resistors connected in series?
A counter-EMF.
37.3 kilowatts
Voltmeter.
60 ohms.

46. The most common reason that solid state devices fail is...
Heat
400 ampere-hours.
Until the victim receives medical attention.
100 ohms

47. What is the opposition to flow of electric current?
The opposition to flow of electrons in a circuit.
Compound-wound and shunt-wound.
Reverse.
Resistance.

48. Which of the following stays the same in all parts of a series circuit?
Current
Resistance.
100 ohms
Clean water.

49. Which of the following is a requirement of an explosion-proof enclosure?
75 volts.
It must prevent ignition of surrounding methane atmosphere.
Hydrogen.
In series.

50. When should water be added to a battery?
Reverse.
After charging
Current that flows in one direction only.
Hydrogen.