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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. The instrument used to check the electrolyte of a battery is a...
Power.
Hydrometer.
500 volts.
In series.

2. You have three 12-volt batteries. How should you connect them in order to supply 36 volts?
Stays the same.
In series.
Heat
Voltage.

3. Which of the following motors are considered to be constant or nearly constant speed?
96 volts.
Compound-wound and shunt-wound.
36 volts.
No.4 AWG.

4. What is the rate that work is done or heat is dissipated?
Decrease.
A. Total resistance is less than the smallest resistor.
Current that flows in only one direction.
Power.

5. In a parallel circuit...
A. Total resistance is less than the smallest resistor.
Less than the resistance of either resistor.
Hydrogen.
Better speed control on motors.

6. The advantage of DC over AC is that DC offers...
There is a hazard of blowing the contents back into your face - 'explosive reaction'.
Better speed control on motors.
Direct current.
36 volts.

7. Not a requirement of an explosion-proof enclosure?
1.260 to 1.280.
Stays the same.
It must prevent internal explosions.
Hydrogen.

8. What is Ohm's Law?
Clean water.
Voltmeter.
96 volts.
E=IR.

9. Chemical burns caused by battery acid should be washed with clean water for at least...
15 minutes.
The opposition to flow of electrons in a circuit.
96 volts.
Ohms.

10. What is the flow of electrons in a conductor?
Current.
A. Total resistance is less than the smallest resistor.
Power.
Until the victim receives medical attention.

11. Like poles of a magnet will...
Burns will appear only at the point where contact is made to the energized circuit.
A wire wound resistor.
Repel each other.
There is a hazard of blowing the contents back into your face - 'explosive reaction'.

12. What is the equivalent resistance of an 8-ohm and a 12-ohm resistor connected in parallel?
100 ohms
4.8 ohms
36 volts.
60 ohms.

13. Define direct current...
No.4 AWG.
Current that flows in one direction only.
Resistance.
Voltmeter.

14. How must two 12-volt batteries be connected in order to increase the current capacity?
Heat
In parallel.
No.4 AWG.
Resistance.

15. What is the equivalent resistance of two 16-ohm resistors connected in parallel?
8 ohms.
Heat
746 watts.
Current that flows in one direction only.

16. The dangerously explosive gas emitted by charging a lead-acid storage battery is...
746 watts.
Hydrogen.
60 ohms.
The opposition to flow of electrons in a circuit.

17. What is the total voltage of two 6-volt batteries connected in parallel?
A bi-directional device that can pass current in either direction.
75 volts.
6 volts.
Flush the burn the clean water.

18. Current is measured with a (an)...
Voltmeter.
Flush the burn the clean water.
Attract each other.
Ammeter.

19. What is the total resistance of four 15-ohm resistors connected in series?
60 ohms.
Flush the burn the clean water.
Stays the same.
Compound-wound and shunt-wound.

20. If the cross-sectional area of a conductor is increased - its resistance will...
746 watts.
In parallel.
Decrease.
No.4 AWG.

21. The most common reason that solid state devices fail is...
Current.
Heat
4.8 ohms
Less than the resistance of either resistor.

22. A triac is?
Voltage.
In parallel.
Soft iron.
A bi-directional device that can pass current in either direction.

23. What is the opposition to flow of electric current?
Resistance.
Hydrogen.
Hydrometer.
Ventilation.

24. What voltage would be required to force 10 amps through a 20-ohm resistor?
Attract each other.
Current that flows in only one direction.
Flush thoroughly with water.
200 volts

25. Not an electro-magnet?
Attract each other.
It must prevent internal explosions.
Ohms.
A wire wound resistor.

26. Voltage in a parallel circuit...
A wire wound resistor.
400 ampere-hours.
Voltage.
Stays the same.

27. The unit of measurement of current is...
E=IR.
500 volts.
Amperes.
Watts.

28. Not true about electrical shocks?
Wattmeter.
Burns will appear only at the point where contact is made to the energized circuit.
Stays the same.
Ventilation.

29. The explosive gas that is generated when a battery is charging is...
48 volts
Hydrogen.
75 volts.
Flush the burn the clean water.

30. Unlike poles of a magnet will...
200 volts
Burns will appear only at the point where contact is made to the energized circuit.
Attract each other.
Current

31. Which of the following motors CANNOT be run without a load?
Series-wound.
Power.
Heat
No.4 AWG.

32. Which current flows in only one direction?
Ammeter.
Ventilation.
Resistance.
Direct current.

33. Trailing cable on DC-powered mobile haulage equipment must be at least...
8 ohms.
Direct current.
No.4 AWG.
E=IR.

34. Storage battery charging stations must be provided with what kind of current protection?
Reverse.
48 ohms.
Flush the burn the clean water.
Decrease.

35. The unit of measurement of power is...
Hydrometer.
Stays the same.
Watts.
500 volts.

36. When should water be added to a battery?
After charging
Series-wound.
15 minutes.
The opposition to flow of electrons in a circuit.

37. The core of an electro-magnet should be made of...
A wire wound resistor.
Attract each other.
There is a hazard of blowing the contents back into your face - 'explosive reaction'.
Soft iron.

38. What should be used in treating an eye injury caused by battery acid?
No.4 AWG.
Clean water.
Treat for physical shock.
Hydrogen.

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

40. What must be provided at underground battery charging stations?
Direct current.
Amperes.
Resistance.
Ventilation.

41. The best insulator against the lines of magnetic force is...
Repel each other.
4.0 ohms.
Distance.
E=IR.

42. Define current...
Clean water.
Voltmeter.
The movement of electrons in a circuit.
No.4 AWG.

43. How many watts are in one horsepower?
There is a hazard of blowing the contents back into your face - 'explosive reaction'.
746 watts.
In parallel.
37.3 kilowatts

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.
Higher current with voltage remaining the same.
Flush thoroughly with water.

45. Resistors are rated in ohms and...
Burns will appear only at the point where contact is made to the energized circuit.
Resistance.
Soft iron.
Watts.

46. Batteries connected in parallel provide...
After charging
200 volts
Repel each other.
Higher current with voltage remaining the same.

47. What is the total voltage of eight 12-volt batteries connected in series?
Hydrometer.
Treat for physical shock.
Flush thoroughly with water.
96 volts.

48. What is the total voltage of four 9-volt batteries connected in a series?
The opposition to flow of electrons in a circuit.
36 volts.
746 watts.
Voltage.

49. What is the total resistance of four 25-ohm resistors connected in series?
Flush the burn the clean water.
Soft iron.
Heat
100 ohms

50. Define direct current...
Ohmmeter.
Current that flows in only one direction.
Heat
It must prevent ignition of surrounding methane atmosphere.