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DC Theory

Instructions:

Answer 50 questions in 15 minutes.
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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 is required to force 5 amps through a 15-ohm resistor?
It must prevent internal explosions.
The movement of electrons in a circuit.
75 volts.
Current that flows in only one direction.

2. Resistors are rated in ohms and...
Stays the same.
Watts.
75 volts.
Heat

3. The armature of a direct current motor - when running - generates...
Series-wound.
6 volts.
A counter-EMF.
Soft iron.

4. The longer the conductor - the greater the...
Treat for physical shock.
Repel each other.
Resistance.
4.8 ohms

5. Define direct current...
Current.
The movement of electrons in a circuit.
A. Total resistance is less than the smallest resistor.
Current that flows in only one direction.

6. Which of the following motors are considered to be constant or nearly constant speed?
Compound-wound and shunt-wound.
In series.
Better speed control on motors.
Attract each other.

7. What is the total resistance of four 15-ohm resistors connected in series?
60 ohms.
Wattmeter.
4.0 ohms.
A. Total resistance is less than the smallest resistor.

8. Like poles of a magnet will...
A bi-directional device that can pass current in either direction.
1.260 to 1.280.
Repel each other.
Resistance.

9. Chemical burns caused by battery acid should be washed with clean water for at least...
Amperes.
15 minutes.
A bi-directional device that can pass current in either direction.
Flush thoroughly with water.

10. The combined resistance of two resistors in parallel is...
It must prevent internal explosions.
1.260 to 1.280.
Less than the resistance of either resistor.
Distance.

11. The core of an electro-magnet should be made of...
Soft iron.
Amperes.
Direct current.
Hydrogen.

12. Trailing cable on DC-powered mobile haulage equipment must be at least...
Watts.
No.4 AWG.
Burns will appear only at the point where contact is made to the energized circuit.
Direct current.

13. What is Ohm's Law?
75 volts.
200 volts
E=IR.
6 volts.

14. In a parallel circuit...
A. Total resistance is less than the smallest resistor.
Distance.
After charging
48 ohms.

15. Not an electro-magnet?
There is a hazard of blowing the contents back into your face - 'explosive reaction'.
A wire wound resistor.
48 volts
Repel each other.

16. What is the opposition to flow of electric current?
Resistance.
1.260 to 1.280.
Voltage.
Attract each other.

17. If the cross-sectional area of a conductor is increased - its resistance will...
Decrease.
Distance.
Current that flows in only one direction.
A. Total resistance is less than the smallest resistor.

18. What should be used in treating an eye injury caused by battery acid?
Current.
Voltmeter.
Clean water.
In parallel.

19. The first step in treating a chemical burn - such as one caused by battery acid - is to...
The opposition to flow of electrons in a circuit.
Soft iron.
Flush thoroughly with water.
Current.

20. A triac is?
A bi-directional device that can pass current in either direction.
400 ampere-hours.
15 minutes.
Current that flows in one direction only.

21. What is the total resistance of three 16-ohm resistors connected in series?
Soft iron.
37.3 kilowatts
48 ohms.
Current that flows in one direction only.

22. Batteries connected in parallel provide...
No.4 AWG.
96 volts.
Ohms.
Higher current with voltage remaining the same.

23. The minimum allowable size of trailing cable on DC-powered mobile haulage equipment is...
No.4 AWG.
Treat for physical shock.
Series-wound.
Amperes.

24. The most common reason that solid state devices fail is...
Voltmeter.
48 volts
Heat
200 volts

25. Voltage is measured with a...
Less than the resistance of either resistor.
Voltmeter.
Better speed control on motors.
4.0 ohms.

26. The unit of measurement of resistance is?
Hydrometer.
Ventilation.
In series.
Ohms.

27. Which of the following motors CANNOT be run without a load?
Until the victim receives medical attention.
Series-wound.
15 minutes.
Voltage.

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

29. What is the total voltage of four 9-volt batteries connected in a series?
36 volts.
746 watts.
In series.
E=IR.

30. Current in a series circuit...
E=IR.
Stays the same.
In parallel.
Attract each other.

31. What must be provided at underground battery charging stations?
Ventilation.
Reverse.
A counter-EMF.
Resistance.

32. What is the total voltage of eight 12-volt batteries connected in series?
96 volts.
In series.
Voltmeter.
Flush thoroughly with water.

33. The unit of measurement of power is...
Watts.
In series.
No.4 AWG.
Burns will appear only at the point where contact is made to the energized circuit.

34. What is the equivalent resistance of two 16-ohm resistors connected in parallel?
Current.
8 ohms.
Ohmmeter.
Wattmeter.

35. Not a requirement of an explosion-proof enclosure?
In series.
It must prevent internal explosions.
It must prevent ignition of surrounding methane atmosphere.
Watts.

36. The explosive gas that is generated when a battery is charging is...
Better speed control on motors.
Hydrogen.
Flush the burn the clean water.
Flush thoroughly with water.

37. Power is measured with a...
Treat for physical shock.
The movement of electrons in a circuit.
Wattmeter.
A. Total resistance is less than the smallest resistor.

38. How many kilowatts are used to develop 50 horsepower?
Hydrogen.
It must prevent ignition of surrounding methane atmosphere.
Attract each other.
37.3 kilowatts

39. Which of the following is a requirement of an explosion-proof enclosure?
100 ohms
Treat for physical shock.
48 volts
It must prevent ignition of surrounding methane atmosphere.

40. Current is measured with a (an)...
Direct current.
Repel each other.
Ammeter.
The opposition to flow of electrons in a circuit.

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

42. The dangerously explosive gas emitted by charging a lead-acid storage battery is...
Hydrogen.
1.260 to 1.280.
Repel each other.
Hydrometer.

43. What is the equivalent resistance of two 8-ohm resistors connected in parallel?
Flush thoroughly with water.
The movement of electrons in a circuit.
Higher current with voltage remaining the same.
4.0 ohms.

44. When should water be added to a battery?
In series.
Stays the same.
After charging
Repel each other.

45. What voltage would be required to force 10 amps through a 50-ohm resistor?
500 volts.
200 volts
Voltage.
Voltmeter.

46. What is the rate that work is done or heat is dissipated?
Power.
No.4 AWG.
Flush the burn the clean water.
746 watts.

47. Unlike poles of a magnet will...
Amperes.
8 ohms.
6 volts.
Attract each other.

48. The best insulator against the lines of magnetic force is...
A wire wound resistor.
Ohmmeter.
Distance.
After charging

49. What voltage would be required to force 10 amps through a 20-ohm resistor?
200 volts
Amperes.
Clean water.
15 minutes.

50. The advantage of DC over AC is that DC offers...
Better speed control on motors.
There is a hazard of blowing the contents back into your face - 'explosive reaction'.
4.0 ohms.
A bi-directional device that can pass current in either direction.

Can you answer 50 questions in 15 minutes?

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DC Theory

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