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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 voltage is required to force 5 amps through a 15-ohm resistor?
75 volts.
15 minutes.
48 volts
It must prevent ignition of surrounding methane atmosphere.

2. Current in a series circuit...
In parallel.
Wattmeter.
Stays the same.
The opposition to flow of electrons in a circuit.

3. Batteries connected in parallel provide...
Stays the same.
Higher current with voltage remaining the same.
A wire wound resistor.
Series-wound.

4. What is the total resistance of three 16-ohm resistors connected in series?
8 ohms.
Distance.
48 ohms.
The opposition to flow of electrons in a circuit.

5. What is the equivalent resistance of two 16-ohm resistors connected in parallel?
A counter-EMF.
The movement of electrons in a circuit.
8 ohms.
60 ohms.

6. What is the equivalent resistance of an 8-ohm and a 12-ohm resistor connected in parallel?
A. Total resistance is less than the smallest resistor.
4.8 ohms
Soft iron.
Series-wound.

7. What is the first step in treating a chemical burn of the eye?
Current
Distance.
Flush the burn the clean water.
Less than the resistance of either resistor.

8. Which current flows in only one direction?
Resistance.
Hydrogen.
Direct current.
Better speed control on motors.

9. What is the total resistance of four 15-ohm resistors connected in series?
60 ohms.
Distance.
It must prevent internal explosions.
Clean water.

10. Like poles of a magnet will...
There is a hazard of blowing the contents back into your face - 'explosive reaction'.
Repel each other.
Watts.
Ohmmeter.

11. The armature of a direct current motor - when running - generates...
A counter-EMF.
No.4 AWG.
100 ohms
1.260 to 1.280.

12. Not true about electrical shocks?
Current
Series-wound.
Burns will appear only at the point where contact is made to the energized circuit.
75 volts.

13. Define direct current...
Current that flows in one direction only.
Less than the resistance of either resistor.
Watts.
746 watts.

14. What is the rate that work is done or heat is dissipated?
Heat
Ohmmeter.
Power.
200 volts

15. The combined resistance of two resistors in parallel is...
Less than the resistance of either resistor.
4.8 ohms
A. Total resistance is less than the smallest resistor.
Wattmeter.

16. The minimum allowable size of trailing cable on DC-powered mobile haulage equipment is...
Treat for physical shock.
48 volts
No.4 AWG.
Watts.

17. If the cross-sectional area of a conductor is increased - its resistance will...
The opposition to flow of electrons in a circuit.
Ammeter.
Decrease.
Watts.

18. What must be provided at underground battery charging stations?
500 volts.
Ventilation.
Ohms.
4.8 ohms

19. Trailing cable on DC-powered mobile haulage equipment must be at least...
Higher current with voltage remaining the same.
Clean water.
No.4 AWG.
Flush the burn the clean water.

20. Storage battery charging stations must be provided with what kind of current protection?
It must prevent ignition of surrounding methane atmosphere.
Less than the resistance of either resistor.
Reverse.
746 watts.

21. Which of the following motors are considered to be constant or nearly constant speed?
Compound-wound and shunt-wound.
Current.
400 ampere-hours.
Series-wound.

22. Chemical burns caused by battery acid should be washed with clean water for at least...
15 minutes.
Watts.
37.3 kilowatts
Hydrometer.

23. What should be used in treating an eye injury caused by battery acid?
Clean water.
Direct current.
A bi-directional device that can pass current in either direction.
37.3 kilowatts

24. When should water be added to a battery?
After charging
37.3 kilowatts
It must prevent internal explosions.
In series.

25. What is the total voltage of four 12-volt batteries connected in series?
48 volts
15 minutes.
400 ampere-hours.
A. Total resistance is less than the smallest resistor.

26. Which of the following motors CANNOT be run without a load?
1.260 to 1.280.
4.0 ohms.
Series-wound.
Burns will appear only at the point where contact is made to the energized circuit.

27. Define direct current...
E=IR.
75 volts.
Current that flows in only one direction.
Hydrogen.

28. The best insulator against the lines of magnetic force is...
There is a hazard of blowing the contents back into your face - 'explosive reaction'.
60 ohms.
Distance.
A wire wound resistor.

29. What is the total resistance of four 25-ohm resistors connected in series?
Heat
Power.
Current that flows in one direction only.
100 ohms

30. The advantage of DC over AC is that DC offers...
Current.
400 ampere-hours.
96 volts.
Better speed control on motors.

31. What voltage would be required to force 10 amps through a 50-ohm resistor?
Ohms.
500 volts.
100 ohms
No.4 AWG.

32. What is the total voltage of eight 12-volt batteries connected in series?
Watts.
96 volts.
8 ohms.
Better speed control on motors.

33. A battery capable of producing 20 amperes steadily for 20 hours at 80 degrees Fahrenheit would have an ampere-hour rating of...
Heat
400 ampere-hours.
Higher current with voltage remaining the same.
Current

34. Resistance is measured with a...
15 minutes.
Voltage.
Ohmmeter.
746 watts.

35. You have three 12-volt batteries. How should you connect them in order to supply 36 volts?
In series.
The movement of electrons in a circuit.
Flush the burn the clean water.
746 watts.

36. What is the equivalent resistance of two 8-ohm resistors connected in parallel?
100 ohms
Flush the burn the clean water.
Watts.
4.0 ohms.

37. What voltage would be required to force 10 amps through a 20-ohm resistor?
Resistance.
Current
200 volts
37.3 kilowatts

38. The most common reason that solid state devices fail is...
A counter-EMF.
Less than the resistance of either resistor.
In parallel.
Heat

39. The longer the conductor - the greater the...
Resistance.
It must prevent internal explosions.
Current that flows in one direction only.
Current that flows in only one direction.

40. Power is measured with a...
In series.
Voltage.
Wattmeter.
Decrease.

41. How many kilowatts are used to develop 50 horsepower?
37.3 kilowatts
The opposition to flow of electrons in a circuit.
Until the victim receives medical attention.
100 ohms

42. Not an electro-magnet?
A wire wound resistor.
E=IR.
37.3 kilowatts
Heat

43. The specific gravity of the electrolyte of a fully charged battery should be...
Ventilation.
1.260 to 1.280.
60 ohms.
Resistance.

44. You have three 9-volt batteries. How should you connect them in order to supply 27 volts?
In parallel.
Repel each other.
In series.
Hydrogen.

45. What is the total voltage of two 6-volt batteries connected in parallel?
6 volts.
Ohms.
Stays the same.
Attract each other.

46. Unlike poles of a magnet will...
In series.
Attract each other.
Amperes.
Distance.

47. The core of an electro-magnet should be made of...
Resistance.
Soft iron.
Direct current.
6 volts.

48. Not a requirement of an explosion-proof enclosure?
Stays the same.
100 ohms
It must prevent internal explosions.
Heat

49. Voltage in a parallel circuit...
Current
Stays the same.
Current.
Watts.

50. What is the opposition to flow of electric current?
Ohms.
400 ampere-hours.
Stays the same.
Resistance.