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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. Define direct current...
Ohmmeter.
A. Total resistance is less than the smallest resistor.
Current that flows in one direction only.
746 watts.

2. What is the opposition to flow of electric current?
746 watts.
Clean water.
Resistance.
400 ampere-hours.

3. You have three 12-volt batteries. How should you connect them in order to supply 36 volts?
Stays the same.
A counter-EMF.
It must prevent ignition of surrounding methane atmosphere.
In series.

4. Voltage is measured with a...
37.3 kilowatts
1.260 to 1.280.
Voltmeter.
Soft iron.

5. The core of an electro-magnet should be made of...
Ammeter.
Current that flows in one direction only.
Better speed control on motors.
Soft iron.

6. Trailing cable on DC-powered mobile haulage equipment must be at least...
A. Total resistance is less than the smallest resistor.
No.4 AWG.
Current.
In series.

7. Chemical burns caused by battery acid should be washed with clean water for at least...
60 ohms.
15 minutes.
There is a hazard of blowing the contents back into your face - 'explosive reaction'.
In series.

8. What is the unit of electromotive force or electric pressure?
Hydrogen.
Voltage.
Flush thoroughly with water.
Less than the resistance of either resistor.

9. The first step in treating a chemical burn - such as one caused by battery acid - is to...
Until the victim receives medical attention.
Flush thoroughly with water.
Heat
Ventilation.

10. Power is measured with a...
No.4 AWG.
Wattmeter.
After charging
Current.

11. The dangerously explosive gas emitted by charging a lead-acid storage battery is...
Hydrogen.
Compound-wound and shunt-wound.
Treat for physical shock.
Ventilation.

12. Resistors are rated in ohms and...
Ammeter.
Watts.
Series-wound.
500 volts.

13. In a parallel circuit...
No.4 AWG.
48 volts
In parallel.
A. Total resistance is less than the smallest resistor.

14. What is the equivalent resistance of an 8-ohm and a 12-ohm resistor connected in parallel?
Power.
4.8 ohms
There is a hazard of blowing the contents back into your face - 'explosive reaction'.
Stays the same.

15. What is the total resistance of three 16-ohm resistors connected in series?
Treat for physical shock.
48 ohms.
There is a hazard of blowing the contents back into your face - 'explosive reaction'.
In series.

16. A triac is?
Treat for physical shock.
A bi-directional device that can pass current in either direction.
Direct current.
37.3 kilowatts

17. What voltage would be required to force 10 amps through a 50-ohm resistor?
6 volts.
500 volts.
8 ohms.
Treat for physical shock.

18. Storage battery charging stations must be provided with what kind of current protection?
96 volts.
Reverse.
Resistance.
6 volts.

19. Current is measured with a (an)...
Resistance.
No.4 AWG.
Ammeter.
Repel each other.

20. What is the total resistance of four 25-ohm resistors connected in series?
Flush thoroughly with water.
Burns will appear only at the point where contact is made to the energized circuit.
Stays the same.
100 ohms

21. The advantage of DC over AC is that DC offers...
8 ohms.
Until the victim receives medical attention.
Better speed control on motors.
Amperes.

22. The instrument used to check the electrolyte of a battery is a...
Clean water.
After charging
Ohmmeter.
Hydrometer.

23. Current in a series circuit...
There is a hazard of blowing the contents back into your face - 'explosive reaction'.
400 ampere-hours.
E=IR.
Stays the same.

24. Unlike poles of a magnet will...
Ohms.
37.3 kilowatts
Attract each other.
Compound-wound and shunt-wound.

25. The specific gravity of the electrolyte of a fully charged battery should be...
200 volts
Attract each other.
1.260 to 1.280.
Voltmeter.

26. Define current...
The movement of electrons in a circuit.
A bi-directional device that can pass current in either direction.
Clean water.
Better speed control on motors.

27. How many watts are in one horsepower?
Attract each other.
746 watts.
Current
Compound-wound and shunt-wound.

28. What is the equivalent resistance of two 8-ohm resistors connected in parallel?
Series-wound.
4.0 ohms.
Compound-wound and shunt-wound.
E=IR.

29. Define resistance...
Resistance.
The opposition to flow of electrons in a circuit.
Ohmmeter.
Stays the same.

30. What is the total voltage of four 12-volt batteries connected in series?
48 volts
37.3 kilowatts
Power.
E=IR.

31. What voltage would be required to force 10 amps through a 20-ohm resistor?
Stays the same.
60 ohms.
200 volts
Heat

32. The armature of a direct current motor - when running - generates...
A counter-EMF.
48 ohms.
Power.
8 ohms.

33. Voltage in a parallel circuit...
Clean water.
Wattmeter.
Ohms.
Stays the same.

34. The unit of measurement of resistance is?
Ohms.
Hydrometer.
In series.
400 ampere-hours.

35. What is the first step in treating a chemical burn of the eye?
Flush the burn the clean water.
Current
The movement of electrons in a circuit.
A. Total resistance is less than the smallest resistor.

36. The longer the conductor - the greater the...
Resistance.
Burns will appear only at the point where contact is made to the energized circuit.
Ventilation.
No.4 AWG.

37. Which of the following motors are considered to be constant or nearly constant speed?
Compound-wound and shunt-wound.
4.8 ohms
Watts.
Attract each other.

38. How must two 12-volt batteries be connected in order to increase the current capacity?
Clean water.
Heat
In parallel.
400 ampere-hours.

39. The unit of measurement of power is...
Watts.
Compound-wound and shunt-wound.
Hydrometer.
Stays the same.

40. Not true about electrical shocks?
E=IR.
Decrease.
Burns will appear only at the point where contact is made to the energized circuit.
Wattmeter.

41. Which of the following is a requirement of an explosion-proof enclosure?
It must prevent ignition of surrounding methane atmosphere.
After charging
Resistance.
The opposition to flow of electrons in a circuit.

42. The minimum allowable size of trailing cable on DC-powered mobile haulage equipment is...
746 watts.
No.4 AWG.
Current
Hydrogen.

43. The most common reason that solid state devices fail is...
Decrease.
No.4 AWG.
Heat
6 volts.

44. What is the total voltage of four 9-volt batteries connected in a series?
6 volts.
36 volts.
Soft iron.
75 volts.

45. If the cross-sectional area of a conductor is increased - its resistance will...
1.260 to 1.280.
The opposition to flow of electrons in a circuit.
400 ampere-hours.
Decrease.

46. Resistance is measured with a...
There is a hazard of blowing the contents back into your face - 'explosive reaction'.
Attract each other.
Ohmmeter.
8 ohms.

47. When should water be added to a battery?
Current that flows in one direction only.
It must prevent ignition of surrounding methane atmosphere.
After charging
In parallel.

48. The unit of measurement of current is...
Current.
Better speed control on motors.
Amperes.
1.260 to 1.280.

49. The best insulator against the lines of magnetic force is...
Flush thoroughly with water.
Distance.
A. Total resistance is less than the smallest resistor.
Current that flows in one direction only.

50. Which current flows in only one direction?
Ammeter.
Flush the burn the clean water.
Direct current.
Hydrometer.