Test your basic knowledge |

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. If the cross-sectional area of a conductor is increased - its resistance will...
Wattmeter.
Flush thoroughly with water.
Heat
Decrease.

2. The longer the conductor - the greater the...
Resistance.
Decrease.
Voltage.
Ammeter.

3. What is the total resistance of three 16-ohm resistors connected in series?
8 ohms.
48 ohms.
36 volts.
400 ampere-hours.

4. The combined resistance of two resistors in parallel is...
4.0 ohms.
Current that flows in only one direction.
Amperes.
Less than the resistance of either resistor.

5. The explosive gas that is generated when a battery is charging is...
A. Total resistance is less than the smallest resistor.
15 minutes.
Current
Hydrogen.

6. What is the total resistance of four 25-ohm resistors connected in series?
Soft iron.
A. Total resistance is less than the smallest resistor.
100 ohms
In series.

7. What is the unit of electromotive force or electric pressure?
Voltage.
36 volts.
Power.
Flush thoroughly with water.

8. How must two 12-volt batteries be connected in order to increase the current capacity?
In parallel.
E=IR.
36 volts.
Current

9. Which of the following stays the same in all parts of a series circuit?
Current
Current that flows in only one direction.
Resistance.
37.3 kilowatts

10. In a parallel circuit...
Better speed control on motors.
Power.
A. Total resistance is less than the smallest resistor.
500 volts.

11. What is Ohm's Law?
Ohmmeter.
48 ohms.
E=IR.
Flush thoroughly with water.

12. Resistance is measured with a...
48 volts
Watts.
Ohmmeter.
Reverse.

13. What is the rate that work is done or heat is dissipated?
In series.
746 watts.
Reverse.
Power.

14. Define direct current...
A counter-EMF.
400 ampere-hours.
Current that flows in only one direction.
The opposition to flow of electrons in a circuit.

15. Which of the following motors are considered to be constant or nearly constant speed?
Series-wound.
Heat
Less than the resistance of either resistor.
Compound-wound and shunt-wound.

16. Power is measured with a...
Flush the burn the clean water.
Wattmeter.
Amperes.
The movement of electrons in a circuit.

17. Not an electro-magnet?
A wire wound resistor.
A. Total resistance is less than the smallest resistor.
Heat
Repel each other.

18. The most common reason that solid state devices fail is...
No.4 AWG.
A counter-EMF.
Heat
Resistance.

19. What is the total resistance of four 15-ohm resistors connected in series?
Hydrogen.
Better speed control on motors.
It must prevent ignition of surrounding methane atmosphere.
60 ohms.

20. Define resistance...
The opposition to flow of electrons in a circuit.
36 volts.
Distance.
A wire wound resistor.

21. Define current...
The movement of electrons in a circuit.
Burns will appear only at the point where contact is made to the energized circuit.
In parallel.
The opposition to flow of electrons in a circuit.

22. What is the equivalent resistance of an 8-ohm and a 12-ohm resistor connected in parallel?
4.8 ohms
No.4 AWG.
A. Total resistance is less than the smallest resistor.
Burns will appear only at the point where contact is made to the energized circuit.

23. What is the total voltage of four 9-volt batteries connected in a series?
Soft iron.
Until the victim receives medical attention.
Stays the same.
36 volts.

24. Not true about electrical shocks?
Hydrometer.
60 ohms.
1.260 to 1.280.
Burns will appear only at the point where contact is made to the energized circuit.

25. What is the equivalent resistance of two 16-ohm resistors connected in parallel?
Flush the burn the clean water.
Current that flows in only one direction.
8 ohms.
After charging

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

27. Not a requirement of an explosion-proof enclosure?
Watts.
Power.
It must prevent internal explosions.
Clean water.

28. What voltage would be required to force 10 amps through a 50-ohm resistor?
500 volts.
Flush the burn the clean water.
A bi-directional device that can pass current in either direction.
100 ohms

29. The minimum allowable size of trailing cable on DC-powered mobile haulage equipment is...
It must prevent internal explosions.
No.4 AWG.
Flush the burn the clean water.
Ventilation.

30. Voltage is measured with a...
200 volts
Resistance.
Wattmeter.
Voltmeter.

31. What should be used in treating an eye injury caused by battery acid?
Heat
1.260 to 1.280.
Clean water.
The movement of electrons in a circuit.

32. You have three 9-volt batteries. How should you connect them in order to supply 27 volts?
6 volts.
48 ohms.
Until the victim receives medical attention.
In series.

33. Which of the following is a requirement of an explosion-proof enclosure?
Compound-wound and shunt-wound.
Ammeter.
It must prevent ignition of surrounding methane atmosphere.
Treat for physical shock.

34. The specific gravity of the electrolyte of a fully charged battery should be...
Ohms.
Current
1.260 to 1.280.
Watts.

35. What must be provided at underground battery charging stations?
400 ampere-hours.
Ventilation.
It must prevent ignition of surrounding methane atmosphere.
Clean water.

36. Current in a series circuit...
96 volts.
Stays the same.
Voltage.
15 minutes.

37. What is the opposition to flow of electric current?
After charging
Resistance.
4.0 ohms.
A counter-EMF.

38. The advantage of DC over AC is that DC offers...
Current.
Ammeter.
Better speed control on motors.
Attract each other.

39. When should water be added to a battery?
100 ohms
Compound-wound and shunt-wound.
Current.
After charging

40. Unlike poles of a magnet will...
Resistance.
Stays the same.
Attract each other.
4.8 ohms

41. Resistors are rated in ohms and...
Resistance.
Watts.
75 volts.
After charging

42. The core of an electro-magnet should be made of...
Soft iron.
Hydrogen.
It must prevent ignition of surrounding methane atmosphere.
E=IR.

43. What is the total voltage of eight 12-volt batteries connected in series?
96 volts.
The movement of electrons in a circuit.
A counter-EMF.
500 volts.

44. What is the first step in treating a chemical burn of the eye?
E=IR.
Resistance.
Flush the burn the clean water.
1.260 to 1.280.

45. How long should treatment for shock be continued?
Current that flows in only one direction.
E=IR.
200 volts
Until the victim receives medical attention.

46. Trailing cable on DC-powered mobile haulage equipment must be at least...
96 volts.
Ammeter.
No.4 AWG.
746 watts.

47. The dangerously explosive gas emitted by charging a lead-acid storage battery is...
Better speed control on motors.
A wire wound resistor.
Hydrogen.
Decrease.

48. The unit of measurement of power is...
A wire wound resistor.
Flush thoroughly with water.
Less than the resistance of either resistor.
Watts.

49. The first step in treating a chemical burn - such as one caused by battery acid - is to...
In parallel.
No.4 AWG.
Flush thoroughly with water.
It must prevent internal explosions.

50. A battery capable of producing 20 amperes steadily for 20 hours at 80 degrees Fahrenheit would have an ampere-hour rating of...
400 ampere-hours.
1.260 to 1.280.
100 ohms
6 volts.