Electrical Exam Prep Unit 8

Front 1

1. The cross-sectional area of a conductor is commonly expressed in ______.

Back 1

Circular mils

Front 2

2. According to Chapter 9, Table 8, what's the cross-sectional area in circular mils for a 4 AWG conductor?

Back 2

41,740 cmil

Front 3

3. According to Chapter 9, Table 8, what's the cross-sectional area in circular mils for a 2 AWG conductor?

Back 3

66,360 cmil

Front 4

4. According to Chapter 9, Table 8, what's the cross-sectional area in circular mils for a 1 AWG conductor?

Back 4

83,690 cmil

Front 5

5. According to Chapter 9, Table 8, what's the cross-sectional area in circular mils for a 1/0 AWG conductor?

Back 5

105,600 cmil

Front 6

6. According to Chapter 9 Table 8 what's the cross-sectional area in circular mils for a 3/0 AWG aluminum conductor?

Back 6

167,800 cmil

Front 7

7. The resistance of a conductor is directly proportional to its length. True or false?

Back 7

True

Front 8

8. The resistance of a conductor changes with temperature. Temperature coefficient describes the effect temperature has on the resistance of a conductor. Conductors with a _________ temperature coefficient have an increase in resistance with an increase in temperature.

Back 8

Positive

Front 9

9. The larger the cross-sectional area of a conductor, the _______ the number of paths for elections, which lowers the resistance of the conductor.

Back 9

Greater

Front 10

10. Conductor resistance is determined by the _______.

Material type

Cross-sectional area

Conductor length

All of these

Back 10

All of these

Front 11

11. The NEC lists the resistance and area in circular mils for both direct current and alternating current conductors. Direct current conductor resistances are listed in Chapter 9, Table_____ and alternating current conductor resistances and reactance are listed in Chapter 9, Table____.

Back 11

8,9

Front 12

12. What's the direct current resistance of a 6 AWG copper conductor that's 400 ft long?

Back 12

.20 ohms

Front 13

13. What's the direct current resistance of a 1 AWG copper conductor that's 200 ft long?

Back 13

.0308 ohms

Front 14

14. What's the direct current resistance of a 3 AWG aluminum conductor that's 1000 ft long?

Back 14

.403 ohms

Front 15

15. What's the direct current resistance of a 1/0 AWG aluminum conductor that's 800 ft long?

Back 15

.16 ohms

Front 16

16. What's the direct current resistance of a 1 AWG copper conductor that's 100 ft long?

Back 16

.0154 ohms

Front 17

17. What's the direct current resistance of a 3 AWG aluminum conductor that's 500 ft long?

Back 17

.2015 ohms

Front 18

18. What's the direct current resistance in ohms for three 300 kcmil copper conductors in a parallel run that are 1000 ft long?

Back 18

.014 ohms

Front 19

19. The intensity of a magnetic field depends on the intensity of alternating current. The greater the current flow, the greater the overall magnetic field.

True or false?

Back 19

True

Front 20

20. In alternating current circuits, the expanding and collapsing magnetic field within the conductor induced an electromotive force that opposes the flow of alternating current. This opposition to the flow of alternating current is called "inductive reactance."

True or false?

Back 20

True

Front 21

21. _______ currents are small independent currents that are produced as a result of the expanding and collapsing magnetic field. They flow erratically within the conductor opposing current flow and consuming power.

Back 21

Eddy

Front 22

22. The expanding and collapsing magnetic field induces a counter voltage within the conductors, which repels the flowing electrons towards the conductor surface. This is known as "_______ effect."

Back 22

Skin

Front 23

23. The opposition to current flow is greater for alternating current circuits than for direct current circuits because of ______.

Eddy currents

Skin effects

Inductive reactance

All of these

Back 23

All of these

Front 24

24. The alternating current conductor resistances listed in Chapter 9 Table 9 of the NEC are different for copper and aluminum, and for nonmagnetic and magnetic raceways.

True or false?

Back 24

True

Front 25

25. What's the alternating current ohms-to-neutral resistance for a 2/0 AWG copper conductor that's 300 ft long?

Back 25

.03 ohms

Front 26

26. What's the alternating current ohms-to-neutral resistance for a 500 kcmil copper conductor installed in an aluminum raceway that's 1000 ft long?

Back 26

.032 ohms

Front 27

27. What's the alternating current ohms-to-neutral resistance for a 3 AWG copper conductor that's 100 ft long?

Back 27

.025 ohms

Front 28

28. What's the alternating current ohms-to-neutral resistance of a 500 kcmil copper conductor installed in PVC conduit that's 400 ft long?

Back 28

.0108 ohms

Front 29

29. A 2-wire circuit supplies a 36A load that's located 100 ft from the panelboard. The load is wired with 1 AWG aluminum conductors in PVC conduit. What's the total alternating current ohms-to-neutral resistance of the circuit conductors?

Back 29

.62 ohms

Front 30

30. What size copper conductor in a steel raceway can be used to replace 1/0 AWG aluminum conductors that supply a 110A load?

Back 30

2 AWG

Hint 30

Hint: find a copper conductor with the same resistance per foot as the existing aluminum conductors.

Front 31

31. What's the alternating current ohms-to-neutral resistance for three 1/0 AWG aluminum conductors run in parallel for 1000 ft installed in a steel raceway?

Back 31

--

Front 32

32. The opposition to current flow results in voltage drop. All circuits have voltage drop, simply because all conductors have resistance.

True or false?

Back 32

True

Front 33

33. When sizing conductors for feeders and branch circuits, the NEC _______ that we take voltage drop into consideration.

Back 33

suggests

Front 34

34. When a conductor resistance caused the voltage to be dropped below an acceptable point, the conductor size should be increased.

True or false?

Back 34

True

Front 35

35. How can conductor voltage drop be reduced?

Increase the supply voltage

Increase the conductor size

Decrease the conductor length

All of these

Back 35

All of these

Front 36

36. If the branch circuit supply voltage is 208V, the maximum recommended voltage drop of the circuit shouldn't be more than_____.

Back 36

6.24V

Front 37

37. If the feeder supply voltage is 240V, the maximum recommended voltage drop of the feeder shouldn't be more than______.

Back 37

3.60V

Front 38

38. What's the voltage drop of two 12 AWG conductors supplying a 12A continuous load located 100 ft from the power supply?

Back 38

4.75V to 4.80V

Front 39

39. What's the voltage drop of two 12 AWG conductors that supply a 10A, 120V, single phase load located 100 ft from the power supply?

Back 39

4V

Front 40

40. A 240V, 20A, single phase load is located 100 ft from the panelboard and is wired with 10 AWG conductors. What's the voltage drop of the circuit conductors?

Back 40

4.80V

Front 41

41. A single-phase, 5 HP motor is located 110 ft from a panelboard in a dry location. The nameplate indicates that the voltage is 115V and the FLA is 52A. What size conductor is required?

Note: Apply the NEC recommended voltage drop limit for this branch circuit.

Back 41

3 AWG

Front 42

42. A single-phase, 5 HP motor is located 110 ft from a panelboard. The nameplate indicates that the voltage is 230V and the FLA is 26A. What size conductor is required?

Note: Apply the NEC recommended voltage drop limits.

Back 42

8 AWG

Front 43

43. What size conductor should be used to limit voltage drop from exceeding three percent of the equipment nameplate indicates an 18A continuous load at 480V, three phase and it's located 300 ft from the power supply?

Back 43

10 AWG

Front 44

45. A 240V, 24A l, single-phase load is located 160 ft from the panelboard. The load is wired with 10 AWG conductors. What's the approximate voltage drop of the branch circuit conductors?

Back 44

9.50V

Front 45

46. A 100A, three phase load is located 100 ft from the panelboard and is wired with 1 AWG aluminum conductors. What's the approximate voltage drop of the circuit conductors?

Back 45

4.40V

Front 46

47. What's the approximate distance that a 240V, 31A, single-phase load can be located form a panelboard so the voltage drop doesn't exceed three percent? The load is wired with 8 AWG copper.

Back 46

145 ft

Front 47

48. What's the approximate distance a 480V, 45A, three phase transformer, wired with 6 AWG copper can be located form a panelboard so the voltage drop doesn't exceed three percent?

Back 47

375 ft

Front 48

51. What's the maximum recommended continuous load that should be placed on 1/0 AWG aluminum conductors in a nonmetallic raceway to a panelboard located 200 ft from a 240V, single-phase power source so the NEC recommendation for volt drop isn't exceeded?

Back 48

90A

Front 49

49. What's the maximum distance a 240V, single-phase, 10A continuous load can be located from a panelboard so the voltage drop doesn't exceed three percent? The load is wired with 12 AWG.

Back 49

182 ft.

Front 50

50. What's the maximum distance a 100A, 208V, three phase non-continous load wired with 1 AWG conductors can be located from a panelboard so the voltage drop doesn't exceed three percent?

Back 50

234 ft