Exam prep unit 8

(7) _____ 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.

Eddy

(14) The larger the cross-sectional area of a conductor, the _____ the number of paths for electrons, which lowers the resistance of the conductor.

Greater

(5) 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

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

True

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

0.03 ohms ( ch 9 table 9)

(18) What's the direct-current resistance of a 1 AWG copper conductor that's 200 ft long?

0.0308 ohms ( ch 9 table 8)

(20) What's the direct-current resistance of a 1/0 AWG aluminum conductor that's 800 ft long?

0.16 ohms (ch 9 table 8)

(10) 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

(3) What's the direct-current resistance of a 3 AWG aluminum conductor that's 500 ft long?

0.2015 ohms ( ch 9 table 8)

(19) What's the direct-current resistance of a 3 AWG aluminum conductor that's 1,000 ft long?

.403 ohms ( ch 9 table 8)

(12) 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.

Positive

(17) What's the direct-current resistance of a 6 AWG copper conductor that's 400 ft long?

.20 ohms ( ch 9 table 8)

(9) The opposition to current flow is greater for alternating-current circuits than for direct-current circuits because of _____.

All of these

(1) The resistance of a conductor is directly proportional to its length.

True

(2) What's the direct-current resistance of a 1 AWG copper conductor that's 100 ft long?

0.0154 ohms ( conductor properies table Ch9 table8)

(8) The expanding and collapsing magnetic field induces a counter voltage within the conductors, which repels the flowing electrons toward the conductor surface. This is known as "_____ effect."

Skin

(4) What's the direct-current resistance in ohms for three 300 kcmil copper conductors in a parallel run that are 1,000 ft long?

0.014 ohms(Ch 9 table 8)

(13) What's the alternating-current ohms-to-neutral resistance for a 500 kcmil copper conductor installed in an aluminum raceway that's 1,000 ft long?

0.032 ohms ( Ch 9 table 9 )

(16) The National Electrical Code 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 _____.

8,9

(15) Conductor resistance is determined by the _____.

All of these ; material/ cross- sectional area/conductor length