Exam Prep. Unit 8 Voltage Drop.

What's the coltage drop of two 12 AWG conductors that supply a 10 A, 120 V, single-phase lad located 100ft from the power supply?

4V.

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.

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.

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

True.

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

0.0108 ohms.

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.

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

0.03 ohms.

What size conductor should be used to limit voltage drop from exceeding three percent if the equipment nameplate indicates an 18A continuous load at 480V, three-phase and its located 300 ft from the power supply?

10 AWG.

A 120 volt single phase branch circuit using 12 AWG copper conductors is supplying a 15 ampere load located sixty feet from the panelboard. Determine the approximate voltage drop.

4 volts.

A 208/120 volt three phase feeder using size 4 AWG aluminum conductors is to supply an 80 ampere load located one hundred feet from the switchboard. Determine the approximate voltage drop.

7 volts.

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.

A 240V, 24A, 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?

9.50V.

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

0.03 ohms

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

0.0308 ohms.

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

0.0308 ohms.

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

0.16 ohms.

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

0.20 ohms.

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

0.2015 ohms.

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

0.2015 ohms.

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

0.403 ohms.

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

6.24 V.

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.

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

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

0.0154 ohms.

Conductor resistance is determined by the _____.

material type. cross-sectional area. conductor length.

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

0.025 ohms.

What size copper conductors in a steel raceway can be used to replace a 1/0 AWG aluminum that supplies an 110A load? Hint: Find a copper conductor with the same resistance per foot as the existing aluminum conductor. Note: We don't want to increase the circuit voltage drop.

2 AWG.

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

375 ft.

A 240 volt single phase 52 ampere load is located two hundred feet from the panelboard. What minimum size copper branch circuit conductors should be used to supply this load when voltage drop is to be limited to 3 percent?

4 AWG.

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?

4.40V.

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

4.75V to 4.80V.

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

4.76 V.

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 are listed in Chapter 9, Table ___.

8, 9.

_____ 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.

The larger the cross-sectional area of a conductor, the ____ the number of paths for electrons, which lowers the resistance of the conductor.

greater.

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

0.0108 ohms.

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

0.20 ohms.

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

0.20 ohms.

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

greater.

What's the maximum recommended continuous load that should be placed on a 150A rated feeder containing 1 AWG copper conductors in an aluminum raceway to a panelboard located 150 ft from a 208V, three-phase power source so the NEC recommendation for voltage drop isn't exceeded?

104 A ??

According to Table 8 of Chapter 9, what's the cross-sectional area in circular mills for a 1/0 THHN conductor?

105,600.

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

145 ft.

An existing installation consist of 1/0 AWG copper conductors in a nonmetallic raceway to a panelboard located 200 ft from a 240V, single-phase power source. What's the maximum load that can be placed on the panelboard so the NEC recommendations for voltage drop aren't exceeded?

147 A.

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

eddy currents. skin effect. inductive reactance.

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.

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.