Licensed Electrical Contractor Wiring Methods and Materials Questions and Answers

Question 1

An electrical contractor is installing conductors in a raceway located on a rooftop where the ambient temperature is expected to reach 125°F (52°C).
The design requires using 4/0 AWG THHN copper conductors.
According to NEC Table 310.16, the ampacity of 4/0 THHN is 260A at 30°C.
What is the corrected ampacity of these conductors after applying the required temperature correction factor from Table 310.15(B)(1)?

Accepted Answer

189.8A

Answer

260A

Answer

213.2A

Answer

236.6A

Question 2

When installing a multiconductor Type NM cable through a series of bored holes in wood studs, what is the minimum distance the edge of the hole must be from the nearest edge of the wood member to avoid the need for a protective steel plate?

Accepted Answer

1 1/4 inches

Answer

3/4 inch

Answer

1 inch

Answer

1 1/2 inches

Question 3

According to NEC Chapter 9, Table 1, what is the maximum permitted conduit fill percentage for a raceway containing three or more conductors?

Accepted Answer

40%

Answer

31%

Answer

53%

Answer

60%

Question 4

A contractor is wiring a Class I, Division 1 hazardous location. Which of the following wiring methods is generally required to contain a potential explosion?

Accepted Answer

Threaded Rigid Metal Conduit (RMC) with explosion-proof fittings

Answer

Electrical Metallic Tubing (EMT) with compression fittings

Answer

Type MC cable with standard connectors

Answer

PVC conduit sealed at all joints

Question 5

Which of the following must be bonded together to create an effective ground-fault current path in a commercial installation using metallic cable trays?

Accepted Answer

All metallic cable tray sections, fittings, and the equipment grounding conductor system

Answer

Only the sections of the cable tray containing power conductors

Answer

All metallic cable tray sections, but not necessarily to the grounding conductor

Answer

Only the supporting hardware for the cable tray

Question 6

A contractor needs to run conductors in parallel in separate raceways. According to NEC 310.10(G), which of the following conditions must be met for conductors of size 1/0 AWG and larger?

Accepted Answer

The conductors must be of the same length, material, cross-sectional area, and insulation type.

Answer

The conductors must be of different lengths to balance impedance.

Answer

The conductors can be of different materials if the ampacity is the same.

Answer

The conductors must be terminated using different methods to ensure secure connections.