Licensed Electrical Contractor Code, Theory, and Calculations 3

Question 1

What NEC section governs the installation of conductors in raceways, and what is the maximum fill percentage for a single conductor in a conduit?

Accepted Answer

NEC 300.17 — 53%

Answer

NEC 300.17 references Chapter 9 Table 1, which allows 53% fill for a single conductor in a conduit.

Question 2

What is the reactance of a 60 Hz circuit with an inductance of 0.5 H?

Accepted Answer

188.5 Ω

Answer

Inductive reactance XL = 2πfL = 2π × 60 × 0.5 ≈ 188.5 Ω.

Question 3

Under NEC 210.8(A), GFCI protection is required for all 125 V, 15 A and 20 A receptacles in which residential location?

Accepted Answer

All outdoor locations

Answer

NEC 210.8(A) requires GFCI protection for all 125 V, 15 A and 20 A receptacles installed in outdoor locations of dwelling units.

Question 4

A 480 V, 3-phase, 4-wire wye system has a line-to-neutral voltage of approximately:

Accepted Answer

277 V

Answer

Line-to-neutral voltage = line voltage ÷ √3 = 480 ÷ 1.732 ≈ 277 V.

Question 5

Per NEC 250.122, the minimum size equipment grounding conductor (EGC) for a circuit protected by a 200 A overcurrent device is:

Accepted Answer

6 AWG copper

Answer

NEC Table 250.122 specifies a minimum 6 AWG copper EGC for circuits protected by overcurrent devices up to 200 A.

Licensed Electrical Contractor Practice Test