Journeyman Electrician’s Exam Journeyman Electrician's Boxes and Enclosures 3

Question 1

Per NEC 314.20, in walls or ceilings constructed of combustible material (such as wood paneling), electrical boxes must be installed:

Accepted Answer

Flush with or projecting from the finished surface

Answer

NEC 314.20 requires that boxes in combustible walls or ceilings be flush with or project beyond the finished surface to prevent fire hazards from air gaps.

Question 2

Per NEC 314.20, in noncombustible walls such as plaster or tile, what is the maximum allowable setback of an electrical box from the finished surface?

Accepted Answer

1/4 inch

Answer

NEC 314.20 permits boxes in noncombustible surfaces to be set back a maximum of 1/4 inch from the finished surface.

Question 3

According to NEC 314.23(B)(1), a box mounted without a direct structural connection must be fastened to a structural member within:

Accepted Answer

12 inches

Answer

NEC 314.23(B)(1) requires boxes to be secured to a structural member within 12 inches of the box to ensure stable support.

Question 4

A 4-11/16 inch square metal box 2-1/8 inches deep has a listed volume of 42 cubic inches. Using only 10 AWG conductors (no devices), how many conductors are permitted?

Accepted Answer

16 conductors

Answer

Each 10 AWG conductor occupies 2.50 cubic inches per Table 314.16(B); 42 ÷ 2.50 = 16.8, which rounds down to 16 conductors.

Question 5

Which of the following is a true statement regarding nonmetallic (plastic) electrical boxes used with nonmetallic-sheathed cable (NM)?

Accepted Answer

The equipment grounding path is carried by the EGC wire in the cable, not the box

Answer

Nonmetallic boxes are non-conductive, so the equipment grounding path relies entirely on the EGC within the NM cable rather than the box body itself.

Journeyman Electrician’s Exam Practice Test

Journeyman Electrician’s Exam Practice Test

Journeyman Electrician’s Exam Journeyman Electrician's Boxes and Enclosures 3