Outlet Boxes, Conduit Fill & Raceways practice test: free California General Electrician questions

Sample Practice Questions for Outlet Boxes, Conduit Fill & Raceways

1. Question 1Ref: NEC 314.16(B) — Installation: Boxes and Conduit Bodies: Box Fill Calculations

   During rough-in inspection, the inspector flags a junction box that appears too small. The box contains six 12 AWG conductors, two device pigtails, and one device clamp. What is the minimum cubic-inch volume required?

   A18.0 in³B20.25 in³C21.0 in³D24.0 in³
   Show Answer & Explanation

   Correct Answer
   C. 21.0 in³

   The keyed answer is "21.0 in³". Six 12 AWG conductors at 2.25 in³ each equals 13.5 in³, plus two device pigtails at 2.25 in³ (4.5 in³), plus one internal clamp at 2.25 in³ equals 20.25 in³, rounded up to 21.0 in³ minimum box fill.

2. Question 2Ref: NEC Chapter 9, Table 1 — Installation: Conduit Fill

   An electrician needs to pull four 10 AWG THHN conductors through a 3/4-inch EMT raceway. Is this installation permitted?

   ANo, because 10 AWG requires a minimum of 1-inch conduitBNo, because 3/4-inch EMT only allows three 10 AWG conductors at 40% fillCYes, but only if the conductors are nylon-jacketedDYes, because 3/4-inch EMT has sufficient fill for four 10 AWG conductors
   Show Answer & Explanation

   Correct Answer
   D. Yes, because 3/4-inch EMT has sufficient fill for four 10 AWG conductors

   The keyed answer is "Yes, because 3/4-inch EMT has sufficient fill for four 10 AWG conductors". Per NEC Chapter 9 Table 1, 3/4-inch EMT at 40% fill has a cross-sectional area of 0.213 in². Four 10 AWG THHN conductors at 0.0211 in² each equals 0.0844 in², which is well within the allowable fill.