Wiring Methods, Materials, and Installation Practices
Installation mechanics
Chapter 3 answers 'how is it installed': Article 300 (general), 310 (conductors), 314 (boxes), 320-340 (cables), 342-362 (raceways), 376-392 (wireways, busways, trays).
Key rules a candidate must know: 300.4 requires protection from physical damage where cable or tubing is within 1 1/4 in. of the framing edge (steel nail plates); 300.5 and Table 300.5 set burial depths, with 24 in. as the general direct-burial depth for 0-1000 V and reduced depths (12 in. and 18 in.) limited to specific GFCI-protected residential circuits; 300.14 requires at least 6 in. of free conductor, with 3 in. outside the raceway; 314.16 governs box fill volume; 314.28 sizes pull boxes (8 times the largest raceway for straight pulls, 6 times for angle or U pulls); 358.30 supports EMT within 3 ft of each box and every 10 ft; 334.10 and 334.12 list where nonmetallic-sheathed cable is permitted and prohibited; 310.16 provides ampacities, and 240.4(D) caps 18-10 AWG at 15, 20, and 30 A.
Worked example (box fill): a box contains three 12 AWG ungrounded, three 12 AWG grounded, one 12 AWG equipment grounding conductor, and one duplex receptacle. Count six conductors plus one for all grounding conductors plus two for the device = nine equivalents. At 2.25 in.3 each, 9 x 2.25 = 20.25 in.3. A 4 x 4 x 1 1/2 in. box (21 in.3) is adequate.
Traps: counting each grounding conductor separately; using the table ampacity as the circuit rating without applying 240.4(D); assuming flexible conduit is always a legal equipment grounding conductor (250.118 has length and fitting conditions); ignoring expansion fittings for PVC outdoors.