In compliance with the rules established by the NEC®, all 120-volt, single-phase, 15- and 20-ampere branch circuits supplying outlet or devices in specific areas or rooms of a dwelling unit shall be provided with arc-fault circuit-interrupter protection. Where Type NM cable is used as the wiring method for "home runs" in the dwelling, the maximum length of the cable from the overcurrent device to the first outlet shall not exceed _____ for size 14 AWG NM cable and _____ for size 12 AWG NM cable.

Most states require an electrician to pass an exam to receive a journeyman or master electrician license.  State exams cover these topics:  Electrical Theory, Trade Knowledge, Grounding and Bonding, Wiring Methods and Installation, Overcurrent Protection, Load Calculations, etc.