Electrician's Licensing Practice Exam 2025 - Free Electrician License Practice Questions and Study Guide

The marking that indicates aluminum wire used with receptacles must be designated as "CO/ALR." This designation stands for Copper-Aluminum alloy and signifies that the wire is specifically designed for use with aluminum wiring and has special coatings or treatment to reduce the risk of fire and improve connection reliability.

Using "CO/ALR" helps electricians and others recognize that the wire is safe for connections with devices that may otherwise not be compatible, ensuring proper installation and reducing the likelihood of oxidation or other issues that could compromise electrical safety.

In contrast, the other choices do not carry the specific implication of safety and suitability for connections with aluminum wiring. "ALUM" simply indicates general aluminum, while "CO/AL" suggests compatibility without the enhanced measures of the "R" designation. "ALR ONLY" lacks the context of proper connection standards and does not reflect an accurate marking for electrical safety requirements.