Final answer:
The white or gray conductor in a cable assembly is designated as the neutral and cannot be used as the live/hot wire in switch loop wiring. It serves as a safe, zero-volt return path for electric current to maintain electrical safety.
Step-by-step explanation:
The white or gray conductor in a cable assembly, when used in switch loop wiring, is not permitted to be used as a live/hot wire. In electrical systems, the white or sometimes gray wire is designated as the neutral wire, which serves as the return path for current to complete the circuit. It is kept at zero volts relative to the ground, making it safe to touch if the insulation is damaged or missing. The neutral wire's key role ensures that the electrical system's safety is maintained by providing a clear and distinguishable return path for electric current. On the other hand, the live/hot wire is responsible for supplying voltage and current to operate appliances. It is important in electrical safety to correctly identify and maintain the function of each wire within a cable assembly to prevent hazardous situations.