What is the maximum voltage rating for NM-B cable?

• A. 300 V
• B. 450 V
• C. 600 V
• D. 750 V

Answer: (C)

The maximum voltage rating for NM-B (non-metallic sheathed) cable is 600 volts. NM-B cable is commonly used in residential wiring and is designed to be used in dry locations, primarily for light and power circuits.

The 600-volt rating indicates the highest voltage that the cable can safely handle without risking insulation failure or hazards, which is essential for ensuring both the safety and functionality of the electrical system. This rating aligns with the standards set forth by the National Electrical Code (NEC), which regulates the use and installation of electrical wiring in the United States.

Understanding the voltage rating is important for compliance with electrical codes and for selecting the appropriate type of wiring for specific applications, ultimately ensuring safe installation practices.