What outer layer is referred to by 'NM'?

The term 'NM' refers specifically to Nonmetallic Sheath. In the context of electrical wiring, NM cable, commonly known as "Romex," is a type of nonmetallic sheathed cable widely used in residential wiring. The outer layer of NM cable is made of a durable plastic material that provides insulation and protection for the insulated conductors inside. This design helps prevent moisture, physical damage, and electrical hazards, ensuring both safety and reliability in electrical installations.

The use of a nonmetallic sheath is advantageous for applications where flexibility and ease of installation are required, as it is lighter and more manageable than metal-sheathed alternatives. Moreover, the nonmetallic sheath also helps with reducing electromagnetic interference, making NM cable a preferred choice for many electrical projects in homes. Understanding this concept is key for anyone involved in electrical power production or wiring installations.