What must be done when nonmetallic sheathed cable passes through a floor?

When nonmetallic sheathed cable, commonly known as NM cable, passes through a floor, it is essential to enclose it in a pipe or conduit. This requirement serves multiple purposes, primarily focusing on protection. The enclosure safeguards the cable from physical damage due to impacts, moisture, or potential hazards that may be present in the floor assembly.

Additionally, enclosing the cable in a conduit helps to maintain the integrity of the electrical installation by providing a pathway that minimizes the risk of damage from surrounding construction materials or movement within the building. This protective measure ensures compliance with electrical codes and safety standards, which are designed to prevent accidents and electrical failures.

The other options do not provide the necessary level of protection required for nonmetallic sheathed cable. Insulation might be important for certain applications, but it does not offer the physical protection that conduit provides. Running the cable without protection or placing it on the floor surface exposes it to a higher risk of damage and does not meet the safety requirements established by electrical codes.