What does NEC require for the conductors exposed to physical damage?

The National Electrical Code (NEC) requires that conductors exposed to physical damage must have a metal covering. This requirement is in place to ensure that the conductors are adequately protected from any potential hazards that could arise from physical impacts or damage. Metal coverings provide a robust defense against such occurrences, significantly reducing the risk of short circuits, electrical fires, or other safety issues that could result from compromised conductors.

While options like plastic and rubber coverings can offer some degree of protection, they may not suffice in environments where the risk of physical damage is high. The necessity for no covering is not acceptable under the NEC due to the inherent safety risks that unprotected conductors would pose. Therefore, the correct choice aligns with the objective of maintaining safety standards in electrical installations, particularly in areas where conductors might be more susceptible to damage.