Final answer:
Unused knockouts and openings in electrical boxes and cabinets are required to be closed according to the National Electrical Code (NEC).
Step-by-step explanation:
Electrical Engineering
In electrical engineering, unused knockouts and other openings in electrical boxes and cabinets are required to be closed according to the National Electrical Code (NEC). The NEC is a set of regulations and guidelines for safe and effective electrical installations.
These knockouts and openings are typically used for routing electrical wires or cables. When they are not in use, they must be closed to prevent the entry of dust, debris, and moisture, which can pose a safety risk and affect the performance of electrical equipment.
Examples:
For example, if you have an electrical junction box with unused knockouts, you can use knockout covers or plugs to close them off. These covers are designed to fit into the knockout holes and provide a secure seal. Similarly, openings in electrical cabinets can be closed using blanking plates or covers specifically designed for that purpose.