National Electrical Code. This is the electrical code recommendation of the National Fire Protection Association (NFPA) and is revised every three years.

National Electrical Manufacturers Association. This trade association sets standards for motors, enclosures and similar equipment.

neutral ground
A ground connection to a neutral wire or to the neutral point of a circuit.

noise (audible)
Sound that is caused by the physical vibration of an object. Frequencies in the range of 20 to 20,000 Hz are audible to most humans. The larger the amplitude of the vibration and the larger the surface that is vibrating, the louder the sound. Sound levels are measured in decibels (dB) See decibel.

noise (electrical)
Undesirable electrical disturbances imposed on an electrical wave. Electrical noise may cause other electrical equipment to malfunction or operate erratically. Electrical noise can be conducted through wires or radiated through air.

see line notching