breakers, grounding, insulation, wiring methods • power transmission and distribution, such as transformers, transmission lines, substations • electrical loads, such as motors, lighting, heating, and cooling systems • electrical measurements, such as voltage, current, power, energy • electrical safety, such as electrical hazards, safety precautions, personal protective equipment • electrical codes and standards, such as National Electrical Code (NEC), International Electrotechnical Commission (IEC) standards.