A unit of an electrical system that carries or controls electrical energy is best defined as what?

A unit of an electrical system that carries or controls electrical energy is best defined as a device. In electrical terminology, a device encompasses a range of components that can manage the flow of electricity. This includes equipment like switches, circuit breakers, relays, and more, all of which serve to control electrical energy through various functions.

While a conductor is essential for carrying electrical current, it does not encompass the control aspect, which is integral to the definition of a device. Similarly, a transformer is a specific type of device that changes the voltage of electricity; however, it does not represent the broader category of devices that manage electrical energy. A load refers to any component that consumes electrical power, such as appliances or machinery, but again, it does not cover the full spectrum of units that can control or manage electrical energy. Thus, "device" is the term that includes all these functions and is the most suitable answer.