What is defined as a unit of an electrical system that carries or controls electric energy?

The term that best describes a unit of an electrical system that carries or controls electric energy is "device." In electrical terminology, a device is any functional entity that can either consume or manage electrical energy. This encompasses a wide variety of units, including switches, lamps, and generators, all of which are integral in controlling or using electric energy within a system.

While the other terms might seem related, they have more specific meanings. A load refers specifically to a component that consumes electrical power, such as a motor or a light fixture, but does not inherently imply control of electrical energy. A component is a broad term that can refer to any part of a system, including devices, but doesn’t specifically highlight its function regarding energy. A transformer is a specific type of electrical device that adjusts voltage levels, but it is categorized under the broader concept of devices in an electrical system.

Thus, defining a unit of an electrical system that carries or controls electric energy as a device accurately captures its role in managing electrical processes.