Transformers are among the most basic electrical components in use. They provide the function of either reducing or increasing—termed stepping down or stepping up, respectively—voltage or current. These devices contain few parts, but they perform a vital role in many different electrical applications. From the large plugs on most electronic charging devices for cellular phones and tablet computers to the huge transformers mounted to power poles and located at substations, these devices are so common precisely because they are so useful.
There are some types of transformers that have fallen out of usage over time, just as is the case with all electrical components. Transformers are usually thought of as the types of larger, physical devices that one could pick up and hold in their hands, but they also come in sizes that are appropriate for the digital age. For example, a transformer can be etched onto a printed circuit board, just as can most electrical components.