What is the primary purpose of a transformer?

The primary purpose of a transformer is to change AC voltage levels. Transformers are electrical devices that transfer electrical energy between two or more circuits through electromagnetic induction. They primarily serve to step up (increase) or step down (decrease) voltage levels while maintaining the same frequency, which is essential for efficient power distribution across long distances.

By adjusting voltage levels, transformers help to reduce energy losses during transmission. Higher voltages are used for long-distance transmission to decrease current, thus minimizing resistive losses in transmission lines. Conversely, they step down voltage levels for safe use in residential or commercial applications. This function is crucial for electrical power systems, as it ensures that electricity can be efficiently transmitted from power generation facilities to consumers.

The other options do not accurately represent the primary function of a transformer. For instance, transformers do not store electrical energy, measure current flow, or act as switches; these roles are fulfilled by other devices in electrical systems.