The function of current and potential transformers can be summarized as:

Current and potential transformers serve crucial roles in electric systems by stepping down high levels of current and voltage to lower, more manageable levels. This is essential for safe and accurate measurement and monitoring within electrical systems. By reducing these levels, these transformers allow instruments and protective devices to interface safely with the high-voltage, high-current environments typically found in power systems without risking damage or inaccurate readings.

In contrast, other options refer to functions that are not the primary roles of current and potential transformers. Energy loss and efficiency are considerations in overall circuit design but are not the direct function of these transformers. Similarly, while transformers can be involved in energy management, they do not store energy or directly power devices like batteries do. Measuring resistance is a different electrical function that is handled by other types of instruments and is not a task for current and potential transformers.