Electrician's Licensing Practice Exam 2026 - Free Electrician License Practice Questions and Study Guide

Transformers are commonly categorized based on their cooling methods and construction. The correct classification includes both liquid-filled and dry versions. Liquid-filled transformers utilize oil for insulation and cooling, which allows for efficient heat dissipation and provides additional insulation properties, making them suitable for many industrial applications. Dry transformers, on the other hand, are cooled by air and do not contain any liquid insulating medium, making them more environmentally friendly and easier to maintain.

This dual classification reflects the intended application and environmental considerations associated with transformer deployment. While the other classifications—such as high voltage versus low voltage, cooling types like air-cooled, and design types like single-phase and three-phase—are important, they do not encompass the specific focus on transformer types based on fill materials and insulation methods as effectively as the correct answer.