How is "transformer impedance" defined?

Transformer impedance is correctly defined as the opposition a transformer presents to the flow of alternating current. This impedance encompasses both the resistance and reactance of the transformer, which affects how it operates in a circuit. In electrical systems, understanding transformer impedance is crucial for determining voltage drop, short-circuit current, and overall system performance.

The impedance is not directly associated with the transformer’s physical size, cost, operational lifespan, or energy efficiency as suggested in the other options. Instead, it primarily relates to how the transformer interacts with the electrical circuit, including its impact on efficiency and load capacity. Thus, the correct definition aligns closely with this understanding of how transformers behave in AC circuits, making it essential knowledge for electrical professionals.