What is the term used to express the relationship between the transformer primary winding and the secondary winding?

The term that accurately describes the relationship between the primary winding and the secondary winding of a transformer is "turns ratio." This ratio represents the number of turns of wire in the primary winding compared to the number of turns in the secondary winding. It is a fundamental principle in transformer operation, dictating how voltage and current are transformed from one side to the other.

The turns ratio is crucial because it determines the voltage output based on the input voltage. For example, if the primary winding has more turns than the secondary, the transformer is a step-down transformer, resulting in a lower output voltage. Conversely, if the secondary has more turns, it acts as a step-up transformer, increasing the output voltage. Understanding this relationship is central to effectively using transformers in electrical systems.

The other terms listed do not accurately define this specific relationship. Resistance ratio would refer to the comparison of resistances, voltage ratio would imply a direct comparison of voltages rather than the underlying turns, and current ratio would deal more with the currents based on transformer load rather than the winding structure itself. Hence, “turns ratio” distinctly captures the essential relationship in the context of transformers.