How does the resistance of a transformer vary?

The resistance of a transformer primarily refers to the resistance of its windings, which is typically fixed and does not change significantly under normal operating conditions. However, the effective impedance seen by the primary or secondary side can vary based on load conditions and frequency. Additionally, factors such as temperature changes can affect the resistance of the windings, as resistance generally increases with temperature. Overall, while the intrinsic resistance remains constant, the apparent resistance can vary due to external factors.