What is the term for the total opposition to the flow of current in a transformer?

The total opposition to the flow of current in a transformer is referred to as impedance. Impedance is a comprehensive term that encompasses not only the resistance to current flow but also the reactive components that arise from inductance and capacitance in an AC circuit, which are particularly relevant in the context of transformers.

In a transformer, the opposition is not solely due to resistive losses (which would be referred to as resistance); it also includes the effects of the transformer coils' inductance, which contributes to the overall opposition when alternating current flows through the system. Reactance, while related, is specifically the opposition due to inductance and capacitance, which are frequency-dependent elements.

Therefore, impedance is the appropriate term as it reflects the total opposition faced by the current, combining both resistive and reactive components. This concept is crucial in understanding how transformers function in AC circuits and how they respond to varying frequencies and loads, making impedance a fundamental aspect of electrical engineering, particularly in transformer applications.