A saturable-core reactor operates on the principle of controlling a load winding's inductance by changing the permeability of the core. How is this accomplished?

Correct Answer: Option D — varying the core's saturation

A saturable-core reactor utilizes a DC control winding to vary the magnetic flux density within the iron core. By driving the core toward magnetic saturation, the permeability decreases, which in turn reduces the inductive reactance of the load winding, allowing more current to flow through the circuit.