In synchro transmitters and receivers, stator coils serve as the ____________ windings of a variable transformer.

In synchro transmitters and receivers, the stator coils function as the primary windings of a variable transformer due to the role they play in generating an alternating magnetic field. When the rotor is driven to a certain position, the stator coils detect this positional information through electromagnetic induction. The varying position of the rotor induces a voltage in the stator windings, which is analogous to how primary windings in a transformer interact with the magnetic field created by a current flowing through them. This principle is foundational in understanding how synchros transmit positional data; the stator's response to the rotor's position is crucial in determining the output signal, which mirrors the action of primary windings transferring energy in a transformer system.

The other options do not accurately represent the role of the stator coils in this context. For instance, secondary windings typically respond to the magnetic field created by the primary windings, while inductor and auxiliary do not describe the function of the stator coils in this specific application.