What moves the windings apart on a constant current transformer?

The reason magnetic repulsion is the correct answer lies in the operating principles of a constant current transformer. In this type of transformer, the windings are designed to create a magnetic field when electric current flows through them. According to the laws of electromagnetism, like poles repel each other.

When the transformer operates, the current in the primary winding generates a magnetic field that can interact with the magnetic field produced by the currents in the secondary winding. If the winding configurations and the flow of current result in the similar poles facing each other, magnetic repulsion will naturally occur, leading to the separation of the windings.

This magnetic interaction is key to maintaining the correct air gap and efficiency of the transformer while ensuring stability in operation under different load conditions. The other provided choices do not accurately describe the mechanics involved in this specific scenario; they relate to other phenomena but not to the movement of windings in this context.