The concept of a magnetic field being formed around a conductor when current flows through it is called __________.

The phenomenon where a magnetic field is generated around a conductor as an electric current flows through it is referred to as electromagnetism. This principle is fundamental in physics and is the basis for many electrical devices and technologies. When electricity moves through a wire, it creates a magnetic field in the surrounding space, and the strength and direction of this field depend on the current's magnitude and direction. This interplay between electricity and magnetism is central to understanding how motors, transformers, and inductors function.

The other concepts listed, like flux and capacitance, relate to different aspects of electricity and magnetism. Flux generally refers to the rate of flow of a property through a surface, while capacitance is a measure of a capacitor's ability to store charge. Neither directly describes the relationship between current flow in a conductor and the resultant magnetic field. Therefore, the correct answer is rooted in the fundamental principles of electromagnetism as it explains the behavior of currents and their associated magnetic fields comprehensively.