What characterizes isolated transformers?

Isolated transformers are characterized by their magnetic coupling. This means that they transfer electrical energy between their primary and secondary windings through a magnetic field, without any direct electrical connection between the two circuits. This design is pivotal in providing electrical isolation, which enhances safety and reduces the risk of electrical shock.

In an isolated transformer, the primary winding creates a magnetic field when an alternating current flows through it, and this magnetic field induces a voltage in the secondary winding. The absence of direct electrical coupling is key to the transformer’s functionality, ensuring that the circuits remain isolated from one another, which is beneficial for protecting sensitive components and implementing safety measures in electrical systems.

The other aspects of transformers highlighted in the incorrect choices do not apply to the definition of isolated transformers. For example, transformers do not increase primary voltage unless they are designed specifically for that purpose, nor do they act as a source of power in the sense of generating electricity; they are designed to transfer power from one circuit to another while providing isolation and maintaining the system's integrity.