What is the primary effect of eddy currents in a transformer's iron core?

Eddy currents are loops of electrical current that are induced within conductors by a changing magnetic field due to Faraday's law of induction. In the context of a transformer's iron core, these currents flow in closed loops perpendicular to the magnetic field, generating heat as a result of the resistance of the iron to the flow of current. This heating is known as "core loss," which can have significant implications for the efficiency of the transformer.

The presence of eddy currents leads to energy losses in the form of heat, which means less of the input electrical energy is effectively converted to usable energy at the output. This heating can reduce the overall efficiency of the transformer and must be managed through design choices, such as using laminated core materials that restrict the flow of eddy currents.

Understanding this phenomenon is crucial for designing electrical devices like transformers to ensure they operate at optimal efficiency while minimizing energy loss through unwanted heating. This delineation makes it clear that the primary effect of eddy currents in a transformer's iron core is indeed the unnecessary heating rather than any benefits such as improving magnetic flow or enhancing efficiency.