What causes core loss in transformers?

Core loss in transformers primarily results from hysteresis and eddy currents. When an alternating current flows through the transformer's windings, it generates an alternating magnetic field which magnetizes and demagnetizes the core material. This process induces losses due to two main phenomena: hysteresis loss and eddy current loss.

Hysteresis loss is caused by the lagging of magnetic domains within the core material as the magnetic field fluctuates. As these domains realign with the alternating magnetic field, energy is lost as heat due to resistance in the core material. The magnitude of hysteresis loss depends on the properties of the core material—particularly its magnetic permeability and the frequency of the magnetic flux changes.

Eddy current loss occurs when changing magnetic fields induce circulating currents within the core itself. These currents flow in loops within the conductive material, and as they encounter resistance, they generate additional heat, contributing further to core loss. To minimize these losses, transformer cores are often made from laminated sheets of steel or other materials to restrict the flow of these eddy currents.

Thus, the correct answer indicates the two primary components of core loss, demonstrating a fundamental understanding of transformer operation and the associated energy losses.