What physical principle does a step-down transformer operate on?

A step-down transformer operates on the principle of electromagnetic induction. This principle explains how a changing magnetic field can induce an electromotive force (EMF) in a conductor. In the case of a transformer, an alternating current (AC) flowing through the primary coil creates a changing magnetic field, which then induces a voltage across the secondary coil.

The design of a step-down transformer, which has more turns in the primary winding than in the secondary, allows for the transformation of a higher input voltage to a lower output voltage. This voltage transformation is crucial for various applications, such as reducing voltage levels for safe use in homes or other electrical devices.

While other options touch on relevant electrical concepts, only electromagnetic induction specifically describes the mechanism by which transformers operate.