What is the principle behind the operation of a transformer?

The operation of a transformer is fundamentally based on electromagnetic induction. This principle involves the generation of an electromotive force (EMF) in a coil of wire when it is exposed to a changing magnetic field. In a transformer, an alternating current (AC) flowing through the primary coil creates a varying magnetic field around it. This magnetic field then induces an alternating voltage in the secondary coil, which is placed within the magnetic field created by the primary coil.

This process allows the transformer to convert electrical energy from one voltage level to another, enabling efficient transmission and distribution of electricity. The relationship between the primary and secondary voltages is determined by the turns ratio of the coils, illustrating how the transformer can increase (step up) or decrease (step down) voltage levels.

Other options do not accurately define the primary principle of a transformer. For instance, magnetic resonance typically pertains to the behavior of particles in a magnetic field, while electrical induction isn't the most precise term for what occurs in a transformer. Mechanical induction is unrelated to the operation of transformers and generally refers to the transfer of energy through mechanical means, which is not applicable in this context.