How does a transformer change voltage levels?

The correct answer is based on the principle of electromagnetic induction, which is the fundamental operation of a transformer. A transformer consists of two coils of wire, known as the primary and secondary windings, that are magnetically linked through a core, typically made of iron.

When alternating current (AC) flows through the primary winding, it creates a fluctuating magnetic field around it. This changing magnetic field induces a voltage in the secondary winding through the process of electromagnetic induction. The voltage induced in the secondary winding depends on the turns ratio of the windings; if there are more turns in the secondary than in the primary, the voltage is increased (step-up transformer), and if there are fewer turns in the secondary, the voltage is decreased (step-down transformer).

This process allows transformers to efficiently change voltage levels for various applications in power distribution and electrical systems without the need for additional power loss or alterations in the electrical characteristics of the current itself.