What type of device is used to change AC voltage from one value to another?

The device used to change alternating current (AC) voltage from one value to another is a transformer. A transformer operates on the principle of electromagnetic induction and consists of two or more coils of wire (windings) wrapped around a magnetic core. When an alternating current flows through one winding, it creates a varying magnetic field that induces a voltage in the other winding.

The ratio of the number of turns in the primary winding to the number of turns in the secondary winding determines whether the transformer increases (steps up) or decreases (steps down) the voltage. This ability to modify voltage while maintaining the same frequency makes transformers essential in power distribution systems, where they allow for efficient transmission of electricity over long distances by stepping up the voltage to minimize losses, and then stepping it down for safe use in homes and businesses.

Other devices mentioned serve different purposes: a rectifier converts AC to DC, an amplifier boosts signal strength, and an inverter changes DC to AC. These functions are distinct and do not involve changing the value of AC voltage directly.